A group of paleontologists, park rangers, and geologists have discovered a new species of ancient shark in the rock layers of Mammoth Cave National Park in Kentucky. It was uncovered in a large fossil deposit that includes at least 40 different species of shark and their relatives, and even well-preserved skeletal cartilage. 

[Related: Megalodons were likely warm-blooded, despite being stone-cold killers.]

The new species is named Strigilodus tollesonae and is a petalodont shark. These extinct  sharks had petal-shaped teeth and lived about 337 million years ago. According to the National Park Service, it is more closely related to present day ratfish than sharks or rays and it was identified from teeth found in the cave’s walls. Strigilodus tollesonae likely had teeth that included one rounded cusp used for clipping and a long, ridge inert side that crushed prey the way molars do. Paleontologists believe that it likely lived like modern day skates and fed on worms, bivalves, and small fish. 

Strigilodus tollesonae translates to “Tolleson’s Scraper Tooth” and it is named after Mammoth Cave National park guide Kelli Tolleson for her work in the paleontological study that uncovered the new species. 

The limestone caves that make up the 400-mile long Mammoth Cave System were formed about 325-million-years ago during the Late Paleozoic. Geologists call this time period the Mississippian Period, when shallow seas covered much of North America including where Mammoth Cave is today. 

In 2019, the park began a major paleontological resources inventory to identify the numerous types of fossils associated with the rock layers. Mammoth Cave park staff reported a few fossil shark teeth that were exposed in the cave walls of Ste. Genevieve Limestone in several locations. Shark fossils can be difficult to come by, since shark skeletons are made of cartilage instead of bone. Cartilage is not as tough as bone, so it is generally not well-preserved in the fossil record. 

The team then brought in shark fossil specialist John-Paul Hodnett of the Maryland-National Capital Parks and Planning Commission to help identify the shark fossils. Hodnett and park rangers discovered and identified multiple different species of primitive sharks from the shark teeth and fine spine specimens in the rocks lining the cave passages.

“I am absolutely amazed at the diversity of sharks we see while exploring the passages that make up Mammoth Cave,” Hodnett said in a statement. “We can hardly move more than a couple of feet as another tooth or spine is spotted in the cave ceiling or wall. We are seeing a range of different species of chondrichthyans [cartilaginous fish] that fill a variety of ecological niches, from large predators to tiny little sharks that lived amongst the crinoid [sea lily] forest on the seafloor that was their habitat.”

[Related: This whale fossil could reveal evidence of a 15-million-year-old megalodon attack.]

In addition to Strigilodus tollesonae, the team have identified more than 40 different species of sharks and their relatives from Mammoth Cave specimens in the past 10 months. There appear to be at least six fossil shark species that are new to science. According to the team, those species will be described and named in an upcoming scientific publication.

The majority of the shark fossils have been discovered in areas of the park that are inaccessible to the public, so photographs, illustrations, and three-dimensional models have been made to display the discovery. The park also plans to celebrate the new shark fossils with multiple presentations and exhibits on Monday October 23. 

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This article was originally featured on Hakai Magazine, an online publication about science and society in coastal ecosystems. Read more stories like this at hakaimagazine.com.

To see a great white shark breach the waves, its powerful jaws clasping a shock-struck seal, is to see the very pinnacle of predatory prowess. Or so we thought. Several years ago, in South Africa, the world was reminded that even great white sharks have something to fear: killer whales.

Long before they started chomping on yachts, killer whales were making headlines for a rash of attacks on South African great white sharks. The killings were as gruesome as they were impressive. The killer whales were showing a deliberate sense of culinary preference, consuming the sharks’ oily, nutrient-rich livers but leaving the rest of the shark to sink or wash up on a nearby beach.

From the initial news of the attacks, the situation only got weirder. Great white sharks started disappearing from some of their best-known habitat around South Africa’s False Bay and Gansbaai regions, in the country’s southwest.

“The decline of white sharks was so dramatic, so fast, so unheard of that lots of theories began to circulate,” says Michelle Jewell, an ecologist at Michigan State University Museum. In the absence of explanation, pet theories abounded. Some proposed that overfishing of the sharks’ prey to feed Australia’s fish and chips market led to the shark’s declines. Other activists misinterpreted that idea and went on to campaign against what they thought was the recent inclusion of great white shark meat as a surprise ingredient in Australian fish and chips. That idea was, fortunately, thoroughly debunked.

Others thought the disappearance was directly caused by the killer whales. Perhaps they were killing all the sharks?

“Any time you see large population declines in local areas, it’s cause for conservation concern,” says Heather Bowlby, a shark expert with Fisheries and Oceans Canada. “In a place where animals used to be seen very regularly, and suddenly they’re not there anymore, some were concerned that they all died.”

Now, though, scientists finally know what happened. In a recent paper, Bowlby and her colleagues show that the sharks’ disappearance was, actually, caused by the killer whales. But the sharks aren’t dead. They just moved. Across South Africa, the scientists found, the white shark population has taken a pronounced eastward shift.

To Jewell, who wasn’t involved in the research, this makes sense. “We know that predators have a huge influence on the movement and habitat use of their prey, so this isn’t really surprising,” she says. “The issue is that lots of people weren’t used to thinking of great white sharks as prey.”

Alison Kock, a marine biologist with South African National Parks and a coauthor of the study, says they cracked the mystery after reports started flowing in from sites farther east that white sharks were showing up unexpectedly. “As False Bay and Gansbaai had major declines, other places reported huge increases in white shark populations,” she says. “Too rapid to be related to reproduction, since they don’t reproduce that fast.”

“It had to be redistribution,” she says, adding: “The white sharks moved east.” Places like Algoa Bay and the KwaZulu-Natal coastline had seen great white sharks before but not anywhere near this many.

In the white sharks’ absence, South Africa’s west coast is changing. New species like bronze whalers and sevengill sharks have moved into False Bay. For the tour operators who ran shark dives in the area, however, the shift has been difficult. Some have survived by switching to offering kelp forest dives—driven in part by the popularity of the documentary My Octopus Teacher. Many, though, have gone under.

But what of the great white sharks’ new home farther east? No one quite knows how these regions are adapting to a sudden influx of apex predators, but scientists expect some significant ecological changes. They’re also warning of the potential for increased shark bites, since people living in the white shark’s new homes are not as used to shark-human interactions.

We may never know exactly how many white sharks died in killer whale attacks. The prized, presumably tasty, livers targeted by the killer whales help white sharks float, which means many dead white sharks may have sunk uncounted. Overall, though, Kock is glad to see the mystery solved.

“This has been very worrying for me, and it was good to see evidence that they hadn’t all died,” says Kock. “But it’s still unbelievable to me that I can go to [False Bay’s] Seal Island and not see any white sharks. It’s something I never expected, and I miss them a lot.”

This article first appeared in Hakai Magazine and is republished here with permission.

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Weeks before we even think about getting sandbags or boarding up windows to prevent hurricane damage, an underwater evacuation begins. Sharks, sea snakes, and other wildlife will make preparations to escape becoming trapped or hurt as massive storms approach a coast. 

Much of Florida’s aquatic life—including species as diverse as manatees and alligators—know what to do in a storm like Hurricane Idalia. After all, these native animals have had millions more years of practice than us. But those age-old skills will only become more useful as hurricanes become more intense from climate change. 

“Aquatic animals respond to storms for the same reason we do—to avoid injury, death, and the destruction from hurricanes,” says Bradley Strickland, a postdoctoral researcher who studies aquatic animal response to hurricanes and climate change at William and Mary’s Virginia Institute of Marine Science. Still, some animals are better equipped to weather or evade the storms than others. And sharks are among the best. 

[Related: Sharks are learning to love coastal cities]

Even when a hurricane is far on the horizon, the atmosphere changes: the barometric pressure drops. “From two weeks out of a hurricane, sharks can actually detect the change and start heading for deeper water,” says Neil Hammerschlag, director of the shark research and conservation program at the University of Miami. The air around a hurricane decreases in pressure as a storm strengthens and wind speeds increase. Sharks can sense that, allowing them to flee long before Florida’s human residents were given mandatory evacuation orders. 

“Similar to the way we use meteorological technologies and observations about the changing wind and temperature before a storm, aquatic animals have ways to sense the approach of a storm,” Strickland says. Sharks use their sensitive inner ears to detect a gathering storm’s pressure changes, he adds. And, because of their incredible swimming abilities (some can swim up to 45 miles per hour), they can quickly escape oncoming storms—that is, if they choose to. 

Smaller shark species and juveniles opt to escape to deeper water to avoid the turbulence near the shore. For them, “staying in shallow water would be like a shark tornado,” Hammerschlag says, because hurricanes can push currents up to 300 feet below the ocean’s surface. For smaller sharks that remain in the shallows, they risk being swept inland.

Yet other larger predators, like tiger sharks that grow up to 14 feet and 1,400 pounds, view hurricanes as an opportunity for the ultimate sea smorgasbord. By tracking tiger sharks during and after Hurricane Irma, Hammerschlag noticed that “not only did they not run away, but they may have been taking advantage of the things that were dying, either birds that got washed into the water or fish and invertebrates that collided with debris.” After the storm, he adds, there were “higher numbers of tiger sharks in the area for about two weeks.”

For aquatic and semi-aquatic animals that can’t ride out the storm or swim beyond its reach, finding shelter may be the superior option for survival. “Sea snakes will seek refuge in volcanic rocks to avoid typhoons,” Strickland says. “Alligators likely hunker down to weather a storm by finding easy to get in and out of places,” he adds. Some smaller gators may get swept away by hurricanes; others might change their foraging patterns altogether to stay safe. 

Other species may be less lucky. After Hurricane Ian struck Florida in 2022, clean-up crews had to remove debris from the holes where burrowing owls live, since the threatened birds can’t claw through the trash on their own, as one wildlife rehabilitation expert told CNN. And when storms shove salty seawater inland, increases in salinity can disturb trees or turtles that dwell in freshwater ecosystems.

Along the coast, graceful manatees, too, have been found in particularly sticky situations post-hurricane. Although weight-wise they are comparable to a tiger shark, speed-wise they are definitely not, cruising up to 15 mph only if they really push it. And try as they might to hunker down before a storm, this doesn’t always work out for them. Instead, they may get swept out of coastal waters by floods. Others, curious to explore new streams, have been found stuck in smaller ponds, forests, or even by roads after post-storm swims through flooded areas. Yet hurricanes rank low on the dangers to manatees, a threatened keystone species in Florida often imperiled by watercraft.

Even if Hurricane Idalia is the first big tempest that a Floridian animal will experience, the odds are good it will take some kind of action. “We see animals evacuating the places they call home in advance of a major storm despite, in some cases, having never experienced a hurricane within their lifetime,” Strickland says. “This shows just how innate it is to protect yourself from a storm by preparing or fleeing compared to just waiting it out.”

This post has been updated. It was originally published on September 28, 2022.

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Oh, the wonders scientists see in the field. Documenting the encounters can be an integral part of the discovery process, but it can also pull others into the experience. These seven photos and illustrations are the winners of this year’s BMC Ecology and Evolution image competition, which gets submissions from researchers all around the world each year. It includes four categories: “Research in Action,” “Protecting our planet,” “Plants and Fungi,” and “Paleoecology.”

See the full gallery of winners and their stories on the BMC Ecology and Evolution website. And explore last year’s winners here.

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Since the 1960s, the oxygen level in the world’s oceans has dropped by about 2 percent. While that may not sound like a lot, the continuous decline in oxygen content of oceanic and coastal waters, called deoxygenation, can alter marine ecosystems and biodiversity. This is largely happening due to global warming and nutrient runoff.

Greenhouse gas (GHG) emissions from anthropogenic activities like deforestation and fossil fuel use trap the sun’s heat, warming the planet and heating up the ocean. Oxygen becomes less soluble at higher temperatures, which means warm water holds less oxygen than cold water. Eutrophication due to excess inputs of nutrients like nitrogen and phosphorus from agriculture or wastewater also stimulates algal blooms, resulting in oxygen depletion when they decompose.

[Related: Scientists say the ocean is changing color—and it’s probably our fault.]

Deoxygenation affects living resources and disrupts natural biogeochemical processes, says Nancy Rabalais, professor and chair in oceanography and wetland studies at Louisiana State University who researches coastal eutrophication and hypoxic environments. Oxygen concentrations play a role in the rates of breakdown of organic matter and the cycling of different elements in the environment. For instance, deoxygenation may enhance phosphorus recycling, reduce nitrogen losses, and initially enhance the availability of iron, all of which can alter the productivity of coastal and ocean ecosystems.

Loss of oxygen content also has significant impacts on marine microbes and animals. Deoxygenation can alter their abundance and diversity, reduce the quality and quantity of suitable habitats for them, and interfere with reproduction. The oxygen decline doesn’t have to be major to potentially cause ecosystem-wide changes. In oxygen minimum zones that may already be close to physiological thresholds, even small oxygen declines can have drastic impacts.

When oceans lose oxygen, marine organisms become stressed and need to adapt—if they can—to survive. Species that are especially sensitive to oxygenation changes, like tuna and sharks, are being driven to shallower habitats as oxygen-deficient zones expand, says Anya Hess, PhD candidate at Rutgers University who studies ocean oxygenation. Deoxygenation also threatens the ocean’s food provisioning ecosystem services for humans, potentially leading to reduced catches for fisheries and the collapse of regional stocks. 

Although new research suggests deoxygenation may eventually reverse, it might not happen until the far future. In a recent study published in Nature, Hess and her co-authors looked to the Miocene warm period about 16 to 14 million years ago when temperatures and atmospheric carbon dioxide concentrations were higher than today to study a “possible example of how oceans behave during sustained warm periods,” she says.

Their results show that the eastern tropical Pacific—a major oxygen-deficient or “dead” zone that has been losing oxygen as the climate warms—was well oxygenated at that time, which suggests that deoxygenation could reverse on long timeframes as the climate continues to warm.

[Related: A deep sea mining zone in the remote Pacific is also a goldmine of unique species.]

Climate models from a 2018 study published in Global Biogeochemical Cycles predict oxygen concentration may start increasing and oxygen-starved regions in the ocean can begin shrinking by 2150 through 2300 due to decreasing tropical export production—the nutrient supply from the ocean interior—combined with increased ocean ventilation or the transport of surface waters into the interior. But marine ecosystems are already facing various impacts today—and rebounding is hard because deoxygenation can reconfigure food webs and organisms that can’t avoid low oxygen levels can become lethargic or die.

“I don’t think we should wait around to see whether deoxygenation will reverse as the climate continues to warm,” says Hess. “We know that rising temperatures are causing ocean deoxygenation, so if we want to stop it we know what we need to do—reduce greenhouse gas emissions.”

Policymakers can also establish long-term monitoring programs around the world to study oxygen measurements, which will help identify patterns and predict biological responses. All in all, deoxygenation trends may eventually reverse in the future, but taking the steps to mitigate climate change and control nutrient runoff will benefit humans and marine ecosystems today.

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Most fish are cold-blooded, which means that they rely on the temperature outside of their body to regulate their internal temperatures However, some sharks are surprisingly warm-blooded, storing the heat that is generated by their muscles the way many mammals do. A study published June 26 in the journal Proceedings of the National Academy of Sciences finds that their evolutionary ancestors—the mighty megalodon—also share this endothermic nature. The amount of energy that the meg used to stay warm may have contributed to its extinction roughly 3.6 million years ago, and could help scientists study the impacts of future environmental changes.

[Related: 3D models show the megalodon was faster, fiercer than we ever thought.]

“Studying the driving factors behind the extinction of a highly successful predatory shark like megalodon can provide insight into the vulnerability of large marine predators in modern ocean ecosystems experiencing the effects of ongoing climate change,” co-author and UCLA biologist Robert Eagle said in a statement.

The megalodon stalked the world’s oceans from about 20 million years ago, and likely measured up to 50 feet in length. That’s roughly three times larger than the modern great white shark. The marine giants could have eaten a meal the size of an orca whale in about five bites, and boasted impressive chompers that could grow to the size of a human hand. 

They also belonged to a group of sharks called mackerel sharks, which includes present day thresher sharks and the infamous great white. Mackerel sharks keep the temperature of all or parts of their bodies a bit warmer than the water surrounding them, unlike most fish that are cold-blooded and keep their bodies the same temperature as the water.  

In the new study, a team analyzed the isotopes in the tooth enamel from fossilized megalodon teeth and concluded the ancient shark could maintain a body temperature that was roughly 13 degrees Fahrenheit warmer than the water it lived in. That temperature difference is large enough to categorize the megalodon as endothermic, or warm-blooded, according to the team.

They used a novel geochemical technique that uses a clumped isotope thermometry and phosphate oxygen isotope thermometry to test their “Megalodon Endothermy Hypothesis.”

“Studies using these methods have shown them to be particularly useful in inferring the thermo-physiologies of fossil vertebrates of ‘unknown’ metabolic origins by comparing their body temperature with that of co-occurring fossils of ‘known’ metabolisms,” co-author and William Patterson University geochemist Michael Griffiths said in a statement.

[Related: This whale fossil could reveal evidence of a 15-million-year-old megalodon attack.]

While the megalodon has a rich fossil record, its biology is less understood since no complete skeleton of the extinct beast is known in the fossil record. Using geochemistry techniques on the numerous teeth left behind can help paleontologists peer into the past. 

A mineral called apatite is a primary component of teeth. It contains atoms of both carbon and oxygen that come in “light” or “heavy” forms known as isotopes. The amount of light or heavy isotopes that make up apatite as it forms can vary based on multiple environmental factors. The isotopes that make up fossil teeth can then reveal insights into where the animals lived, what it ate, and for marine vertebrates like the megalodon, some hints on the chemistry of the seawater that it lived in and its body temperature. 

“You can think of the isotopes preserved in the minerals that make up teeth as a kind of thermometer, but one whose reading can be preserved for millions of years,” co-author and UCLA doctoral student Randy Flores said in a statement. “Because teeth form in the tissue of an animal when it’s alive, we can measure the isotopic composition of fossil teeth in order to estimate the temperature at which they formed and that tells us the approximate body temperature of the animal in life.”

The megalodon’s warmer body allowed it to move faster and not only tolerate colder water, but spread all over the world’ oceans. However, this evolutionary advantage may have contributed to its downfall. The megalodon lived during the Pliocene Epoch (5.33 million years to 2.58 million years ago), which was known for some massive environmental changes as the world cooled and sea levels changed. 

Sustaining and maintaining an energy level that allowed for the megalodon’s higher body temperature would have required quite a bit of food. As the ecosystem changes, food may have become more scarce, especially when factoring in competition with newcomers in the marine environment–like our friend the great white. 

The team hopes to apply a similar approach to studying other extinct species. “Having established endothermy in megalodon,” co-author and UCLA geologist Aradhna Tripati said in a statement, “the question arises of how frequently it is found in apex marine predators throughout geologic history.”

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This article was originally featured on Hakai Magazine, an online publication about science and society in coastal ecosystems. Read more stories like this at hakaimagazine.com.

Out in the Atlantic Ocean, roughly 100 kilometers off the northwest coast of Africa, lies an archipelago known as the Canary Islands, created millions of years ago by intense volcanic activity. The biggest and most populated island, Tenerife, rises from the deep-ocean floor to a series of peaks, one of which is the third-largest volcano in the world. Tenerife’s interior highlands are a moonscape, while its coastline of lava rock and sheer cliffs is pounded by surf. In contrast to most of the island’s stark geology, north of the island’s capital, Santa Cruz, is a long crescent-shaped beach of soft yellow sand, with groves of palm trees and a calm bay created by a long breakwater. This is Playa de las Teresitas, a magnet for northern European tourists craving winter sun.

But most of the people sunbathing on Teresitas are likely unaware of what lurks in the shallow waters lapping the shoreline. The bay—engineered and less than 10 kilometers from the Canaries’ second-largest city—is a surprising haven for pups of one of the world’s most critically endangered fish: the angelshark.

When the Spanish took control of the Canaries in the 1400s, they began cultivating cash crops: cochineal and sugar cane in the beginning, and later adding bananas, tomatoes, and other valuable commodities. For centuries, the islands’ economy thrived, but it was a fragile wealth. Over the years, livelihoods were threatened by cycles of crop disease, competition from cheaper markets, and lava flows that wiped out harvests and turned good agricultural land into barren terrain. In the 1950s, the boom in package tourism showed promise as a new cash crop. But while the islands had the sunshine, warm climate, and ease of access from Europe needed for this new industry, they were missing a vital element: picture-postcard sandy beaches.

Cue planners on Tenerife, who concocted an audacious plan to make over one of the island’s exposed lava-rock beaches. They chose a stretch of coastline close to Santa Cruz and expropriated the avocado farms and other smallholdings. Earthmovers leveled the foreshore and intertidal zone, and they constructed a breakwater over a kilometer long. And then, from the Western Sahara on Africa’s northwest coast, they shipped in the pièce de résistance: 240,000 tonnes of sand.

By 1973, this gargantuan project, environmentally questionable from today’s viewpoint, was complete. As anticipated, tourists arrived. Unanticipated was what their presence gave to one of the world’s most endangered fish species—visibility. Maybe angelsharks always gathered here, but until recently, no one really knew.

Along Playa de las Teresitas, rows and rows of tourists lounge on beach chairs under umbrellas or pad across soft sand to cool down in the water. The breeze creates tiny sapphire-tipped waves on the water’s surface, a magical cover for what lies beneath—an angelshark nursery.

Female angelsharks regularly migrate to these ideally sheltered waters to give birth to anywhere between eight and 25 live pups, who remain in the shallows for about a year. Feeding on cuttlefish and other small prey, they grow to around 50 centimeters, about the same length as a newborn baby. Then they disappear for years until they are mature. Where they go is a mystery.For centuries, angelsharks had been common along the Atlantic coast of North Africa and Europe, as well as the Mediterranean. The ancient Greeks fished them; Pliny the Elder described the use of their skin to polish wood and ivory. On the British Isles, they were called monkfish for their resemblance to a monk’s hooded robes. With the advent of industrial bottom trawling in the late 1800s, they were easily caught and became a common food fish. By the 1960s, aggressive fishing of angelsharks, coupled with their extremely low reproductive rate, led to a dramatic decline in their populations. Targeting them eventually became commercially unviable and the name monkfish was relegated to another species, the anglerfish.

But angelsharks were still by-catch in other fisheries, and by the early 1970s, as developers barged Saharan sand to Tenerife, the fish were pushed close to extinction in most parts of the North Atlantic and the Mediterranean.

In the European Union and the United Kingdom, it has become illegal to fish or retain angelsharks. If one is accidentally caught, fishers must return it alive to the sea. But the main threat to angelsharks remains the powerful bottom-trawling industry, which accounts for over 30 percent of fish landed in the European Union.

The story in the Canary Islands is slightly different. Michael Sealey, a marine biologist with the Angel Shark Project (ASP) in Tenerife, says that bottom trawling has never been as viable in the Canaries as in most of Europe and the Mediterranean. The seabed is mostly too deep, he explains, the underwater topography laced with jagged seamounts and reefs where fishing gear can get hung up. On top of that, the European Commission has halted all trawling in the Canaries since 2005.

But biologists only became aware about a decade ago that the Canaries host an angelshark population. Subsequently, in 2014, the Universidad de Las Palmas de Gran Canaria, Museum Koenig Bonn, and Zoological Society of London collaborated to establish ASP. The project’s goal: to gather data on critical habitats, movement patterns, and reproductive biology of angelsharks, and work with local communities and officials to protect the fish. Life history information is crucial for developing effective conservation strategies and protecting valuable, if improbable, habitat—like Playa de las Teresitas.

But angelsharks are not the easiest of research subjects. They are masters of disguise, so spotting them is a challenge. They have a peculiar flattened shape and spend most of their time lying on the ocean bottom partially covered by sand. Their coloring—reddish- or greenish-brown scattered with small white spots—helps them blend into the seabed.

Gathering data on such elusive animals, with low population densities spread over a huge area, is labor intensive. Help has come in the form of citizen science: everywhere in the Canary Islands, recreational divers and fishers are invited to make online reports of any sightings or accidental catches of angelsharks. Through an ASP initiative, dive operators conduct friendly competitions to see which company can record the most sightings, thereby increasing data collection, particularly from citizen scientists.

Rubén Martinez, a dive instructor in Lanzarote, the easternmost island of the Canaries, is a keen advocate of angelsharks and regularly volunteers for ASP surveys. He helps with procedures such as tagging the fish with either spaghetti tags—an easily attached plastic loop—or acoustic tags. Both are done on the spot without having to catch the fish or lift it out of the water. “We work in a team and practice beforehand,” Martinez says. After an angelshark has been spotted in the sand, the team places a mesh attached to a sturdy frame over the animal. They take a small sample of fin for DNA analysis and attach a tag to the base of the dorsal fin. The whole procedure, when done properly, takes less than a minute.

Surveys have shown that other beaches in the Canary Islands are also potential nursery sites. Interestingly, most of them have been altered, like Teresitas, to make them more attractive to people. On Lanzarote, Playa Chica boasts another long sweep of imported sand. It’s a magnet for divers—as well as a spectacular and easily accessible site—so the number of sightings of mature angelsharks off this shoreline is one of highest in the whole archipelago. How do the sharks react to these shoals of wetsuited humans? Alba Esteban Pacheco, a biologist and former dive instructor with Euro Divers Lanzarote, admits that while there have been instances of divers getting too close to the sharks, most dive companies are sensitive in this regard and brief their clients well. They have little choice: in 2019, Spain introduced legislation in the Canaries that made disturbing the sharks or harming their habitat and breeding grounds a criminal act subject to large fines.

Pacheco is very clear that she keeps her dive clients at least the recommended one meter distance from any angelsharks they find hiding in the sand. “Also,” she says, “these days, with everyone videoing everything and posting it on social media, it’s hard for divers to step out of line.”

But is this enough? Eva Meyers, a cofounder of ASP, acknowledges that the diving community plays a crucial role in conservation of the species. But she adds that much more needs to be done to ensure the long-term survival of angelsharks in areas like Playa Chica.

A recovery plan ASP developed with local authorities is in the final stages. It will include measures such as signage along sensitive coastlines and establishing a code of conduct for divers throughout the Canaries.

Among international dive communities, the word is out about the chance to see mature angelsharks in the Canaries, and this is a growing part of the tourism sector. Indeed, shark diving all over the world is a boon to economies. It generates over US $24-million yearly in the Canaries. Globally, shark-diving tourism generates over $300-million yearly, and local communities benefit much more from shark diving than from shark fishing. In some cases, this has led to the creation of marine reserves, such as in Fiji, which help other marine species as well.

Many divers may now be cognizant of the fragility of the angelshark population, but what about all those people splashing about and swimming in the all-important nursery areas just off the beaches? Sealey thinks that human activity in the shallow nursery areas influences angelshark behavior. On busy beaches like Teresitas, juveniles normally retreat to deeper water during the day when lots of people are around. During the COVID-19 pandemic, restrictions kept people off the beach. After almost two years of peace, angelsharks seemed unprepared for the people wading back into the water, as swimmers reported an unusual number of bites soon after restrictions lifted. The fish rely on their camouflage for protection, but when stepped on, they might lunge up from their hiding place and bite, though they usually swim away. Known locally as “gummings,” the bites are not serious and rarely draw blood. But the increase in gummings was an indication that the juveniles had adapted to remaining hidden in the shallows 24/7 to conserve energy. Post-pandemic, angelsharks have adapted again, by heading into deeper water earlier in the day and avoiding interactions with humans, as do many other urban wildlife species.

Back in the 1970s, did angelsharks also adapt to the Canaries’ headlong efforts to redesign itself for tourists? It’s intriguing to think that the massive, environmentally disruptive projects to remake beaches could have accidentally enhanced the habitat for one of the world’s rare fish species. But what’s clear is that after the breakwater was built and the sand arrived, people followed, and in the calm, shallow waters they began to see baby angelsharks. And unlike how many an association between humans and wildlife ends—in conflict and dead animals—this time it led to conservation.

This article first appeared in Hakai Magazine and is republished here with permission.

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This article was originally featured in Knowable Magazine.

Every four months, pathologist Aaron LeBeau scoops into a net one of the five nurse sharks he keeps in his University of Wisconsin lab. Then he carefully administers a shot to the animal, much like a pediatrician giving a kid a vaccine. The shot will immunize the shark against a human cancer, perhaps, or an infectious disease, such as Covid-19. A couple of weeks later, after the animal’s immune system has had time to react, LeBeau collects a small vial of shark blood.

Halfway across the country, immunologist Hidde Ploegh goes through the same steps, but with alpacas that live on a farm in western Massachusetts. The scientists are after the same thing: tiny antibodies, made only by certain animals, that may have big implications for human health.

Most antibodies — those molecules that course through our blood and tissues patrolling for pathogens — are fairly hefty as proteins go. But the antibodies made by camels and sharks and their close relatives are simpler and smaller. Since their discovery in the late 1980s, researchers have learned that these antibodies pack a big punch: They can latch onto hidden parts of molecules and can penetrate tissues more deeply, enhancing their potential as therapies. 

“They can get into little nooks and crannies of different proteins that human antibodies cannot access,” LeBeau says.

In the last decades, investigations of these diminutive antibodies have surged. Not only can they sneak into small places, they are also easy to work with — sturdier than their ordinary counterparts — and relatively cheap to make in large quantities. All these features make the antibodies promising treatments for a host of diseases, whether clotting disorders or Covid-19. Researchers are also exploring their use for diagnosing conditions such as cancer, and they’re becoming a key tool in other kinds of research, like mapping cells’ insides.

The full promise of these antibodies may still take years to realize, but researchers are very excited about their possibilities. “I think they have potential to save the world,” LeBeau says.

Luck of the blood draw

A group of biology students were the first to discover these unusual antibodies — quite by chance — back in 1989. The students of Free University in Brussels needed some blood for an exam in which they were tasked with separating an antibody into its two main parts: two heavy protein chains, which form a Y shape, and two light protein chains, which flank the prongs at the top of the Y.

Human blood seemed too risky to work with, given concerns at the time about potential HIV exposure, and the students didn’t want to kill a mouse. But the students’ professor, the late Raymond Hamers, happened to be studying sleeping sickness in large animals. He gave the students some blood from a camel, says immunologist Serge Muyldermans, who was then a post-doctoral researcher at the university.

Strangely, the students found only heavy chain proteins in the blood even though antibodies were supposed to also have light chains. As Muyldermans tells it, everyone thought that the camel antibodies had degraded — or that the students had done something wrong — so Hamers went to the Antwerp Zoo to collect fresh camel blood. But the students had not screwed up: Camels make antibodies with only heavy protein chains.

The potential applications of camelids’ small antibodies dawned on Hamers during those early years, says Muyldermans, who details their myriad uses in the 2021  Annual Review of Animal Biosciences. Like antibodies from people or mice, the camelid antibodies could be further pared down into even smaller, yet still effective, fragments — just the tips of the Y. These fragments, called variable domains, are the business end of any antibody — they act as the antibody’s “sensor” and can stick to parts of pathogens or toxins, whatever substance is recognized as foreign and a possible threat.

In standard antibodies (which camels also make), the variable domains come in pairs, one from the heavy chain and one from the light chain. But the variable domains of the camelid’s heavy-chain-only antibodies are singletons. The researchers realized these solitary fragments might be able to grab onto parts of foreign molecules that conventional antibodies were too bulky to reach.

In 1993, the team published the discovery in Nature. The next year, Hamers  patented the production of these camelid antibody fragments (they are also known as VHH antibodies or “nanobodies,” a trademarked term). A few years later, a different group of researchers reported that  sharks also make antibodies with only heavy chains and these have an even smaller tip (these shark end fragments are called variable new antigen receptors, or VNARs).

When the primary patent expired in 2013, research investigating the antibodies really surged, says Ploegh, an immunologist at Boston Children’s Hospital. “That’s sort of when the dam broke and a lot of folks got in on the game.”

Scientists have since learned a lot about the advantages of these mini antibodies. Some is practical: Unlike full-size antibodies, the fragments are stable at room temperature so there’s no need to keep them in a freezer or ship them cold. The mini antibodies of sharks can even be boiled with no effect on their function, LeBeau says. And while full-size antibodies require mammalian cells to be grown in a flask, which can be complicated and expensive to maintain, the fragments can be manufactured in large quantities using bacteria, saving time and money.

These mini antibodies also tend to self-assemble properly, keeping their correct shapes, making them a promising alternative to full-size antibodies, which have more pieces and thus can misfold. Such misfolding may expose parts that are more likely to be recognized by the immune system as foreign molecules, which can provoke a negative immune response in the body, with potentially serious consequences for patient health.

But the standout trait of the mini antibodies is their versatility. All antibodies, whether from human or shark, have variable domains at their tips, but those of sharks and camels have unique traits. They have an especially long, slender finger called a CDR3 loop that can poke into places that human antibodies can’t access. They appear to easily adopt different shapes — LeBeau describes that feature as “molecular yoga.” This means mini antibodies can get into tight spots, whether into tissues of the body or on minuscule parts of individual molecules.

Anti-cancer antibodies

Research into these unusual mini antibodies is now starting to bear fruit. In 2019, the first mini antibody medical treatment to be approved by the US Food and Drug Administration, called Cablivi, came on the market. It treats a rare blood disorder that leads to clots in small blood vessels. The treatment uses nanobodies to bind to a protein in platelets, which stops them from sticking together.

Mini antibodies could become a valuable tool for cancer treatment. Full-size antibodies are already used in immunotherapies to treat certain cancers; in some cases, the antibody tags cancer cells so that the body’s own immune system cells can then recognize and kill the rogue cells; in others, it might bring immune cells closer to the cancer cells so the body can better fight the cancer. The mini antibodies can do the same tasks, but can also be used in other ways, such as targeting proteins to reduce tumor growth or blocking blood vessels from feeding a tumor. And the smaller antibodies also may be less likely to trigger a negative immune response than full-size immunotherapy antibodies, which may lead to dramatic treatment improvements, Ploegh says.

LeBeau, for his part, is focused on developing mini antibodies targeted for prostate and lung cancer. The sharks in his lab, each named for James Bond bad guys — Goldfinger, Hugo Drax, Mr. Stamper, Oddjob and Nick Nack — keep him supplied with antibodies that he uses in lab experiments. His lab recently identified a shark antibody fragment that is specific for a highly aggressive, and currently untreatable, form of lung cancer. He’s hopeful that this new mini antibody could help combat the cancer, and has studies in progress to test it.

The mini antibodies are also helping physicians detect cancers more readily, pinpointing diseased cells with more precision. By attaching radioactive tracer molecules to specific antibodies that seek out cancer cells, physicians can locate cancerous cells on a PET scan, potentially with greater resolution than with standard antibodies because they can penetrate deeper into tissues. One such nanobody-based tracer detected several tumors in mice with  higher specificity than conventional imaging, a team reported in  PNAS in 2019.

Vanquishing viruses

Scientists are also harnessing mini antibodies to fight infectious diseases, including Covid-19. Wai-Hong Tham, an infectious disease researcher at the University of Melbourne and the Walter and Eliza Hall Institute of Medical Research, has been working to generate nanobodies that grab onto part of the spike protein of SARS-CoV-2, to prevent the virus from entering cells in the body.

In a preliminary study, published in PNAS in 2021, Tham and her colleagues identified several nanobodies from alpacas that interfered with the spike proteins’ ability to latch onto the molecular doorknob it uses to get into cells; cocktails of the nanobodies also reduced the amount of virus in experiments with mice. Ideally, Tham says, they could find a nanobody that universally blocks Covid-19 regardless of the coronavirus variant. Other nanobody cocktails also appear promising: Four nanobodies, mixed and matched in various combinations, disabled the spike protein in experiments in cells, a separate team reported in 2021 in  Science.

Mini antibodies might be delivered via mRNA technology so the antibodies assemble inside people’s cells, Tham says. Vaccine-like injections might work against other  infectious diseases, counter toxins such as  botulism, or even deliver therapeutics for cancer or other conditions.

And with a simple pill, mini antibodies could be delivered directly to the gut, which could help to block a number of pathogens, for example rotavirus, that enter the body through the digestive tract. Small microbes — such as yeast, bacteria and algae — can’t efficiently make full-size antibodies because these are too complex. However, researchers have proposed genetically engineering  spirulina (a blue-green alga that’s often sold as a nutritional supplement) or harmless bacteria called  Lactobacilli  or  Lactococcus that could deliver therapeutic nanobodies via a pill, which would be much more cost effective than producing a drug, Tham says.

Sleuthing cell mysteries

The diminutive antibodies are also a boon for scientists who study proteins and investigate interactions between molecules. The size and long finger of these antibodies can help solve protein structures, map proteins  inside cells and show how molecules within cells  interact with each other.

Researchers recently solved the structure of a human protein called ASIC1a, for example — it forms a type of channel that lets sodium into nerve cells and plays an important role in pain perception and several neurodegenerative diseases. Stabilizing the protein with a nanobody allowed the researchers to determine its structure with greater resolution, the team reported in 2021 in  eLife.

Single-domain antibodies “have the potential of mapping interactions that would be very difficult to study otherwise,” says Ploegh, coauthor of an overview of their traits in the 2018  Annual Review of Immunology. Scientists are even investigating their potential use in the brain — a tricky task because the blood-brain barrier likes to keep foreign molecules out. An international team recently reported using nanobodies as  sensors to study whether or not a protein in a mouse brain was activated, and where it was located.

Ploegh says that mini antibodies are exceptionally useful and have significant advantages over full-size antibodies, but they remain somewhat niche because of limited access to the animals that make them — not every researcher has nearby camels, llamas or, in LeBeau’s case, sharks. (“Probably very few people are crazy enough to actually build a shark tank and work with sharks. But we are,” LeBeau says.)

But this is starting to change as interest ramps up. Researchers are also developing new approaches, such as creating synthetic nanobodies and developing mice with “camelized” immune systems for research.

Scientists still don’t know why camelids and cartilaginous fishes, like sharks, are the only animals known to make heavy chain antibodies. Sharks are the most ancient living organisms to rely on antibodies as part of their immune systems, and their antibodies are more stable than those of camelids. Scientists speculate that sharks rely on these antibodies because of the high concentrations of urea in their blood, which would degrade the antibodies of most mammals.

Sharks evolved some 350 million years before camels, yet camelid heavy chain antibodies are also relatively ancient: They are found in both Old World camelids, like camels, and New World camelids, like llamas and alpacas, suggesting that the antibodies may have developed early in the lineage’s evolution. Perhaps “there are certain pathogens that are unique to the camelids that are best fought with these heavy chain antibodies,” Ploegh says.

The heavy chain antibodies of sharks might well be the most ancient immune molecules still in existence — but LeBeau is exuberant about what they could accomplish in the future. “Whenever you work with them, you see something new every day. And that’s really exciting,” he says.

And as for his two-foot-long sharks, when they outgrow their tank, they’ll retire to the local aquarium.

This article originally appeared in Knowable Magazine, an independent journalistic endeavor from Annual Reviews. Sign up for the newsletter.

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Let’s talk about sex. Partnerless sex that is. While this form of sex isn’t typically associated with reproduction, generating offspring without a partner is common in small, spineless animals like sea stars and stick insects, but it is more rare in vertebrates. Through a process called parthenogenesis, some female animals in the order elasmobranch that includes sharks, rays, and skates can fertilize an egg using their own genetic material. 

This process is usually reserved as a last resort for sharks if there aren’t any mates to go around, but a recent study revealed that female zebra sharks at Shedd Aquarium in Chicago, Illinois, reproduced by themselves, even though there were healthy males in the same enclosure.

[Related: Shark Week may be hurting, not helping, its namesake creature]

“This changes what we think we know about parthenogenesis and why it occurs,” says Lise Watson, assistant director of animal operations and habitats at Shedd Aquarium and a co-author of the study, in reference to the biological phenomenon behind these partner-less births. “From observing our population for 20 years, we have a long history with them. One thing that we’ve noticed is sometimes the females are not very receptive to males at certain times, or at all.”

While previous studies have detailed parthenogenesis in zebra sharks at other aquariums, the report published in December 2022 in the Journal of Fish Biology is another step in understanding why these births happen. This research focuses on a female zebra shark—a dark fish with yellowish stripes found in the Pacific and Indian Oceans—that lived in Shedd’s Wild Reef exhibition.

In 2008, Watson and her colleagues moved a clutch of eggs to a baby shark nursery behind the scenes, where they could safely hatch beyond the limelight of an aquarium tank.

An analysis of the newly hatched shark pups’ DNA revealed seemingly impossible results. The pups didn’t have any genetic markers with any of the potential fathers. They had identical copies of some alleles, or alternative versions of a gene. This showed that they were getting DNA strands from their mother rather than two different parents. 

“These pups didn’t match any of the mature males that were in the enclosure. But they did match the female that laid the eggs,” says Kevin Feldheim, a biologist and researcher at the neighboring Field Museum and co-author of the study, in a statement. 

Offspring born from parthenogenesis often die young, and the shark pups in this study only survived for a few months.

“We don’t exactly know why they have shorter lifespans,” Feldheim tells Popular Science. “In genetics, in general, inbreeding is bad and what can happen is the expression of a lethal recessive [gene], or the expression of two alleles that essentially cause you to die.” 

But it’s still unclear exactly what causes animals born in this manner to die before sexual maturity, while others will survive. “In one species called the white spotted bamboo shark, an aquarium found that one of their females gave birth by parthenogenesis, and then one of those offspring actually went on to reproduce parthenogenetically herself,” says Feldheim.

The findings in zebra sharks have implications for not only the continued care of zebra sharks in zoos and aquariums, but also for conservation efforts focused on their wild counterparts.

“Sharks studied in the field always face some barriers,” says Sara Asadi Gharabaghi, a PhD candidate at Shahid Beheshti University in Tehran and member of Minorities in Shark Sciences, who was not involved in the study. One of those barriers is not being able to access the DNA of all of all adults and offspring to find biological parents.

“Sharks are the same as all animals trying to survive, so it would not be surprising to have pups from virgin birth either in the wild, even if we can’t prove it,” Asadi explains. It’s possible that sharks living in deep sea zones might use the same tactic, she adds

[Related: Baby sharks are eating the birds that live in your backyard]

For scientists studying endangered sharks in the wild and in aquariums, understanding reproduction will help conservation strategies. 

Zebra sharks are listed as threatened on the IUCN Red List, and aquariums like Shedd are working to preserve the species. Their genetic tests are part of a Species Survival Plan, or SSP, which brings together expert advisors to maximize genetic diversity and protect endangered species long-term. 

One aspect of an SSP is to determine “the genetics of the population and the sustainability of that population,” Watson says. Through genetic analysis she and her colleagues can make assumptions about how related an individual shark is to the whole group. From there, they can measure what the population size might look like for the next 100 years. 

“Studying these animals in our care is the foundation of us being able to help this species in the wild,” says Watson. “The care that we do for these animals here is of utmost importance for us.”

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This article was originally featured on Hakai Magazine, an online publication about science and society in coastal ecosystems. Read more stories like this at hakaimagazine.com.

It’s 8:00 a.m. on a sunny 29 °C Saturday at Alexandra Headland on the Sunshine Coast of southeast Queensland, Australia. Swimmers porpoise through the shimmering water, while farther offshore surfers straddle their boards in anticipation of the next big wave. If anyone is worried about a shark bite, you wouldn’t know it.

“Not really, probably should,” says 18-year-old surfer Jake Hazelwood of Cairns, a city farther to the north. “When you’re out there, you just zone everything else out.”

Hazelwood is also oblivious to the drone taking off from the beach just 20 meters away, the state government’s latest tool to help keep popular coastal areas safe for humans—and safe for sharks.

For decades, Queensland has relied on nets and baited-hook drumlines to help protect beachgoers from sharks. But that safety comes at a cost to marine life. Last year alone, that equipment caught 958 animals, including 798 sharks—70 percent of which died. Sixteen turtles also perished as unintended victims along with 10 dolphins and two dugongs, a vulnerable species in Queensland. And in 2022, 15 humpback whales were caught in shark nets, though all of them were safely removed.

The government is considering replacing its lethal measures with using camera-equipped drones to search for sharks, and Alexandra Headland is one of the locations for a trial program that is already showing success.

It’s surprisingly easy to spot sharks when you fly over them, says Rob Adsett, the chief remote pilot with the Australian Lifeguard Service. “Technology is getting better.”

The infrared-equipped drone that Adsett and his colleagues used off Alexandra Headland can fly for 20 minutes in winds above 35 kilometers per hour. The pilots fly the drone along a 400-meter route parallel to shore behind the surf break. On busy beach days, the drone zips along at up to 20 kilometers per hour, staying out of the way at an altitude of 60 meters. When pilots detect a shark, they lower the drone to 30 meters so they can identify the animal’s size and species, a task that can become more difficult when it is raining or if the water is murky or rough.

If the pilots deem the shark a danger, they can evacuate the beach while lifeguards follow in inflatable boats or personal watercraft to track the animal and monitor the threat.

During their trials in 2020 and 2021, which involved 3,669 drone flights at seven beaches, drone pilots detected 174 sharks, including 48 that were greater than two meters in length. For beach users and lifeguards, the presence of big sharks, especially white, tiger, and bull sharks, is the greatest concern, and these sightings led to four beach evacuations.

Queensland’s effort is following on the heels of a similar project that has been underway in New South Wales, the state just to the south, since 2017.

For conservationists, the switch away from nets and drumlines can’t come soon enough. Any further delay in removing the lethal deterrents “is baffling,” says Leo Guida, a shark scientist with Australian Marine Conservation Society. “They’ve got the solution on the table.”

Drones, says Guida, can also save people by dropping life-saving equipment to someone struggling in the water. “You’re more likely to save someone from drowning than interacting with a dangerous animal,” he says. “There are clear benefits across the board” to having drones at the beach.

The toll of the nets and drumlines on sharks also has to be balanced against the threat sharks actually pose to beachgoers. According to Adsett, “You’ve got more of a chance of getting hit by a car on the way to the beach than getting attacked by a shark.”

Still, shark bites do happen. Though infrequent, bite rates are increasing.

The Australia Shark Incident Database recorded 1,196 shark bites in the country over the past 231 years, from 1791 to 2022. Those bites caused 250 deaths, while 723 people suffered injuries. No one was injured in the other 223 cases, which cover incidents such as bites to surfboards.

Shark bites jumped from an average of nine per year in 1990–2000 to 22 per year in 2010–2020, in part because of the increasing human population along the coast.

But even nets and drumlines, Guida argues, are no guarantee against bites because sharks can simply swim around them. That’s what happened in 2020 when a male surfer in Queensland died after being bitten at Greenmount Beach, a stretch of coastline equipped with nets and drumlines. As for whether the nets can be replaced with drones, the Queensland government has at least seen enough to continue their trials. They’ve committed to expanding the project, which will continue through June 2025 at a cost of roughly US $1.3-million per year.

This article first appeared in Hakai Magazine, and is republished here with permission.

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Millions of sharks, rays, and skates are accidentally killed every year as bycatch within the global fishing industry—an especially staggering number when considering that a quarter of all those species are currently considered endangered. Previously, fishers could do very little to discourage the predators from going after the longline bait meant for intended targets like tuna, but a simple and ingenious new technology is showing huge promise in finally changing course. Highlighted via a study published earlier today in Current Biology, a small device dubbed SharkGuard recently decreased the number of unintended shark catches by as much as 90 percent through exploiting one of the animals’ most impressive senses.

The premise behind SharkGuard is relatively simple, but extremely effective: the device is essentially a small, localized electric pulse emitter attached alongside longline lure bait. As fishers draw their many lines through the ocean waters, the invention shoots out an electric field that discourages sharks, rays, and similar predators who hunt primarily through electroreceptors located in their snouts, known as ampullae of Lorenzini. While unpleasant to the sharks, the charges don’t seem to bother tuna much at all.

[Related: Tiger sharks helped scientists map a vast underwater meadow in the Bahamas.]

According to the new study, two fishing boats went on a total of 11 trips off the coast of southern France last year, during which they used 22 longlines deployed with over 18,000 hooks. The resulting hauls showed 91 percent fewer sharks and 71 percent fewer rays, while tuna harvests were barely affected by the SharkGuard additions. Although each SharkGuard currently requires frequent battery recharges and a set of 2,000 costs around $20,000, researchers are currently working to improve the charge times. But when it comes to large-scale commercial tuna harvesting budgets, $20K is, well, relatively small fish.

In the near future, scaling up SharkGuard availability could have an extremely dramatic and near immediate effect on reversing an unnecessary, destructive byproduct of commercial fishing. Until then, keep an eye on those great white shark counts off US coasts—more of them is a good thing, actually.

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Given their fierce and carnivorous-sounding name, it might be surprising to find out that tiger sharks (Galeocerdo cuvier) spend a lot of their time swimming with lush marine greenery.

A study published today in the journal Nature Communications, details how tiger sharks helped a team of researchers map out a giant meadow of seagrass. The data from underwater shark-piloted cameras helped the team discover one of the largest seagrass meadows on Earth, located in the warm waters of The Bahamas.

Researchers from institutions including Carlton University in Canada, King Abdullah University of Science and Technology in Saudi Arabia, Trinity College in Ireland, and Beneath the Waves, a Virgina-based conservation nonprofit, used satellite tags to track individual tiger sharks as they traversed the Bahamas with bio-logging cameras. According to the authors, the study shows the first-ever use of 360-degree cameras on a marine animal.

“In confirming the various benthic habitat types in The Bahamas, and their corresponding use by sharks, we found that tiger sharks spent around 70 percent of their time swimming over seagrass meadows,” says Wells Howe, a program manager on Beneath the Waves‘ Blue Carbon project, in an interview with PopSci.

[Related: Sea cucumbers have a secret superpower.]

The sharks allowed the researchers to see into areas that aren’t easily accessible by humans to map the seagrass meadows. The satellite-tagged tiger sharks swam more than 2,485 miles in both regions of The Bahama Banks, located near Andros Island, Grand Bahama, and Great Abaco. Since they’re sharks, these big fish can explore deeper areas than those surveyed by humans.

“The tiger sharks extending well below the depth limit of seagrass and further into the interior of the vast Great Bahama Bank, areas not logistically possible for human access,” Howe explains. “When reviewing the camera footage, the biggest notable behavior was just how much of their time is spent patrolling seagrass meadows.” Howe is also a co-author of the new study.

Swimming in the grass helped the team map out a seagrass meadow that was even bigger than they had imagined. The Bahamas Seagrass Meadow is one continuous ecosystem that spans 35,521 square miles across The Bahama Banks. This study shows a 41 percent increase from the previous projected global estimate of seagrass.

[Related: The truth about carbon capture technology.]

The findings also suggest that all of this greenery plays a major role in absorbing some of the excess carbon in the ocean due to burning fossil fuels. One study suggests seagrass can remove carbon 30 times faster than the rainforest.

“When referred to global seagrass carbon stock estimates, our results indicate that seagrass in The Bahamas may contain 19.2 to 26.3 percent of all the carbon sequestered in seagrass meadows on Earth,” says Howe.

All of this seagrass also supports the ocean’s biodiversity and fish stocks.

“In The Bahamas, for example, these meadows serve as key nursery grounds for a host of commercially relevant marine species such as the Nassau Grouper, Queen Conch, Lobster, Manatees, and also they serve as key habitat for threatened species like shark and sea turtles,” says Beneath the Waves project manager and study co-author David Harris in an interview with PopSci.

Measures to protect seagrass are included in the Climate Change and Carbon Market Initiatives Act passed in May by the Bahamian Government. The team will continue to work with government support to understand seagrass’ role in supporting the entire ocean.

“The health of the ocean is clearly linked to the ocean’s top predators,” says Harris. “By protecting these animals, and learning about their daily lives, we have discovered one of the largest marine findings in the ocean over the last 20 years. Imagine what else we will find as we continue to protect and partner with sharks!”

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This article was originally featured on Hakai Magazine, an online publication about science and society in coastal ecosystems. Read more stories like this at hakaimagazine.com.

Few people have gotten close enough to a shark to pet it. If you could run your hand from a shark’s head to its tail—not that you should—it would feel smooth, almost like suede. Reverse direction and it’s rough like sandpaper. Viewed under a microscope, shark skin is composed of ribbed, dragonesque scales layered over each other like shingles on a roof. These structures, called dermal denticles, are more like teeth than skin. Made of dentin and enamel, they are innervated, and their ribbed and layered pattern guides water across the shark’s back, reducing friction and drag. Sharks’ impressive skin helps them glide through the water, with some species reaching speeds as fast as 50 kilometers per hour.

Shark denticles are the envy of engineers. To mimic sharks’ impressive hydrodynamic prowess, materials scientists have designed shark-inspired surfaces for the hulls of boats, wind turbines, and even high-end swimsuits, all in an attempt to maximize efficiency.

But in a new study, researchers from Harvard University in Massachusetts, led by ichthyologist Molly Gabler-Smith, have for the first time compared materials that attempt to mimic shark skin with the real thing. As it turns out, the engineered materials have a long way to go.

Previously, scientists have examined shark denticles in impressive detail using scanning electron microscopes, a technology that can take images of structures just a few nanometers wide. But the images scanning electron microscopes put out are two-dimensional. And if you’ve ever seen a car in a wind tunnel, you’ll know that when it comes to reducing drag and friction, an object’s 3D structure is incredibly important.

So using a technique called surface profilometry, an imaging technology in which a scientist essentially uses a thin layer of gel to make a mold of the surface to be studied, Gabler-Smith and her team viewed shark skin in 3D. “It’s almost like looking at a topographic map,” says Gabler-Smith. “You can see where there’s peaks and valleys.”

Gabler-Smith used the technique on skin samples from 17 different shark species. She also looked at two Speedo swimsuits marketed as mimicking shark skin—the FS Fastskin II swimsuit and the Lzr Racer Elite 2—as well as a 3D printed surface created in her lab. She compared the proportions of the denticles and the height and spacing of the riblets and found substantial differences between real shark denticles and the artificial materials.

A close-up analysis shows the differences between real shark skin (top right) and several synthetic materials including a 3D-printed material (bottom right), the Speedo FS Fastskin II (bottom left), and the Speedo Lzr Racer Elite 2 (top left). Photos courtesy of Molly Gabler-Smith

“I hesitate to say that [the swimsuits are] really mimicking shark skin, because they really aren’t at all,” Gabler-Smith says. One of the biggest differences, she says, is that unlike a ribbed fabric, real shark skin is made of hard enamel structures on a flexible surface. When asked to rate the swimsuit materials out of 10, Gabler-Smith gave the FS Fastskin II and Lzr Racer Elite 2 a three and a seven, respectively, and her lab-made engineered surface an eight or nine.

“[The swimsuit designers are] doing a pretty good job of taking all of the information that biologists are measuring from actual shark skin, but there’s still so much to do,” she adds. In theory, she says, adding riblets or other bumpy textures to swimsuits or the surfaces of watercraft should reduce drag, but these surfaces are still a way off from functioning like the real thing.

Amy Lang, an aeronautical engineer at the University of Alabama who studies shark skin and was not involved in the research, says that replicating the drag-reducing properties of shark skin is even more difficult than just having denticle-like riblets. To actually decrease drag instead of increasing it, she says, the riblets must be the right size and depth. She adds that while it is interesting to use surface profilometry to directly compare shark skin with engineered materials, it’s equally important to test how synthetic materials actually work in the water.

But now that scientists have updated information on the 3D structure of shark denticles across a variety of different species, engineers may be one step closer to mimicking one of nature’s most efficient swimmers.

This article first appeared in Hakai Magazine, and is republished here with permission.

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Great white sharks are the epitome of an apex predator. In the ocean, these toothy creatures easily hold one of the top spots on the food chain (though the odds of one killing a human are 1 in 3,700,000). But recent drone and helicopter footage of an aquatic attack reveals that another marine mammal seems to have an upper hand. 

For the first time, biologists filmed direct evidence of killer whales attacking and killing white sharks in South Africa. The first video was captured by drone in May 2022 in the Mossel Bay region, revealing three orcas cornering and fatally biting a three meter-length white shark. The shark’s body was not seen or recovered after the bloody battle. This video, along with extended helicopter footage of this attack and shark tag data, were published this week in the journal Ecology. 

The first video recorded by a drone pilot was initially released in June, but the team later received cell phone footage recorded from a helicopter pilot that had been filmed on the same day. They were able to identify that the killer whales in the helicopter video were the same ones in the drone pilot video—spotting a particularly well-known shark hunter, named Starboard. The evidence suggests that the pod had gone on an hour-long hunting spree, killing potentially four white sharks in total. The researchers decided to adjust and resubmit the paper with the new information. This provides new insight into the rarely-seen evasive behavior of great whites—a species that had once dominated South African waters but is now experiencing a rapid decline. 

“I still remember viewing the footage for the first time and feeling a whole mixed bag of emotions,” Alison Towner, lead study author and senior shark scientist at Marine Dynamic Academy in Gansbaai, South Africa, told PopSci in an email. “We had been analyzing evidence on these interactions since 2017 and had often been challenged on whether this really was occurring in South Africa. I guess the footage put those questions to bed as it is irrefutable evidence that orcas are hunting white sharks here.”

[Related: Even blue whales aren’t safe from orcas]

Orcas are like “wolves of the ocean,” says Towner—they commonly capture prey in organized pods. In two of the recorded attacks, the team was able to witness the killer whales slowly and closely approach sharks. Instead of fleeing, the great white will swim in tight circles around the orca while keeping it within sight—sharks being highly visual creatures. This is a common strategy that seals and turtles also use to successfully evade sharks, explains Towner. But since killer whales hunt in groups, the tactic might not be as effective. 

“I was in awe of how the orcas strategize and hunt but one cannot help but feel for the sharks, too,” Towner says. “It’s quite haunting seeing white sharks being circled and killed by larger predators.” 

Particularly, the orcas seem to have a taste for liver. The video shows them chomping on the sharks’ abdomen and tearing out their liver, which could be seen floating to the surface where the killer whale gobbles it up. White sharks’ livers are oily and nutrient-rich, making an ideal meal, Towner explains. The footage gives an explanation for previous shark carcasses washed ashore that were missing livers, the team wrote in the study. 

This might actually be a relatively common phenomenon. Killer whales are the only known marine predator of great white sharks. In South Africa, Starboard, and partner-in-crime Port, have been reported preying on other shark species and have been linked to white shark deaths since around 2017, but this is the first time the showdown was seen in action. Before killer whales started hunting in Mossel Bay, white sharks were frequently seen—sometimes recorded every day by research surveys. The study authors collected drone and dive boat data before and after the predation events, and found that white sharks fled the area immediately after the attacks. Only a single white shark was seen in 45 days after the predations were reported. 

[Related: Great whites don’t hunt humans—they just have blind spots]

“Killer whales are highly intelligent and social animals,” marine mammal specialist and study co-author Simon Elwen said in a press release. They are known to learn and pick up behaviors or skills from each other in their unique cultural system. 

If the hunting practice spreads among killer whales over time, it might be tough to be a shark in South African waters. Orcas are already pushing great whites out of Gansbaai, a fishing town east of Cape Town that’s popular for shark tourism. Human-caused climate change and fishery activity have already been linked to the decline of shark populations, Towner explains. Orcas pose an additional pressure into the mix, motivating Towner and researchers to closely monitor shark and orca dynamics, and the potential influences it might have on South Africa’s ocean ecosystem. 

“While these interactions may be fascinating it is important to understand that white sharks face a whole host of threats in South Africa and now orcas are an additional threat to their already fragile populations,” Towner says. “This information will need to be considered in future studies and in management moving forward here in South Africa.”

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Without its scary rows and rows of razor sharp teeth, your average great white shark (Carcharodon carcharias) wouldn’t be quite as terrifying. Their ancient ancestors (known as acanthodians) were even more prickly, with bristly spines along their fins. Now, a new fossilized fish skeleton found in China is older than the next-oldest specimen by a whopping 15 million years and is the, “oldest undisputed jawed fish.”

In a paper published in the journal Nature, the team of researchers from the Chinese Academy of Sciences, Qujing Normal University, and the University of Birmingham in the United Kingdom write that the new species Fanjingshania renovatais (F. renovata for short) has a body is similar to a spiny acanthodian. They lie somewhere between the class chondrichthyans (modern sharks and rays) and the group osteichthyans (bony fish). They lived in the the Paleozoic period, and F. renovata may be the close relative of a yet-to-be discovered common ancestor of both modern class and group of fish.

The team thousands of tiny skeletal fragments to reconstruct F. renovata, which show that it is a is a funky fish with an external bony “armor” and multiple pairs of fin spines. These spines set it apart from current jawed fish as well as cartilage containing sharks and rays and bony ray- and lobe-finned fish. The new species was uncovered in the bone bed samples of the Rongxi Formation in South China and named after the UNESCO World Heritage Site Fanjingshan.

[Related: 3D models show the megalodon was faster, fiercer than we ever thought.]

“This is the oldest jawed fish with known anatomy,” ZHU Min from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences said in a press release. “The new data allowed us to place Fanjingshania in the phylogenetic tree of early vertebrates and gain much needed information about the evolutionary steps leading to the origin of important vertebrate adaptations such as jaws, sensory systems, and paired appendages.”

This discovery shows evidence that major vertebrate groups began to diversify tens of millions of years before the beginning of the Devonian period, or the Age of Fishes, about 419.2 million and 358.9 million years ago when many different kinds of fishes began to swim Earth’s oceans.

According to the study, there are several features that set apart F. renovata from any known modern or ancient vertebrate. Its has armor along its shoulders that fuse together as a unit that covers more area than other known acanthodians.

Its spiny fins were covered in unusual teeth-like scales, that possibly would fall out in clumps and regrow. Sharks living today also shed and regrow teeth, but aren’t replaced in this way. F. renovata‘s fossilized bones show evidence of resorption, or when parts of bones or teeth break down and are later replaced. This process usually occurs during the organism’s development.

[Related: This whale fossil could reveal evidence of a 15-million-year-old megalodon attack.]

“This level of hard tissue modification is unprecedented in chondrichthyans, a group that includes modern cartilaginous fish and their extinct ancestors,” lead author Plamen Andreev, a researcher at Qujing Normal University, said in a statement. “It speaks about greater than currently understood developmental plasticity of the mineralized skeleton at the onset of jawed fish diversification.”

F. renovata is one of several fossils that this same team uncovered at the Rongxi Formation site. The team describes another species of extinct jawed fish (Qianodus duplicis or Q. duplicis) published in a separate study in Nature. This species is also about 439 million years old, but it was described only from fossilized scales and teeth, so the researchers are more uncertain about exactly which fish group it may have been a member of.

Three other extinct fish species unearthed at the site include Xiushanosteus mirabilis, Shenacanthus vermiforis, and Tujiaaspis vividus. While none of them were quite as old as F. renovata or Q. duplicis, X. mirabilis and S. vermiforis are still older than any other known species of early jawed fish.

The newly discovered species are changing what scientists already knew about the evolution of jawed fishes. While researchers first estimated this evolution took place about 420 million years ago, now we can place its jump 20 million years earlier than that.

“The new discovery puts into question existing models of vertebrate evolution by significantly condensing the timeframe for the emergence of jawed fish from their closest jawless ancestors,” said Ivan J. Sansom from the University of Birmingham, in a statement. “This will have profound impact on how we assess evolutionary rates in early vertebrates and the relationship between morphological and molecular change in these groups.”

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About 15 million years before the blockbuster hit “Jaws” snapped up the attention of generations of movie goers, the mightly megalodon (Otodus megalodon) stalked the Earth’s oceans. The ancestor of modern-day sharks could eat prey the size of an orca whale in only about five bites. The largest specimens reached between 58 and 72 feet long and had teeth that are almost three times the size of a modern-day great white.

Now, a team of researchers in southern Maryland have unearthed fossil evidence of a possible bottoms-up megalodon attack on a whale. The fossils were found close together in southern Maryland’s Calvert Cliffs, by Mike Ellwood, a Calvert Marine Museum volunteer and fossil collector. They date back to the Miocene Epoch (about 23 million to 5.3 million years ago), when Maryland was covered in a warm and shallow coastal sea with big plumes of sea algae and succulent aquatic plants that supported turtles, crustaceans, and marine mammals.

In an interview with Live Science, Stephen J. Godfrey, a curator of paleontology at the Calvert Marine Museum in Solomons, Maryland and lead author of the study said “in terms of the fossils we’ve seen on Calvert Cliffs, this kind of injury is exceedingly rare. The injury was so nasty, so clearly the result of serious trauma, that I wanted to know the backstory.”

[Related: 3D models show the megalodon was faster, fiercer than we ever thought.]

The study, published last month in the journal Palaeontologia Electronica, details their examination of two fossils from the whale’s fractured vertebrae and one megalodon tooth. They used CT scans and other medical imaging techniques at a local hospital to get a closer look inside the ancient remains.

One of the vertebrae shows evidence of a compression fracture. The study proposes that the whale’s backbone must have been forcefully bent into such a tight curve, that pressure from the vertebra right next to it smashed into one another to sustain this kind of injury.

“We only have circumstantial evidence, but it’s damning circumstantial evidence,” Godfrey told Live Science. “This is how we see the story unfolding. Although there are limitations to what we can claim, and we want the evidence to speak for itself.”

Another possible cause of this kind of injury to the backbone could be that the whale ingested a toxic algae that caused it convulse so violently that it broke its own back. The authors, however, argue that a megalodon attack is the most likely cause due to the magnitude of the injury to the spinal column bones.

The team also examined a megalodon tooth that was uncovered alongside vertebrae fossil. The tip of the tooth broke off, which could occur after it struck something hard like a bone. It also could have fallen out while swimming or feeding on an already dead or injured whale’s remains. But the team isn’t ruling out the possibility that a megalodon lost its tooth while ramming its jaws into a whale.

[Related: Megalodons liked to snack on sperm whale snouts.]

The teeth of extinct sharks are a common discovery in Calvert County Maryland and they come from a wide variety of shark species, according to the Maryland Geological Survey. Citizen scientists and paleontologists alike have uncovered teeth from Galeocerdo contortus and Galeocerdo triqueter (similar to modern day tiger sharks), Sphyrma prisca (a relative of the hammer head shark), and Odontaspis elegans (the Sand Shark). It’s thought that this area was a whale and dolphin calving ground, which potentially made the smaller whales easier targets for hungry megalodons.

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One of the last places you want to be hungry out on the open ocean is the North Pacific Subtropical Gyre. Being home to the Great Pacific Garbage Patch is just one factor. A gyre is a large system of rotating currents ocean currents. There are five of major ocean gyres, where the ocean churns up eddies (smaller and more temporary loops of swirling water), whirlpools, and deep ocean currents. Even without trash islands, gyres are typically nutrient poor (ie not a lot of snacks), yet help sustain some of the ocean’s top predator fish.

The reason may lie in some of the gyre’s eddies. A study published yesterday in the journal Nature finds that marine predators (tunas, billfishes, and sharks, for example) get together in rotating ocean eddies that spin clockwise and are anticyclonic, or rotating around the center of a high pressure in the reverse direction of a cyclone. The study suggests that the predators are moving with these temporary loops of water as they travel throughout the open ocean and foraging on the biomass (or life) that is within the eddies.

“We discovered that anticyclonic eddies—rotating clockwise in the Northern Hemisphere—were associated with increased pelagic predator catch compared with eddies rotating counter-clockwise and regions outside eddies,” said Martin Arostegui, a Woods Hole Oceanographic Institution (WHOI) postdoctoral scholar and paper lead-author, in a press release. “Increased predator abundance in these eddies is probably driven by predator selection for habitats hosting better feeding opportunities.”

[Related: Climate change is making the ocean lose its memory. Here’s what that means.]

The team from WHOI and the University of Washington Applied Physics Laboratory (UW APL) focused on more than two decades of commercial fishery and satellite data from the North Pacific Subtropical Gyre, as well as an mix of predators from varying ocean depths, regions, and physiologies (both cold and warm-blooded animals). They investigated predator catch patterns within and around the eddies, concluding that the swirling loops of ocean water influence the ecosystems of the open ocean at all levels of the food chain.

The data suggests a fundamental relationship between opportunities for predators for forage and the underlying physics of the ocean.

“The idea that these eddies contain more food means they’re serving as mobile hotspots in the ocean desert that predators encounter, target and stay in to feed,” added Arostegui.

[Related: “With new tags, researchers can track sharks into the inky depths of the ocean’s Twilight Zone.”]

Understanding how eddies influence the dining behavior of open ocean predators in these food-scarce areas of the deep ocean can better inform species, fisheries, and ecosystem management. It can also help policymakers regulate harvesting and fishing for deep ocean plants and animals without negatively affecting dependent predators or the ocean’s ability to store carbon and regulate the climate.

“The ocean benefits predators, which then benefit humans as a food source,” said Arostegui. “Harvesting the food that our food eats, is something we need to understand in order to ensure the methods are sustainable for both the prey and the predators that rely on them. That is critical to ensuring both ocean health and human wellbeing as we continue to rely on these animals for food.”

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A 58-year-old woman from Pennsylvania was killed by a bull shark yesterday while snorkeling in The Bahamas, according to local authorities. The yet to be identified woman and her family were passengers onboard Royal Caribbean’s Harmony of the Seas.

According to Royal Bahamas Police spokeswoman Chief Superintendent Chrislyn Skippings, the family was at a popular snorkeling spot near Green Cay off of the coast of Nassau in the northern Bahamas. She added that the family witnessed the attack and identified the shark involved in the incident as a bull shark. Police also say that the tour company and woman’s family were involved in the rescue.

In a statement to the Associated Press, Royal Caribbean International said that the injured woman died after arriving at a local hospital for treatment. The company also added that they are helping the loved ones and that the family was participating in an independent shore excursion in Nassau.

[Related: Everything you need to know about shark bites.]

The beach where the incident occurred has subsequently been closed and the investigation is ongoing.

Shark attacks on humans are still exceedingly rare. The odds of a fatal shark attack remain less than 1 in 4 million. By that same metric, the risk of death from the flu, drowning, and fireworks are all greater than being killed by a shark.

According to the Florida Museum of Natural History’s International Shark Attack File, last year there were there were 73 confirmed unprovoked attacks (defined as incidents which occurred in the shark’s natural habitat without human provocation) globally, nine of which were fatal. The Bahamas is home to the majority of shark attacks in the Caribbean. Two attacks were reported in 2019, with one of them fatal. The fatal incident involved a Southern California woman who was attacked by three sharks near Rose Island, located just a half mile from where yesterday’s attacked occurred.

[Related: You should never have to fight off a shark—but here’s how to do it (just in case).]

While it is still unclear why sharks attack humans, most scientists agree that it is a case of mistaken identity, where the shark believes that a human is a seal or fish. The Shark Attack File lists white, tiger, and bull sharks as the shark attack “Big Three,” due to their proximity to areas where humans like enter the ocean, sheer size .and teeth designed to shear rather than hold. This makes them incredibly capable of inflicting serious injuries to a victim.

In an interview with Popular Science in July, John Chisholm, an associated scientist at the New England Aquarium who studies great white sharks, recommended taking precautions when entering the ocean. “If you’re going into the ocean, if you’re going into a wilderness area, you have to be proactive,” he says. “Before you go to the beach, you check the weather and traffic. Take a moment to check Sharktivity and with the local lifeguards [for shark sightings], too.” Experts also recommend swimming in groups, removing jewelry which might flash like a fish and attract younger sharks, and avoiding swimming by that sharks like to eat (seals, schools of fish, etc.).

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Since they were first recorded by Irish scientist John Tyndall in 1859, scientists have observed how greenhouse gases (GHG) like carbon dioxide, methane, and nitrous oxide and act like a giant blanket around the Earth. Like a greenhouse does for plants, these gasses trap heat and warm the planet. In May, the National Oceanic and Atmospheric Administration’s (NOAA) Mauna Loa Baseline Observatory measured the amount of carbon dioxide in the atmosphere at an astounding 421 parts per million, a range not seen on Earth in millions of years.

This drastic change to the chemistry in the atmosphere has lead to major consequences to our land and seas and it will only worsen as the climate continues to change. A study published on August 22 in the journal Nature Climate Change found that if greenhouse gases continue to be emitted at their current rate, nearly 90 percent of all marine species could face extinction by the end of this century. The most impacted groups would be the ocean’s top predators (particularly tuna and shark, since they are hunted by humans for food), areas with large amounts of biodiversity, and coastal fisheries of low-income nations, according to the study.

The international team of researchers created a new scorecard called the Climate Risk Index for Biodiversity (CRIB). They used it to examine about 25,000 species of marine life, including animals, plants, protozoa, and bacteria.

[Related: Climate change is making the ocean lose its memory. Here’s what that means.]

“We created a ‘climate scorecard’ for each species and ecosystem that tells us which will be winners or losers under climate change,” says Daniel Boyce, the study’s lead author and a research associate at Dalhousie University, in a press release. “It allows us to understand when, where and how they will be affected, as well as how reducing emissions can mitigate climate risk.”

In a blog post for CarbonBrief, Boyce explains that the framework uses data from analyzing how a species’ innate characteristics like body size and temperature tolerance interact with past, present, and future climate conditions. They evaluated climate risk under two different scenarios: one where emissions continue to be high and another where emissions are sharply reduced in accord with the Paris Agreement’s goal to keep warming below 3.6 degrees Fahrenheit (2 Celsius).

According to the study, under the worst-case emissions scenario, 87 percent of marine species would be under high or critical climate risk, species were at risk across 85 percent of their distribution on average, and climate risk was heightened in coastal ecosystems and closer to the equator, disproportionally threatening tropical biodiversity hotspots and fisheries

However, if GHG emissions are curbed, there is an opportunity to course correct and prevent this mass extinction from happening. Reducing GHG emissions would limit the risk for virtually all species on Earth and help minimize disruption to 98.2 percent of the fisheries and ecosystems in the study.

[Related: These Hawaiian corals could hold the secret to surviving warming waters.]

“The benefits of emission mitigation for reducing climate risk are very clear,” said co-author Boris Worm in a press release. “Mitigation provides the most straightforward path to avoiding the worst climate impacts on oceans and people, setting the stage for global recovery under improved management and conservation.”

On August 16th, President Biden signed the Inflation Reduction Act, which provides $369 billion to fund energy and climate projects with the goal of reducing carbon emissions by 40 percent in 2030. While climate experts have called a major step in curbing GHG emissions, the legislation also comes soon after the Supreme Court of the United States ruled to limit the Environmental Protection Agency’s (EPA) ability to regulate emissions at power plants. in West Virginia v. EPA.

“The reality is that climate change is already impacting the oceans, and even with effective climate mitigation, they will continue to change,” Boyce and co-author Derek Tittensor wrote in CarbonBrief. “Therefore, adapting to a warming climate is crucial to building resilience for both ocean species and people.”

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About 23 to 3.6 million years ago, a shark roughly three times the size of the great white shark (Carcharodon carcharias)—arguably made famous in the blockbuster 1975 movie JAWS—roamed the oceans of the world. The megalodon (Otodus megalodon or O.megalodon) is believed to be the largest shark that ever has lived, measuring 34 to 66 feet and weighed upwards of 100,000 pounds. That’s about the weight of a train car.

New research published this week in the journal Science Advances suggests that the sizable shark was not only the apex predator of its day, but a “transoceanic super-predator” that could travel thousands of miles across oceans on long migrations, even faster than modern-day sharks. The research by Swansea University PhD student Jack Cooper, shark expert Catalina Pimiento from the Paleontological Institute and Museum at the University of Zurich, and John Hutchinson from the Royal Veterinary College shows the sharks may have eaten meals that were the size of an orca whale, consumed in an about five or more bites.

The researchers used data from an O. megoladon fossil vertebral column, various teeth, and a chondrocranium from our friend the great white shark (its closest living relative) to build out the 3D model.

“The 3D modeling of O.megalodon was only possible thanks to a rare and exceptional vertebral column specimen from Belgium: 141 vertebrae from a single shark,” said Cooper, in an e-mail to Popular Science. “It’s a one of a kind specimen that may well hold the key to further discoveries on this giant shark, having mostly been in museum storage in Brussels since the 1860s.”

Professor Hutchinson added, “Computer modeling provides us with an unprecedented ability to use exceptionally well-preserved fossils to reconstruct the entire body of extinct animals, which in turn allows estimations of biological traits from the resulting geometry. Models of this nature represent a leap in knowledge of extinct super predators such as megalodon and can then be used as a basis for future reconstruction and further research.”

The 3D model allowed the team to figure out the shark’s length, volume, and gape size. These measurements, in turn, helped them calculate its body mass, inferring swimming speed, energetic demands, and stomach volume based on the relationship between these variables and body mass in living sharks. The newly calculated swimming speed means that the shark was potentially able to swim further distances than its competitors, increasing how quickly it could migrate and eat its way around the ocean, larger like marine mammals prey included.

“Megalodon’s large body size and potential energetic demands suggest that it would need/prefer highly caloric prey, like whales. Prey encounters relate with not only preference, but also prey availability and abundance,” Pimiento added.

It is a lack of abundance that potentially drove the megalodon into extinction, roughly 3.3 million years ago, during the Pliocene epoch. A 2016 study published in the Journal of Biogeography and authored by Pimento suggests that the megalodon’s demise came not from dramatic swings in the climate, but due to a decrease its primary food source at the time (baleen whales) and increase in other predatory sharks (the great white included) and whales in the Orcinius genus.

As the prehistoric ocean’s top predator and resident globetrotter, O. megalodon’s extinction would have post major changes on global nutrient transfer and ocean food webs throughout the world.

“The extinction of this iconic giant shark likely impacted global nutrient transport and released large cetaceans from a strong predatory pressure,” said Pimiento.

Correction (August 23, 2022): A previous version of this post stated that the megalodon weighed similarly to the Space Shuttle Endeavour. The Endeavour weighed around 4.4 million pounds fully loaded.

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This summer has seen a historic number of shark sightings and encounters along US coasts. Especially at beaches on Long Island, New York, and Cape Cod, Massachusetts, where several shark bites prompted beach closures, there are growing concerns of threatening predators filling up the waters. 

“I’ve always thought ‘shark-infested waters’ is a funny term because sharks live in the ocean—really, it’s people-infested,” says Carlee Jackson, a shark researcher and the director of communications for Minorities in Shark Sciences. “Just because they scare us doesn’t mean that they’re not important for the ecosystem.”

Indeed, based on experts’ best guesses as to why people are seeing (or occasionally being attacked by) sharks more frequently, there’s no need to panic. In fact, it’s probably a sign that coastal biomes in the US are healthy. The increase in shark sightings, biologists think, is due to growing populations, more folks in the water, and better technology for both experts and the public to see and track the marine creatures. With efforts that began decades ago to protect sharks now paying off, it’s on humans to understand how to stay safe in the ocean.

[Related: New tags can track sharks into the inky depths of the ocean’s Twilight Zone]

Unprovoked great white shark attacks in particular are still incredibly rare—so much that driving to the beach is riskier than running into sharks there. And while the number of shark bites did increase in the US last year (73 in 2021, compared to 52 in 2020), only one person died—fewer than the 11 killed by lightning strikes in the same year. 

Data around sightings is a little hazier because people often mistake various other swimming creatures, like seals and different shark species, for great whites, which are the most dangerous. Not because they’re more aggressive, but because even a small bite from them can do a lot of damage.

“The only way sharks can figure out what something is is by biting it,” Jackson explains. Once the shark realizes you’re a human, not a seal or fish, they almost always will move on. 

John Chisholm, an adjunct scientist at the New England Aquarium, sees firsthand just how often people’s fear or excitement messes with their ability to judge what is and isn’t a great while. Part of his work is verifying public submissions to the Atlantic White Shark Conservancy’s tracking app, Sharktivity. With the app, people can report sightings along the Massachusetts coast, receive notifications of confirmed sightings near beaches, and check recorded locations of tagged great white sharks. 

“Most of the reports are not actually sharks,” says Chisholm. “But it’s kind of a good thing, because it means people are paying attention. And we still have to err on the side of caution, because we know the sharks are out there.”

Misidentifications by citizen scientists aside, researchers are fairly confident that great white populations are increasing, at least in US waters. Populations of the species around North America have grown steadily in the past three decades, thanks to federal and state laws preventing people from killing them or catching them accidentally, and protecting their prey (seals in most cases). Still, great whites in most other parts of the world are struggling. 

[Related: Sharks are learning to love coastal cities]

Chris Lowe, the director of the Shark Lab at California State University Long Beach, also points to better technology as key to improved scientific and popular understanding of sharks’ numbers. The widespread use of GoPros, phone cameras, and drones have been useful tools for biologists, and have made it easier for more beachgoers to capture and disseminate videos, photos, and shark alerts. 

Climate change could be behind the increase in shark sightings and encounters, too, according to Lowe and other researchers. Warmer temperatures are forcing more people to hit the ocean to escape the heat, increasing the odds that someone will bump into a shark cruising the shallows. “Millions of people are using SoCal beaches alone,” Lowe explains. “And the more people there are in the water, the greater the probability of an encounter.”

Shark researchers like Lowe don’t know exactly how healthy the great white population is right now, because there isn’t good data on their numbers before they were overfished in the 1970s and ’80s. For the same reason, they’re not sure when the species’s population will stop increasing. But it’s a heartening example of successful conservation interventions that could be applied to other shark species and populations around the world. “Sharks have been around for around 450 million years, before trees existed,” says Jackson. If humans aren’t killing them or their prey, she says, “It’s amazing how resilient they are.”

On the flip side, like cougars, wolves, and other large predators that people brush up against, sharks basically never kill and eat humans for prey. But since accidents can happen, Chisholm and other shark experts recommend taking precautions when entering salt water, just like you would for a hike in bear country. Taking steps to avoid the cartilage-filled predators, and appropriate responses if you do bump into them, have been shown to vastly improve your chances of walking (or swimming) away from surprise encounters unharmed. 

[Related: You should never have to fight off a shark—but here’s how to do it (just in case)]

“If you’re going into the ocean, if you’re going into a wilderness area, you have to be proactive,” Chisholm says. “Before you go to the beach, you check the weather and traffic. Take a moment to check Sharktivity and with the local lifeguards [for shark sightings], too.” Staying in groups further decreases the odds of a violent encounter, and removing jewelry, which might flash like a fish that younger sharks prey on, is also a good idea.

Most importantly, pay attention to your surroundings when you’re in the water. Don’t just steer clear of fins—also look out for anything sharks actually do want to eat, like fish schools, seals, and bait. There are more sharks and humans in the water than there used to be, but there should also be plenty of room for both to coexist.

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Ancient megalodon sharks may have snacked on sperm whale snouts, according to new analysis of the marine mammals’ fossilized skulls. An international team of researchers described signs of this “focalized foraging”—aka deliberate munching—in 7-million-year-old whale bones in Proceedings of the Royal Society B: Biological Sciences. 

Both modern and fossilized sperm whales sport distinctive “supercranial basins” (read: giant noggins) that take up around a third of its body length, which can reach around 60 feet. These massive heads house their incredibly complex sound-production organs, which enable them to make louder noises than any other animal on the planet. But most of the supercranial basin is filled with an extremely fatty substance called spermaceti. 

In the new study, which analyzed various sperm whale specimens held at the Natural History Museum in Lima, paleontologists found bite mark clusters that corresponded with the fattiest nasal regions. 

“Many sharks were using these sperm whales as a fat repository,” lead study author Aldo Benites-Palomino, a doctoral candidate at the Paleontological Museum of the University of Zurich in Switzerland, told Live Science. “In a single specimen, I think that we have at least five or six species of sharks all biting the same region—which is insane.” 

[Related: How great white sharks probably hastened the demise of megalodon]

Unlike baleen whales that feed on tiny organisms, sperm whales are toothy predators that munch on fish and other marine critters. But Benites-Palomino and colleagues posit that their fatty schnozzes would have provided a much more appealing food source than the more docile, but slim marine mammals that swam in the oceans at the time. Plus, it’s likely that sperm whale noses only got nibbled on once the behemoths died of other causes.

“Our findings indicate that all of these were post-mortem events,” Benites-Palomino told Newsweek. “The carcasses were floating for days until all the fat was ingested by sharks, not being able to float any more.”

The research team found an assortment of bite marks that match multiple species of hungry sharks, but it’s no surprise that megalodon is the nose-biter making the most headlines. Otodus megalodon, which went extinct some 3 million years ago, is one of the only other carnivores in history to have rivaled sperm whales in size. Scientists are still figuring out how the ancient beasts lived and died, and Hollywood remains obsessed with the notion that they might still lurk in the deep. 

In June, an unrelated study published in Science Advances suggested that megalodon might have been at the very top of the food chain—hunting other large predators and perhaps even engaging in cannibalism. But their status as apex predator is still up for debate, as other researchers have concluded that megalodon was likely on the same level of the food chain as ancient great white sharks. In fact, competition between them may have helped drive meg to extinction. 

While this latest study gives us just a small taste of the intriguing megalodon’s diet, it does serve as a reminder that even the most aggressive predators are generally not above grabbing some fast food in the form of a whale carcass. 

“More than actually answering questions, I think this is making me have more inquiries around all of these discoveries,” Benites-Palomino told Live Science.

With creatures as mysterious and fascinating as giant-headed sperm whales and long-lost mega sharks on the menu, it’s no surprise that researchers are hungry to learn more.

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It’s hard to think of beachgoing season without our minds jumping to sharks. The predators tap our curiosity, fill movie theaters, and (whether it’s founded or not) stir fear of attacks. Our mere presence, new research hints, may be influencing their behavior in ways we didn’t predict. A study published earlier this month in the journal Marine Ecology Progress Series has shown that cities may be drawing sharks closer to our shorelines. 

Researchers at the University of Miami and collaborators tracked the movement of three species—great hammerheads, bull sharks, and nurse sharks—in and around Florida’s Biscayne Bay between 2015 and 2019. Stressors on the region, including pollution from power plants and boat traffic, led the team to assume that the ocean predators would shy from the area, especially during periods when crowds descended. But the human presence may be having the opposite effect. 

Terrestrial creatures like black bears, bobcats, and coyotes tend to shy from cities—especially during the day—and the authors assumed sharks would be no different. “Few studies have investigated the movements of ocean predators in relation to urbanization, but since other studies have shown that land predators are urban avoiders, we expected sharks to be too,” said Neil Hammerschlag, lead author and director of the University of Miami Shark Research and Conservation Program, in a statement. 

Based on acoustic trackers the team placed on 36 great hammerheads, 24 bull sharks, and 27 nurse sharks, the scientists saw that the species were actually “urban adapters”—a.k.a., ones that prefer to hang out in and around cities now. Of the tagged animals, 14 hammerheads, 13 bulls, and 25 nurses were seen hanging out in the Miami area close to shore. The greatest density of sightings was in the northern end of the bay closer to hotspots like South Beach and the Seaquarium. 

[Related: Why we can’t stop searching for the megalodon]

A trio of causes may be contributing to this unexpected result. First, the sharks might be attracted to nutrient runoff from canal outflows and sewer discharge into the Biscayne Bay. Second, they could be scavenging for grub: Fishers tend to discard carcasses when they return to marinas, luring hungry predators in the process. Refuse and fish parts tossed by staff at the Seaquarium have anecdotally been known to draw in snacking sharks.

The authors also note that a range of other factors—including salinity, depth, nutrient density, and oxygenation—also influence where sharks like to hang out. 

It’s important to remember, though, that this behavioral change is worse for the sharks than it is for people. 

Shark attacks are rarer than Hollywood would have us believe. The predators kill only about five people a year, and, in 2020, sharks non-fatally nibbled on 57 people. Surfers, swimmers, and divers experienced the majority of unprovoked attacks; the highest geographical concentration in the US, however, was in fact Florida, with 16 incidents. 

[Related: How to fight off a shark]

Meanwhile, for marine life, swimming closer to urban areas has its own risks. Sharks searching for food closer to marinas and population centers often end up in spots with crummier water quality and pollutants. The Biscayne Bay is particularly bad in those regards. A 2021 analysis through the city of Miami found that water samples from high-traffic areas were as much 66 percent below acceptable contamination levels for recreational use at the time. 

Still, the study authors note that their tracking does help isolate areas where swimmers may be at greater risk for shark encounters. The data traced a greater density of sharks hanging out at the northern end of the bay, a zone where swimmers have been bitten in the past. Understanding how our own activities might invite those ruins is an important facet to prevention—and in teaching us how to share the shore with wildlife. 

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It’s got to be out there. It doesn’t matter that Otodus megalodon has by all scientific accounts been extinct for more than 3 million years. The ongoing earthly presence of the enormous shark persists in our collective imagination thanks to rumors, legends, and summer B flicks.

Meg mythology often posits that the 50-foot predator has been hiding for epochs somewhere at the bottom of the ocean. It’s a notion that’s launched more than a few books and pseudo-docs, all hinging on the fact that most of the planet’s nether waters are unexplored—and therefore rife with primo dens for enigmatic beasts. But based on what we know of the biological adaptations required for life down below, not many animals could pull off a deep-sea disappearing act. If megalodon is still out there (and that’s a pretty big if), it’s not what it used to be.

Fossil shark teeth got people hooked on the Meg long before paleontology took off in the early 19th century, when scientists started cataloging fossils with gusto. In 1835, Swiss naturalist Louis Agassiz described triangular, finely serrated teeth, which had been found worldwide since antiquity, as belonging to a “megatooth” relative of the great white.

Discoveries around the world—in locations as diverse as Panama, Japan, Australia, and the southeastern United States—piled up over time, but one particular find raised the specter of a Meg still swimming in the deep. In 1875, during an expedition for the Royal Society of London, the HMS Challenger dredged up 4-inch-long teeth from a depth of 14,000 feet near Tahiti. In 1959, zoologist Wladimir Tschernezky, who made a hobby of researching “hidden animals” like Bigfoot, estimated the specimens were just 11,300 years old. Other scientists have since dismissed this dating, but unscrupulous documentarians and curious amateurs still highlight the research as a hint that Meg might persist.

Save for the outliers found by the Challenger, the megalodon’s fossil record indicates it was a shore-hugging creature, similar to its distant cousin the great white. “Remains generally come from coastal marine rock deposits formed in tropical-temperate areas,” says DePaul University shark researcher Kenshu Shimada. The species’s dietary habits further confirm a shallow lifestyle, with gnawed ancient whale bones showing Meg’s preference for marine mammals. These air breathers had to break through the surface for oxygen, so paleontologists expect megalodon, like them, hung out near the shore.

The exact combination of factors that pushed the ancient shark into extinction is still murky. We do know that shallower oceanic zones were undergoing dramatic changes around 3.5 million years ago, when the giant disappears from the fossil record. Water was growing cooler, making marine mammals less abundant, and the newly evolved great white may have served as a nimble competitor for resources. But there’s no way to prove definitively what did in the Meg.

The lack of certainty helps some maintain hope of finding one in the deep. Believers have at least one thing right: The bottom of the sea is an enigma. Even though satellites have mapped 100 percent of its floor, a low-resolution chart alone doesn’t give us great insight into what actually lives there, says Louisiana Universities Marine Consortium Executive Director Craig McClain, who specializes in cataloging oceanic systems. While the idea of a deep-dwelling ancient creature is highly improbable, he says, the sliver of possibility is still tempting. Less imposing critters have indeed shown up unexpectedly; in 1938 biologists identified a living coelacanth—a species of fish presumed extinct for about 65 million years.

If the megalodon were living in the dark, inky depths, though, it would have had to become a very different sort of creature—one we might not find nearly as cinematic. For one thing, Shimada says, its ravenous metabolism would need to fundamentally change. Preliminary geochemical analysis of isotopes in remains, which can help scientists estimate the body temperature of prehistoric organisms, indicates that megalodon was “warm-blooded” in the same sense as the great white. That predator’s active ocean cruising generates enough body heat to keep it toastier than surrounding seawater, an effort that burns through the equivalent of about six pounds of flesh a day. Meg may have weighed as much as three times more, and would have presumably required proportional grub. Yet animals near the ocean floor have to get by on teensy scraps, preying on the scant species that live there or hoovering up biological detritus that sinks down from carcasses above.

This scarcity of food tends to make organisms evolve small, efficient forms, making many low-living sharks relatively sluggish and slight. A megalodon living far enough down to evade human detection might now look something like a sleeper shark—a long, cigar-shaped animal that’s about as lively as it sounds—as opposed to a burly, toothy beast.

Yet even if Meg had assumed a slender and slow disguise, we’d probably have seen evidence of it by now. “Ocean giants that we do know about have global distributions,” McClain says. Even if we rarely spy creatures like giant squids, which live in the more forgiving upper ranges of what we’d call the deep sea, they leave markers of their existence strewn around the world in the form of carcasses (and bites taken out of unlucky critters). We’ve yet to spot any such refuse, if it even exists.

But these realities can’t extinguish the Meg’s enduring myth (and summer movie franchises). “As a deep-sea explorer and as a scientist who spends a lot of time researching known ocean giants, I really want there to be some unknown one that is undiscovered, and to make that discovery,” McClain says. Its mysterious nature—what we know of it comes largely from studying teeth—makes it enticing to imagine the Meg’s pulled off the ultimate vanishing act and could, perhaps, reemerge at any moment. The key is where scientists decide to look. While paleontologists are almost certain megalodon doesn’t swim in our modern seas, they might still find more details about the species in the depths of the fossil record—and its enduring secrets could break the surface when we least expect.

A history of the megalodon

16 million years ago – Otodus megalodon evolves from an ancestral group of megatooth sharks—the last member of a line that began 60 million years ago.

10 million years ago – The shark spreads to coastal waters worldwide. Clusters of baby teeth near Panama suggest nurseries were close to shore.

5 million years ago – Great white sharks evolve, and likely compete with the massive Meg to eat the same marine mammals, such as whales.

3.5 million years ago – Otodus megalodon seemingly goes extinct around a time of upheaval, including cooling seas and a dip in the species it munched on.

70 CE – Pliny the Elder notes that large “tongue stones” found in the rock strata of Europe may fall from the heavens during lunar eclipses.

1666 – Danish scientist Nicolas Steno dissects the head of a shark found off the coast of Italy and speculates that “tongue stones” are teeth.

1835 – Swiss naturalist Louis Agassiz coins the name Carcharodon megalodon in describing a set of the creature’s giant chompers.

1875 – The HMS Challenger dredges up megalodon teeth from the deep sea near Tahiti, fueling speculation about the shark’s survival.

1909 – Researchers build a model of a Meg jaw that fits six standing adults—suggesting an 80-foot body. This is now considered oversize.

1919 – Fishers in Australia claim to see a massive shark eat multiple lobster pots. The legend eventually makes its way into megalodon lore.

1974 – Peter Benchley publishes Jaws, which plays with the idea that a prehistoric man-eater might lurk in the deep. The public is hooked.

2016 – After decades of debate on the specifics of Meg’s family tree, the giant shark gets the new scientific name Otodus megalodon.

This story appears in the Fall 2020, Mysteries issue of Popular Science.

Is your head constantly spinning with outlandish, mind-burning questions? If you’ve ever wondered what the universe is made of, what would happen if you fell into a black hole, or even why not everyone can touch their toes, then you should be sure to listen and subscribe to Ask Us Anything, a podcast from the editors of Popular Science. Ask Us Anything hits Apple, Anchor, Spotify, and everywhere else you listen to podcasts every Tuesday and Thursday. Each episode takes a deep dive into a single query we know you’ll want to stick around for.

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Great whites are the largest predatory sharks to roam the world’s seas, reaching up to 20 feet in length. But that wasn’t always the case. Millions of years ago, the megatooth shark family spawned one of the largest carnivores that ever lived: Otodus megalodon, which is estimated to have grown to 50 to 60 feet. 

Yet the immense megalodon abruptly vanished from the fossil record around 3.6 million years ago—not long after the emergence of great white sharks. Scientists have speculated that the two species might have competed for prey, ultimately contributing to megalodon’s extinction. 

A study published on May 31 in Nature Communications offers indirect support for this idea. Researchers compared the chemical composition of teeth from living and extinct sharks, and concluded the great whites and megalodon occupied similar rungs of the prehistoric food chain.

“Megalodon is an enigma in many ways,” says Alberto Collareta, a paleontologist at the University of Pisa in Italy, who wasn’t involved with the research. Collareta has studied bite marks, probably made by megalodon sharks, on the fossilized bones of small baleen whales and pinnipeds (the group encompassing seals and their relatives). Our understanding of megalodon’s diet is based primarily on such markings and on the sharks’ serrated teeth, which are more likely to fossilize than their cartilage skeletons.

The new paper “is very helpful and very insightful in that it provides quantitative, geochemical data to check against previous hypotheses,” Collareta says. 

Great white sharks began venturing beyond the Pacific Ocean and showing up in seas around the world about 4 million years ago. That event may have hastened the demise of megalodon, as Robert Boessenecker, a paleontologist at the College of Charleston in South Carolina who also wasn’t involved in the research, and his colleagues previously suggested.

“At the time I figured it was a bit of a shot in the dark, and didn’t really think too hard about how the hypothesis would be tested,” Boessenecker wrote in an email. The new study “not only attempted to do so, but found evidence strengthening the hypothesis!”

An animal’s diet reveals a lot about its behavior and role in the ecosystem, says Jeremy McCormack, a geoscientist at Goethe-University Frankfurt in Germany and co-author of the new paper. Within each ecosystem, animals exist in a hierarchy known as trophic levels—whether they’re herbivores, top predators, or somewhere in between. Researchers typically determine an animal’s level by looking at different versions, or isotopes, of nitrogen in their bodies. Animals accumulate the “heavier” nitrogen isotope from their prey: The isotope is more prevalent in predators’ tooth dentine, bone collagen, and keratin. However, these tissues don’t fossilize well, so the technique only works for modern and recently-fossilized animals. 

By contrast, zinc—an essential nutrient for plants, animals, and other organisms—is deposited in the strongest part of the teeth: the enamel, or in the case of sharks, enameloid. This is preserved when the teeth fossilize. What’s more, the proportion of “lighter” zinc increases relative to the “heavier” zinc isotope in animals higher up the food chain. Scientists have only recently begun using this technique, McCormack says, and his team’s study is the first to apply it to sharks.

The researchers examined teeth from 20 present-day species of sharks and other fish, including tiger sharks, bull sharks, mako sharks, monkfish, and halibut, as well as 14 fossilized sharks. The analysis included both present-day and fossilized great white shark teeth. 

[Related: Great whites don’t hunt humans—they just have blind spots]

When they compared the zinc levels in megalodon and fossilized great white shark teeth, they found similar ratios of light to heavy zinc isotopes. This indicates that the animals fed at similar positions in the food chain. They may have targeted some of the same marine mammals.

“I wouldn’t necessarily say they were definitely the top predators of that marine ecosystem,” McCormack says. But both shark species “were high up the food chain for sure.”

Tiger shark teeth had the same zinc isotope ratios as prehistoric ones, suggesting that their trophic level hasn’t changed much for millions of years. But modern great white sharks seem to have ascended to a somewhat higher level than their predecessors. Additionally, the shark with the highest trophic level was not megalodon but its ancestor Otodus chubutensis. 

The rise and fall of certain prey animals—petite baleen whales—may underlie these trophic shifts. 

Baleen whales consume vast quantities of organisms low in the food chain such as krill, instead of the bulkier fish, seals, and other animals favored by toothed whales such as orcas. Baleen whales were “quite rare” during the time of O. chubutensis, Boessenecker said. This means that O. chubutensis probably fed on toothed whales instead.

[Related: Scientists discovered new shark species with chainsaw-like noses]

Later, baleen whales—much smaller than their present-day relatives—appeared on the scene and might have been fair game for megalodon and early great whites. These whales mostly disappear from the fossil record around the time that megalodon went extinct. Their absence may have led modern great whites to dine higher in the food chain. 

Expanding the zinc isotope analysis to marine mammals that megalodon and great white sharks might have eaten could add weight to the conclusion that the animals fed at similar trophic levels, Collareta says. 

“We show for the first time that zinc isotopes do preserve the dietary signal over millions of years,” McCormack says. “This method is very promising, but of course we need to investigate this further to really get a grasp of how zinc behaves within an organism and throughout different trophic levels.” 

Other paleontologists are excited by the promise of ancient zinc. “This is a powerful new tool to further examine trophic structure of extinct marine vertebrates,” Boessenecker said, “and I eagerly look forward to similar methods being used on fossil marine mammals.”

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Researchers have identified two new species of shark in the waters off eastern Africa. The rare little creatures range from about three to four-and-a-half feet in length and belong to a group called sixgill sawsharks. Their discovery came as a surprise to scientists, who previously knew of only a single species of sixgill sawshark.

“The present study…[reinforces] both how important the western Indian Ocean is in terms of shark and ray biodiversity, but also how much we still have left to find,” Simon Weigmann, a marine biologist at the Elasmobranch Research Laboratory in Hamburg, told Popular Science in an email. He and his colleagues reported their findings on the new sharks on March 18 in the journal PLoS ONE.

Sawsharks are known for their long, flat snouts studded with teeth, which they use to slash their prey to ribbons. The sea animals have similar chainsaw-like mouths to another ocean fish, known as the sawfish, though they aren’t at all related. Sawfish are actually rays and can grow up to 23 feet long.

Most sawsharks have five gill slits on each side of their bodies, as is typical for sharks. Until now, the only sawshark species thought to have six gill slits—known as Pliotrema warreni—was found in the waters around South Africa and southern Mozambique.

This unusual feature doesn’t seem to play a vital role in the sharks’ survival. “The presence of six (or seven) gill slits per side is considered a characteristic of very primitive sharks,” Weigmann said. “There is no advantage known for them in having six gill slits.”

The first hint that P. warreni wasn’t the only six-gilled sawshark in the sea came in 2017, when a fisherman in the village of Andavadoaka in southwest Madagascar contacted Weigmann’s colleague Ruth Leeney, who is based at the Natural History Museum in London. At the time, she was studying sawfish in Madagascar. The fisherman told her that he’d just caught two of the rays. But the animals turned out to belong to an entirely new species of six-gilled sawshark rather than a new variety of ray. Weigmann and his team were able to identify several more members of this previously overlooked species in museum collections.

Then in 2017 and 2019, a few more of Weigmann’s colleagues mailed him two sawsharks that fishermen had captured as by-catch off the coast of Zanzibar. After a thorough examination, the researchers declared the specimens to be a third species of sixgill sawshark.

The newly recognized sharks were named Kaja’s sixgill sawshark and Anna’s sixgill sawshark in honor of Weigmann’s daughter and niece. Their snouts are shaped slightly differently from that of their cousin P. warreni. All three sharks have whisker-like organs called barbels that they use to detect food; they’re also found on catfish. However, the newly discovered sharks’ whiskers are placed farther from the mouth. It appears that none of the sixgill sawshark species have overlapping ranges.

“The identification and formal description of the two new species is extremely important for evaluating their rarity and population status, as well as for assessing their vulnerability to fishing operations,” Weigmann said. He is particularly concerned about Anna’s sixgill sawshark, which has, as of yet, only been seen in shallow waters, a location where it might easily end up in a fisherman’s catch by accident.

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There’s just a 1 in 3,700,000 chance a person will be killed by a shark in their lifetime, but the fear is still enough to have swimmers worrying about being perceived as prey. Now, new research supports the long-standing theory that when great whites do go in for a bite, it’s a case of “mistaken identity.”

A team of biologists from the UK and Australia compared footage of seals swimming with videos of humans swimming  (with and without paddle surfboards). They then edited the clips to simulate a great white’s vision—the sharks are likely colorblind, and they can’t make out fine detail—and found that from the ocean inhabitant’s point of view, humans do indeed bear a strong resemblance to seals. The findings were published yesterday in the Journal of the Royal Society Interface.

“Great white sharks are often portrayed as ‘mindless killers’ and ‘fond of human flesh.’ However, this does not seem to be the case, we just look like their food,” Laura Ryan, a neurobiologist at Macquarie University in Australia and lead author of the study, told Live Science.

Despite their less-than-stellar vision and subpar spatial perception, great white sharks are highly visual creatures, and rely on motion and shadows when on the lookout for prey. To really see through the species’s eyes, the research team had to get creative. 

[Related: Shark Week may be hurting, not helping, its namesake creature]

“We attached a GoPro to an underwater scooter, and set it to travel at a typical cruising speed for predatory sharks,” Ryan said in a statement. The researchers then paired the recordings with computer models to simulate how similar people look from a shark’s distorted view below the surface. The results showed a striking closeness to seals and other pinnipeds, supporting the “mistaken identity” theory.

“I knew there would be some similarities, but maybe not to the extent we found,” Ryan told Live Science. “Specifically, I thought swimmers might not be as similar as a surfer to a seal as they typically aren’t involved in as many shark bites. However, the swimmers were also difficult to tell apart from a seal.”

Shark attacks may be frightening and dangerous, but they are quite rare. In 2020, there were 57 confirmed unprovoked cases worldwide, according to the University of Florida’s International Shark Attack File; of those, 10 were fatal. The 2015 to 2019 average was 80 incidents per year. 

“They eat seals everyday and bites on people are incredibly rare,” Catherine Macdonald, a marine scientist at the University of Miami not involved in the study, told the New York Times. “So if they’re not solving the problem visually, then how do we think they’re solving it?” To hit the right targets, shark could be relying on other senses, like scent. If that’s the case, additional studies on how great whites utilize those senses could help establish interventions to prevent further attacks.

As Ryan put it in a statement: “Understanding why shark bites occur can help us find ways to prevent them, while keeping both humans and sharks safer.”

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Now in its 33rd year, Shark Week is the longest-running cable event in history reaching 27 million viewers—a gigantic audience for marine biologists and conservationists. Discovery Channel claims the goal of Shark Week is to shed light on the latest scientific findings on these underwater predators and encourage conservation efforts of the often misunderstood creatures.

Shark conservation is crucial in today’s world. About 27 percent of cartilaginous fish, including sharks, are estimated or assessed to be threatened with extinction, says Lisa Whitenack, an associate professor of biology and geology at Allegheny College. 

But, according to researchers, the iconic week of television might be hurting those it claims to help. According to a talk given by Whitenack at the American Elasmobranch Society (AES), an organization dedicated to the research of sharks, skates, and rays, Shark Week fails to deliver on this goal. The analysis, which is currently under review at PLOS one, found Shark Week consistently portrays sharks negatively, airs falsehoods, and does not adequately represent shark scientists. 

As apex and mid-level predators, sharks play a critical role in underwater ecosystems. By gobbling up weak and sick fish, these herculean beasts ensure species diversity and healthy competition. In fact, the loss of sharks in particular habitats can lead to a decline in coral reefs and seagrass. Efforts to protect these agile marine residents are essential to protecting even the smallest living things in the ocean. 

The takeaways from hundreds of hours of of Shark Week 

To understand Shark Week required hours of binge-watching—around 201 episodes out of 273 aired over three decades of shark obsession“We watched a whole lot of TV, basically as many episodes as we could get our hands on,” says Whitenack, whose research usually centers on shark teeth and the evolution of these mighty swimmers. 

What the researchers found was that over 50 percent of the episodes contained negative images of sharks or negative statements about sharks, like calling them killers or describing them as hunting humans — which, by the way, sharks rarely do. Only about a dozen of more than 300 species of sharks have been reported attacking humans, and if they do, it’s probably a mistake: sharks prefer snacking on seals, sea lions, and other marine mammals. 

Shark bites were also the third most common episode topic, and almost 22 percent of episodes had damaging titles with words like attack, fear, deadly, and monster. And, only six episodes gave viewers action-based advice for supporting shark conservation, like donating to conservation efforts. 

[Related: Sharks have a sixth sense for navigating the seas.]

But, at the same time, over 50 percent of the episodes also mentioned, if only briefly, the importance of shark conservation and their role in the ecosystem. “It was a whole lot of negative with a quick positive statement or a quick pro-conservation statement at the end,” says Whitenack. 

The contradictory message could be confusing for viewers, especially when paired with gory, dramatic reenactments of shark attacks. 

“I can say, personally for me, there were a lot of painful moments of stuff that was over the top in reenactments,” says Whitenack. “I have an eight-year-old and an eleven-year-old. They love sharks just like their mom, and they really like watching some of these shows, but they did not like seeing the blood and I didn’t want them seeing all that gore either.”

Another cause of concern was about 22 percent of the 204 “experts” featured on the programming had no published research. In fact, the most prolific expert, having appeared on 43 episodes, had no scientific credentials. 

“Some of the people who are being presented as shark experts are either filmmakers or divers,” says Whitenack. “They are experts at underwater cinematography and experts at diving with sharks, but that is absolutely not the same thing as being an expert who knows about the biology of a shark and how they work.” Sometimes, the stories told weren’t even rooted in science at all— 16 percent of episodes contained no scientific research, and seven percent are purely based on myths and legends of sharks that never existed.

For example, Shark Week aired a fictional feature on Megalodon, the world’s biggest shark that went extinct about 2 to 3 million years ago during the Pliocene. There was a short disclaimer about the story’s basis in fiction, but the message didn’t stick with viewers, according to Whitenack. In fact, 73 percent of viewers in a poll conducted by Discovery after the show aired believed the Megalodon was swimming the deep seas. 

[Related: Sharks and rays are far less abundant in the world’s oceans than 50 years ago.]

The final problem Whitenack and her colleagues found was the lack of diversity amongst shark experts presented. Almost 79 percent used male pronouns and 93 percent were white or white-passing. This is especially problematic due to filming taking place in predominately non-white populations like Mexico, the Bahamas, and South Africa. Today 55 percent of AES members are female and 33 percent do not identify as white, according to Whitenack, so there’s no shortage of diverse shark experts. 

How can Shark Week improve? 

Despite these troublesome statistics, Shark Week still presents a unique opportunity to educate the general population about the importance of these sea-swimming predators. And while there were problems with plenty of episodes of Shark Week, Whitenack says she still found a couple of favorites in the show Alien Sharks that were “factual and true.”

“We’d like to see more fact-based and positive programming, and a lot less fear-based and contradictory programming, so that there is a clear, positive message about these sharks,” Whitenack says. “We’d also like them to add actual conservation content, so they aren’t just stating sharks are in trouble or they’re important for the ecosystem, but giving people ways they can help.” 

Some ways people can actually help sharks is by voting for politicians who support marine conservation efforts, signing conservation petitions, and donating money to conservation efforts, says Whitenack. And pushing out that information instead of fear and terror on one of TV’s most iconic weeks of programming can make it so these mesmerizing creatures can keep gracing our screens for years to come. 

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This story originally featured on Field & Stream.

This year is shaping up to be the season of the great white shark. After a brief stop in Delaware Bay, one tagged shark swam along the Jersey Shore, paused near Atlantic City, and then headed north. She didn’t stop for the gambling.

The shark has a name, Freya, and is being tracked by OCEARCH, a research agency, which focuses on providing scientists with difficult-to-attain data. According to their records, Freya is an 11.2-foot female and weighs an estimated 883 pounds. She was tagged in Onslow Bay, North Carolina, on March 25, 2021, and has consistently moved north along the coast.

Last week, a ping showed Freya moving into Delaware Bay, an area not recognized as a white shark hotspot. From there, she moved along the Jersey Shore, spent some time near Atlantic City, and then headed out to sea. Freya reappeared off the Hamptons, a summertime celebrity hot spot, and her latest ping was on June 21. Freya was on the Rhode Island/Massachusetts border and was headed for Cape Cod.

Track Freya as she plays an important role participating in this system: https://t.co/0AwJIuFQeM@ASAFishing @njdotcom @delawareonline @DelawarePublic @WITN22Wilm @AsburyParkPress @ThePressofAC @6abc @CBSPhilly

— OCEARCH (@OCEARCH) June 18, 2021

Many of those coastal areas are not known for their seal populations, so what is holding this shark’s attention? Schools of menhaden. Menhaden, a forage fish, are currently managed by Amendment 3 (2017) to the Interstate Fishery Management Plan (FMP), and according to the Atlantic States Marine Fisheries Commission, exist in healthy numbers. “The single-species assessment indicates the stock is not overfished nor experiencing overfishing.” Ample quantities of menhaden are good for the environment and are considered striped bass candy. But the forage fish are targeted by other predators. “Marine animals from sportfish to seabirds to whales, and even white sharks like Freya, all benefit from the conservation of these forage fish,” tweeted OCEARCH.

Finding a conservation balance is key, but what’s in the shark’s name? Freya comes from Norse mythology, and is associated with lust, beauty, gold, and death. It’s a fitting name for a great white shark off the Jersey Shore en route to Cape Cod, don’t you think?

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Ampullae of Lorenzini on a tiger shark

Swimming around in the dark haze of the open ocean, a tiger shark silently glides through the water. Suddenly, the tiny little pores speckling its nose and head tingle with the faintest disturbance in the water’s electrical field ahead of it—food! With a swipe of its tail and explosion of speed the tiger shark is soon rewarded with a fishy meal.

The little pores known as ampullae of Lorenzini (AoL) that dot the heads and noses of sharks, rays, and skates (collectively known as elasmobranchs) have long been known to be able to detect electrical currents in some fashion and aid in prey detection. But the mystery of exactly how they do so may now be solved.

Scientists studying these bizarre organs have discovered that a particular jelly tucked inside the pores is highly conductive to protons—an uncommon occurrence in nature—and it is so far the most highly proton-conductive biological material ever reported. Their findings are published today in Science Advances.

It is the most highly proton-conductive biological material ever reported.

Named after the 17th century Italian ichthyologist who described them, each ampulla organ is composed of an open pore that is attached to a little sac of electrosensitive cells. Connecting the pore to the cell bundle is a fleshy canal filled with the mysterious jelly that was the focus of this study. The jelly itself is viscous, clear, and largely full of water.

Although the purpose of the AoL has been known for some time, how the jelly fits into that hasn’t. So researchers from UC Santa Cruz, the University of Washington (UW), and the Benaroya Research Institute at Virginia Mason went to work to see if they could crack the case of this peculiar gel.

Hungry hungry sharks

After squeezing out gobs of jelly from pores on the noses and heads of a bonnethead shark (Sphyrna tiburo), a longnose skate (Raja rhina), and a big skate (Raja binoculata), they subjected the puzzling goo to a series of electrical tests.

The scientists found the jelly to be highly proton-conductive. In fact, it appears to have the highest proton conductivity ever found in a biological material, and it’s only slightly less conductive than the state-of-the-art synthetic conducting polymer we use in fuel cells. “The first time I measured the proton conductivity of the jelly, I was really surprised,” said electrical engineering doctoral student and first author Erik Josberger of UW in a statement.

Marco Rolandi, an associate professor of electrical engineering at UC Santa Cruz and corresponding author of the study, thinks that perhaps keratan sulfate, a carbohydrate found in high concentrations in the jelly, might contribute protons of its own to the water mixed in with the gel, thus making it more conductive. “It has an acid group that might donate protons,” he surmised.

In a separate statement, Rolandi summed up the findings by saying that “the observation of high proton conductivity in the jelly is very exciting,” and explained further that it could be useful in materials science, or for unconventional sensor technology.

As sharks prowl corals, shallow seas and the open ocean, the electrical disturbances in their watery surroundings are picked up by the jelly in the ampullae of Lorenzini and transferred to the electrosensitive cells at their base. All the pores covering their nose and heads form a network of jelly-filled canals that integrate multiple electrical signals at a time, allowing these master predators to detect changes in the electrical field of as small as 5 nanovolts per centimeter. “Ampullae of Lorenzini are quite exceptional electric field sensors,” says Rolandi. It’s just one more weapon in the evolutionary arsenal that has allowed these ancient predators to persist for hundreds of millennia.

Ampullae of Lorenzini help guide sharks, rays and skates to prey

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A fin cutting through the surface of the water, black eyes and white teeth gleaming beneath the surface, a sleek, smooth body gliding silently beneath the waves. It’s the stuff of beach-goers’ nightmares.

Every once in a while, a beach you want to swim at may be closed due to increased shark activity. But the truth is, encounters with these regal creatures of the deep are extremely rare—more so, in fact, than getting struck by lightning or succumbing to insect stings.

But if you spend a significant amount of time in shark territory (i.e. the ocean), it doesn’t hurt to be informed before you strap on your flippers. That way if you do spot one of the oversized fishes, you’ll know exactly what to do to limit the damage.

Shark encounters are rare

For starters, any type of shark encounter is rare, but fatal events especially so. Only about five people are killed by sharks worldwide every year, so there’s just a 1 in 3,700,000 chance you’ll be killed by a shark in your lifetime. That means you have a greater chance of dying due to a fall or rip currents than a shark bite.

[Related: How to avoid an alligator encounter]

“There’s a whole a list of things that are more likely to kill you than sharks,” says Kristine Stump, marine biologist and co-founder of Field Lab Consulting, which provides collaborative support services for marine research. “My favorite one is that you’re more likely to be bitten by a New Yorker than a shark.”

And Stump would know. She works day-in and -out researching, interacting with, and educating others about the creatures. And even she has only been bitten once—a minor nip when she was handling a small lemon shark years ago.

Even the risk of non-fatal bites is low: There were 57 unprovoked shark bites worldwide in 2020. The US saw the greatest number of those encounters (33) with Florida, not surprisingly due to its miles of beaches and busy migration routes, topping the list of states with reported incidents (16). The largest number of global encounters—again, not surprisingly—involved surfers (61 percent or about 34 people), followed by swimmers (26 percent or about 15 people), and finally snorkelers and scuba divers (only 4 percent or 2 people in each category).

As for which species should be treated with the most caution, great whites, striped tiger sharks, and bull sharks have logged the most unprovoked attacks on humans.

Why sharks strike

When sharks do end up biting someone, it’s not because they’re big, bad carnivores that want to snack on your flesh. “It’s mistaken identity. Absolutely no species of shark includes human in their diet,” Stump says. 

Simply put, sharks mistake people for other forms of prey like fish or seals. Most encounters involve bite-and-release situations, which occur because inquisitive sharks often perform a test chomp to see if an object is palatable. (They have a high concentration of nerve receptors in their teeth.)  If not, they spit it out and move on their way. They certainly don’t want to eat you, especially since most sharks aren’t much bigger than the average person. “Animals don’t usually attack things that are the same size as them from a self-preservation standpoint,” Stump explains.

In fact, sharks prefer to keep their distance. Many swimmers, surfers and beach goers don’t even realize when they’re in the area. Stump recalls aerial videos from last year showing kayakers paddling in the ocean alongside a handful of sharks; the people make it to shore without realizing that they were a few paddle lengths away from the animals. 

That’s because sharks are very perceptive. They have the same five senses as humans—up to two-thirds of the weight of their brains is dedicated to smell—plus two more: electroreception and pressure sensing. The first allows them to detect the muscle contractions of their prey and the Earth’s geomagnetic fields for navigation. The second allows them to sense pressure waves in the water when a potential meal is near.

In essence, “they know you’re there well before you do,” Stump says, and will more than likely stay away. If you do manage to actually see a shark, consider yourself lucky.

For starters, Stump suggests that you avoid swimming or diving near where people are fishing. Anglers use bait and chum, which draw large fish from the surrounding area. That, in turn, might bring in sharks that want to feed on those large fish. By the same logic, the presence of diving birds like gannets or pelicans can also indicate that sharks are nearby.

[Related: Could an ancient megashark still lurk in the deep seas?]

When swimming in open waters, always buddy up. Avoid taking dips at night, dawn, and dusk when many species are actively hunting, and avoid wearing jewelry when snorkeling, surfing, or engaging in other water sports as the reflective quality can resemble the shimmer of fish scales and other shark-prey attributes.

There’s a common rumor that period blood attracts sharks. No one has found data to support this, so don’t feel like you have to stay out of the water just because you’re wearing a tampon.

What to do during a shark encounter

In the mighty rare chance that a shark comes near enough to bite you, there are some expert-approved strategies to help you survive the ordeal. 

If a shark swims too close for comfort, kick at it or hit it in the face with a stick, swim shoe, or even your fist. That’s usually enough to send the shark fleeing in the opposite direction. Once it leaves, get out of the water as soon as possible—it will be less inclined to back off during a second or third attack. Swim slowly and calmly to shore or a nearby boat, keeping your eyes on the animal if it’s still hanging around.

If a shark is acting aggressively while you’re scuba diving (rushing at you, hunching its back, lowering its side fins, swimming in a fast zig zag or up and down motion), back up against something solid like a reef or boulder to decrease the number of angles from which the animal can get to you. If that’s not an option, swim slowly to the surface back-to-back with your dive partner until you reach the boat.

If a shark bites you—it will likely be on a limb—and doesn’t let go right away, fight back by hitting and clawing at sensitive areas like its eyes and gills. If you sustain any type of wound, Stump says to treat it like any other injury: Get out of the water, focus on first aid, stop the bleeding, and go to the hospital for more serious treatment.

The bottom line is, you can’t let a fear of sharks keep you from savoring your vacation on the ocean. Swim smartly, recreate responsibly, and remember that you’re more likely to get hurt by a hotel toilet than a shark.

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The Earth’s magnetic field covers the entire planet like an invisible three-dimensional film. This all-encompassing force doesn’t drive human behavior (at least, as far as we know), but it’s an important factor in some animals’ ability to navigate—and that group has just expanded to include sharks, according to a new study in the journal Current Biology. The new research suggests that bonnethead sharks, just like certain species of migratory birds, sea turtles, eels, and others, use the Earth’s magnetic field to help them find their way. 

“We know that sharks, rays, and skates”—a group of fish known as ‘elasmobranchs’—“are sensitive to the electromagnetic field,” says lead author Bryan Keller, a PhD student in oceanography at Florida State University. But researchers hadn’t yet managed to demonstrate whether  they use that sensory ability for navigational purposes. 

“What we were specifically interested in testing, was if that ability allows them to infer map-like information from the Earth’s magnetic field,” says Keller.  

The team of researchers, funded in part by the Save Our Seas Foundation, a nonprofit that supports marine conservation research, looked at bonnethead sharks, a relatively small (and therefore lab-friendly) coastal species that had been shown to travel back to specific locations on a seasonal basis. The researchers captured 20 young bonnetheads in the Gulf of Mexico off the coast of Florida and brought them back to a lab, where they were placed in a tank inside a magnetic coil system that exposed the sharks to magnetic fields that resembled different geographic locations. They used software to track the sharks’ responses, observing which direction in the tank they were trying to swim towards. 

[Read more: Baby mantis shrimp punch their prey with superior strength]

“The main test we were interested in is exposing the shark to a magnetic field that represents the location far south of their preferred habitats where they spend their summers, up in the northern Gulf,” says Keller. For this test, they oriented the sharks about 600 kilometers (373 miles) south of where they were captured. Instead of swimming randomly or in circles around the edge of the tank, as they did in a control test that mimicked the magnetic field where they were captured, in this case the sharks swam in a kind of half-moon formation, moving leftwards and then rightwards in an apparent attempt to push north. 

In a test that looked at the opposite—whether they would try to move south if placed farther north than expected—the sharks did not demonstrate such a trend. The authors speculate that this could be because the sharks had no experience with this more northern magnetic field, suggesting that their “magnetic map” was something they learned to access through experience, rather than an innate ability they were born with. “But really, in order for us to make that claim, we need to do some more research,” says Keller. 

This study is “a big step forward in our general understanding of the navigation capabilities of these animals,” says Yannis Papastamatiou, an assistant professor of biology at Florida International University who was not involved in the research. “It’s not an experiment in the field,” he says, “but it’s still pretty convincing evidence.” Papastamatiou notes that researchers have used similar experimental techniques to show that turtles can navigate using magnetic fields.

The evidence here would have been even stronger if a second change resulted in a different direction, wrote Catherine Lohmann, a biologist at the University of North Carolina at Chapel Hill, in an email to Popular Science. “I would have liked to see the responses to a western location, for example.” 

The magnetic field might be especially useful for marine animals because they don’t have as much access to landmarks, stars or other guides, wrote Lohmann, who was not involved in the research. Overall, the research “adds to the larger idea that magnetic maps may actually be common in marine migrants.” 

And if they’re widespread in the sea, she suggested, “then they also may be widespread among animals in other kinds of habitats.”

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↑ Melissa Márquez, shark biologist and founder of the Fins United Initiative

As a shark biologist, I know study­ing big predators has risks. Earlier this year, I went to Cuba to film a segment about hammerheads for Discovery Channel’s Shark Week. I was kneeling on the sea­floor when I felt a hard, intense pres­sure on my lower left leg. Then some­thing started slowly dragging me backward. But it wasn’t a shark.

We had seen a crocodile earlier on that dive, and I quickly realized one of them had me. I kept telling myself not to panic: I had a scuba tank of oxygen and wasn’t yet in pain. Thanks to my experience with sharks, I suspected the reptile wasn’t trying to eat me—both animals use exploratory chomps to figure out what something is. Still, saltwater crocs have one of the most powerful bites in the world; if I moved my leg, it could clamp down harder, breaking my bones or puncturing an artery. I tried to hold on to something, but we were in a sandy area with nothing, not even a rock, for me to grab.

After pulling me for maybe five or 10 seconds—which felt much longer—the animal realized I wasn’t its usual prey (my neoprene suit probably helped) and released me. I survived with the limb intact, and only ugly purple scars to show for my close encounter.

As told to Lexi Krupp

This article was originally published in the Winter 2018 Danger issue of Popular Science.

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CNN: It is an odd sensation. Lowering yourself into water teeming with great white sharks. There is a cage between you and the sharks, but its open on the top, and when the first shark emerges from the shadows, moving full speed toward you, its giant mouth open, revealing rows of razor sharp teeth, the cage is little comfort.

I spent a week last August off the coast of Cape Town, South Africa for Planet in Peril: Battle Lines. The second installment of our documentary series. Sharks are hated creatures, and because of that there is little outcry at their destruction. Each year, as many as a hundred million sharks are killed, many slaughtered for their fins which are used to make shark fin soup, a delicacy in Asia.

Great white sharks however are a top predator in the sea, and if they disappear, the entire underwater ecosystem will be affected.

What’s really interesting is that scientists don’t know much about great white sharks. They’ve never been seen mating, or giving birth. We get glimpses of great whites, but they are difficult to track, and even harder to observe underwater. That’s why we went to the frigid waters off Cape Town. Each year, around this time, great whites gather, eating seals which are plentiful in South Africa’s water.

We wanted to get as close as possible to the great whites, and we teamed up with a shark expert named Mike Rutzen. He runs a cage diving operation for tourists, and is one of the few people in the world who actually free dives with the great whites — without a protective cage. He argues that only by free diving can you really see that great whites are not the man-eating killers they are made out to be in movies. They are dangerous, no doubt about it, but Rutzen believes there is much we can learn about the sharks by observing them up close.

I’ve always been very fearful of sharks, but I must admit, after diving multiple times with them last week, I have a much greater understanding of them, and appreciation for their role in the sea. They are magnificent animals. I’m not saying they still don’t make my heart race faster when I see them, but I no longer think they are simple man-eaters, out to get bathers and surfers.

The chances of getting attacked by a shark are extremely small. More people are hurt by dogs each year, and car accidents, and lightning. I kept reminding myself of that when I was underwater with them last week. I clung on to that, almost as tightly as to the bars of the cage I was diving in.

CNN’s Planet in Peril debuts tonight.

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Over the past half-century, oceanic sharks and rays have diminished around the globe, an international team of scientists reported on January 27 in the journal Nature. The researchers analyzed records dating back to the 1970s to track 18 species that dwell on the high seas, and found that their populations had dropped by 71.1 percent overall. Additionally, the team analyzed the IUCN Red List of Threatened Species’ extinction risk assessments (which evaluates the risk of extinction for different species) for 31 oceanic sharks and rays and found that about 77 percent of those 31 species are now threatened with extinction.

“What we observed was that the global abundance of sharks and rays has declined by nearly three quarters over the last 50 years and it’s primarily due to overfishing,” says Nathan Pacoureau, a marine biologist at Simon Fraser University in Burnaby, British Columbia and coauthor of the new findings. “The opportunity for saving these iconic creatures is rapidly closing.”

In some cases, sharks and rays are caught for their meat or liver oil. In other instances, though, they are accidentally snared along with commercially valuable species like tuna and swordfish. These animals’ populations are particularly vulnerable to overfishing because they cannot quickly repopulate. “Oceanic sharks have a very slow pace of life, so they take generally a decade, or even several, before they can mature,” Pacoureau says.

Researchers have been observing serious declines in oceanic and coastal shark populations around the Atlantic Ocean and in the waters off of South Africa and Australia for decades. To investigate how sharks have been doing around the globe, Pacoureau and his colleagues pored over scientific papers, government reports, and other records and examined how the populations of different shark and ray species have changed over time.

They found that every species had decreased in abundance since 1970, with the exception of the smooth hammerhead shark. In the Indian Ocean in particular, shark and ray populations had dropped by 84.7 percent over the past 50 years. After an initial steep drop, sharks in the Pacific Ocean have declined at a slower rate since 1990. Meanwhile, shark populations eventually began to stabilize in the Atlantic Ocean after 2000. A few species have even begun to rebuild their numbers since the turn of the century, including the great white and porbeagle sharks.

When the researchers consulted the listings from the International Union for Conservation of Nature’s Red List of Threatened Species for 31 species, they found that the risk of extinction has increased since 1980—a time when only nine species were considered under threat. Now, 24 species are threatened with extinction. Three have become critically endangered, including the oceanic whitetip, scalloped hammerhead, and great hammerhead sharks. An additional four species are categorized as endangered.

For all 31 species, the Red List indicated that overfishing was the biggest threat (although several species face additional risks such as ship strikes). Since 1970, catch rates have tripled for sharks and rays. Additionally, more sharks and rays are kept after being captured to meet the growing demand for their fins. Pacoureau and his team estimate that, since 1970, sharks and rays have faced an 18-fold increase in relative fishing pressure, which measures changes in catch rates relative to the number of fish remaining.

It’s likely that shark and ray populations have been waning even before the period the researchers tracked. “Our analysis starts in the ’70s, but we know that fishing fleets have been expanding globally since even before the ’50s,” Pacoureau says.

Sharks and rays play an important role as predators in marine ecosystems, as well as being a vital source of sustenance for many people. The overexploitation of these species “risks the food security for some of the world’s poorest countries…and can also squander ecotourism opportunities,” Pacoureau says. However, relatively few countries impose catch limits on oceanic sharks, he and his colleagues note in the study.

“Over the last few decades, we have seen a steady positive shift in the public’s perception of sharks. That concern has helped drive significant conservation policy advances, particularly through global wildlife treaties,” Sonja Fordham, president of the nonprofit Shark Advocates International and another coauthor of the research, said in an email. “In most countries, however, concrete restrictions on the main threat—fishing—have not kept pace.”

To protect sharks, the researchers concluded, it’s important to enact rules such as catch limits and minimize accidental captures and deaths with steps such as avoiding known shark hotspots. The good news is that these actions have already begun to replenish some shark populations. In the waters off the Atlantic and Pacific coasts of the United States, fishermen have been prohibited from keeping great white sharks since the 1990s. Meanwhile, catch limits have been placed on hammerhead sharks.

“It’s important to note that these measures have not been perfectly implemented nor have they eliminated all incidental mortality, and yet we’re seeing the tide turning,” Fordham said. “The key point is to start with a concrete fishing limit based on scientific advice and the precautionary approach and build on it over time.”

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A massive survey of hundreds of coral reefs along the coasts of nearly 60 nations found that overfishing has significantly diminished the numbers of sharks that live within these tropical habitats. Scientists did not see any sharks on nearly 20 percent of the reefs they examined, and saw only half as many sharks as they predicted in 35 nations.

However, the biologists found that sharks were thriving in a few countries. Those nations used sanctuaries and other conservation strategies, which the researchers think may be playing a significant role in restoring shark populations elsewhere that have taken a hit, the researchers reported on July 22 in the journal Nature.

“There are certain places where the shark population seems to be in reasonably good shape but…that’s probably not an accident,” says Michael Berumen, a professor of marine science at the King Abdullah University of Science and Technology in Saudi Arabia and coauthor of the new findings. “Almost all of them are places that have made the investment—the time and energy and resources—to have effective protections in those coral reef systems.”

Marine biologists have long known that in the open seas, decades of overfishing have devastated shark populations in many regions. Shark populations in coastal areas are less well understood, however.

“We really didn’t know a lot about how they were doing at a global scale,” says Mike Heithaus, a marine ecologist and dean of the college of arts, sciences, and education at Florida International University in Miami. To find out, Heithaus, Berumen, and their colleagues—a team of more than 100 scientists from around the world—placed cameras baited with ground-up fish in 371 coral reefs from 58 nations between 2015 and 2018.

The researchers, along with hundreds of volunteers, then combed through more than 15,000 hours of video footage. They counted very few sharks from reefs in a number of nations, including the Dominican Republic, Qatar, and Vietnam. On the other hand, sharks were generally plentiful in Australia, the Bahamas, French Polynesia, and several other countries.

Countries where sharks were abundant tended to employ a number of tactics like creating shark sanctuaries, areas where commercial shark fishing and trade in shark products is banned, setting limits on the number of sharks that can be caught, or restricting the use of gillnets and longlines. “They catch fairly indiscriminately,” Heithaus says. “Getting rid of those [fishing] gears is one of the biggest things that can be done to help rebuild coastal shark populations.”

Key to protecting sharks is figuring out which approach will work best in a particular region. In French Polynesia, where shark fishing has never been a huge part of the economy, the establishment of a sanctuary has led to an “incredible” abundance of sharks, Heithaus says.

In other places, people rely on shark fishing for their livelihood. Banning particularly destructive tools like gillnets may make more sense in these regions. Transitioning from fishing to ecotourism may also be effective in areas with particularly clear water. “You have to make sure that the benefits go to the people who would be losing out from not fishing anymore,” Heithaus says.

In Saudi Arabia, longlines aren’t often used to catch sharks so banning them would not have a very large impact, Berumen says. Establishing catch limits or a shark sanctuary in the Red Sea may be more effective.

Overall, the researchers observed 59 shark species in reefs around the world, from nurse sharks in Florida to grey reef and lemon sharks in French Polynesia. The roles that sharks play in these ecosystems are still somewhat mysterious. One possibility, though, is that sharks keep smaller predators in check that would otherwise gobble up fish further down the food chain that graze on algae.

Without these herbivorous fish, algae may be able to run rampant, especially after hurricanes, bleaching events, or other disturbances destroy coral populations. “When corals die the first thing that starts to take over the empty space left over by the corals are algae, and that algae can grow fast and they can prevent new corals from becoming established,” Berumen says. “If you don’t have sharks, the rest of the reef population might at first look to be okay, but if a disturbance comes that reef ecosystem may be poorly prepared to bounce back.”

Coral reefs help buffer coastlines from storms, shelter fish and other animals that people depend on for sustenance and income from fishing or tourism. “When you are talking about the immense value of coral reefs that are already under stress from changing temperatures, ocean acidification, and other human effects, you don’t want to be picking out other pieces that could be important to the health of the ecosystem,” Heithaus says.

However, he and his team are optimistic that shark populations can be rebuilt on many reefs where they are currently struggling.

“These [conservation] methods are not groundbreaking, earth-shattering new ideas,” Berumen says. “They’re pretty straightforward management methods that probably just need to be implemented in more places.”

At the same time, he warns, we cannot become complacent in areas where sharks appear to be plentiful.

“Just because a place has a good number of sharks right now, it doesn’t mean that we don’t have to worry about those places; it doesn’t mean that we can stop the actions that have maintained those populations,” he says.

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Hannah Verkamp is a PhD student in marine biology at Arizona State University. This story originally featured on The Conversation.

If you have a toddler, or if you encountered one in the last year, you’ve almost certainly experienced the “Baby Shark” song. Somehow, every kid seems to know this song, but scientists actually know very little about where and when sharks give birth. The origins of these famous baby sharks are still largely a mystery.

Many of the large iconic shark species—like great whites, hammerheads, blue sharks and tiger sharks—cross hundreds or thousands of miles of ocean every year. Because they’re so wide-ranging, much of sharks’ lives, including their reproductive habits, remains a secret. Scientists have struggled to figure out precisely where and how often sharks mate, the length of their gestation, and many aspects of the birthing process.

I am a Ph.D. student studying shark ecology and reproduction and am on a team of researchers hoping to answer two important questions: Where and when do sharks give birth?

In need of innovation

Until very recently, the technology to answer these questions did not exist. But marine biologist James Sulikowski, a professor at Arizona State University and my research mentor, changed that. He developed a new satellite tag called the Birth-Tag with the help of the technology company Lotek Wireless. He has no stake in the company. Using this new satellite tag, our team is working to uncover where and when tiger sharks give birth and is demonstrating a proof of concept for how scientists can do the same for other large shark species.

The Birth-Tag is a small, egg-shaped device that we insert into the uterus of a pregnant shark where it will remain dormant and hidden among the fetal sharks throughout pregnancy. This kind of tag has never before been used on sharks, but similar implanted tags have been used to figure out the birthing locations of terrestrial mammals, such as deer, for decades with great success. When a tagged mother shark gives birth, the tag will be expelled alongside the babies and float to the sea surface. Once it senses dry air, the tag transmits its location to a passing satellite, which then sends that location and time of transmission back to our lab. As soon as we download this information, we know where and when that shark gave birth.

After years of fine-tuning this new technology, we launched the first phase of the study in December of 2019 and began deploying the tags. Once the study was approved by the Institutional Animal Care and Use Committees at both Arizona State University and the University of Miami, as well as the Bahamian government, we set out to find some tiger sharks. To do this, our team of researchers from the Sulikowski Shark and Fish Conservation Lab and the Shark Research and Conservation Program at the University of Miami led by marine biologist Neil Hammerschlag, traveled to the crystal-clear waters of Tiger Beach off Grand Bahama Island to tag tiger sharks.

Up close with an apex predator

Tiger Beach is a hot spot for female sharks of many different life stages, including large pregnant individuals. These pregnant females may be aggregating in the warm, calm waters of Tiger Beach to take refuge and speed up their gestation.

The high number of pregnant sharks in this small area makes finding one much easier, but actually catching and bringing a 10-foot-plus shark to the boat is no easy task. We fish for the sharks using drumlines, and it can take several hours to safely catch, pull in by hand, and secure one of these powerful creatures next to the boat.

Once we catch a female tiger shark, we first take several length and girth measurements to get an idea of her general health and to see if she is sexually mature. Then we check for bite marks, which are evidence of a recent mating event.

After we collect this baseline information, we rotate her upside down to coax her into a trance-like state called tonic immobility. This is a natural reflex in many sharks that induces a state of physical inactivity. This keeps the powerful shark calm and still for the most exciting part of the workup, the part where my experience comes into play: the pregnancy check.

Someone’s expecting

Just like the ultrasounds used on humans, we use a mobile ultrasound machine to figure out if a shark is expecting. I put on a pair of goggles that allow me to see everything the ultrasound sees, lean over the side of the boat, and place the probe onto the upside down shark’s abdomen. The image is usually fuzzy at first as water splashes over the shark and up onto the boat. The team holds the shark still as I slowly maneuver the probe along her belly. Then, if she’s pregnant, something magical happens.

Wriggling baby tiger sharks, up to 40 of them packed tightly together inside their mother’s womb, appear in front of my eyes. The image also appears on a screen held by another team member on the boat, and everyone cheers as they gather around to take a peek into the secret world of unborn sharks. We spy on them as they pump fluid through their still-developing gills, and we watch in awe as they wiggle around, blissfully unaware that anything extraordinary is happening outside in the world. Once we have enough data on the approximate size of the offspring—which gives us an idea of how far along the pregnancy is—it’s time to tag the mama shark.

As I hold the probe as still as possible to keep a visual of the shark’s internal anatomy, Dr. Sulikowski takes the Birth-Tag and uses a custom-designed applicator to carefully insert it into the uterus through the urogenital opening. No surgery required, the tagging procedure is complete in a matter of minutes. Once the tag is inside the uterus, we rotate the shark upright to wake her and release her back to the open ocean. I am filled with hope as I watch her swim gracefully away to continue her pregnancy, with a stow-away Birth-Tag hidden among her unborn offspring.

Solving the mystery

Last December, we deployed the first Birth-Tags on three pregnant tiger sharks. For tiger sharks, pregnancy is thought to last 12 to 16 months, but researchers have little in the way of hard data. Since these tagged sharks ranged from recently mated to mid-gestation, an added bonus of this study is that it might help refine estimates of the length of pregnancy for this species.

Although we work in The Bahamas, a shark sanctuary where it is illegal to kill sharks, tiger sharks migrate extensively. As such, each tagged shark will likely spend time outside of The Bahamas in unprotected waters where she will have to navigate carefully to avoid interaction with fishing gear. Tiger sharks are considered near threatened by the International Union for Conservation of Nature, and their populations are currently in decline. The data we gain from this first round of tags will give us and policymakers information that could guide future protections for this species.

We’re currently waiting to receive a notification from our online ARGOS satellite system that will alert us that one of our sharks has given birth. When that happens, we will be the first in the world to know, in close to real time, where and when tiger sharks give birth.

Many species of shark are threatened with extinction, and understanding their reproductive cycles is key to the effective conservation of these ecologically important and beautiful creatures. Using the Birth-Tag, we’re at the cusp of unlocking this information about tiger sharks and will hopefully show that this can be done for many more species.

We’re planning future expeditions to deploy many more Birth-Tags, but for now, we’ll just have to keep singing the “Baby Shark” song as we patiently wait for our first glimpse into the private lives of these incredible creatures.

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In the waters surrounding Australia, Indonesia, and Papua New Guinea, there lives a very unusual kind of shark. Known as walking sharks, the nine species of the genus Hemiscyllium have the ability to crawl across the seafloor.

“They’ll stand up on their very muscular pectoral fins and they’ll kind of wiggle along and walk instead of swimming,” says Shannon Corrigan, an evolutionary biologist at the Florida Museum of Natural History in Gainesville.

Walking sharks can even tolerate short stints in open air as they scramble between tidal pools in their shallow coral reef habitats during low tide. But they’re also noteworthy for another reason: Walking sharks are one of the newest groups of sharks on the planet, appearing on the animals’ evolutionary tree around 44 million years ago, Corrigan and her colleagues reported January 21 in the journal Marine and Freshwater Research. And they suspect that the group may not be done splintering into new species yet.

The researchers looked at when and how the animals evolved into their own species. They found that their ancestors might have colonized different locations by hitchhiking on roving islands. The team hopes that studying these mysterious little sharks can give conservationists information about how best to protect them and perhaps even lead to broader insights about shark evolution in general.

Corrigan is among a group of collaborators who have spent the past 11 years studying walking sharks, work that has included the discovery of four of the group’s nine species. The first ever species of walking shark was described in 1788 and the most recent in 2013. Some walking sharks range across wide swaths of Australia’s northern coast, while others are confined to very small areas. Their territories don’t overlap, but seem to form a rough ring around northern Australia, the island of New Guinea, and several satellite islands.

The researchers suspected that the walking sharks might have split into different species around this ring. But when they began investigating how these sharks evolved over time, they realized that the shark’s history is probably a lot more complicated. “We found this really weird pattern of relationships between the species,” Corrigan says.

The researchers examined genetic material from tissue samples taken from both live walking sharks as well as museum specimens. From there, they constructed an evolutionary tree for the entire group. In several cases, one kind of walking shark was found far from its next closest relative. Walking sharks aren’t very strong swimmers and cannot cross areas of deep water, so they probably didn’t travel so far on foot (or rather, on fin).

Instead, the explanation for the sharks’ scrambled distribution might align with the geologic history of their home region.

“It’s been extremely geologically complex over relatively recent times, so you have a lot of different plates moving together and colliding, and that’s…constantly creating new habitats for marine species,” Corrigan says. “A lot of that ties in pretty nicely with the patterns we were seeing.”

She and her team think that small groups of walking sharks hitched on small island fragments. As these islands were moved about by plate tectonics, the sharks were carried to a new territory far from their fellows. Eventually, barriers the sharks could travel over, such as channels of deep water, formed between the groups. Over time, the two separated groups of sharks would have evolved into different species.

The easiest way to tell the different kinds of walking sharks apart is by their striking color patterns; the team has noticed variations in these patterns even within the range of a single species. It’s possible that new species are soon to emerge, or already have emerged but haven’t been recognized yet.

“It really is this nice natural experiment of how sharks evolve,” Corrigan says. “We can go sample and study it in the present day because it’s still happening, we think.” This makes walking sharks ideal for studying more ancient events that might have caused other shark species to evolve as well.

Today, the parts of northern Australia, Papua New Guinea, and eastern Indonesia where the sharks live are hotspots for biodiversity, particularly among fishes. But they are also currently facing habitat destruction, pollution, and overfishing. The fact that most walking shark species are restricted to very small areas makes them particularly vulnerable to these threats. However, because so little is known about walking sharks, scientists aren’t sure yet whether they are in danger.

Corrigan and her collaborators are now working to understand in more detail where exactly each of these sharks is found, how tied they are to particular regions, and what threats they face. Hopefully, this will give scientists the information they need to come up with strategies to protect each of these species.

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Sharks elicit outsized fear, even though the risk of a shark bite is infinitesimally small. As a marine biologist and director of the Florida Program for Shark Research, I oversee the International Shark Attack File—a global record of reported shark bites that has been maintained continuously since 1958.

We are careful to emphasize how rare shark bites are: You are 30 times more likely to be struck by lightning than be bitten by a shark. You are more likely to die while taking a selfie, or be bitten by a New Yorker. In anticipation of the anxiety that’s typically generated by the Discovery Channel’s Shark Week programming, here are a few things about sharks that are often overlooked.

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Dr. Greg Skomal, of @massmarinefisheries, working with the Atlantic White Shark Conservancy, tagged 4 sharks today off Wellfleet and Truro, bringing the total tagged this season to 12.

A post shared by Atlantic White Shark Cons. (@a_whiteshark) on Jul 16, 2019 at 2:05pm PDT

A big, diverse family

Not all sharks are the same. Only a dozen or so of the roughly 520 shark species pose any risk to people. Even the three species that account for almost all shark bite fatalities—the white shark (Carcharodon carcharias), tiger shark (Galeocerdo cuvier), and bull shark (Carcharhinus leucas)—are behaviorally and evolutionarily very different from one another.

The tiger shark and bull shark are genetically as different from each other as a dog is from a rabbit. And both of these species are about as different from a white shark as a dog is from a kangaroo. The evolutionary lineages leading to the two groups split 170 million years ago, during the age of dinosaurs and before the origin of birds, and 110 million years before the origin of primates.

Yet many people assume all sharks are alike and equally likely to bite humans. Consider the term “shark attack,” which is scientifically equivalent to “mammal attack.” Nobody would equate dog bites with hamster bites, but this is exactly what we do when it comes to sharks.

So, when a reporter calls me about a fatality caused by a white shark off Cape Cod and asks my advice for beachgoers in North Carolina, it’s essentially like asking, “A man was killed by a dog on Cape Cod. What precautions should people take when dealing with kangaroos in North Carolina?”

Know your species

Understanding local species’ behavior and life habits is one of the best ways to stay safe. For example, almost all shark bites that occur off Cape Cod are by white sharks, which are a large, primarily cold-water species that spend most of their time in isolation feeding on fishes. But they also aggregate near seal colonies that provide a reliable food source at certain times of the year.

Shark bites in the Carolinas are by warm-water species like bull sharks, tiger sharks, and blacktips (Carcharhinus limbatus). Each species is associated with particular habitats and dietary preferences.

Blacktips, which we suspect are responsible for most relatively minor bites on humans in the southeastern United States, feed on schooling bait fishes like menhaden. In contrast, bull sharks are equally at home in fresh water and salt water, and are often found near estuaries. Their bites are more severe than those of blacktips, as they are larger, more powerful, bolder, and more tenacious. Several fatalities have been ascribed to bull sharks.

Tiger sharks are also large, and are responsible for a significant fraction of fatalities, particularly off the coast of volcanic islands like Hawaii and Reunion. They are tropical animals that often venture into shallow water frequented by swimmers and surfers.

Humans are not targets

Sharks do not “hunt” humans. Data from the International Shark Attack File compiled over the past 60 years show a tight association between shark bites and the number of people in the water. In other words, shark bites are a simple function of the probability of encountering a shark.

This underscores the fact that shark bites are almost always cases of mistaken identity. If sharks actively hunted people, there would be many more bites, since humans make very easy targets when they swim in sharks’ natural habitats.

Local conditions can also affect the risk of an attack. Encounters are more likely when sharks venture closer to shore, into areas where people are swimming. They may do this because they are following bait fishes or seals upon which they prey.

This means we can use environmental variables such as temperature, tide, or weather conditions to better predict movement of bait fish toward the shoreline, which in turn will predict the presence of sharks. Over the next few years, the Florida Program for Shark Research will work with colleagues at other universities to monitor onshore and offshore movements of tagged sharks and their association with environmental variables so that we can improve our understanding of what conditions bring sharks close to shore.

More to know

There still is much to learn about sharks, especially the 500 or so species that have never been implicated in a bite on humans. One example is the tiny deep sea pocket shark, which has a strange pouch behind its pectoral fins.

Only two specimens of this type of shark have ever been caught—one off the coast of Chile 30 years ago, and another more recently in the Gulf of Mexico. We’re not sure about the function of the pouch, but suspect it stores luminous fluid that is released to distract would-be predators—much as its close relative, the tail light shark, releases luminous fluid from a gland on its underside near its vent.

Sharks range in form from the bizarre goblin shark (Mitsukurina owstoni), most commonly encountered in Japan, to the gentle filter-feeding whale shark (Rhincodon typus). Although whale sharks are the largest fishes in the world, we have yet to locate their nursery grounds, which are likely teeming with thousands of foot-long pups. Some deepwater sharks are primarily known from submersibles, such as the giant sixgill shark, which feeds mainly on carrion but probably also preys on other animals in the deep sea.

Sharks seem familiar to almost all of us, but we know precious little about them. Our current understanding of their biology barely scratches the surface. The little we do know suggests they are profoundly different from other vertebrate animals. They’ve had 400 million years of independent evolution to adapt to their environments, and it’s reasonable to expect they may be hiding more than a few tricks up their gills.

Gavin Naylor is Director of the Florida Program for Shark Research, University of Florida. This article was originally featured on The Conversation.

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What’s the weirdest thing you learned this week? Well, whatever it is, we promise you’ll have an even weirder answer if you listen to PopSci’s hit podcast. The Weirdest Thing I Learned This Week hits Apple, Anchor, and everywhere else you listen to podcasts every Wednesday morning. It’s your new favorite source for the strangest science-adjacent facts, figures, and Wikipedia spirals the editors of Popular Science can muster. If you like the stories in this post, we guarantee you’ll love the show.

This week’s episode is a recording of our latest live event at Caveat in New York City. Don’t worry, we’ll have another one soon. We can’t share all of our silly powerpoint visual aids in this article, but you’ll find the rules to the referenced drinking game at the bottom of this post! Enjoy the show:

Fact: Naked mole rats will inherit the earth

By Rachel Feltman

Summarizing my live fact is simple, because it was based on an existing PopSci article. Check out some breathtaking facts about an animal you likely don’t give nearly enough credit. Spoiler alert: naked mole rat queens use their poop to keep underlings from getting pregnant. How? You’ll have to listen to learn!

Fact: Prior to the Industrial Revolution, humans had two sleeps a night

By Claire Maldarelli

For the past few months, I’ve been waking up at nearly the exact same time every night: 2 a.m. Conversing with friends, I learned that plenty of people have experienced this same issue. But when I turned to the medical literature, I found something even more bizarre: Apparently, prior to the 18th Century, us humans used to split our night’s rest into two phases. One started shortly after dusk and ended at midnight, and we followed it with another that began at 2 a.m. and ended just after daybreak.

If you are following the timing, that left about two hours free in the middle of the night. By analyzing books, medical and court documents, and other texts from the time, historians have surmised that people indeed slept in two phases, and spent the middle bit of the night essentially having a blast. They socialized, read, drank, and some even worked. At least some scholars said it was the ideal time to have sex if you wanted to conceive. It seemed like a great time to be alive—and awake.

This bi-phasal sleeping pattern wasn’t reserved for the rich, and it wasn’t just something that people did during a time of leisure. It was the norm. Listen to the rest of this week’s episode to understand more about first sleep and second sleep, why it quickly ceased, and why, maybe, this sleeping system should be making a comeback.

Fact: Baby sharks chow down on the same birds that live in your backyard

By special guest Ryan F. Mandelbaum

Baby sharks don’t just blow up the internet with viral earworms. They also eat. And according to a recent study involving lots of baby shark puke, juveniles in the Gulf often eat birds. Not birds that are known for spending time around water, like ducks or pelicans—but the same kinds of birds that live in your backyard. Find out more on this week’s episode of Weirdest Thing, and check out my article about the study over at Gizmodo.

Drinking game rules

Take a drink of your fabulous and refreshing beverage of choice whenever:

• Someone makes a pun (two drinks if it gets a groan!)

• Rachel makes a joke about the fact that we obviously planned the live show in advance even though the podcast is totally spontaneous we swear

• Unexpected butts

• Someone in the audience is audibly appalled (or just appallingly audible)

• A cast member says the word “Weird”

• Ryan finds an excuse to bring up birds

• Body horror or otherwise excessive mention of viscera

• If we try to declare a tie you have to finish your drink, so you’d better cheer loud for your fave

If you like The Weirdest Thing I Learned This Week, please subscribe, rate, and review us on Apple Podcasts (yes, even if you don’t listen to us on Apple—it really does help other weirdos find the show, because of algorithms and stuff). You can also join in the weirdness in our Facebook group and bedeck yourself in weirdo merchandise from our Threadless shop.

The post The weirdest things we learned this week: Two sleeps are better than one appeared first on Popular Science.

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If you’re even a little bit on the internet—or have a child who is—you’re bound to have heard the song. Baby shark, do-do-do-do-do-do-… And now it’s stuck in your head again. You’re welcome.

But Marcus Drymon doesn’t know it, because he’s too busy studying the real thing as a fisheries ecologist at Mississippi State University. He’s always going out on the Gulf, surveying the waters, pulling up baby sharks, taking a gander at their emptied stomach contents, sending that barf up to Chicago for DNA sequencing… you know, the usual.

At least, that’s what he did for his most recently published study, which appeared Tuesday in the journal Ecology. By analyzing baby tiger shark barf with the help of a bird ecologist at the Illinois Natural History Survey and a molecular ecologist at the Field Museum, Drymon found the little guys weren’t just dining on fish and crustaceans. They also eat birds. And not just gulls and other seafaring avians, either. They consistently ate common backyard birds like sparrows, doves, and woodpeckers.

Drymon fist had an inkling this might be going on while conducting a routine survey. He and his colleagues frequently use a mile-long, heavy-duty fishing line to sample the Gulf of Mexico and get an idea of what’s living in it, around 100 times a year. One day back in 2010, Drymon wrestled a baby tiger shark on board, which isn’t a terribly uncommon occurrence. But he was flabbergasted when it barfed up a few feathers onto the deck. “It was so wild, very unexpected,” he says.

Eager to learn more, Drymon brought the feathers back to his lab. He patted them dry and paraded them around to some colleagues in ornithology, but no one could identify them with certainty (understandable, given that they were partially digested). “Ultimately, I turned to a good friend of mine, a molecular ecologist at the Field,” says Drymon, speaking of his co-author Kevin Feldheim. “I called him up and said ‘Hey Kevin, man, this is the wildest thing! Could you use your molecular techniques to figure out what kind of bird this is?’ And of course he did.”

Feldheim used a technique called DNA barcoding to figure out what kind of bird the shark had eaten. After isolating genetic material from the sample Drymon sent him, Feldheim could then look for well-known sequences in the DNA that were unique to a certain species. It’s important to note the technique isn’t perfect. Since it requires quite a bit of precision, either a processing mistake on the scientist’s side or slight variation in a single organism’s DNA could cause an incorrect reading. Broadly, it’s kind of like when your cashier scans a cucumber at the grocery store, but a smudge on the label means it comes up on the register as a sweet potato.

In this case though, Paul Hebert, a molecular biologist at the University of Guelph who played a major role in developing DNA barcoding but wasn’t involved in this particular study, says he “sees no reason to question the conclusions.” North American bird genomes have been sequenced enough times that their presence in reference libraries for barcoding is very well outlined, making it easy to define species “in nearly all cases, including those species reported from tiger sharks.”

When it came to the barfed-up feathers, Feldheim’s work showed they belonged to a brown thrasher.Drymon was taken aback—he thought he was dealing with a gull or a pelican, not something found in backyards from New Jersey to Oklahoma. From then on, he added another task to his surveys: analyze the stomach contents of tiger sharks whenever possible.

For the next nine years, he and his colleagues did just that. Sometimes they could leaf through the contents of a dead shark’s stomach, and other times they sampled tummies of living ones using a tube-down-the-throat and upside-down-shark maneuver. (The authors assure that no sharks were harmed, and were all tagged and returned to the ocean.)

In total, they looked at over 100 tiger sharks, and a shocking 40 percent of those bellies contained some form of avian remains. “All of the sudden, it’s not just a gee-whiz observation,” Drymon says, “it’s something they do relatively frequently.”

Once again enlisting the help of Feldheim, the team found evidence of 11 different bird species in shark stomachs, including swamp sparrows, yellow-bellied sapsuckers, house wrens, and white-winged doves. Curiously, though, Feldheim wasn’t able to find any marine bird DNA. So Drymon turned to another colleague, bird ecologist Auriel Fournier who’s currently affiliated with the Illinois Natural History Survey, to figure out why tiger sharks were eating so many terrestrial birds.

Right off the bat, they realized the birds were all migratory species, which would put them in the airspace over the Gulf twice a year. In the spring, many birds fly north from the Carribean, Central America, and South America to spend warm summers nesting in North America. Come fall, they make the return trip, often with new offspring in tow. To cross-reference the timing of when birds should be flying over the Gulf with when bird remains ended up in shark stomachs, the team used the citizen science database eBird, where users log birds they encounter from day to day. Lo and behold, tiger sharks ate the most birds in early September, right at the start of the fall migratory period.

So how do migrating birds in the sky end up in shark’s mouths in the water? Previous studies may provide an answer. Research suggests that when errant weather systems like unexpected cold fronts move in, a solid number of songbirds die and fall into the coastal ocean. That makes them an easy snack.

The final piece of the puzzle: Half the bird-munching tiger sharks in Drymon’s surveys were extremely young, clocking in under a year old. Adults can live to be over 15 years old, weigh over 1,000 pounds, and stretch up to 14 feet long. But these sharks were essentially babies, only a couple feet long. This leads Drymon to believe that pregnant tiger sharks use these coastal areas as nurseries for their newborns. With plentiful dead birds for easy nibbling, they’d be practicing a crucial skill for adult life, as tiger sharks are notorious scavengers that’ll eat just about anything.

“It was really mind-blowing when we were able to put this together,” he says. Still, more research and data will be needed to fully confirm the tidy narrative.

Going forward, Drymon hopes to learn more about these nurseries and the sharks who frequent them. Plenty of shark populations are at risk from fishing pressure, but protecting certain swaths of water, especially those home to pregnant females and newborn babies, could change that.

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At 10:00 p.m. on May 5, a team of people quietly approached a leatherback lying in the sand on the Florida beach. Working quickly while the female sea turtle laid her eggs, they drilled two small holes in the back of her shell. Through the holes they threaded zip ties, affixing a small transmitter with epoxy on the back for added security.

Over the next few months, members of the non-profit, Florida Leatherbacks, Inc, watched as Isla the sea turtle visited the beach a few more time to lay new clutches of fragile eggs in the sand, before starting her late summer migration north along the East Coast.

“We’re monitoring where she is right now, and it just happens to be in the middle of a hurricane,” Kelly Martin says.

Isla the #leatherback #seaturtle has stopped moving south and is now about 65 miles off Kitty Hawk North Carolina in 120 ft water. She will be experiencing high surf for the next 48 hours.
Please be safe out there! #HurricaneFlorence @windyforecast pic.twitter.com/BmikEwYLSr

— Florida Leatherbacks (@LeatherbacksFLA) September 14, 2018

Isla is now off the Outer Banks of North Carolina, to the north of where Hurricane Florence made landfall late last week. For a while it seemed like she would get caught in the massive storm as it slid past the coast. She wound up north of the worst of it, but still experienced rough seas over the weekend. Even before the hurricane hit, she surfaced in an area where waves reached 14 feet high.

“Turtles are air breathers, so they need to come to the surface periodically to breathe, but I suspect many dive below the surface to weather the storms,” Kate Mansfield, director of the Marine Turtle Research Group at the University of Central Florida, says in an email. “I have tracked turtles through some storms in the past and never saw any sort of movement that suggested they were trying to get away from the storm (or that the storms shifted their paths). The turtles I tracked were larger juveniles—at that size they can dive 100s of meters deep.”

Mansfield points out that there is some data from a 2006 paper on how Hawksbill turtles behave during a hurricane. While they stayed in roughly the same place, not making any movements to avoid the storm, they also became more active—staying beneath the waves for longer periods of time.

Other animals have different coping mechanisms. Nick Whitney is a Senior Scientist at the New England Aquarium’s Anderson Cabot Center for Ocean Life. He studies and tracks sharks, which, especially at a young age, tend to react very differently to hurricanes than turtles do.

Young sharks, Whitney says, tend to stay in shallow water close to shore, where there are fewer predators like large fish or other sharks that might see them as a meal. But when a hurricane approaches, these youths head to deeper waters.

“We know they can tell how deep they are,” Whitney says, noting that the drop in atmospheric pressure with an approaching storm might be enough to trigger the behavior. “It may be as simple as that it feels like they’re in water that’s way too shallow.”

Both turtles and sharks are tracked using satellite tags, but getting a satellite reading in a hurricane isn’t easy. “There are a lot of conditions that have to be just right,” Whitney says. In addition to needing relatively low cloud cover for the signal to reach the satellite, the satellite also has to be in the right place, Whitney explains. And that’s not all. “The animal has to break the surface, and the tag has to be dry for at least a few seconds.”

There’s still a lot we don’t know about animals in hurricanes, and it will take more than occasional bits of data to really understand how different species act in the system. Often the data we get on animals in hurricane is gathered by luck, when animals like Isla that have already been tagged cross paths with a storm.

Part of the issue is that in the scale of scientific research, storms happen quickly and are hard to predict, so getting funding for a study can be tricky. And tracking costs money—a lot of money. The transmitter attached to Isla cost thousands of dollars, an expense that the small non-profit could afford thanks to partnership with the Canadian Department of Fisheries and Oceans.

In part because of the expense, Florida Leatherbacks, Inc. is only tracking one animal this season—Isla. They’re thrilled to have the chance to see how Isla (and by extension other leatherbacks) might behave in a hurricane. In the end, to the people participating, the research is more than worth the cost. When asked why he studies leatherbacks, Martin’s colleague Chris Johnson is effusive.

“They’re big rubbery dinosaurs and they nest on the beaches that we live on,” Johnson says. “They’re just the coolest animals.”

You can follow along with Isla’s progress on Twitter.

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The first underwater footage isn’t quite the magical seascape you may have envisioned. It depicts a dead horse, a fearless filmmaker, and the slaughter of a shark.

In 1914, a young journalist named J.E. Williamson invented the “photosphere,” a device used to capture scenes under the sea. Williamson’s father was a sea captain, and had built an interlocking iron tube with a windowed chamber to aid him in deep sea scavenging. Williamson realized if he added a lamp and a larger viewing chamber, he could clamber down the tube with a camera and record what no one else ever had before.

After a test run with a still camera, Williamson’s next goal was to make a motion picture. But first, he needed money. So he promised his financiers the ultimate battle: man versus shark. Williamson set out for the Bahamas on the Jules Verne, a barge that would later set the stage for the world’s first underwater movie: Thirty Leagues Under the Sea (then later known as, The Terrors of the Deep).

The climax of the hour-long documentary was exactly what Williamson promised. Through the eyes of the photosphere, you see a dead horse suspended upside down beneath the warm ocean waters, bobbing rhythmically, as if it were trying to win a slow-motion underwater race. A shark takes the bait, while Williamson lies in wait.

In his memoir, Williamson remembered it like this: “I grasped the monster’s fin, felt my hand close upon it. With a twist, I was under the livid white belly at the spot I was trying to reach. With all my remaining strength I struck. A quivering thrill raced up my arm as I felt the blade bury itself to the hilt in the flesh…Then a blur, confusion—chaos.”

A century later, this violent underwater scene, which had set the precedent for the film adaptation of Verne’s 20,000 Leagues Under the Sea in 1916, had all but been forgotten, left behind like sunken treasure.

“Regarding film material, as far as I can determine, Thirty Leagues Under the Sea is still considered a lost film,” says Josie Walters-Johnston, reference librarian at the Library of Congress’s Moving Image Research Center.

So here it is, revived, a magic window into the very real story of Thirty Leagues Under the Sea.

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Fidel Castro was known for his love of scuba diving, so much so that the CIA once schemed a potential (though never carried through) plan to hide a bomb near his favorite dive spot, a chain of islands off the southern coast of Cuba. Decades later, in 1996, Castro named the place a marine sanctuary, known as Jardines de la Reina or Gardens of the Queen. Only a few hundred miles from Miami, the reserve is home to one of the most pristine reefs in the Caribbean, and maybe the world.

“I’ve never dived in such a healthy system in my life,” says Tristan Guttridge, a behavioral ecologist and previous director of the Bimini Shark Lab in the Bahamas. “Every dive was just mind-blowing,” he says. Guttridge visited the sanctuary this spring in search of great hammerheads—in particular, animals of a certain imposing size. The Discovery Channel documented his trip to kick off Shark Week on Monday.

Everything about the Gardens of the Queen is big. The reef itself extends over 60 miles along the coast, crocodiles as long as minivans wade through its mangrove forests, gaping-mouthed fish called goliath groupers weigh in at over 600 pounds, and then, there are the sharks. The sanctuary is home to silky sharks, Caribbean reef sharks, nurse sharks, whale sharks, and others. Dive in its waters, and you’re guaranteed to see hoards.

“Cuba has a lot of myths and legends about big sharks,” says Melissa Marquez, a marine biologist and founder of Fins United Initiative who joined Guttridge on the trip. A lore surrounds a certain shark in the sanctuary, known as “the Queen,” likely not one but a group of monster-sized great hammerheads that haunt the reef, Marquez says.

We don’t know much about great hammerheads at all, beyond their tendency to migrate hundreds of miles all over the world and their love of snacking on stingrays. During surveys, biologists often clump the species with their hammerhead cousins, so population estimates are generally not reliable, Guttridge says. He and Marquez visited Cuba’s sanctuary as an exploratory trip to see if they could find any great hammerheads and document the reef’s condition. They want to go back to tag individual animals and collaborate on research with Cuban scientists.

As of now, no one knows how many great hammerheads use Cuba’s reefs as a pit stop on their migrations, or where the animals head off to in the summer. “The waters around Cuba have been relatively untapped outside of Cuban locals and fisherman,” Marquez says.

On their last dive in the sanctuary, Marquez and Guttridge managed to take a snapshot of a great hammerhead. The animal measured 13 feet across, big for sure, but certainly not close to the largest great hammerheads ever seen.

More impressive than the one hammerhead is the sheer number of sharks of all species teeming in the waters. The presence of sharks indicates a thriving reef, and the Gardens of the Queen is no exception. Sharks are 10 times more likely to be found inside the reserve and many fish species are more than twice as numerous within the sanctuary than outside its boundaries. The Cuban government permits less than a thousand divers to enter the area each year and limits fishing to a number of lobstermen on the preserve’s outskirts. The reefs are a source of national pride.

“That’s what all coral reefs around the world should look like,” Marquez says. “It’s going to be hard diving elsewhere now.”

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In the middle of the ocean, sharks’ wanderings are bound to cross paths with commercial fishing boats—after all, we are both looking for the same tasty morsels. And now, you can watch the action unfold. Oceana, an ocean advocacy group, released an interactive map this week which tracked 45 ocean-faring sharks and showed how often they overlap with human fishing activity in the Atlantic Ocean.

Over a period of six years, marine biologists along the east coast of the U.S., from Miami to Wood’s Hole, caught and tagged open-ocean shark species under threat, including blue sharks, shortfin makos, hammerheads, and tiger sharks—many of which are not afforded any protections like fishing restrictions.

“It’s a tough ocean out there for those species,” says Austin Gallagher, a marine biologist at Beneath the Waves, and one of the lead researchers on the project. “Being an open-ocean shark, you have to investigate anything that shows up when you’re swimming around. And many times, there’s a hook attached to it.”

Biologists have been placing satellite tags on sharks for more than a decade, but no researchers have used that data to overlay the animals’ activity with that of large fishing vessels on a large enough scale to truly see any patterns.

The data they’ve found have confirmed what researchers already knew about the dangers to sharks imposed by large fishing vessels: outside the protection of coastal waters, sharks are at great risk. But conservationists say that tools like the interactive map will get more people concerned about the welfare of sharks. This new data could also help researchers better assess where sharks are likely to run into trouble, Gallagher explains.

So far, Gallagher and other biologists have tagged 45 sharks. He says he plans to tag more, though finding, capturing, and safely releasing the sharks back into the open ocean is no small feat.

“There’s a lot of long hours sitting on a boat, rocking side to side waiting for sharks,” Gallagher says. “It can be quite grueling, to be honest.”

The work can be just as dangerous as it is tedious. Although the animals he’s catching aren’t interested in taking a bite out of people, Gallagher still has to deal with a huge, unhappy fish. “Having a big, thrashing mako shark on the side of the boat is something you definitely need to prepare for.”

Once Gallagher catches a shark and deems it healthy enough, he bolts a GPS tag to its fin. If all goes well, every time the sharks’ fin breaches the water’s surface, the device will ping a satellite overhead, relaying its location for up to two years.

These monitors only show the minimum distance a shark may have traveled, says Stephen Cain, the assistant director of the shark research lab at the University of Miami, another group that collaborated on the mapping project. “It could have been doing pirouettes out there for all we know,” he says.

As the sharks move around, researchers keep careful tabs on their movements. “These are like our kids,” Gallagher says. “We want them to do well. We want them to transmit.”

But not everything is a smooth ride. Sometimes transmissions from a shark prematurely go blank, a likely sign the animal has been caught by fishermen. Certain species are especially under threat from incidental capture or direct targeting. “Blue sharks and makos are getting absolutely crushed,” Gallagher says. “Blue sharks are probably the most exploited large animal on the planet over 50 pounds,” he says.

Cain is hopeful tools like the map will help increase public engagement. “We’ve seen successes in the international community when it came to whaling,” he says. “That was done with public will and power.”

But Gallagher wouldn’t take his chances. “I would not want to be reincarnated as a blue shark,” he says.

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Standing still is apparently no way to hook a shark. On a sunny Tuesday in May, I’m with Mark Quartiano, a fishing charter captain who unabashedly catches and kills these marine predators. We’re 5 miles out in the Atlantic Ocean off Florida’s coast aboard Striker-1, his 50-foot vessel, and prospects are good. The spring months usually yield great catches, so long as I don’t buck superstition. “Don’t be a mannequin,” he says. “Move around. It’s bad luck not to.”

Soon, Ryan Wallach, Quartiano’s fishing buddy since 1996, rushes to the stern, where a resting fishing rod has just dipped, the telltale sign a shark’s on the line. Looking at me, Wallach shouts, “Get in the chair!” — an elevated, cushioned seat with a footrest for bracing oneself when wrestling large ocean creatures. I scramble up as he moves the heavy-duty rod from the stern to the chair, hooking it into place in front of me. I have 1,500 meters of tough nylon to work with, and for the next 20 minutes, I steadily reel it in, until the outline of an 8-foot hammerhead peeks through the water’s surface.

“Scalloped hammerhead,” Quartiano says, pointing out the indents in the cephalofoil, the term for its flattened, tool-shaped skull. Then he reaches into the water, grabs the shark’s head, and hauls it onto the deck.

Better known as Mark the Shark, Quartiano might be America’s most famous seafaring hunter. He’s operated his charter business since 1976, hooking and killing, by his estimate, at least 50,000 sharks. Clients as varied as Clint Eastwood and the Jacksonville Jaguars cheerleaders call him if they want a set of jaws, a trophy catch to mount, or just an adrenaline-packed excursion. Some 120,000 people follow his exploits on Instagram. Quartiano, 64, says he’d like nothing better than to hand the whole thing over to his son, Maverick, now 12, when he’s ready to retire.

But Quartiano’s way of life might be as threatened as the creatures he’s famous for catching. A recent university study concluded that perhaps 100 million sharks die annually worldwide, with commercial fishing the leading culprit. Yet in U.S. waters over the past few years, recreational angling — in tournaments, by solo enthusiasts, and on charter boats like Quartiano’s — emerged as the bigger hazard to the larger varieties: From 2012 to 2016, recreational fishing of sharks averaged 3.8 million pounds per year, compared to commercial fishing, which averaged 3.4 million pounds per year, according to NOAA Fisheries, an office of the National Oceanic and Atmospheric Administration. The agency counts six species as overfished, meaning their numbers are depleted: blacknose, dusky, porbeagle, sandbar, shortfin mako, and, as I later discovered, scalloped hammerhead.

Some sharks are endangered, and many more are in trouble. That’s led state and federal agencies that regulate fishing to increase rules aimed at rebuilding diminished populations and protecting others. Maintaining stable stocks is crucial for delicate marine ecosystems, which need large predators to keep the food chain in balance. In recent years, a schism has formed within the recreational fishing community between conservationists who strictly catch and release sharks and people like Quartiano, who refuses to throw off the hunter’s mantle. “I’m the Darth Vader of the fishing world,” he says unapologetically.

  The popularity of shark fishing as a pastime can be traced back to a man and a movie. The man was the late Frank Mundus. A charter captain from Montauk, New York, he ran shark-hunting expeditions and popularized the phrase “monster fishing” in the 1960s. The movie was Jaws, Steven Spielberg’s 1975 blockbuster in which a great white terrorizes a sleepy summer beach town until an expedition led by the colorful captain Quint — widely thought to be modeled on Mundus — kills the behemoth. Recreational shark hunting exploded after Jaws. Like Mundus, Quartiano got his start on Montauk, hooking a thresher shark when he was around 8 years old. In 1964, when he was 10, he moved to South Florida to join his father after his parents divorced. He started doing charter excursions post-Jaws in the late ’70s, often running two trips a day. Around this time, kill tournaments, in which anglers caught dozens of the fish and received cash prizes for bagging the biggest, proliferated along America’s coasts. For five straight years starting in 1979, Quartiano competed in and won the Marathon Jaycees World Championship Shark Tournament off the Florida Keys. Today Quartiano’s pace has slowed slightly: 450 trips annually. Because of regulations, he now mostly catches and releases his quarry, mailing information about its physical characteristics to NOAA Fisheries after tagging the fish with a plastic dart, a signal to other anglers that it has been previously caught. Some of his customers are happy with that same outcome; for others, the kill is the thrill, as it remains for Quartiano. “I can kill a shark a trip, which I normally do,” he says. “It all depends on the client — the client decides.”   Obsessing over sharks as toothy commodities ignores their great variety, as well as the important role they play in marine ecosystems. There are about 450 species, ranging in size from cigar to school bus. There’s a direct correlation between the health of coral reefs, the diversity and abundance of the marine life they support, and the presence of apex predators. Pull out all the sharks, and midsize fish species will flourish, overfeeding on smaller swimmers that act as reef cleaners. Moreover, sharks typically feast on weaker or sicker members of schools, in effect culling out disease and encouraging a more robust ecosystem.

After Jaws, commercial shark fishing increased too, as demand grew for shark meat and fins to be used for fillets and shark fin soup. Finning is illegal now, but oil from shark livers still ends up in everyday products such as cosmetics and sunscreen. By the late 1980s, surveys began to show the toll on the bigger species. One annual survey by the Virginia Shark Monitoring and Assessment Program showed they had been “severely depleted between the late 1970s and the early 1990s.” In 1993, NOAA Fisheries released its first management plan, including commercial and recreational regulations designed to end overfishing and rebuild stocks.

The agency subsequently tweaked the rules for commercial outfits, which had been catching sharks by the hundreds using longlines dropped deep into the ocean. In 1999, it began requiring commercial operations in the Atlantic Ocean to obtain a specific limited permit. The agency issued only 287, and no new ones have been granted since; as of 2017, the number had dropped to 221 due to permit holders leaving the industry. In addition, NOAA Fisheries has also implemented rules on how many sharks can be kept on each commercial trip. For example, NOAA revised the limit earlier this year from 25 sharks per vessel per trip to just three.

“We’ve been doing more assessments and getting a better handle on the status of fisheries,” says Enric Cortes, a NOAA Fisheries biologist, using the term for areas of the ocean where sharks are caught. He notes the agency nowadays has a better sense of which species are sustainably managed compared to the ones that are overfished.

The regulations, he says, have worked, over time reducing the number of sharks killed. Still, the largest of them remain in trouble due to the volume of recreational angling.

  Sport fishing boomed throughout the 1980s, when prevailing sentiment dictated the only good shark was a dead one. Charter-boat businesses and kill tournaments enjoyed increasing success. Miami media especially loved chronicling the feats of Mark the Shark. Quartiano became a local celebrity. In turn, he attracted the attention of national celebrities — Robert De Niro, Shaquille O’Neal, Ice-T — keen to catch their own sharks. The negative effects were overlooked, but in 2005, a study estimated that recreational catches of large coastal sharks were greater than commercial catches in 15 of the 21 years that encompassed 1981 through 2001.

In tournaments and on charter trips, the biggest sharks commanded the most attention. But culling the big ones harms breeding populations. Most sharks only reach sexual maturity late in life; even then, they produce few offspring, a problem for such a slow-growing species.

Regulators have increasingly turned their attention to the impact of recreational fishing. Since 1999, NOAA Fisheries has required all shark tournaments to register a month in advance. Contest operators also keep records of anglers and the fish they catch, and there are rules about which species can be kept. And starting this year, the agency requires circle hooks — rounded hooks that curve backward — for commercial and recreational use alike. The traditional J-shaped type often sticks in the fish’s gut or gills, shredding tissue, whereas the circle version usually stays put in a shark’s maw. Recreational anglers must also watch a video online that teaches them to identify the 21 species of sharks that are illegal to keep. That’s all in addition to the federal permits someone like Quartiano must hold in order to run his business.

The upshot of all these mandates? “As a whole, sharks are not overfished,” says Karyl Brewster-Geisz, a branch chief of the Atlantic Highly Migratory Species Management division within NOAA Fisheries.

Attitudes seem to have shifted along with the rules. Since the advent of educational programs like those in the mix on Discovery Channel’s Shark Week, celebrating its 30th anniversary this week, conservation has become a buzzword, and catch-and-release is the new norm. Some tournaments even ask competitors to release all sharks and take photographs instead, or to bring only one fish above a certain weight back to the dock.

David Conway, managing editor of Florida Sportsman magazine, describes the change as twofold: Today’s recreational anglers are more concerned about the sustainability of shark species and simultaneously turned off by wanton killing — of any fish. “The idea of manhandling beasts is vintage Hemingway, but it’s been a century since Hemingway’s time, and the vast majority of recreational anglers have moved beyond that motivation,” he says.

Attitudinally, says Terry Gibson, of the Marine Fish Conservation Network, a group of commercial and recreational associations concerned about overfishing, “the Mark the Sharks of the world are dinosaurs.”

Sentiment had already shifted significantly by 2005, the year Quartiano, his trademark brashness on display, distributed a photo of himself lying on top of four dead sharks he had hauled onto Striker-1. It was the sort of photo that once won him acclaim. Instead, several weeks later, the Miami Herald asked if Quartiano was a hero or a butcher.

Customers leave him glowing reviews on TripAdvisor. But elsewhere online, voices are more critical. On the boating and fishing forum The Hull Truth, an entire thread is dedicated to Mark the Shark. “Seems like he kills every shark he catches,” writes one user. Another writes: “He’s much maligned on Florida Sportsman forum and among the fishing community in south Florida. a real POS.” Quartiano bites back. “It’s all bullshit, man,” he says. “It’s totally fake news. I’m one guy. One guy can’t make a dent in the population. Do you know I tag more sharks than anybody in the world? Probably 400 in the last year.” It’s true he does afford his prey a degree of respect. Last December, three Florida men were charged with animal cruelty for dragging a shark behind their boat. They had sent video of their encounter to Quartiano, assuming he would be impressed. Instead, he posted the video on Instagram and denounced the brutality. “For once I may have to agree with @PETA,” he wrote, referring to the animal rights organization.   The last I saw of our scalloped hammerhead, it was swimming in the Atlantic, diving down beneath the hull of Striker-1. Because it was longer than 78 inches and pulled from federal waters, we could have legally kept it. Instead, we measured, tagged, and released it. Afterward, Quartiano filled out a card with the female shark’s length to mail to NOAA Fisheries, along with details on the tag now attached to it. On the way back to shore, Wallach cracks me a cold 16-ounce Miller High Life, my reward for a good catch. Then he says dolefully, “In 10 to 15 years, this won’t exist anymore.”

Wallach is talking about angling in general, let alone fishing for sharks, a sentiment his sporting companion appears to share. “It’s not the way it was years ago,” Quartiano says. “There was a lot of fish around, and a lot of people who wanted to fish. Now only a few people want to.”

When it comes to shark hunting, well, cultural forces aren’t aligned with Quartiano. Bagging the big one, not in a tournament or to eat, but rather to mount as a trophy — a testament to man’s dominion over nature — is going away.

“I make great money, and Maverick can just step right into it if he wants to do it,” Quartiano says. “But it’s not the way it was. Back in the day, there were hundreds of boats out this time of year. It’s a dying business, for sure.”

At his Miami office near the docks, Quartiano takes a seat behind a cluttered desk covered with stacks of printed photos, of customers posing with sharks they caught, that he needs to mail. Surrounding him are dozens of shark jaws that hang from the ceiling like nightmarish wind catchers. Whether Maverick occupies that seat someday depends on there being a new generation of customers awaiting its chance to go fishing for a monster.

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If you’ve ever wondered what the vegetarian sharks in Finding Nemo actually ate, you might ask the bonnethead shark. These little sharks don’t actually survive on nothing but plants, but they do eat quite a lot of seagrass. And they aren’t just swallowing plants and pooping them out undigested, either, scientists reported earlier this month at the Society for Integrative and Comparative Biology annual meeting in San Francisco. Bonnetheads can actually break down seagrass pretty efficiently, thank you very much, indicating that vegetation is an important part of this unusual species’ diet.

Bonnethead sharks are the most petite members of the hammerhead family, and only grow to about a yard long. Their digestive tract appears very similar to those of other sharks. “Up until ten years ago we assumed that they were carnivores like all other sharks,” says Samantha Leigh, a graduate student in ecology and evolutionary biology at University of California, Irvine who led the new research.

That changed in 2007, when scientists examined the gut contents of bonnethead sharks in the Gulf of Mexico. “Over half of their diet in some cases was this plant material, which is obviously really weird for a carnivore,” Leigh says.

To find out if the sharks are actually able to digest that seagrass, Leigh and her colleagues captured five bonnethead sharks in the Florida Keys and put them on a near-vegetarian diet for three weeks. Leigh coaxed the animals to eat their seagrass by feeding them “little sushi rolls,” she says. “I would create a bundle of seagrass and wrap a really thin sheath of squid around the outside and present that to the sharks, and they would eat ‘em right up.”

Though their diet was 90 percent seagrass, all the sharks gained weight during the experiment. When Leigh sifted through their poop, she was surprised to discover they’d digested over half of the plant matter. That means the bonnethead sharks are about as efficient at breaking down seagrass as sea turtles, which live and graze on the same meadows but are almost entirely herbivorous.

The researchers also found enzymes that break down plant material in the sharks’ guts. And when they sampled the animals’ blood, they saw a spike in the amounts of a nutrient that had been present in the seagrass. This suggested that the sharks’ bodies were actually making use of the plants they’d broken down.

Leigh is now trying to identify whether bacteria dwelling in the bonnetheads’ guts might help them digest the seagrass. “There’s probably a symbiotic relationship going on there that other sharks may not be able to sustain,” she says. Although some people have reported seeing lemon sharks nibbling mangrove leaves, there’s no actual evidence that any species of sharks other than bonnetheads eat plants, Leigh says. Even the bonnetheads probably aren’t chowing down on seagrass on purpose. It’s more likely the sharks swallow it while hunting crabs, shrimp, or fish in the seagrass meadows.

Unlike most of its hammerhead relatives, the bonnethead shark is not vulnerable or endangered. However, seagrass meadows are threatened by pollution, construction, and climate change. These environments are also extremely valuable to people, Leigh says. “They take [carbon dioxide] out of the atmosphere, they produce a lot of the oxygen that we breathe, provide habitat for a lot of the fish species that we eat.”

It seems that bonnetheads aren’t simply predators that control fish and crab populations from their position atop the food chain. Figuring out what roles they play in the seagrass meadow ecosystem might help us figure out how to conserve it. “It’s really important to understand how these sharks are eating, how they’re processing that food, and what they’re excreting and giving back to all these environments worldwide,” Leigh says.

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We’ve been here before: someone pulled something freaky-looking out of the bottom of the ocean, and now Google News is flooded with headlines about “dinosaur-era” or “prehistoric” sharks and “living fossils.”

Indeed, the frilled shark (Chlamydoselachus anguineus) looks like something from another (much scarier) time. But no, scientists didn’t just trawl up some time-traveling dinosaur fish.

“Living fossil conjures up the idea of long-lived species or organisms out of time longing for the good old days of the Devonian and disdainful of whippersnappers with their colour vision and adaptations to human pollution,” Mark Carnall wrote in The Guardian in 2016. But, he went on to note, the phrase is misleading: these so-called fossils aren’t actually identical to ones that lived in prehistoric times. The phrase usually refers to animals that have retained an unusual number of “primitive” features (quirks that were weeded out of all their cousins long ago), leaving them looking more like relatives that lived and died millions of years ago than their fellow extant species.

It might be the last remnant of an old lineage that has otherwise died out, but you better believe even the relatively isolated frilled shark has had to adapt and change at some point over the past few million years. Natural selection may happen sluggishly in the isolated confines of the deep sea, but it still happens. No species gets to sit this stuff out.

If this is your first time meeting the fair frilled shark, you probably think it looks rather monstrous—which only adds to the illusion that it comes from another world entirely. But in the deepest, darkest corners of the ocean, it has a lot of competition for the title of weirdest-looking shark. Here are a few other favorites:

Goblin sharks' use a technique called slingshot feeding to eat where they shoot out their jaws 14/10 Gob-win pic.twitter.com/zkbGb6Zd1E

— We Rate Sharks (@WeRateSharks) July 26, 2017

The goblin shark

Yes, Chlamydoselachus anguineus has a terrifying maw. Those 300-or-so bristle-like teeth are used to trap fish and squid in a predatory lunge.

But the goblin shark gives the frilled shark a run for its money in the maw department. You know how the alien in Alien has a jaw-within-a-jaw that pops out to attack its prey? Well, the goblin shark does that, too. The shark’s anatomy suggests it might be on the slow side, but the ability to quickly snap its jaw forward allows it to ambush passing prey without moving the rest of its body.

The goblin shark is also sometimes called a living fossil, as it’s the last remaining member of the 125-million-year-old Mitsukurinidae family. You’ll find it more than 4,000 feet below the ocean surface, assuming that you want to find it.

Cookiecutter shark

A cookiecutter shark sounds like it should be adorable, or at least boring. But while there’s nothing too shocking about its body, the creature’s name actually refers to the cookie-cutter-like wounds it leaves behind in prey. Oh, and it gets worse: the name is terribly misleading in the worst way. The shark latches onto its prey’s flesh and twists around, scooping out a deep chunk of meat with it saw-like set of chompers. That’s our best guess based on the wounds, anyway; no one has seen a cookiecutter shark feed.

“These chunks are conical, so the cookie-cutter metaphor isn’t quite right; ‘Ice cream scoop shark’ or ‘watermelon baller shark’ are more accurate, if less catchy,” Ed Yong wrote for National Geographic in 2013.

Yum.

The resulting wounds are pretty gnarly, but you can see examples here.

The ghost shark

This strange little pup is my personal fave; it looks like a truly mediocre puppeteer’s attempt at creating a shark for a Tim Burton film. The fish’s lineage broke away from true sharks and rays some 300 million years ago, giving them the lost-deep-sea-dinosaur appeal of the frilled shark with none of the frills.

The ghost shark is practically a surface-dweller compared to the species above—it chills out around 650 feet down—and may sometimes even migrate into bays to mate in the spring. As such, we eat it. The Florida Museum reports that the species is often sold as whitefish in Australia and New Zealand, ending up in fish and chips. So the next time you find yourself eating a fish stick down under, know that the meat may have come from a “living fossil.”

Bluntnose sixgill shark

The bluntnose sixgill migrates vertically throughout the day (it goes up and down) but prefers to live some 6,000 feet deep. The species proves that fossil-esque features don’t necessarily look nightmarish; it’s known for sharing an unusually close resemblance with 200-million-year-old fossils, but it doesn’t look that weird—save for its particularly gilly neck (hence the name). Then again, weirdness is in the eye of the beholder. You may disagree.

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When you think of a zeppelin, you probably don’t picture a large, cartilaginous fish with rows of pointed teeth. But perhaps you should. There are similarities between the two that you’ve almost certainly never considered—and these shared aerodynamic properties have given us insight into how sharks evolved their buoyancy.

The thing about living underwater is that your body has to be approximately the same density as the liquid surrounding it. Too dense, and you spend all your energy trying not to sink. Too airy, and you just float right on up to the top. Land animals don’t have this problem, since we’re all more dense than air. But sea creatures have to evolve a way to balance their buoyancy and their ability to swim, or else they’d never survive in the ocean.

Fish do this with a swim bladder, which sounds like an old-timey swimming cap, but is actually an organ filled with gas that allows some swimmers to adjust their buoyancy at will. It looks rather like a fleshy, inflated balloon. Bony fish (that is, non-cartilaginous ones) can change how much gas is inside their swim bladder to float at any depth they’d like, without having to expend energy when they’d rather stay in one place.

Sharks don’t have that. Instead, they’ve evolved very fatty livers. Fat, in addition to being delicious, is much less dense than water. This is why (generally speaking) humans with more body fat tend to be more buoyant. It’s the same basic principle, except that we carry our fat on the outside and sharks store theirs in the liver.

But not all shark livers are created equal. Buoyancy is a delicate balance, and each species of shark has evolved a specific level of floatiness. Biologists from the U.S. and Australia set out to study how 32 shark species vary in density, size, and swimming habits to figure out how this balance actually evolved. They recently published their results in the journal Proceedings of the Royal Society B.

Some sharks, like Greenland or bramble varieties, swim exceptionally slowly at intense ocean depths, where the water is more dense. They need to be less buoyant at those sea levels—but also swim exceptionally slowly to conserve energy—so they need to have enough upward lift from their livers to allow steady motion. These are the blimp sharks; they’re perfectly adapted to constant motion at moderate speeds.

Other, faster species have different priorities. Blacktip and silky sharks live in relatively shallow waters, where they need to be able to catch lightning quick small prey. Having a less buoyant body allows them to maneuver more nimbly (as anyone who’s ever tried to swim in a life vest will understand), and more energy-efficiently. These plane-like sharks have smaller livers, often so small that the fish would sink if they weren’t moving forward. As a result, their fins are shaped like wings to provide upward lift in lieu of internal flotation support. The trade-off is that they’re poorly suited to slow, constant movement.

Your intuition probably tells you that bigger sharks tend to swim more slowly, and based on all this new information, that they probably have higher buoyancies. And you’d be right. Large sharks tend to have large livers, though that wasn’t necessarily a given. The researchers weren’t sure that the livers would scale in proportion to overall body size, or whether some species would have inordinately large or small flotation devices in their guts. But it turns out that the greater the liver volume, the larger the rest of the body needs to be to accommodate it—the additional liver doesn’t replace lean muscle tissue.

Of course, none of this means that blimpy sharks can’t also be terrifying, toothy, speedy predators. Sharks are still extremely efficient swimmers—it’s just that bulky, buoyant species are more energy efficient at slower speeds. The blimp-esque bluntnose sixgill shark is roughly 12-foot-long, fat-headed, and so sluggish it’s earned the noble nicknamed of “cow shark.” They are, however, distinctly un-blimp-like in their capacity to rip an animal to shreds with their six rows of teeth. Even large sharks typically rely on their speed, agility (and, let’s be honest, their toothiness) to catch food.

Sharks may be really good at hunting down their food, but these are killing machines that deserve more respect than fear. Even in the death trap colloquially known as Australia, sharks have only killed 16 people since 2000, and that’s the country with the most shark-related fatalities in the world. You’re more likely to die by cow attack or, for that matter, by deer—and that’s not counting how many people die in car crashes caused by deers. A literal deer just being a deer is more likely to kill you than is a shark is. Fear the deer—not the great white.

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The shortfin mako is a strikingly blue, athletic shark with a dubious honor: its meat is considered delicious. While other species are spurned as being tough or unappealing, mako frequently shows up on restaurant menus.

“A lot of sport fishermen will keep mako sharks, but none of them keep a blue shark because blue shark meat is pretty gross,” says Michael Byrne, a wildlife ecologist at University of Missouri in Columbia. “It tastes like eating piss.”

Mako sharks are revered for another reason as well: they put up a tremendous fight for sport fishermen. The shortfin mako (Isurus Oxyrinchus) is the world’s fastest species of shark, swimming up to 45 miles per hour. The creatures also tend to leap dramatically when hooked. “They kind of jump straight up and twirl around,” Byrne says. “There’s been cases of people hooking them near the boat and then they jump and land in the boat.”

It’s no wonder mako sharks are so highly regarded. But the mako shark’s popularity is not doing it any favors, Byrne has found. He and his colleagues tracked satellite tagged sharks and saw that they were caught and died at rates 10 times higher than reports from fishermen suggested. This indicates that the sharks are being overfished, the team reported in August.

Other shark scientists are also finding evidence that makos in the North Atlantic are being caught at unsustainably high levels. What’s more, the fast, flavorsome, but slow-growing mako may be even more vulnerable than other species to overfishing. The time has come, they say, to take action on the mako shark’s plight.

“We definitely need to be concerned, and need to definitely start thinking about putting catch limits on the species which haven’t existed in this part of the world before,” Byrne says.

A perfect storm

The mako shark has a few things working against it.

Mako sharks range over temperate and tropical waters around the world. In the North Atlantic, they are often in the wrong place at the wrong time. Commercial fishermen don’t target makos, but the sharks tend haunt the same areas as tuna and swordfish and are caught accidentally. “They like the same water, they like the same food, and the fishermen are not trying to catch them, but they’re there,” says Steven Campana, a marine biologist at the University of Iceland in Reykjavik.

Makos also reproduce slowly. “Mako sharks are particularly vulnerable even among threatened sharks because they take a long time to reach sexual maturity,” David Sims, a professor of marine ecology at the University of Southampton in England, said in an email. For females, this can take 18 years; even then, a mako will only give birth to a handful of pups once every three years.

Most of the sharks caught are juveniles that have not yet had a chance to reproduce, Byrne says. “You’ve got a pool of adults that are out there which we don’t see very often, they’re hard to catch, they’re hard to find,” Byrne says. “The problem is eventually they’re going to get old and eventually going to start dying…and we’re going to have this vacuum where they’re not going to be replaced at the same numbers.”

And then of course there’s that tasty meat. “Their meat is valuable, so there’s an incentive for them to not be released if they’re captured alive,” Byrne says. “They’re one of the few species that kind of drew the bad luck in life in that regard.”

But other sharks don’t deserve such a bad rap for unappetizing meat, according to his teammate Mark Sampson, founder of Fish Finder Adventures, a charter fishing service based in Ocean City, Maryland. “Even mako shark meat, if it’s mishandled, will exhibit that very strong ammonia smell,” he says. In fact, that pungent tang occurs when shark meat isn’t cleaned and put on ice quickly enough and begins to warm up.

“A lot of people won’t give other shark species a fair break when it comes to flavor,” Sampson says. They “think that, well if it’s not a mako shark then it’s not a good eating shark, which is really not true.”

Even if people were willing to chow down on other sharks, however, makos would still be in high demand. “Commercial fishermen are probably always going to welcome these sharks onboard their boat,” Sampson says.

Like other species, makos also suffer from shark finning. Sharks are often still alive when they’re tossed back into the ocean after their fins are cut off, Campana says. “The new generation in some of the Asian countries is aware of this problem, and they’re spurning things like the Chinese wedding soup—which is often the place where the shark fins go,” he says.

Stirrings of trouble

Initially, Byrne and his team had been tracking mako sharks to learn more about their movements. But they were struck by how many were caught and kept by fishermen.

So the team followed 40 satellite-tagged juvenile sharks in the North Atlantic over three years. The sharks passed through the exclusive economic zones of 19 different countries. Twelve of the sharks (about 30 percent) wound up caught by fishermen from the United States, Canada, Mexico, Spain, and Cuba.

The scientists were shocked by just how many of the sharks died. “It’s not uncommon for animals you tag to get nabbed by a hunter or a fishermen, but it’s a really big ocean,” says Byrne, who was then at Nova Southeastern University in Fort Lauderdale, Florida. “To have that percentage of the animals that you tag…[be] harvested by fishermen, it’s crazy.”

He and his colleagues calculated that each shark had a roughly 72 percent chance of surviving a year without being captured, and that the sharks were perishing at rates 10 times higher than previous estimates indicated. This suggests that makos are being fished beyond sustainable levels in this part of the Atlantic.

Earlier estimates for the sharks’ mortality were based on how many makos fishermen reported catching, compiled by the International Commission for the Conservation of Atlantic Tunas (though ICCAT is focused primarily on conserving commercially fished species like tuna, the intergovernmental agency also collects data on sharks).

But not everybody reports when they catch a shark, and conventional tags sometimes fall off before a shark is captured. “I wish I knew how many of the makos that we’ve tagged with the other, regular types of tags were captured and nobody reported them,” Sampson says. “Apparently a lot of them are being recaptured and [the tags] are just not being turned in. Either that, or the sharks we put the satellite tags on are just the dumbest sharks in the ocean.”

The satellite transmitters, while pricier, made it easy to tell when a shark had been snared. “The shark would be out in the ocean doing shark things and then suddenly it would be transmitting from a fishing dock,” Byrne says.

They plan to repeat the study with more sharks, find some adults to tag, and track makos in different regions of the Atlantic. Meanwhile, other researchers will have to attempt similar studies to see if they find the same disturbing mortality rates, Campana says.

Even if the new estimate is spot on, makos aren’t in immediate danger of extinction. But the results do indicate that their numbers are steadily dwindling. “That high a fishing mortality on makos means that the mako population is going to go down, down, down,” Campana says.

Sims says that the new findings fit with his own observations of mako sharks. “Shortfin mako sharks are less common in their oceanic habitats than they used to be,” he says. “Finding enough makos to satellite tag even in hotspots is a real challenge. There just don’t seem to be many out there compared to only a decade or so ago.”

He and his colleagues have identified hotspots where mako, blue, and tiger sharks congregated across the North Atlantic, and found that 80 percent of those preferred habitats overlapped with longline fisheries. This suggested that the shark were likely being overfished in these hotspots, Sims says.

“If fishing continues at the current levels there is the chance that the shortfin mako population in the North Atlantic will reach such a low level that recovery may prove impossible even if fishing is removed,” Sims says.

As a top predator, mako sharks play an important role in maintaining the stability of ocean ecosystems. It’s hard to predict what will happen if most of them are wiped out. “In cases where you lose a predator from an ecosystem, it’s very rarely a good thing,” Byrne says.

Some of the fish that makos prey on could become more abundant—or another large predator might swoop in and eat even more of them. “The only thing you can predict safely is that there will be big changes,” Campana says. “It would be like wiping out the lions on the Serengeti plains of Africa, you would have huge impacts.”

Setting limits

About two-thirds of the ocean lies outside national jurisdictions, so mako shark fishing is unregulated over much of their range, Sims says. “There is an urgent need to introduce catch limits for shortfin mako, particularly in the North Atlantic which is fished more intensively than other oceans,” he says. “And in the longer term more large shark reserves in the open ocean will need to be considered.”

Byrne agrees that annual catch limits on mako sharks for commercial fleets could make a difference. “Those regulations don’t exist for mako sharks in the Atlantic yet, but that would go a way towards helping,” he says.

Byrne and his colleagues hope that the management agency ICCAT, which has 51 nations as members, will propose restrictions on mako fishing. The annual ICCAT meetings are underway, and the organization is considering conservation measures for shortfin mako in the Atlantic, says Enric Cortés, a research fisheries biologist at the National Oceanic and Atmospheric Administration, who is another coauthor of the new paper and a member of ICCAT’s Standing Committee on Research and Statistics.

Currently in the United States, a boat full of recreational anglers can keep one shark they catch per trip, provided that shark is longer than 4.5 feet from its snout to the fork in its tail. Makos don’t reach maturity until they are several feet larger. However, catch and size limits for mako sharks are grouped together with blue sharks, tiger sharks, and a few other species. “Fisheries have been reluctant to have specific catch limits for each different species because a lot of anglers can’t tell one…from another,” Sampson says. There are no minimum size limits on makos caught by commercial fishermen, and catch limits are looser than for sport fishermen.

If the makos do need protection, Sampson says, it might be time to increase the minimum size limit for this species. Makos do have a few distinctive features that should make them easier for anglers to identify than other sharks. “They’re very blue in color, they’ve got a very pointed nose, they’ve got a very stout tail, and all that…distinguishes them from the other types of sharks that are a lot more generic in shape and color,” Sampson says.

Many sport fishermen already follow stricter size limits than the law demands. “We’ve always said if we’re going to keep a mako it’s got to be at least 100 pounds…we just estimate it,” Sampson says. Still, “There’s a lot of recreational anglers who say, if it’s legal it’s legal, and we’re going to keep it.”

If a shark that has been captured is released alive, it has a good chance of surviving, Byrne says. However, the stress of being captured does take a toll on sharks, and makos might more vulnerable than other species, Campana has found.

He and his colleagues have also tracked mako sharks with satellite tags, as well as porbeagle and blue sharks. Some of the animals that were captured by fishermen died even after being set free, and makos were especially sensitive. “Between a third and a half of them were dying either when they were on the hook struggling or afterwards when they were released,” Campana says. “That’s a lot of sharks that are being killed for basically accidental reasons.” Porbeagle sharks fared similarly, but blue sharks were a little more resilient, he says.

Being snagged and released can be a harrowing experience. “They’re thrashing around in the water, they’re building up stress hormones,” Campana says. “In high enough levels these make any animal more susceptible to death.”

As fast, active sharks, makos and porbeagles need a lot of oxygen, he says. But when they are on the hook, their range of movement is limited. “They simply can’t swim to ram the water and the oxygen over their gills fast enough,” Campana says. “Some of them are dying form lack of oxygen before they get pulled up on the boat.”

Another problem is that not all fishermen will release a shark by snipping the fishing line or using a dehooking tool. “It can be fairly brutal, it could involve the fisherman cutting the jaw open to retrieve the hook or trying to rip it out of its mouth,” Campana says.

If a shark survives the first day or two after it is released, it has a good chance of weathering its injuries and stress, Campana says. But his findings indicate that releasing sharks does not guarantee that they will live. “Certainly catch and release fisheries are good,” Campana says. “But it is a mistake to assume that they’re all going to survive.”

That means that fisheries managers will also have to consider this delayed mortality rate in their calculations. However, there are a few things that sport fishermen can do to make sure that being hooked is minimally traumatic for the sharks.

“It’s mostly just using commonsense practices from the time they hook the fish until they get it to the boat,” Sampson says. “Try to catch the shark in a timely manner, and when you get it to the boat be prepared for it.” That means everyone should have their cameras ready and know where they will stand in a photo, and someone should have wire cutters or a dehooking tool handy so the shark can be released as quickly as possible.

Fishermen can also stick to circle hooks, which are designed to hook in the corner of a fish’s mouth rather than down in the gut. Eventually, the hook will rust and fall out. Starting in 2018, recreational shark anglers will be required to use circle hooks in most circumstances. The new regulations will give makos and other sharks a better chance of survival after release, Sampson says.

Make way for makos

The shortfin mako is considered a vulnerable species worldwide, and researchers are finding more and more signs that the ones dwelling in the North Atlantic are in trouble.

Campana says that he was not surprised to hear Byrne and his colleagues report that the mako’s mortality rate is higher than previous estimates suggested. “I and many other shark biologists have long been worried that the official statistics for mako—how many are caught etcetera—are just grossly, grossly wrong,” Campana says. “It’s a great wakeup up call for what’s going on. Because if the mako are being that underreported almost certainly the other big sharks are as well.”

But there is hope; sharks can bounce back from human meddling. Great white sharks were nearly decimated in the Atlantic between the 1970s and 1980s. Since they became a federally protected species in 1997, the sharks have made a comeback, and the population has grown to 70 percent of what it was in 1961.

Putting limits on the size or number of makos that can be kept by fishermen could help the sharks rebound. But in the meantime, Sampson says, sport fishermen can help by bringing fewer of the makos they catch home for dinner. “Even though mako sharks are food fish, anglers shouldn’t think that it’s okay to harvest them with the same frequency that they do the other food fish,” Sampson says. “There’s lots and lots of tuna and mahi-mahi in the ocean, but there’s only a few sharks.”

Mako sharks have long been valued for their fighting prowess and tasty meat. Now, Sampson says, “It would really be great if more recreational anglers would adopt the respect and the admiration of makos to the point where they would just enjoy the opportunity to catch one, interact with them and turn them loose.”

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The Olympics ended on Sunday, but if we know our readers, many of you were still glued to your televisions as the Discovery Channel’s Shark Week began, with hours upon hours of programming dedicated to these fearsome, fascinating creatures. We at PopSci have to confess to being equally intrigued by sharks, an interest that has continued throughout history.

Though, the farther back you go in our archives, the more our shark coverage seems less like scientific curiosity and more like bloodlust. We were only too happy when shark skin started being turned into leather, for example.

In more recent history, though, the author of “Jaws” wrote a story for us that cast sharks not as the villain, but as a misunderstood monster that is just as afraid of us as we are of it. And lately, our weapon of choice for protecting ourselves against shark attacks is a harmless electronic repellent, not a combination harpoon/shotgun.

You can see all this and more in this week’s archive gallery: a look back at our strained, but evolving, relationship with these toothy terrors of the sea.

Plenty of misunderstanding surrounds sharks, or the “wolves of the deep,” as we so elegantly called them in this 1917 article that attempts to clear up some of the misconceptions. When people are afraid of something, that fear can sometimes blind them to the truth, as anyone who’s seen “Beauty and the Beast” can tell you. In this case, the truth still makes one a little uneasy. For instance, through the advance of underwater photography, we were able to learn that, contrary to popular opinion at the time, sharks do not turn over when attacking so as to more easily bite with their “receding underjaw.” If you’re being attacked, that fact will likely provide little comfort. Humans are just as dangerous to the sharks, though. This article describes an “ingenious method” that allows sharks to be “caught and killed in large numbers:” mounting several rotary wheels to the side of a boat, each of which carries a large, baited fish hook attached to a long, insulated electric cable. The photo to the left is evocative of this struggle between man and beast, and as I could never do the caption from the magazine justice, I will just paste it here: “A shark weighing 800 pounds and more than twelve feet long caught by Mrs. Otto Jaeger at Palm Beach. It was caught with a rod and reel but had to be shot with a heavy caliber rifle.” The article provides no further context.

In besting an adversary as worthy as the shark, we feel a certain sense of smug satisfaction. In this case, people wore the spoils of victory on their feet. At the time we wrote this article, PopSci wasn’t feeling particularly conservationist about the whole thing, as demonstrated by the bloodlusty language we used to describe the shark leather: “We can now sit back and smile with satisfaction at the sight of these tigers of the sea expiating their crimes by cutting down the cost of living. The shark is no longer our implacable enemy. It is a servant that will supply us with uncountable millions of feet of leather.” To make these wearable trophies of war, fresh shark skins were first soaked in a brine bath for eight days, salted for three to five more days, then packed in sugar or flour barrels. They are then subject to a tanning process that involves bathing them in water, slaked lime and hydrochloric acid, oiling them, coloring them, polishing, bleaching and rubbing them with skimmed milk, which apparently makes them “very supple.”

Our cartoonist illustrates the size of “probably the largest creature that ever lived,” the carcharodont shark. “There was room enough in this ferocious monster’s maw for a foursome of bridge,” an image that is quirky and humorous only because the carcharodont’s extinction ensures that it can never take its vengeance for being so caricatured.

Shark fishing was a lucrative business during wartime, especially “after the German occupation of Norway cut off our main source of cod liver oil.” Which, really, is that what we should be focusing on? Either way, our concerns were put to rest when researchers realized that shark liver oil has an even higher vitamin content. We began giving it to pilots to aid their night vision. Like the proverbial buffalo of old, though, the rest of the shark didn’t go to waste. The skins were made into leather, as discussed earlier, teeth and vertebrae were made into stylish jewelry for sun-bleached surfers, fins were made into soup, flesh was canned for food or turned into fertilizer, and physicians made serums from the pituitary gland. With the liver cashing out at $10/lb, and money to be made off the rest of the shark carcass, fisherman started dropping 1,000 foot chains laden with dangling hooks into the ocean, often catching six to 10 sharks per line. “Most of them are already drowned, but an occasional tiger shark will come aboard with plenty of fight in him and will have to be quieted with a crowbar.”

When sharks aren’t a fisherman’s intended quarry, they can be quite a nuisance if they are trapped in a net. Sometimes they destroy the net and release an entire catch of fish, leaving the fisherman to watch their money swim out to sea. Not satisfied with just a harpoon or a shotgun, industrious fishermen combined the best features of both to create this shark gun, which only fires on direct contact with its target, and therefore can’t miss. A pipe reducer coupling holds a 12-gauge shotgun shell in place, and a double-ended spike held in with a spring completes the setup. When contact with the shark forces the spike back, it hits the the shell’s percussion cap, firing it into the belly of the beast. Or the head.

John Fenton’s deep sea dive to test an underwater movie camera soon turned into a briny battle worthy of the silver screen when he encountered an irritable nurse shark and thought it a good idea to pat it on the head. The shark chomped at his arm, but luckily only caught his sleeve, and Fenton was able to fight back, killing the shark with a knife. The good news is, the camera worked perfectly, and caught the whole thing for our horror and enjoyment.

PopSci finally answers the question on everyone’s minds–“Do sharks attack people?”–though perhaps it wasn’t the answer we wanted to hear. “They do.” Of course this answer comes with a boatload of caveats, pun absolutely intended. Harvard’s Bill Schroeder debunked the myth being perpetuated by many, including some skin divers, that sharks are essentially harmless to humans. “Of course, I don’t say that all species of sharks attack men,” Dr. Schroeder said. “Most don’t. Not even all the species known popularly as man-eaters are suspected by scientists of being dangerous. But there’s always a bad actor that comes along.” The baddest of the bad actors is the white shark, whose presence near Sydney, Australia makes its beaches some of the most dangerous in the world. Aside from humans, some strange things have turned up in the stomachs of great whites, including sea lions, horse meat and even an entire Newfoundland dog with its collar still on. Even with that alarming piece of information, our article reassures readers that their chances “of being bitten on any American beach are very very remote.”

Perhaps the biggest culprit of instilling fear of sharks into humanity is Peter Benchley, the author of “Jaws,” the book that spurred the movie, and subsequently, the pulse-quickening song that would forever be associated with shark attacks. But as it turns out, he no longer believes sharks are so bad. A few years after “Jaws” was published, Benchley encountered a great white while diving in the Bahamas. One of the two creatures was literally scared shitless by the chance meeting, but it wasn’t Benchley: “The shark froze, too. And then, abruptly, frantically, implausibly, the great white wheeled around, voided its bowels, and disappeared in a nasty brown cloud.” Though Benchley says his research for the book reflected the wisdom of the times, by the 90s we knew that only 10-12 of the 368 known species of sharks had ever been known to bother humans, and the attacks were often accidental–a human on a surfboard looks remarkably like a sea lion from underwater, apparently. Also, all those years of casting them as our enemies (which, as you’ve seen in this gallery, PopSci was also quite guilty of) resulted in untold millions of dead sharks. “For every recorded attack on a human being, more than four million sharks are destroyed by human beings.”

As humanity and technology evolve, we begin to realize that perhaps there are better ways to protect ourselves from shark attacks than by killing millions of sharks. Enter the Shark POD (protective oceanic device). Two electrical transmitters powered by a nickel-cadmium battery attach to a diver’s oxygen tank and fin. The on-off switch straps on to the diver’s chest or wrist, with an LED light showing when the power is on, or the battery is running low. When activated, the transmitters “generate a low-voltage electrical field that extends 12 to 20 feet from the diver in all directions, aided by the natural conductivity of salt water.” It’s unclear what exactly about the electrical field irritates sharks enough to make them turn tail, but scientists think it might be the pores on their snouts that sharks use to detect low-voltage electrical signals, like a fish’s heartbeat, when hunting prey.

Fabien Cousteau, grandson of Jacques, hid inside a robotic great white shark for more than 100 hours to shoot video footage for a documentary on shark cognition, in order to catch “purer behavior” than he would have if he revealed himself in human form. “My hope is that they think ‘Hey, that looks like my retarded cousin from Australia!'” he said. It seemed to work. Cousteau, using the shark-shaped submarine wittily nicknamed “Troy,” was the first person ever to capture a female shark attacking another female on film.

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Brace yourself. To human senses, the gelid waters of the Arctic and North Atlantic oceans are beyond chilling. Because sea water is salty, the waters can actually reach temperatures below what we think of as freezing (as low as 28.8 degrees Fahrenheit instead of the usual 32) and remain liquid. Without protective gear, the human body can withstand maybe 15 minutes of these temperatures before succumbing to unconsciousness; 45 minutes before death.

And yet somehow, the Greenland shark—a species that can reach more than 15 feet in length and a scale-busting 880 pounds—calls these waters home. These cartilaginous fish do more than tough out frigid temps: they also resist diseases common in humans, like cancer, and may hold secrets to how we might live longer, healthier lives.

“This particular species of shark is fairly understudied, and is not particularly well known to research—or to anyone except for the Greenlanders,” says Holly Shiels. A physiologist at the University of Manchester, Shiels is fresh off an Arctic expedition where an international group of eight scientists aimed to change that.

The elusive shark first attracted widespread attention last year, when it graced the cover of the journal Science. Greenlanders—Inuit people who share a lineage with the native populations in the American Arctic—had long said that the Greenland shark could live for ages. But last year, Danish researchers confirmed their status as the longest-lived vertebrate (that we know of, anyway). They can live up to 400 years, which raises many questions. Questions, says Shiels, like: “Why don’t they have cancer if they live for that long?”

Cancer is a disease of replication. When our cells copy themselves, they sometimes introduce errors—either because of damage or because they’ve reached the end of their natural lifecycle—that can turn into cancer. Generally speaking, the longer you’ve been alive, the more your cells have replicated. That means more opportunities for these kinds of errors to pop up, which is why cancer is more common in adults. But Jeanne Calment, who holds the record for longest-lived human at 122 years, was a mere child in comparison to the Greenland shark. These creatures don’t appear to hit puberty until they’re 150 years old. We’re not sure how the Greenland shark can accomplish this feat, we just know that it does.

“I came in because they wanted somebody to look at the cardiovascular system,” says Shiels. “Heart disease is a disease of the aged. We know that every year you live past 65 increases your incidence of having heart disease by an exceptionally, ridiculously high rate. So how do these animals continue to beat for 400 years? Do they have fibrosis? Do they have arrhythmia? Do they have any of the things that we associate with aging in human hearts?”

Shiels notes that the purpose of the trip, which she and her colleagues are chronicling after the fact in a series of shark diaries, was simply to observe—to help fill in the blank spots in our understanding of the Greenland shark. Researchers like Shiels are in a race against time to learn as much about the shark as possible, both to help protect the species and to see what aspects of their physiology can improve our understanding of human health and wellbeing.

Why the rush? Because escalating fishing pressures in the North Atlantic and the Arctic mean that increasingly, the Greenland shark has been showing up as bycatch; the unwanted creatures caught on fishing hooks and nets. And juvenile Greenland sharks are scarce. Given that it can take up to 150 years before a female shark can reproduce, we shouldn’t expect that to change radically any time soon. So we might be removing sharks from the ocean at a rate faster than they can be replaced.

“When you think of big team efforts, you don’t think of physiology,” says Shiels. “So, it’s quite exciting that there’s a new burgeoning field of conservation physiology, which is understanding how animals work or how they function across all levels of an organization to help inform conservation plans.”

This fear that human pressures may be accidentally harming the Greenland shark has landed them on the IUCN Red List as near threatened. It’s a fact that’s even more disheartening when you consider that we used to actively hunt these creatures for the thick layer of fatty oil that surrounds their liver.

“This particular species was completely overfished in the 1900s to 1940 for its liver, which was used as machine oil in the wars,” says Shiels. “Because they were so massive, their livers were absolutely massive. And because they’re living up in the cold waters, they deposit a lot of fat in their livers. So they were particularly great for this machine oil stuff.”

According to Shiels’ expedition and others like it, there are plenty of cool things to learn about the Greenland shark.

Take their hearts: they beat once every 12 seconds. The human heart, in comparison, beats at least once a second when we’re at rest (and even faster when we’re active or simply young). Our hearts use fast beats with low output—each beat sends only a tiny amount of blood circulating throughout the body. The Greenland shark squeezes a heart’s worth of blood through the body in one mighty pulse, followed by a 12-second pause to refill.

The heart isn’t the only part of the Greenland shark that moves slowly. Their tails are just as poky. On the expedition, a Japanese researcher affixed a biologger, sensors that can collect all sorts of information about living creatures, to some of their tails.

“Their tail beat is the slowest tail beat from extension to extension that has been recorded, even if you scale for size and temperature,” says Shiels.

And while some arctic animals are suffering due to pollution that makes its way north on ocean currents, the Greenland shark seems mostly unscathed. Shiels recalls one study that tested tissue samples for known pollutants to see if they became concentrated within the Greenland shark.

“The interesting thing,” says Shiels, “is they don’t seem to. But one study is not the whole picture.”

Which is exactly why researchers need to continue braving the icy waters to learn more about this shark and its habitat. If we’re lucky, perhaps one day we can steal some of its longevity secrets for ourselves. But if we’re not careful, human behaviors could be the one thing capable of wiping the resilient creature out for good.

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Sometimes nature gives you a gift. This one looks like a two-year-old tried to sculpt a fish out of clay but got distracted halfway through. Its common name is the sunfish, but the German version is more accurate: Schwimmender Kopf, or “swimming head.”

Behold the majesty:

via GIPHY

Here’s a still image so you can fully appreciate just how absurd this creature is:

The mouth: agape. The fins: haphazardly stuck onto the end. The teeth: fused into a beak-like mouth. The butt: oddly fin-less. Embrace the strangeness, then take a moment to appreciate that these bizarre beauties can grow to be over 10 feet long and 14 feet tall—because their fins are placed vertically, for some unknown evolutionary reason. They can weigh over 5,000 pounds.

And now, instead of just three known species of sunfish, the world has been graced with four.

Sunfish are notoriously ridiculous, but they’re also notoriously difficult to capture and study. It took the biologist who recognized this new species four years of examining sunfish samples to ensure she had really found something novel. Genetic samples kept suggesting that there were four species of sunfish, when only three had been recognized. To verify the fourth’s existence, she and her colleagues had to actually go find one of the darn things.

This new species, the Mola tecta (or Hoodwinker sunfish), is a lot like its relatives in that it looks like half a fish. It also sports a characteristically prominent eye that stares blankly at the world. It’s different in that it’s less lumpy.

The lack of bulbous bumps on its pseudo-butt do give it a more streamlined profile—a small one might almost look cute. Baby sunfish, however, do not look like tiny version of their parents. They start out less than an inch long and develop quickly into tiny fry, which look like something between a pufferfish and blob of jelly.

Pufferfish are close relatives of sunfish, so it’s not surprising that there’s a strong infantile resemblance. Sunfish fry even swim like pufferfish. As grown-ups, they use their ridiculously oversized fins to gently scull the water. The clavus—a pseudo-tail that evolved in place of the tail fin found on most fish—helps them steer. Sort of. The sunfish is not exactly a graceful swimmer.

Those enormous vertical fins sometimes get them mistaken for sharks. But sunfish are gentle, blobby giants who like to sunbathe just like you. They don’t spend a ton of time at the surface (they can dive up to 2,000 feet) so when they come up, they rest with their wide, flat bodies spread out to catch the sun’s rays. They do it more to warm their bodies and allow sea birds to eat parasites off of their mucus-y skin than to get a nice tan, but hey.

That’s exactly what the sunfish featured in this 2015 video of a Boston man flipping out over a “sea monstah” was doing. It’s an incredible display of awe, fear, curiosity, and regional accents:

Sadly, since sunfish are fairly isolated creatures, you’re most likely to see one for yourself as it’s ripped apart by seals along the California coast. It’s not clear whether seals (and sea lions) try and fail to eat the fish or if they just like to kill for sport, but the mammals seem to enjoy tearing sunfish fins off and then abandoning the body. Without their fins, the poor sunfish drift to the bottom of the ocean, alive but unable to swim back up. Helpless, they’re slowly eaten by other sea creatures. And so ends the life of the peaceful sunfish. Gone, but not forgotten.

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Humankind has a long and storied history of misunderstanding the menstrual cycle. There was that time when NASA offered astronaut Sally Ride 100 tampons for her week-long mission to space. There’s that super pervasive (and totally unsupported) myth that if you put a bunch of menstruating humans in the same space, they’ll eventually “sync up” and get their periods en masse. Not to mention the countless religious and cultural traditions that deem the natural process to be somehow evil, unsanitary, or unclean.

We could turn PopSci into PeriodSci for a week and still not have time to debunk every myth related to monthlies. But today we’ve got an exceptionally absurd one to tackle: Does period blood attract sharks, making menstruating individuals (and their unfortunate swimming companions) more vulnerable to vicious shark attacks?

Short answer: no. Follow up: why are we even talking about this? Because apparently, it still needs to be said. During a recent video interview with TMZ, surfer Laird Hamilton—who, to his credit, did some very sound myth debunking by reminding viewers that shark attacks are incredibly rare—stated quite matter-of-factly that “the biggest, most common reason to be bitten is a woman with her period, which people don’t even think about that. Obviously, if a woman has her period, then there’s a certain amount of blood in the water.”

Obviously!

But he has a point, right? Because sharks smell blood.

It’s true that sharks have a bloody ridiculous sense of smell. Their nostrils exist for the sole purpose of smelling—not breathing—and they’re very sensitive. Chemicals dissolve into the water of the ocean and that water hits a shark’s sensitive nasal tissues, sending a smell signal to the brain. Here’s more info from the American Museum of Natural History:

So yeah, sharks love them some blood (or the amino acids inside our bodily fluids, anyway)—and they can smell really well. But not that well. If that whole “a shark can smell a drop of blood in a swimming pool” thing were true, sharks would be constantly overwhelmed by the cacophony of smells surrounding them. The Great White Shark can probably detect a drop of blood in about 100 liters of water, which is about 1/25,000th the amount of water in an olympic pool.

It’s a period, not that scene from “Carrie”

The average menstruating person loses about 30 to 40 ml of blood over the course of several days, maxing out around 80 ml for a really heavy cycle. Basically, if you suddenly got a super heavy period and just expelled all of that blood in one go (which, to be clear, is not how periods work), you’d be dumping about 6 tablespoons of blood into the ocean. This is also assuming you’re out there without so much as a tampon to your name, which is really unfortunate given that you just got hit with a totally improbable period scenario! But rest assured, dumping a third of a cup of human blood into the ocean is unlikely to send nearby sharks into a feeding frenzy. And once again: that’s not actually how periods work. Menstrual ‘blood’ isn’t just blood. It’s also the lining of your uterus, cervical mucus, and other totally normal secretions. Your standard menstruating swimmer is going to leave behind the tiniest traces of blood in the water, if any.

Sharks don’t want your stinking blood, anyway

In a 2016 explainer on this same subject—because yeah, people keep asking—Broadly asked Steve Kajiura of Florida Atlantic University’s Shark Lab for his input. He made the point that even when sharks can smell human blood, it’s not like they interpret it as a loudly clanging dinner bell. They’re sniffing for the scent of their prey of choice.

Sharks aren’t even interested in blood so much as they are in detecting amino acids, the building blocks that make up the proteins in all of our bodily fluids. What they want to detect are the amino acids from the blood, guts, and gooey bits of marine animals—the creatures sharks evolved to eat. Our blood, sweat, tears, pee, and cervical mucus are just static noise.

“You can smell a landfill, but it won’t make you want to eat it,” Kaijura said.

Let’s be clear here: periods do not cause shark attacks

“This is one of those misconceptions that refuses to die,” Chris Lowe, a shark researcher at Cal State University of Long Beach, told The Huffington Post in response to Hamilton’s comments. “In fact, the amount of blood loss during menstruation is probably less than average scrape or cut that a kid or surfer may get while playing in the water.”

“I’ve been diving for decades and even got my period while underwater with a school of hammerheads,” Marie Levine, founder and executive director of the Shark Research Institute, told Mother Jones back in 2012. “The sharks were not interested and I had to fin like crazy to get close to them.”

But what if I’m really, really afraid of getting eaten by a shark?

Don’t blame that on your menstruating friends! Outside Magazine points out that the best way to avoid a shark attack is to keep swimming at a nice, consistent pace so sharks don’t single you out as weak, easy prey. And hey: don’t be a dummy when you’re out in the surf, but try to remember that humans are way more likely to kill sharks than the other way around.

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Great white shark pups are spending their youth in the waters off of Long Island’s South Shore, marine biologists believe. The research group OCEARCH has identified what appears to be the first great white nursery in the North Atlantic after catching and tagging nine young sharks during a two-week expedition.

The nursery, where vulnerable shark pups bide their time until they are big enough to venture out of its shelter, may also be a birthing ground. Scientists suspected they might find a nursery in this area, since this is where the majority of small great whites in the North Atlantic have been found over the past 200 years.

The plethora of pups indicates a healthy ecosystem, with plenty of food for the growing sharks to dine on. Adolescent sharks (which are not considered a risk to people) spend about 20 years in nurseries, which have also been identified near Australia and South Africa.

You can see what the great whites and other shark species OCEARCH has tagged are up to with the organization’s shark tracker.

[via Gothamist]

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Move over, Lonesome George. Tortoises like George have long been considered to be among the longest-living vertebrates on Earth, living for over 150 years in many cases, though bowhead whales have given the reptiles a run for their money. But now, a challenger has come along to blow them both out of the water.

Meet the Greenland shark. In a paper published today in Science researchers published evidence that Greenland sharks can live for up to 400 years, only reaching sexual maturity around 150 years of age.

Greenland sharks are remarkably slow and almost blind preferring cold, dark waters and eating anything they can catch at their mincing average speed of 0.76 miles per hour. Sometimes, what they can catch is carrion. Or discarded moose.

Researchers figured out the sharks’ advanced age by dating the eye lenses of sharks that had inadvertently been caught as part of an Annual Fish Survey run by the Greenland Institute of Natural Resources between 2010 and 2013. Radiocarbon dating of the fish eyes showed that the sharks were hundreds of years old, with the oldest clocking in at around 392 years old.

The only animal to beat the Greenland shark is the ocean quahog, a clam that can live for over 500 years. It’s impressive, but we animals have a long way to go before we even come close to plants, which can live for thousands of years.

Bycatch

Tag and Release

Icy waters

Greenland Shark

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In a time long, long ago, say 300 million years ago, North America and Europe were on the equator, covered in hot and humid swamps. Many now-extinct fish species dominated the region, in particular the Orthacanthus, a shark with double-fanged teeth that could grow up to 10 feet long.

Scientist have known that around 260 million years ago, the Orthacanthus was an apex predator in the swamps that would one day become the coal seams mined throughout the Appalachians and western Europe. But a new study in the journal Palaeontology says that the top shark was not only eating all types of other species. It was eating its own children.

The group of international researchers studied fossils in New Brunswick, Canada, looking to focus in on ancient species’ euryhaline nature, or the ability of an organism to live in a wide range of water salinity types. But when they came across the fossilized feces of the Orthacanthus, which is easy to spot from its corkscrew shape, the researchers found baby shark teeth inside.

The researchers theorize that the sharks began to cannibalize its own young not because it was an evil fish of the underworld, but because of lack of food resources. The Orthacanthus was a euryhaline species, and as it moved into different aquatic ecosystem types, it may have run out of food.

Desparation cannibalism

“It’s possible that Orthacanthus used inland waterways as protected nurseries to rear its babies, but then consumed them as food when other resources became scarce,” said co-author Howard Falcon-Lang, paleontologist at the Royal Holloway University of London, in a press release.

But overall, Orthacanthus was able to use it salt-tolerant abilities to live in many different habitats, even with its cannibalistic plan B.

Secrets learned from fossilized poop

“Orthacanthus was probably a bit like the modern day bull shark, in that it was able to migrate backwards and forwards between coastal swamps and shallow seas,” said Aodhán Ó Gogáin, lead author of the study and doctoral candidate at Trinity College Dublin.

“This unusual ecological adaptation may have played an important role in the colonization of inland freshwater environments.”

[Via Motherboard]

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Sharks have a serious public relations problem. Despite being curious creatures with relatively little interest in human flesh, movies like Jaws and The Shallows paint them as bloodthirsty monsters. The booming, tense soundtracks to these films put us on the edge of our seats.

But what if videos of sharks swimming were paired with upbeat, pleasant music instead? Researchers studied the reactions of people watching a variety of shark videos: Overlaid with scary music, uplifting music, and silence. The participants’ feelings toward sharks were more negative after viewing the horror-music-style segments.

They used a clip from the “Ocean World” episode of the Blue Planet: Seas of Life documentary series, which begins with a pleasant musical score when showing schools of fish, but turns to a dark minor key when the sharks show up.

An independent unbiased music expert deemed the music “unsettling.” It aroused negative feelings toward sharks, while a more upbeat score with the same footage produced more positive emotions.

Regardless of their emotional responses toward the shark footage, people didn’t change their minds about shark conservation — they came out of the study with the same opinions they went in with. Nevertheless, the study authors think documentary makers should choose their music wisely.

“For many, documentaries are regarded as objective and authoritative sources of information, and for some, documentaries may in fact be the primary source of information on animals such as sharks,” they write in the paper. It’s up to editors and producers to make sure their subjects are captured in an unbiased, less sensationalist way. “Filmmakers, journalists, and exhibit designers set the tone of their works, and, while an ominous soundtrack may enhance their entertainment aspect, it may also undermine their educational value by biasing viewers’ perceptions of sharks.”

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You often hear that sharks don’t sleep. It’s a legend based on facts, and it has the added benefit of making the world’s favorite summertime horror villain into a juggernaut of nautical death.

But just because sharks don’t sleep, doesn’t mean they don’t nap.

A shark can’t stop swimming: they need to keep moving in order to push water through their gills so they can breath. But to conserve energy at certain times during the day, a shark might, say, find a place with a current, and let the water do more of the work.

Sharks look pretty much the same sleeping as when swimming: dark-eyed nightmares. But maybe it’s less scary if you convince yourself they’re just snoring underwater. Haha, silly sharks.

Watch below:

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Scientists have captured the first-ever shark sonogram, and gosh is it cute. Or creepy. Mostly creepy.

A 12.5-foot tiger shark, named “Emily” by these humans but probably named something a lot cooler by her shark fam, carries 20 pups. Before this, sharks were killed and cut open to study pregnancies.

This aquatic gynecologist appointment will help scientists track where sharks go to give birth: If they go to a nursery field, that area could be preserved and protected from human activities.

The refreshingly non-bloodthirsty video is part of Discovery’s Shark Week, said to be inspiring “Shark n’ Awe,” but apparently not puns beyond the Bush era.

Correction 6/30/2016 at 4:15PM: Tiger sharks, unlike sand tiger sharks, do not have intra-uterine cannibalism as was previously stated in an earlier version of this article. Sorry we accused these unborn sharks of murder.

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Sharks lurk in shallow waters and are drawn to activity—like the flailing of warm-blooded bodies. To ward off attacks, South Carolina father and son David and Nathan Garrison developed Sharkbanz, a wrist strap that repels sharks by deploying a weak electric field.

Sharks rely on electrically sensitive sacks in their snouts to navigate, and Sharkbanz scrambles this sense with annoying interference—almost like shining a bright light in its eyes. The band won’t harm the shark and is only a deterrent­­—so no guarantees.

This article was originally published in the July/August 2016 issue of Popular Science, under the title “A Wristband That Repels Sharks.”

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Nature is more efficient than pretty. Sometimes, there is beauty in that efficiency, like when sunflowers turn to face the sun. And sometimes, that efficiency is grotesque, when maggots transform a corpse into the dirt. Here is something roughly in the middle: 70 tiger sharks, eating a humpback whale in the waters off Dirk Hartog Island on Australia’s western coast, in the aptly named Shark Bay.

Captured by a drone, we can see the turquoise waters bleed red, an inverted southwestern skyscape rendered fresh and fleshy in the water.

The video was captured by Eco Abrolhos, a cruise company in Western Australia. “Passengers on our 14 day Geraldton to Broome and everywhere in between were treated to an unexpected phenomena whilst cruising inside Dirk Hartog Island,” it wrote on Facebook, “Something to show and tell the Grandchildren.”

Watch the video below:

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It’s not every feeding frenzy when a shark becomes the prey instead of the predator. But recently, a drone hobbyist stumbled upon just such an encounter, capturing footage of a pod of whales chasing down a shark off the coast of Sydney, Australia. Experts are having a hard time IDing the juvenile shark, but its hunters appear to be a species called false killer whales (Pseudorca crassidens, not to be confused with killer whales).

The shark’s fate appears grim—in the video, you can see one of the whales briefly surface with the hapless animal firmly clutched in its jaws. Marine biologists, however, are excited to see the pod in action, as false killer whales are rarely spied in the waters around Sydney.

[Motherboard]

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There are lots of species that glow in the dark, especially underwater. These species are genetically diverse, ranging from krill to squid, from sea snails to sharks, which makes researchers think that biofluorescence evolved many times independently. But just what role it plays, or why biofluorescence works to an organism’s advantage, is still a mystery. Now, to better understand how biofluorescence affects how two types of small, deep-dwelling sharks see each other, a team of researchers has created a camera that allows them to see the world as the sharks do, according to a study published today in the journal Scientific Reports.

Biofluorescent animals like sharks or turtles don’t produce their own light; instead, special molecules on their skin absorb surrounding light and reflect it back with a shifted wavelength so that it appears slightly different. But that all looks very different underwater, especially deep down where these live, since the ocean is a “huge blue filter,” David Gruber, a marine biologist at Baruch College and one of the authors of the paper, told The Atlantic.

The researchers first analyzed sharks’ retinas. They found that the sharks had long rods, which enables them to see in low light, and one cone so that they can see blue-green pigments. The researchers then created “shark-eye” camera that uses filters to mimic the light that the sharks see.

Armed with the camera, the researchers dove out into Scripps Bay, off the coast of San Diego, to see how catsharks glow in their natural habitat. Under normal lighting conditions, the researchers could barely see the sharks against the canyon wall. But with the “shark-eye” camera, the sharks’ skin was covered with a glowing green pattern, which differed depending on their species and their sex. The luminescence starts to appear at about 125 feet depth. The researchers suspect that the sharks’ biofluorescent quality makes it easier for them to spot each other in low light, which would help them find mates, while still evading predators that might not be able to see as well at that depth.

It’s like being at a disco party with only blue light, Gruber told National Geographic–some things look darker or lighter bathed in blue. “Suddenly, someone jumps onto the dance floor with an outfit covered in patterned fluorescent paint that converts blue light into green. They would stand out like a sore thumb. That’s what these sharks are doing.”

This isn’t the first time researchers have used visualization techniques to mimic how another organism sees the world. But this one might reveal something important about the role of biofluoresence. Based on how many times biofluorescence has evolved independently, the researchers suspect there’s more to learn about its role in animal behavior and evolution. Plus, there are probably more biofluorescent organisms out there to discover.

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Robots are a great tool for studying sharks. Without the need to breathe, they can stay underwater for a long time, and without any mortality, they have no capacity for fear. Three years ago, a research team led by Greg Skomal of the Massachusetts Division of Marine Fisheries used REMUS torpedo-shaped semi-autonomous underwater drones to study the predatory behaviors of Great White Sharks. And predatory behavior they indeed observed!

At first, the sharks seemed skeptical.

Then they pounced! Though, they quickly became bored of the iron seal and swam away.

Further observations found that the sharks would often lurk below the drones, before suddenly swimming up and striking in the middle, like in the second gif above. Members of the Oceanographic Systems Lab of the Wood Hole Oceanographic Institution captured the footage and compiled it in a video below. The results of the tests were published last month in the Journal of Biology, under the title “Subsurface observations of white shark Carcharodon carcharias predatory behaviour using an autonomous underwater vehicle.” Besides the awesome videos, the reseachers claim “This study demonstrated that an [autonomous underwater vehicle] can be used to effectively track and observe the behaviour of a large pelagic animal, C. carcharias. In doing so, the first observations of subsurface predatory behaviour were generated for this species. At its current state of development, this technology clearly offers a new and innovative tool for tracking the fine-scale behaviour of marine animals.”

Absolutely! Watch it in action below:

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For most us humans, our main navigational tool is eyesight. We rely almost entirely on visual cues and landmarks to find our way from one point to another. And living on land, that’s served us pretty well over the past few millennia. So how do animals in the open ocean, floating in the uniform, middle depths of the water column, find their way from point A to point B–and so often in a straight path, to boot? A study of leopard sharks, published today in the journal PLOS One, found that the sharks travel through the deep blue using their sense of smell.

If a human plopped into the water column of the open ocean, they would be utterly lost and completely helpless. Yet a variety of marine animals make regular migrations, covering vast tracts of the world’s oceans without ever losing their way. Great white sharks (Carcharodon carcharias) in the Pacific, for example, swim from California to Hawaii, a distance of some 2,400 miles. In an attempt to figure out how these animals do it, marine biologist Andrew Nosal from the University of California San Diego and a team of colleagues turned to local leopard sharks to find an answer.

Carcharodon carcharias Great white shark

Leopard sharks (Triakis semifasciata), are a relatively small species of shark (between 4 and 5 feet long), that spend most of their lives in shallow or coastal waters. The leopard sharks that live off the coast of Southern California, however, apparently have refined palates and will often swim out to Santa Catalina Island to feed as well. This is a distance of some 20 miles, with a depth of approximately 2,600 feet at its deepest point—definitely qualifying it as a pelagic, or open ocean environment. Nosal and team wanted to find out how these spotted sharks that spend almost all their time in shallow waters near land—with many landmarks available—navigate the big blue sea.

The team captured 26 sharks along the shore and transported them about 6 miles out to sea. Then, having a hunch smell might have something to do with their navigational abilities, they covered the nostrils of 11 sharks and let all 26 of them go. Using transmitting devices, they were able to trace the routes of the sharks back to shore and found that, sure enough, those with free nostrils were able to easily find their way back. Those with a plugged nose had a much more difficult time making their way home. (Their noses were blocked only temporarily with cotton that disintegrated after the study.)

It might seem obvious, to those who love these ancient fish, that sharks could travel with their nose. They are after all famous for their keen sense of smell (think Finding Nemo when Bruce the great white smells a drop of blood and relapses into his fish-eating ways). However, Nosal points out that “Sharks are known for their keen sense of smell, but mostly as it results to feeding.”

Despite some previous speculation, no one had tested how sharks’ olfactory abilities could play a role in navigation as well as hunting. And while other environmental cues are known to be employed by other marine animals, such as geodynamic, chemical, and hydrodynamic stimuli, how they are used remains poorly understood.

It’s possible that many other species of sharks use their noses for navigation as well–particularly long-distance travelers that live out in the open ocean like great whites, tiger sharks, and blue sharks.

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After the cinematic masterpiece Sharknado came out in 2013 we all had such a good time making up funny sequel ideas. “Wouldn’t Sharkcano be hilarious?” we laughed smugly to ourselves, thrilled by our own cleverness.

Nature is the only one that’s laughing now.

National Geographic just released footage of sharks observed swimming inside the crater of an active underwater volcano called Kavachi near the Solomon Islands.

Just to reiterate, and this cannot be emphasized enough: They found sharks. In a volcano!

With this, we must all accept that the world is weirder than our imagination could ever be.

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The normal human response to reports of a deadly shark in the water is to boil the sea, move inland, and spend the rest of one’s life in peaceful isolation at the top of a remote desert mountain. (Okay, perhaps that’s just me). For Animal Planet’s River Monsters show, Jeremy Wade instead goes into the ocean to look for salmon sharks.

He is aided in his quest by an unmanned underwater vehicle, or sea drone. Tossed from his ship into the water by hand, the VideoRay remotely operated vehicle peers through the green depths off the Alaskan coast, and spies the sharks it seeks. Then, to disprove the theory that salmon sharks are eating people, Wade’s crew tosses herring into the water to get the sharks hungry, and Wade himself dives in after.

Watch the scene below:

Wade is a biologist and an extreme angler, and he emerges from the shark and robot-infested waters unscathed. As he does so, he makes sure to note that, despite fears, the salmon sharks were totally focused on the fish around him, and that rumors of attacks on humans were just that, rumors. Which I guess means I don’t have to retreat to a desert mountain after all.

The Animal Planet special, Alaska’s Cold Water Killers, will air on Sunday, April 26, at 9 PM (ET/PT).

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– An undated photo – of a Great White shark which can now be repelled by a electronic shark shield…

Sharks are incredibly unlikely to bite you. They’re even less likely to kill you. However, we remain fascinated with their ability–and occasional proclivity–to do just that. With so many things more likely to harm us, why do we pay such rapt attention when sharks make headlines?

As a shark researcher and curator of the International Shark Attack File (ISAF), it’s a question I think about each spring when I prepare my annual report of shark-attack statistics. This year we had some good news: In 2014 fatalities were down worldwide, as were attacks. In the US, attacks were up only slightly from 47 last year to 52, with most of those being minor incidents that are more like dog bites than something out of Jaws.

There wasn’t a single fatality in the entire country last year and only three worldwide. In the past decade, the US has averaged less than one per year. To put that into perspective, more people die from drowning every day in this country than were killed by sharks in ten years. In 2013, more people in the U.S. died from encounters with nonvenomous insects, and a lot more–62–were killed by hornets, wasps and bees, according to the Centers for Disease Control and Prevention’s Underlying Cause of Death database.

We’re in their aquatic territory more now

When you think of how much time we spend in the water, it’s amazing how innocuous shark and human interaction is. When the ISAF began in the 1950s, scientists were concerned primarily with shark attacks after ships and aircraft went down at sea.

A lot has changed since then. There are a lot more of us on earth today than there were back then and there will be even more tomorrow. Aquatic recreation has never been more popular. More people are kayaking, surfing, diving and paddleboarding.

It’s partly a generational change. When my parents took a young me to the beach, my mother would lie on the sand and work on her suntan, never going in the water. My dad might have gone in once a day to cool off. Nowadays, if I’m at the beach, I might be boogie boarding or skin diving. Most of us are spending a lot more hours in the water than did our parents and our activities are inadvertently provocative. That creates ample opportunities for sharks and humans to get together.

Numbers may go up, but we’re learning

That’s why, even though fatalities are rare, we can expect to see an increase in the number–but not rate–of attacks. There aren’t a lot of things in science that I am willing to predict with certainty, but I am confident that in the second decade of this century we will see more attacks than in the first. That said, attacks are not rising as fast as we might suppose they would because we’re doing a better job of heeding beach safety and people are more shark-savvy than they were a decade ago. We’re starting to understand how to avoid sharks.

At the ISAF, we investigate every reported shark attack. Some are reported by hospitals, some by volunteers and scientists around the world. Others we find out about through traditional or social media.

In each case, through investigation we confirm that the guilty party was actually a shark. (You’d be surprised how many people who say they were bitten by a shark were bitten by something else, or not bitten at all.) We analyze the bite, which tells us the size of the shark, and sometimes the species. The ecological and behavioral circumstances surrounding the incident–from both the human and shark perspectives–give clues as to why the interaction occurred.

Tracking helps with prevention

There’s practical benefit to tracking these attacks. By creating a rating system–the Shark-Induced Trauma Scale–we’re helping physicians create treatment plans based on the severity of a bite. And we can advise officials in areas that are seeing a spike in shark attacks on how to reduce risk.

Education and outreach are a big part of what we do. We tell people not to swim at dusk and dawn, when sharks are most active, and definitely not at night. (That midnight swim might be romantic, but it could be your last.) We know that you should avoid swimming where people are fishing, or where you can see fish schooling or seabirds feeding, which could mean sharks are feeding, too. We also advise against wearing bright, shiny jewelry into the water, which sharks can confuse for the flashing of fish scales.

A great white shark leaps from South African waters

People need to understand more fully that when we enter the sea, it’s a wilderness experience. We’re eco-tourists and are not owed the right to be 100% safe. That’s what fascinates us about sharks: There’s an innate concern in our psyches about not wanting to get eaten. Almost every other animal on earth has to worry about getting eaten night and day. As humans, we rarely have that concern. People hold sharks in awe as one of the rare species that reminds us we’re still potentially part of a food chain.

You’re much more likely to be injured or die during your evening run than in a shark attack, but don’t expect to turn on the Discovery Channel and see Sneaker Week. For better or worse, we’re hard-wired to pay attention to creatures that can eat us–even if they rarely do.

George Burgess is the director of the University of Florida Program for Shark Research and curator of the International Shark Attack File.

This article was originally published on The Conversation. Read the original article.

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Hexanchus griseus , Sixgill Shark

Sometimes you just have to make a power saw out of shark teeth, for science.

This video shows a reciprocating saw, named Jawzall, that a team of biologists built to investigate the cutting power of the teeth of different species of sharks. Of course! The saw is supposed to mimic how shark teeth work when sharks shake their prey in their mouths to rip them up. Few things must be worse than getting shaken by a shark, but I have to say, power-sawing shark teeth does sound worse.

From the Jawzall, the team learned that shark teeth dull quickly. (They do not make for a reliable saw, it seems.) Perhaps that’s why sharks lose and grow new teeth so often, team members wrote in a research summary they presented at the annual meeting of the Society for Integrative and Comparative Biology. In addition, in yet-unpublished data, they found different species, which have differently-shaped teeth, also have different cutting power. “There actually is a significant effect of tooth morphology. That’s really striking,” Katherine Corn, an undergraduate at Cornell University, tells Popular Science. That’s her narrating the video. “We may be able to extrapolate factors about feeding ecology from tooth morphology,” she says.

Corn worked with a Cornell graduate student, Stacy Farina, and a University of Washington biologist, Adam Summers. Corn had been taking Summers’ class at UW’s Friday Harbor Laboratories, she says, when Summers asked, “Hey, does anybody want to glue shark teeth to a saw?” Corn said yes. Among her duties was defrosting the jaw of sixgill shark that had washed up in Friday Harbor two years ago, to collect the teeth. “It was a big shark,” she says. “Those jaws were magnificent.”

Updated Jan. 14, 2015: The original article sometimes used “chainsaw” to describe the Jawzall. The Jawzall is a reciprocating saw, with teeth that move back and forth, unlike a chainsaw, whose teeth move in a loop. I regret the error. -FD

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Prosthetics With Sensations

Astronaut Selfie

Antarctic Ice Cover

A Dead But Dazzling Star

Great White Shark

Total Eclipse

Earth Timelapse

Diving In A Robo Suit

Synthetic Sidewinder

Laser Scan

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Shark bites are a real threat to undersea fiber-optic cables. No, really. Google actually goes so far as to wrap its wires in a Kevlar-like material to prevent damage from sharks, a company spokesperson recently disclosed. As you can see in the video below, the animals have been known to bite cables.

For some reason, sharks seem to like fiber-optic cables more than old-fashioned coaxial copper wires, although it’s unclear why (“Sharks have shown an inexplicable taste for the new fiber-optic cables that are being strung along the ocean floor,” the New York Times wrote in 1987). It may be because the sharks are “encouraged by electromagnetic fields from a suspended cable strumming in currents,” according to a report commissioned by the United Nations Environment Programme and the ever-sexy International Cable Protection Committee Ltd. Sharks can sense electromagnetic fields, so it’s possible the cables alarm or interest them enough to take a chomp.

Here’s more about shark-cable interactions from the report:

Sharks may also bite the cables simply because they’re curious. “If you had just a piece of plastic out there shaped like a cable, there’s a good chance they’d bite that too,” Chris Lowe, a researcher at California State University, told Wired.

Call me a crank, but it’s somewhat comforting to me that in our modern age, where people “are living in the future” and communications can zip back and forth at the speed of light, that the cables which allow this to happen are still at risk from an ancient predator. “Where’s your homework, Doug?” “Oh, sorry, a shark bit an undersea cable while I was emailing it to myself, so I don’t have it.”

The post Google Protects Its Undersea Fiber Optic Cables… From Sharks appeared first on Popular Science.

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REMUS SharkCam: The hunter and the hunted from Woods Hole Oceanographic Inst. on Vimeo.

Want to see what it looks like when you get chomped on by a great white shark? Of course you do.

This video, made by the Woods Hole Oceanographic Institute, shows great white sharks near Guadalupe Island, Mexico. In 2013, Woods Hole researchers equipped a Remote Environmental Monitoring Unit, A.K.A. a REMUS-100 robot, with five cameras to find sharks and tag them. When the researchers sent REMUS underwater in Mexico, they got an eyeful of the sharks’ territorial and predatory behaviors. The sharks snuck up under the robot in much the same way they stalk and nab seals, the video explains.

REMUS-100s are versatile, underwater vehicles that are able to drive in little surveying patterns on their own. They come in different sizes and engineers are able to attach different instruments to them, including everything from sonar to radiation sensors to bioluminescence sensors. Woods Hole engineers invented them and the institute rents them out to research and military groups for ocean monitoring, seafloor mapping, and missions to find and clear underwater mines. Popular Science has written about their use in searching historical shipwrecks. (Plus, see a REMUS-100 deployment here).

In this case, the Woods Hole researchers were doing their own work with a specially-outfitted REMUS. This conference presentation from 2012 shows they’ve been preparing a REMUS to tag sharks for some time. The paper explains how the vehicle is programmed to spot and stalk sharks on its own, but doesn’t mention the possibility of sharks stalking it.

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Hammerhead sharks’ oversize fins allow them to maneuver underwater with incredible control. The fish evolved this and other traits over the span of 10 million years, turning them into one of the ocean’s most agile hunters. “But today, the rules of the game have changed,” says University of Miami biologist Austin Gallagher. “People are now in the picture.” In a paper published in June, he describes how adaptations that make the sharks so deadly to sea creatures also leave them vulnerable to humans.

Hammerheads, like sports cars, are built to accelerate in short, energy-intensive bursts, Gallagher says, which means encounters with fishhooks are often fatal. Once caught, a super-high stress response causes the shark to fight furiously, often until it dies of exhaustion. Between accidental bycatch, recreational fishing, and a booming shark-fin industry, some populations have plummeted 99 percent in the past century.

Another adaptation could help. Electrosensory organs in the sharks’ heads detect prey in wide swaths of seawater. Lanthanide hooks, which create an electromagnetic field in saltwater, could signal sharks to steer clear.

_This article originally appeared in the August 2014 issue of _Popular Science.

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Besides donning swimwear and slathering on sun lotion, visitors to Australian beaches may also want to check Twitter to see if there are any sharks nearby. The government in the state of Western Australia has now fitted 338 sharks, including great whites, with acoustic tags which send an electronic signal to shore-based receivers when the animals come within about a half mile of the beach. When this happens, the sharks’ location is tweeted out by the Surf Live Saving Western Australia (SLSWA) account. Tweets also include the sharks’ species and size.

Chris Peck, from SLSWA, told Sky News that the shark tweets will notify swimmers much faster than traditional warnings on the radio and in newspapers. There have been six fatal shark attacks in Australia over the past two years, most recently in November, NPR reported.

It should be noted that of course not all sharks have tags (duh), so a lack of tweets doesn’t mean an absence of sharks. And the mere presence of a shark doesn’t mean that swimmers are necessarily in mortal peril. “Just because there’s a shark nearby doesn’t mean to say that there’s any danger,” Kim Holland, a marine biologist at the University of Hawaii, told NPR. “In Hawaii, tiger sharks are all around our coastlines all the time, and yet we have very, very few attacks.”

Although Australia has had more sharks attack than any other country, the animals still present a relatively tiny threat to humans. Fewer than ten people are killed every year by sharks worldwide–in the United States alone, cows kill more people every year (about 22).

The state of Western Australia plans to begin catching and killing large sharks in designated areas near Perth and some popular beaches, starting Jan. 10. But thousands are expected to protest the decision this weekend, and 100 scientists co-signed a letter to the State Goverment calling on it to abandon the shark cull and adopt non-lethal measures to protect beach-goers. Most scientists agree that shark culling is ineffective at preventing attacks, since many large sharks are highly mobile, and don’t stick around any one area for long. Scientists agree that sharks are in trouble; about 100 million are killed every year, partially due to demand for shark-fin soup, an Asian delicacy.

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Happy Shark Week! In honor of the One True American Holiday (all other holidays are less true, due to lower shark content), I spent about an hour reading about sharks on Wikipedia. Important findings from a solid morning’s research: sharks often have weird names. For example: the birdbeak dogfish. That’s a real animal! Ditto the flaccid catshark and, perhaps weirdest of all, the porbeagle, which doesn’t sound like a fish at all. Click through for more.

Click to launch the gallery.

This article originally appeared on PopularScience.com August 14, 2012.

Dumb Gulper Shark

Birdbeak Dogfish

Tasseled Wobbegong

Sickle Fin Lemon Shark

Cookiecutter Shark

Starry Smooth-Hound

Scalloped Bonnethead

Porbeagle

Flaccid Catshark

Bowmouth Guitarfish

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I’m on a small boat. A woman in a bikini stands next to me dumping gallons of blood into the sea. Beside her, a man in board shorts strings barracuda heads onto large fishhooks as crooked as a witch’s finger, and in front of him, toward the bow, an engineer fiddles with an instrument that looks like a cross between a model rocket and a giant hypodermic needle. I’m covered in fish guts.

We are in the Bahamas, in a marine preserve, fishing for sharks. We have a research permit to do what’s otherwise illegal in this country, but the boat and its crew have a rough, paranoid quality to them, everyone as superstitious as pirates. Since I came on board, we haven’t had a single strike. The ocean seems empty, the crew is agitated, and I get the sense that I’m being blamed for the dry spell. The lead fisherman tells me flatly, “I think you’re bad luck.”

Just as the captain raises the anchor to motor to another spot, a spool of 900-pound monofilament begins unwinding furiously off the stern. A buoy attached to the line pinballs across the choppy ocean. A cameraman in a wetsuit readies his $50,000 waterproof HD-camera rig. A scientist grabs a steel lasso and a cordless drill, and an engineer snatches up the rocket-looking thing, which includes a plastic tube filled with sensors and a satellite transmitter.

The rocket-looking thing is one of the reasons we’re all here. It is a prototype of a new kind of shark tag, one designed to last decades, not days or months as current models do. It will record a shark’s behavior every few seconds, beaming back data when it can. If the tags work, scientists will get an unprecedented look into the secret lives of sharks. But in order for them to work, we have to tag a shark. And to tag a shark, we have to catch one.

Then the line goes limp, and the hook comes up empty.

* * *

The shark’s role in our oceans is almost entirely a mystery. Because scientists typically track sharks for only a few months and because sharks live for decades, the gaps in our knowledge are immense. We don’t know—with much detail—their migration patterns or where they mate and give birth. More important, we don’t understand their contribution to the health of the oceans, though it’s almost certainly significant. Most sharks are apex predators, akin to lions on the African savannah or polar bears in the Canadian Arctic, and those predators typically serve critical roles in maintaining the ecosystem.

“The ocean is like a fancy Swiss watch. If you take a major spring out, it’s not going to work as well as it is supposed to.”One thing scientists do know is that sharks are in trouble. Every day, more than a quarter-million sharks die as bycatch or as a result of the finning trade. Some ecologists say populations are down by 90 percent from just a few decades ago. No one knows what might happen if they fall beneath a certain threshold or disappear entirely.

“The ocean is like a fancy Swiss watch,” says Neil Hammerschlag, director of the marine conservation program at the University of Miami. “I don’t know how all the gears work together. But I do know that if you take a major spring out, it’s not going to work as well as it is supposed to.”

Hammerschlag, 34, spends nearly every weekend out on the water in South Florida, armed with hooks, lines, and tags. As a result, he is intimately acquainted with the limits of current technology; most tags, he says, are too expensive and don’t last long enough. Two years ago, he partnered with Marco Flagg, an engineer, to develop a new device. The production version of the HammerTag, he says, will last years and maybe even decades attached to a shark; it will be hundreds of dollars cheaper; and it will provide a thousand times the data.

Data, Hammerschlag says, will lead scientists to identify nurseries and hunting grounds for the first time. It will reveal life cycles to determine when the animals are most vulnerable. And with enough of it, conservationists could influence legislators. Without effective legislation, Hammerschlag says, shark populations will surely continue to decline­—and the ocean with them.

* * *

Apex Predator

The day I’m supposed to fly from San Francisco to the Bahamas to go shark tagging, I fall ill. The fever’s slight, but the cough is the kind that makes your brain rattle in your skull. I manage to let Hammerschlag know I’ll miss the plane and try for one the following day. Then I pass out. Twenty-four hours later I wake up and still feel terrible, but I pack my fins, underwater camera, mask and snorkel anyway. I send the crew members of the research vessel an e-mail saying I’ll be arriving by seaplane—the ship is already 25 miles north of Nassau. They write back that they’ll send a speedboat to pick me up. At the end, they sign off, “Request you bring five cases of beer.”

A red-eye brings me to Nassau, where I deplane, pick up the beer—five cases of High Rock—and meet my seaplane pilot, Paul, who is wearing jean cutoffs and no shoes. Paul has lived in the Bahamas his entire life and has been flying nearly half of it. He rests his toes on the aluminum pedals and says, “Once you fly barefoot, you can never live anywhere else.”

The vessel has a robotic sub, a six-person helicopter, full dive gear, surfboards, jet skis, and small, medium, and large tender craft.After jamming all the beer inside Paul’s tiny plane, I climb in. Paul tells me the research vessel is about 30 minutes away, somewhere between the Berry Islands and Chub Cay. When I first heard that we’d be working from a research vessel, I imagined some grotty live-aboard, given the current state of scientific funding. Not so. The vessel I am flying to meet has a robotic sub, a six-person helicopter, full dive gear, surfboards, Jet Skis, and small, medium, and large tender craft. It also has shag carpet, a hot tub, a bar, an interior design reminiscent of a James Bond set, and a fully uniformed crew, including a chef from Australia. Hammerschlag, it turns out, has some wealthy backers who are willing to let him use their boat. The only stipulation is that passengers sign a nondisclosure agreement. Apparently, the ship’s owners would rather not be named.

As we approach the Berry Islands, Paul angles the plane toward the ocean. The stall sensor goes off a split second before its pontoons slap the water. We’re at low tide, so the water is only about knee deep. I kick open the door and hop down into the lagoon. After a little while, a zodiac from the research vessel shows up. I begin loading the beer and my luggage into the craft, and I ask the driver, “What did I miss?”

“We just caught a 10-foot hammerhead and two juvenile tiger sharks,” he says.

“Where’s Neil?” I ask.

“He got cut up pretty bad wrangling the second tiger.”

Pretty bad, it turns out, means 15 stitches in his finger and blood everywhere. When I see Hammerschlag on the research vessel, he is wearing a large bandage and looks concerned. “Please don’t make a big deal out of my cut,” he says. “I grazed my finger on a tooth. It wasn’t an attack.” He then launches into a volley of shark trivia meant to be comforting. For instance, while shark attacks number 80 a year globally, he says cases of humans biting other humans average an impressive 1,600—and that’s just in the state of New York. Also, sharks tend to mistake humans for food in brackish water, not in clear salty water like the Caribbean. And he explains that during the last moments of their attack, sharks don’t rely on sight or smell. Instead, they rely on gel-filled electromagnetic sensing pores called the ampullae of Lorenzini for direction. It is because of this sixth sense, Hammerschlag theorizes, that he is standing before me with a bandaged hand. As the crew maneuvered the shark onto the stern, it sensed the whirling metal propeller nearby and twisted violently. Without malice or intent, its tooth—corkscrewed on one side to cut through turtle shells—simply happened upon the soft flesh of his finger. It was not an attack.

* * *

Tagging Grounds

I have time only to drop my baggage by a bunk when I get a tap on my shoulder. It’s time to go tagging. I jump on the little boat that will serve as our platform. Scattered over the decks I see spools of lines and giant hooks. It is then that I realize that shark tagging is actually a lot like sport fishing—but with a rodeo at the end. My colleagues on the boat, a combination of shark conservationists and eco-conscious volunteers, would disagree with me. Science and sport are separate, they would say. But it sure does not look like it.

Amid the fishing-like gear, sit several buckets and pipes drilled with holes and stuffed with guts. These are called SADs, or shark attractant devices, and they are thrown overboard to bleed all night in the warm sea. There’s also a four-foot-long cooler filled with chum: fish heads; rotting barracuda, jack, grouper; and a few gallons of fish blood. I ask Hammerschlag what he calls it, but he doesn’t have a name other than “the cooler,” which sounds boring. I christen it “the Chum Coffin.”

As soon as the hooks are out, we chum. The waters run red with blood and white with chunks of hand-mashed fish from the Chum Coffin, leaving an oily sheen on the surface. A field tech, nicknamed Dirty Curt, warns divers to stay clear of the slick.

“Did anyone explain to Brian how Curt got his nickname?” Virginia Ansaldi, Hammerschlag’s lab manager, asks.

“No, and don’t tell him,” Hammerschlag says. Curt, who looks a bit like Popeye, says, “Please don’t call me Dirty Curt.”

The process of taking rotten fish steaks and picking off thumb-size bits of meat is called “chunking.” It tends to leave the chunker smelling badly. But this afternoon it is our only diversion. We get no bites. As the day grows long, a tropical storm creeps overhead, which punctures the sea with pinpricks of rain. I have no rain jacket, and I am cold. My cough rattles back to life. Dirty Curt calls it a day. We might not have gotten a shark today, but with all the chum we’re dumping, we’re bound to get some tomorrow, the crew tells me. At the worst, we’ll get some the following day—the last day of the expedition. That night, the air conditioning breaks. I sleep on deck, under a towel and a bright moon.

* * *

A marine-animal tag is a simple device. It consists of a sturdy outer shell, sensing and communications equipment, and a means to connect the tag to the shark. Some tags transmit their data by satellite link; others quietly log information until they’re recovered by fishermen. Some tags measure general location with light readings; others use magnetometers to get a more accurate north-south position and compass headings.

No matter the tag, though, none are particularly high-tech. Satellite communications that move at one bit per second. The kind of processor used in cheap digital wristwatches and discount microwave ovens. You’ll find more groundbreaking componentry in your grandfather’s cellphone.

If tags are such crude devices, why haven’t scientists made better, cheaper, longer-lasting ones? On a breezeless afternoon, while standing on the bow of our tagging boat, I pose this question to Marco Flagg, the designer of the HammerTag. One reason, he says, is that higher-end electronics use more power, and power management is critical at sea. Another, Flagg tells me, is that there isn’t a lot of money to be made selling marine-animal tags to scientists, with their high standards and tiny budgets. The economics look even worse when devices last years.

Catch and Release

But economics aren’t Flagg’s concern. He’s a self-taught engineer who makes his money doing contract work for the Special Forces and deep-sea outfits. At the time of the expedition, he is developing underwater positioning systems for submarine war games and an alert system for scientists so fascinated by their surroundings that they don’t notice they’re about to run out of air. Tags are just a sideline, and he probably never would have started working on them if a 17-foot great white hadn’t mauled him 18 years ago.

The attack happened off the central California coast, while Flagg was testing a prototype diver-locator beacon. He was in a kelp forest off Point Lobos about 50 feet down when a set of jaws clamped around his torso. The shark probably would have killed him had it not chipped a tooth on his dive tank and the beacon’s metal housing, prompting it to retreat. Flagg managed to get to the boat, where he kept his wetsuit on fearing his guts might fall out, but remarkably, he needed only 15 stitches. When a local shark scientist later interviewed him about the attack, he offhandedly mentioned he needed new tags. Flagg, who had every reason to avoid sharks for the rest of his life, said he’d give it a try.

Since then, Flagg has made various improvements to marine-tag design, but it wasn’t until he met Hammerschlag that he felt compelled to rethink tags entirely. Hammerschlag challenged him to create a tag that could outlive a shark. For an engineer, it was a problem in need of solving.

Flagg began by rethinking the power source. Marine-tag makers have typically eschewed the use of photovoltaics, opting instead for batteries. The assumption was that sharks don’t surface long enough to make use of solar panels. Flagg tested this notion by attaching a solar-powered tag to his back and diving to 100 feet. To his pleasant surprise, he found that his panels still charged effectively in as little as 2 percent of the surface light.

With a new power source in hand, Flagg turned to energy management. He reduced power consumption by 90 percent by better controlling sensor activity and satellite transmissions. Paired with a backup battery that can last two years without recharging, the improved tag, he calculated, could last 50 years, perhaps longer.

Because his new tag was so much more energy-efficient, Flagg could add new sensors, allowing scientists to gather multiple data streams at once, including precise depth, acceleration along three axes, highly accurate location information, and water temperature. He also tweaked the transmission system. The HammerTag can send daily reports whenever it makes a satellite connection, but it also has a failsafe. When it senses that a shark is no longer moving and has reached an unsurvivable depth, it assumes the shark is dead, and a small explosive charge separates the tag from the body. The tag then floats to the surface and transmits a final batch of data.

Even with the improvements, Flagg reduced the price of his tag dramatically. While commercial devices with less capability and a shorter lifetime can cost up to $5,000, the final HammerTag will cost about $2,500. The lower the cost, Flagg argues, the higher the rate of adoption and the more shark data scientists will have.

* * *

Team Shark

Over the course of the second day, we troll different spots, most of which are shallow enough that I can see straight to the sea-grass-covered bottom. When the shallows turn up nothing, we try our luck at the edge of a 6,000-foot trench. We tell stories to pass the hours. Ansaldi recalls the time in Hawaii when she had to stomp barefoot on the carcass of a rancid tuna to create a paste for chumming. Dirty Curt is busy plotting. He says the current will take the bait into the deeper water. “In 30 minutes, we should have a shark,” he says. But as anglers know, predictions are a dangerous business. No sharks appear.

Something bites our line, and the buoy takes off. The boat goes from lethargic to frantic. I get ready to jump in the water.The crew chums more aggressively. I help Ansaldi haul the Chum Coffin onto the rail of the boat, where she dumps a few gallons of blood directly into the sea. Austin Gallagher, one of Hammerschlag’s PhD candidates, is bailing fish over the stern so furiously that he slips and falls headlong into a crimson pool of gore. No matter how much bait we spread, though, our hooks go unnoticed.

That night, I hear crew members whispering to each other about their bad fortune. Dirty Curt comes up to me and says, “We haven’t caught a thing in the last two days, and the only thing that’s changed is you.”

“Well, for surfers, not finding sharks is the best luck you can have,” I say, laughing weakly. Dirty Curt just stares.

* * *
The third day is our last before heading home, and I wake up determined to change our luck. I ditch my plain shirt and put on the official, if slightly dorky, expedition T-shirt that everyone else is wearing. Perhaps solidarity will break the curse.

When I board the tagging boat, I find that Dirty Curt has been considering my luck too and has fashioned me a charm: a necklace of monofilament looped through the eyes of a rotting rock hind grouper. He hands it to me roughly. “Don’t come within 50 feet of the boat without this necklace,” he says. I figure I’ll do just about anything to see a shark at this point, so I throw it on. Grease and blood begin to soak into my expedition T-shirt.

We chum valiantly all day, but with four hours of sunlight left, we’re still coming up empty. The sharks are elsewhere. We motor the boat into a channel between Chub and Bird Cays known for its fast current. Dirty Curt says we may catch sharks as they funnel through the hourglass waterway.

Almost immediately, something bites our line, and the buoy takes off at a furious pace. The boat goes from lethargic to frantic in a matter of seconds, with everyone madly assembling gear. My job is to photograph the tagging from the ocean, providing a shark’s-eye view of the event. I take off the fish head, change into my neoprene rash guard, and get ready to jump in the water. We motor into position, and Dirty Curt begins to reel in the hook, but there’s no resistance. It comes up empty.

Dirty Curt looks slowly around the boat. He sees the fish head hanging from a post.
Hammerschlag, speechless, points a finger at me, and Dirty Curt yells, “No one told you to take the fish head off!“

I can feel every sullen crew member looking at my neck. I don’t say anything—I just slip the necklace back on. I smell like a Chinatown fish market, and I wish this day would end.
The awkward moment is broken by the radio. “Berry Island Club here,” it squelches. A radio operator from a dock a few hundred feet away has been watching us fish. “If you’re looking for sharks, down current there’s a local hammerhead that shows up when we clean our fish,” he says.

Following the tip, we drift a mile down and drop anchor on a sandy shallow bottom. It is our last fishing spot on the trip. We have only a bit of sunlight left before the expedition’s end, but it seems that everyone’s just about given up. I know I have.

* * *
In an age of sensors and networks, animal tagging is ripe for disruption. The HammerTag does not simply imply a new twist on tagging, it represents a paradigm shift. Flagg tells me that he can imagine a day when tag relay stations sit around the world. Instead of satellites, tags would connect to the stations over Wi-Fi, dumping massive loads of data directly into the cloud for all scientists to see. Researchers could monitor sharks and anything else large enough to accommodate a tag. Instead of mapping a single species, the data would convey the movements and actions of an entire ecosystem.

Hammerschlag says he would like to have other kinds of data as well. He is considering a tag that would turn on a video camera when it senses sudden acceleration. Scientists could sit in their offices while watching sharks devour a school of smaller fish. It would be an entirely new way to see the ocean.

Even current tags, which might report as few as five or six location blips a month, have revealed their share of surprises. Scientists have found that hammerheads roam hundreds of miles northeast of their predicted range. Great whites, it seems, can dive nearly half a mile down and also occasionally gather in a place between Hawaii and California known as the shark café. For scientists working to protect sharks and the oceans along with them, this kind of data is invaluable. After all, how can they protect what they don’t understand?

* * *

Big Haul

With an hour of light left on the last day of tagging, the team is already packing its gear, resigned to yet another sharkless afternoon. Hammerschlag tries to put a brave face on things. Even when we don’t find sharks, he says, that’s data. “Apex predators are rare,” Gallagher echoes. “And becoming more so. They’re usually found away from mankind, and so it takes more and more gear to find them.”

As we exchange conciliatory banter, waiting out the day, I look up to see Hammerschlag staring at the horizon. I can’t see exactly what he’s looking at, just that his eyes are tracking something. Then he jumps up and yells the single word we’ve all been waiting to hear, “Shark!“

The buoy is running, but faster than before. Water is spraying off the float as it rips through the chop. Ansaldi and Gallagher pull in the other lines so they won’t tangle. Flagg gets tagging gear ready, including a mini harpoon the size of a leather awl. Dirty Curt readies a lasso made of braided metal for the front of the shark and a rope lasso for the tail.

From a distance of about 10 yards, Hammerschlag identifies our catch as a black-tipped reef shark. It moves erratically, one minute drifting, exhausted, the next thrashing against its invisible foe. Everyone is rushing around.

I ask whether it’s time to take off the fish head, but no one listens to me. I look at the lashings, which seem solid, toss off my charm, and jump into the water. I don’t know what compels me to do so. Perhaps it’s a sense of duty. Perhaps it’s just an excuse to get rid of my foul-smelling necklace.

I spend a few seconds treading water and calming my breath and make three or four spins to scan the blue beneath me for more sharks, which I assume must be everywhere. I can’t see any, other than the one we have on the line.

Hammerschlag jumps up and yells the single word we’ve all been waiting to hear, “Shark!“The shark is perfect, in the scientific sense. It’s old enough and big enough for tagging but young enough that it has no scars from battles with fishermen or prey. I am just feet from it, floating face-to-face with one of nature’s most fearsome creatures. Its jaw hangs open, and I can see row upon row of teeth. As the crew reels the animal toward the boat, I move in to touch it but stop. I feel ashamed, as if I’m grabbing for a trophy that does not belong to me. I’m not a scientist. I’m not helping the species survive. What right do I have to lay a hand on this perfect form?

Standing on the stern, Curt expertly lassoes the shark, settling the noose just behind the dorsal and pectoral fins. Slowly, he and another researcher draw the shark toward the stern of the boat, tying the lasso to the boat once the shark is close enough. Someone puts a piece of PVC pipe attached to a water pump into the shark’s mouth, and oxygenated water begins to gush over its gills.

There is an urgency to the work. When tagging, scientists not only need to land a shark, they have to do so in such a quick and artful manner that the animal feels little stress. Too much strain can exhaust a shark. It might swim off only to die a few days later.

With practiced precision, silent and focused and smiling faintly, Ansaldi and Gallagher use a syringe to draw a vial of blood from a hidden vein, filling it up with blood as red as yours or mine. They also clip a piece of fin as a sample for genetic testing and drill a small hole in the dorsal fin, so they can attach the tag with a zip tie.

And then they’re done. Hammerschlag signals me to get out of the water, and the team works together to loosen the lines and push the shark back into the water. It swims off under the satellite eye of science.

* * *
In the weeks and months following the Bahamas expedition and other weekend trips like it, Hammerschlag and Flagg begin to see results. The tags have flaws; earlier prototypes aren’t transmitting enough data. Flagg has to refit the surface detection sensors so the tags know when to transmit. But even with these shortcomings, the prototypes provide extraordinary amounts of information. By luck, a colleague of Hammerschlag’s recovers a HammerTag from a shark captured in the wild. It contains 200,000 data points—one for every four minutes the shark swam. And it reveals surprising behavior.

“[This] 14-foot tiger made frequent dives during the night to over 1,000 feet, including one massive dive to 1,300 feet lasting two hours, during which the shark was twisting, only returning to the surface to plunge to the depths again and perform the same behavior,” Hammerschlag tells me by phone. “Who knows what it was doing? Perhaps it was battling in the night with other sharks. I can’t say.”

Brian Lam is based in Honolulu. He is still scared but no longer terrified of sharks.

This article originally appeared in the May 2013 issue of Popular Science. See the rest of the magazine here.

The post The Quest To Uncover The Secret Lives Of Sharks appeared first on Popular Science.

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The coast of Western Australia has been particularly dangerous place for shark attacks recent years, earning it the distinction of becoming “shark attack capital of the world.” Between October 2011 and July 2012, great white sharks killed five people in attacks in the area.

In response, a company called Shark Attack Mitigation Systems (SAMS) and University of Western Australia scientists have been working to protect swimmers, surfers and divers from getting chomped on with a line of shark-deterring wet suits. After two years of research and development, the suits went on sale this week.

One version, “Elude,” camouflages the wearer in the water, based on the recent discovery that sharks seem to be color blind. The other, “Diverter,” aims to repel sharks with high-contrast black and white bands, a natural signal the company says tells sharks you aren’t the delicious snack they’re looking for.

“Many animals in biology are repelled by noxious animals – prey that provide a signal that somehow says ‘Don’t eat me’ – and that has been manifest in a striped pattern,” UWA professor Shaun Collin told the Guardian.

The suits’ designs were tested with tiger sharks off the coast of Western Australia, but not with humans inside them. More testing is scheduled for this summer, but the especially brave (or shark-prone) can order a suit now. When you’re talking life or limb, $495 isn’t that pricey.

The Guardian

The post “Invisibility Wetsuits” Hide You From Sharks While You Swim appeared first on Popular Science.

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Shark Tag

Shark behavior is one of the great mysteries of the ocean, and mediocre tags are primarily to blame. Scientists can’t understand something they can’t measure. Compared with other marine-animal tags, the HammerTag, now in prototype, is cheaper by hundreds of dollars, lasts years longer, and stores up to a thousand times more data. It can record a shark’s entire life, and when the shark dies, it will detach—via explosive charge—and float to the surface to make a final data dump.

1) ATTACHMENT

Scientists attach the tag to the shark in two ways. On smaller sharks, they use a small lance. On larger ones, they drill three small holes in the dorsal fin and string a nylon cord through them.

2) NOSE CONE

The nose cone connects the tag to the shark. It remains attached to the shark even after the micro-charge blows.

3) EXPLOSIVE CHARGE

When the device senses that a shark has stopped moving, meaning it’s dead, it triggers a micro-charge to fire. The charge separates the bulk of the tag from the nose cone, freeing it to float to the surface, where it can transmit data.

4) PAYLOAD

Constructed as a modular unit, the payload contains a backup battery, temperature sensor, and three-axis accelerometer that can determine whether the shark is resting or in pursuit.

5) SOLAR PANEL AND MAGNETOMETER

The tag’s photovoltaic cells can collect energy at two times the distance of vertical visibility, so 100 feet at 50 feet of vertical visibility. Near the surface it can charge the battery in 20 minutes. A magnetometer determines a shark’s north-south position depending on the strength of the magnetic field. GPS does not work underwater.

6) FLOAT BODY

A head made from syntactic foam will float a tag to the surface once it detaches from the shark.

7) DEPTH SENSOR

Nested in the foam head, a pressure sensor relays depth information to the central processor.

8) SATELLITE ANTENNA

Providing the shark is near the surface, the ARGOS satellite antenna can transmit up to 120 32-byte packets a day, enough to convey moment-by-moment details or a single-day summary.

This article originally appeared in the May 2013 issue of Popular Science. See the rest of the magazine here.

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Sharks have been mythologized in our culture as ruthless brutes and hunters, but the truth is humans are way, way more of a threat to sharks than sharks are to us. About 100 million sharks are killed annually, mostly related to “finning” (when the shark fins are sliced off and sold, often for soup).

Marketer Joe Chernov wanted to visually express how the amount of shark attacks that kill people in a year stacks up against the number of people attacks that kill sharks. (It takes four seconds for us to kill the number of sharks that kill us in a year.) So Chernov teamed up with designer Robin Richards to make this incredible infographic comparing the stats. Note that the first figure is per year, while the second is per hour. Your jaw is about to fall about as far down as this image.

Shark Attacks By The Numbers

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This is a shark fetus, with two heads. Sharks, according to Michael Wagner, MSU assistant professor of fisheries and wildlife, who confirmed the discovery, usually have only one head (I’m paraphrasing).

This is a bull shark fetus, a very common shark found throughout the warmer waters of the world. Bull sharks are among the most aggressive sharks on the planet; they can survive in brackish (part-freshwater) environments, were probably the inspiration for the movie Jaws, and apparently once mauled a horse in Australia. Which is to say, if you had to pick one shark species that’d be the scariest if it had two heads, it’d probably be a bull shark. I am not sure what kind of shark was the basis for the movie 2-Headed Shark Attack, starring Carmen Electra and Hulk Hogan’s daughter, but the bull shark would have been a good choice.

This particular shark had two distinct heads on a single body; dissection found that it had separate heads, hearts, and stomachs, but that the remainder of its body was that of a single shark. Yeah, dissected: the shark was found in the uterus of a mother bull shark caught in the Gulf of Mexico, and died shortly after it was cut out. It almost certainly would not have survived birth, had it been birthed naturally.

There’s no evidence that the two-headed shark is the result of pollution, even though it was found relatively soon after the Gulf oil spill. Abnormalities like this are not unheard of in nature, though this is the first two-headed shark ever found. The article was published in the Journal of Fish Biology.

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Dolphins are great! Intelligent, charming, cute. This newly-discovered dolphin-like predator: maybe not so great.

_Thalattoarchon saurophagis_–meaning “lizard-eating ruler of the sea” (!)–was at least 28 feet long, and spent its 160 million years on Earth eating creatures that were smaller, the same size, and even bigger than itself, before it died out about 90 million years ago, or 25 million years before the end of the dinosaurs. It used a giant skull with giant teeth to prey on those often-giant sea-dwellers.

Researchers, who first discovered fossil evidence of Thalattoarchon in central Nevada in 2008 and published their findings this week, pin the creature’s heyday at about 244 million years ago. That puts it at 8 million years after a mass-extinction killed as many as 96 percent of ocean creatures. It seems, then, that ecosystems restore balance after a major die-off relatively quickly: if predators this size were able to survive by hunting other large creatures, there must’ve been small creatures at the lower end of the food chain, too.

Still, though: tough luck for those species that barely missed mass extinction, then had to deal with this thing.

LiveScience

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At the Florida Museum of Natural History, filling up two five-drawer file cabinets are 2700 detailed accounts of shark attacks that collectively make up what’s called the International Shark Attack File. The name of the database might be somewhat misleading—two recent stories suggest that shark-human interactions should be referred to as “incidents” rather than “attacks.” But whether we think of them as vicious, violent killers or big, curious fish navigating cloudy waters, one thing is clear from the Shark Attack File: Sharks bite more people in U.S. waters than anywhere else in the world.

According to the File, 39% of the incidents in 2011 involving shark teeth sinking into unwitting human flesh occurred in shallow waters off U.S. beaches. That’s way more than Australia, who racked up 14% of shark attacks last year to come in second. And yet, the United States’ share of incidents was the lowest in over a decade—between 2001 and 2011, an average of 59% of confirmed, unprovoked attacks took place in U.S. waters.

Percentage of Worldwide Shark Attacks Occurring in the U.S.

Apparently, this trend doesn’t have anything to do with the relative deliciousness of American thigh meat. According to an analysis by George Burgess, a shark researcher at the Florida Museum of Natural History and the current keeper of the International Attack File, “the number of shark-human interactions occurring in a given year directly correlates with the amount of time humans spent in the sea.”

And that simple fact could explain why attacks in the U.S. have been on the decline. Americans have likely spent less time in the water since the recession, writes Burgess, limiting their exposure. That might not be the whole story, however; Burgess thinks that worldwide overfishing could also mean there are fewer animals out there mistaking a wetsuited human for a savory seal.

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Speedo’s Fastskin line (including the banned-as-of-2009 LZR suit) of high-tech, high-performance swimsuits were inspired by the skin of a shark–shark skin’s sandpaper-like texture is thought to reduce drag, hence its usefulness in swimming gear. But an ichthyologist at Harvard performed a study and found that Fastskin is “nothing like shark skin at all,” and that its surface properties do not reduce drag one bit.

Shark skin, as well as the skin of related fish like rays and chimaeras, is covered with dermal denticles, almost like little teeth. George Lauder, a professor of ichthyology at Harvard, performed experiments to analyze the purpose of these dermal denticles, and tested the Speedo suits as well, to see how similar they are.

Shark Skin Closeup

What he found was that while the Speedo Fastskin suits may enhance a swimmer’s speed, it’s not due to the reduction of drag. Says Lauder:

“What we found is that as the shark skin membrane moves, there is a separation of flow. The denticles create a low-pressure zone, called a leading-edge vortex, as the water moves over the skin,” he said. “You can imagine this low-pressure area as sucking you forward. The denticles enhance this leading-edge vortex. So my hypothesis is that these structures that make up shark skin reduce drag, but I also believe them to be thrust-enhancing.”

But that drag reduction only occurs when the skin is attached to a flexible body. Human bodies, which are far less flexible, receive no benefits at all from the surface of the suit. Of course, Lauder speculates that the suit could still have speed benefits–it enhances a swimmer’s posture, and its tightness could have a beneficial impact on circulation. But swim like a shark? Nope–it’s going to take more than some artificial shark skin for that.

Harvard

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Last August, while diving to conduct a fish census on Australia’s Great Barrier Reef, marine ecologist Daniela Ceccarelli spotted the ghostly white skin of a brown-banded bamboo shark. When she swam in for a closer look, she saw that the fish’s head had disappeared—into the mouth of another shark.

The predator was a four-foot wobbegong, a bottom-dwelling shark that uses its natural camouflage to blend into the seafloor and ambush prey. Like many sharks, a wobbegong can unhinge its lower jaw to attack large prey; its sharp, rear-pointing teeth then keep the victim from escaping. Both sharks remained motionless for the 30 minutes Ceccarelli and her research partner spent watching them. Ceccarelli says the bamboo shark was almost certainly dead by the time she arrived, and that it probably took several more hours for the wobbegong to finish its meal.

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In 2005, Eric Stroud, the managing partner of Shark Defense, a New Jersey company that specializes in shark-repelling technologies, happened to be carrying a rare-earth magnet as he passed a tank full of sharks. The sharks fled, and Stroud took note. After further tests, Stroud and his colleagues found that sharks that came within 20 inches of rare-earth magnets similar to the one he had been carrying would consistently swim away.

The discovery earned Shark Defense $25,000 from the World Wildlife Fund’s annual International Smart Gear Competition, which rewards inventors who develop new methods to keep animals from getting tangled in commercial fishing lines. Shark Defense is now investigating ways to embed the metals in nets. And Stroud says the same metals, worn as an anklet, could act as a personal shark deterrent.

Field Test

The company is also working on a chemical repellent, a slightly sweet-smelling combination of a dozen compounds that mimics the scent of rotting shark. Patrick Rice, the senior marine biologist at Shark Defense, has developed the repellent in several forms: as a pressurized can of aerosol spray that can create a 50-milliliter cloud and is popular with spear fishers, a pouch that bursts underwater to quickly clear an area, and a gel that can be injected into bait to keep sharks from getting hooked. The chemical repellent is less expensive than rare-earth magnets. Still, Rice says, “just like anything else, nothing’s 100 percent effective. If sharks are in a frenzied state, if they’re hungry enough, they’ll start eating.”

Adapted from Juliet Eilperin’s book, Demon Fish: Travels through the Hidden World of Sharks.

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Great white sharks have been around for more than four million years, yet they remain one of the world’s most mysterious animals. Scientists know that the beasts have special organs for sensing electromagnetic fields and that their jaws can snap down with 4,000 pounds of force. But migration patterns, which are critical for conservation efforts, are mostly unknown.

OMG GR8WHT!

That will change now that marine biologists in Australia can follow the whereabouts of 75 of the man-eaters using radio-transmitter tags and a network of 20 satellite-linked buoys.

It’s not known how far great whites—whose worldwide numbers are estimated to be fewer than 3,500—migrate or if there’s a season when they spend more time near the coast, says Rory McAuley, a senior research scientist with Western Australia’s Department of Fisheries. McAuley hopes that the buoys, along with about 50 sensors on the ocean floor, will also reveal behavior. This information could help authorities better predict the monthly risk at beaches and restrict seasonal shipping routes to protect sharks from boats.

As a bonus, the work could give swimmers a heads-up when a great white is closing in. If a tagged shark swims within approximately a quarter-mile of a coastal buoy, the system sends a text to lifeguards on nearby beaches. Even swimming at top speed, it might take the dangerous fish a couple of minutes to reach shore, possibly enough time for the lifeguards to drop the phone and sunscreen and get folks out of the water.

Satellite-Linked Buoys

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A whale’s skin is easily glommed up with barnacles, algae, bacteria and other sea creatures, but sharks stay squeaky-clean. Although these parasites can pile onto a shark’s rippled skin too, they can’t take hold and thus simply wash away. Now scientists have printed that pattern on an adhesive film that will repel bacteria pathogens from hospitals and public restrooms.

Patented by Sharklet Technologies, a Florida-based biotech company, the film, which is covered with microscopic diamond-shaped bumps, is the first “surface topography” proven to keep the bugs at bay. In tests in a California hospital, for three weeks the plastic sheeting’s surface prevented dangerous microorganisms, such as E. coli and Staphylococcus A, from establishing colonies large enough to infect humans. Bacteria have an easier time spreading out on smooth surfaces, says CEO Joe Bagan: “We think they come across this surface and make an energy-based decision that this is not the right place to form a colony.” Because it doesn’t kill the bacteria, there’s also little chance of the microbes evolving resistance to it. Hey, it’s worked for sharks for 400 million years.

That’s good news for hospitals, where infections from drug-resistant superbacteria like MRSA, a potentially fatal strain of staph, are becoming commonplace. Bagan hopes to stick the skin on nursing call buttons, bed rails, tray tables and other surfaces by next year. Pending FDA approval, the shark pattern could be manufactured directly onto bacteria hotbeds like catheters and water containers by 2012. First, though, look for Sharklet on high-touch surfaces like door handles in restaurant restrooms around the U.S. later this year—a welcome extra line of defense against those who forget to wash their hands.

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Overfishing made the grey nurse shark endangered, but it’s the animal’s bizarre, cannibalistic embryos that are making it difficult for the species to rebound. The gestating shark pups need a “time out,” says Nick Otway, a fisheries biologist at Port Stephens Fisheries Institute in Australia. As a last-ditch effort to keep the species from eating itself into extinction, he built an artificial uterus, a souped-up fish tank that will give each unborn baby its own womb.

Female grey nurse sharks have two uteruses, in which embryos play “king of the uterus”: competing for nutrients, with the strong gobbling up weaker kin. The last shark standing in each womb devours any unfertilized eggs during a yearlong gestation, after which the mother gives birth to the two pups. The shark’s long pregnancy and low birth rate—along with people killing it because they mistakenly assumed it is a maneater—have knocked its numbers down to just a few thousand worldwide. And caretakers have had trouble keeping pups born in captivity alive, producing only nine sharks in 20 years.

Nick Otway Monitors an Artificial Uterus

Last September, Otway conducted the first trial of the acrylic uterus with 10-month-old embryos from a pregnant wobbegong shark, a non-cannibalizing, plentiful species whose young develop on the same schedule as the grey nurse’s. He replicated a shark’s uterus by bathing the embryos in 68˚F seawater. After 17 days, the fake womb “gave birth” to six healthy pups. The team plans to experiment with younger wobbegongs and adjust the mixture in the tank to a watery solution rich in urea, sodium and potassium to match the early stages of a wobbegong pregnancy.

Sharks in a Box

Before Otway rears grey nurse sharks, his crew will study and duplicate the intrauterine solution found in the mothers. Then he’ll build separate wombs for each embryo. If all goes well with the 10-year project, he could increase a mother’s brood to 20. Otway says he could adapt the device for biologically similar species, but he has no plans to make artificial human uteresus. “That might be possible, but I don’t want to get into it because of the ethical issues,” he says. “I’ll stick with sharks.”

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Back to the Drawing Board

In 2002, an Australian company called Shark Shield released a brick-size transponder meant to keep away the worst fear of every diver and surfer: sharks. The thinking behind Shark Shield’s eponymous gadget is simple enough. Sharks have electroreceptors in their snouts, called ampullae of Lorenzini, that detect electric fields for navigation and predation. By emitting an irritating electric field, the idea goes, the Shark Shield would trigger a nasty sensation in the ampullae, forcing even the hungriest hammerhead to turn on its fin.

But this March, during an investigation of a 2005 shark attack in Australia, the shield’s effectiveness came into question after reports surfaced that a great white shark ate a chunk of bait hanging from a float carrying a prototype for surfboards. Could the electric field actually attract sharks? Rod Hartley, a co-founder of Shark Shield, says no and argues that the failed gadget was just a test unit with an undersize antenna. “Our final design works 100 times out of 100,” he insists.

Experts aren’t entirely convinced. Studies have shown that sharks will often turn away when they detect certain types of electric fields, says Christopher Lowe, a marine biologist at California State University at Long Beach. “But we also know that a highly motivated shark—one that’s rushing for prey, for example—can penetrate it.” And it’s important to note Shark Shield’s disclaimer: It works when the board is stationary but could be ineffective if the surfer is paddling or riding a wave.
It’s possible that the electric field only momentarily startles sharks, and scientists don’t think one device will repel (or attract) all species of sharks. “Animal behavior isn’t consistent in different conditions,” says Peter Klimley, an animal behaviorist at the University of California at Davis. “Anyone who says something works [with animals] 100 percent of the time is lying.”

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A metal that reacts with seawater to produce an electric field may help keep sharks at bay. But the idea isn’t to protect humans from shark attacks. Just the opposite: scientists hope the metal will save sharks from senseless deaths in fishing nets.

An estimated 11 million to 13 million sharks die each year as “bycatch,” collateral damage in the hunt for other fish. Sharks grow slowly and can take many years to reach reproductive age, so their populations are being severely impacted by fishing.

In a recent study that offers hope for preventing some of these deaths, scientists from NOAA, four universities, and a research firm that develops shark repellents placed bars of the metal palladium neodymium in tanks holding juvenile sandbar sharks. The sharks avoided the metal bars and weren’t tempted by bait suspended within 12 inches of the bars. The study suggests that the metal could be used to ward sharks away from fishing gear.

Palladium neodymium is machinable and reasonably priced. But more study is needed to determine whether it can resist corrosion and remain effective as a shark repellent over long periods of time.

Comparison

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