Researchers have spotted orcas in the Gulf of California repeatedly attacking and feasting on the livers of juvenile great white sharks in first-of-their-kind observations.

The orcas (Orcinus orca) employed a savage-but-clever method to temporarily paralyze their prey, according to a new study. The technique involved flipping the small sharks upside down, thereby changing their awareness of their surroundings and forcing them into a trance-like state known as tonic immobility.

"This temporary state renders the shark defenseless, allowing the orcas to extract its nutrient-rich liver and likely consume other organs as well, before abandoning the rest of the carcass," study lead author Jesús Erick Higuera Rivas, a marine biologist and director of the nonprofit research organization Conexiones Terramar, said in a statement.

In three separate instances, the orcas were then observed sharing the shark livers among themselves. The attacks were carried out off the coast of Mexico by Moctezuma's pod, an orca group named after a large male member that made headlines last year for brutally slaying a whale shark (Rhincodon typus).

Orcas were already known to hunt great white sharks (Carcharodon carcharias) in some regions, including South Africa and Australia, but records of this behavior in the Northeast Pacific are extremely rare, with the last reliable sighting off the West Coast documented in 1997. Sightings in South Africa and Australia have primarily involved adult great whites, whose large proportions and organs mean more food for the orcas, according to the study.

There is only one previous report of orcas killing a juvenile great white shark. The attack happened in 2023 off the coast of South Africa by an infamous orca named Starboard; the predator gripped onto a young great white shark's pectoral fin, thrusting it forward several times before eviscerating the shark, according to the report.

The new observations, published Monday (Nov. 3) in the journal Frontiers in Marine Science, reveal that orcas attacking young great whites is more widespread than scientists thought.

"This is the first time we are seeing orcas repeatedly target juvenile white sharks," study co-author Salvador Jorgensen, a marine ecologist at California State University, Monterey Bay, said in the statement. "Adult white sharks react quickly to hunting orcas, completely evacuating their seasonal gathering areas and not returning for months. But these juvenile white sharks may be naive to orcas. We just don't know yet whether white shark anti-predator flight responses are instinctual or need to be learned."

Two of the three attacks took place in August 2020, according to the study. Five female orcas from Moctezuma's pod pursued one young great white shark until it tired, pushed it to the surface, and turned it onto its back. The orcas eventually forced the shark underwater, and when they reappeared, they were holding its liver in their mouths, the researchers described. Shortly after this kill, the orcas went for seconds, chasing and gutting a second young great white.

The third attack was in August 2022 and followed a similar sequence. Five orcas, including one adult male, flipped a young great white like a pancake, pushing it to the surface and biting it. Blood gushed from the shark's gills, and its liver protruded from its abdomen enough for the orcas to grasp it.

A closer look at where the sharks' injuries were suggested tonic immobility may minimize the orcas' chances of being bitten as the orcas try to extract the liver. Choosing juveniles as prey also limits the risk to orcas, but it's unclear if orcas in the Gulf of California only kill youngsters or if they regularly attack adult great whites, too.

"This behavior is a testament to orcas' advanced intelligence, strategic thinking, and sophisticated social learning, as the hunting techniques are passed down through generations within their pods," Higuera Rivas said.

One reason this behavior has been spotted now may be that great whites only recently started breeding in Mexican waters. Rising ocean temperatures and climate events such as El Niño appear to have shifted the distribution of great white shark nurseries, and Moctezuma's pod is likely taking advantage of an increased number of juveniles in the Gulf of California.

Other orca pods in the area could catch on, study co-author Francesca Pancaldi, a marine biologist at the National Polytechnic Institute in Mexico, said in the statement. "So far we have only observed this pod feeding on elasmobranchs [sharks and rays]," she said. "There could be more."

Megalodons might have been even larger than we first thought, growing up to 80 feet (24.3 meters) long — 15 feet (4.5 m) longer than previous predictions, according to a new study.

These massive sharks may also have been more slender than originally believed, the researchers said.

"Previous estimates using teeth to predict its size had the shark reaching about 18-20 meters total length (59-65 feet)," study co-author Phillip Sternes, an educator at SeaWorld San Diego, told Live Science in an email.

Megalodon ruled the seas of ancient Earth between around 20 million and 3.6 million years ago. No complete megalodon (Otodus megalodon) skeletons have ever been found, so our knowledge of these behemoths comes from fossils of their vertebrae scales and teeth. The largest megalodon fossil ever found is a 36-foot-long (11 m) section of its spine, which would have been located in the trunk of its body.

In the new study, published Sunday (March 9) in the journal Palaeontologia Electronica, researchers examined megalodon fossils and compared them with more than 150 living and extinct shark species to build a better picture of just how big this giant shark was.

The researchers compared the proportions of the megalodon's trunk with the trunks of 145 modern and 20 extinct shark species.

Related: What did 'the meg' look like? We have no idea

Assuming that the megalodon was roughly proportional to the majority of other shark species, and extrapolating from the 36-foot (11 m) trunk section, the researchers estimated that this individual may have had a 6-foot-long (1.8 m) head and 12-foot-long (3.6 m) tail, giving it a total length of 54 feet (16.4 meters).

However, the largest megalodon vertebra ever found measured up to 9 inches (23 centimeters) in diameter — 3 inches (7.6 cm) bigger than the largest vertebra from the 54-foot shark. Scaling up from this larger vertebra, and based on the previous proportions, the megalodon it belonged to may have measured 80 feet long.

The researchers also found that the megalodon may have given birth to live young measuring 12 to 13 feet (3.6 to 3.9 m) long.

Megalodon shape

The researchers behind the new study also investigated the megaladon's shape.

Megalodon tooth fossils are serrated and resemble the teeth of modern-day great white sharks (Carcharodon carcharias), which previously led researchers to assume that megalodon looked similar to great whites.

"Previous studies simply assumed that megalodon must have looked like a gigantic version of the modern great white shark without any evidence," study lead author Kenshu Shimada, a paleobiology professor at DePaul University in Chicago, told Live Science in an email.

However, according to the new study, the megalodon may have actually looked more slender and streamlined.

Based on the revised maximum body size, as well as hydrodynamic models of how large creatures like whale sharks (Rhincodon typus), basking sharks (Cetorhinus maximus) and whales move through the water, the researchers conclude that the megalodon wasn't stocky like a great white and instead was more similar to a lemon shark (Negaprion brevirostris).

However, until researchers find a larger section of a megalodon's body in the fossil record, we won't truly know how large they could get, or what shape their bodies may have been.

Jack Cooper, a megalodon researcher at Swansea University in the U.K. who was not involved in this new study, isn't convinced by the study authors' argument that megalodon looked more like lemon sharks than great whites.

"The hydrodynamic methods they use to try to rule out these other body forms are based primarily on whales, which have totally different skeletons and modes of swimming to sharks (i.e., vertical vs horizontal tail movements)," Cooper said. "As such, while the proposed body plan is possible, it should be treated as a working hypothesis and previous reconstructions can't yet be definitively ruled out."

Shark quiz: How much do you know about these iconic ocean superstars?

Researchers have tagged a giant great white shark off the East Coast of the U.S. that they say is the largest male they've ever studied in the northwest Atlantic.

The shark, which the researchers named "Contender," measured 13 feet, 9 inches (4.2 meters) long — about as long as a compact car — and weighed an estimated 1,653 pounds (750 kilograms).

Shark non-profit OCEARCH tagged the great white shark (Carcharodon carcharias) on Jan. 17, around 45 miles (70 kilometers) east of the coastline on the Georgia-Florida border. OCEARCH have since shared videos on social media of the moment Contender was caught and released.

Contender is the largest male great white shark ever caught, tagged and released by OCEARCH in the western North Atlantic region, according to the non-profit. OCEARCH researchers tag white sharks spending their winters off the southeastern United States.

Dr. Harley Newton, OCEARCH's chief veterinarian and senior veterinary scientist, told Live Science in an email that Contender was only the third adult animal they'd caught and sampled during the sharks' winter residency.

"Male white sharks mature at approximately 26 years of age and around 11.5 feet [3.5 m], so certainly we were excited to see an animal of his size at nearly 14 feet [4.3 m]," Newton said.

Related: 'Mega momma' great white shark killed on drumline may reveal secrets about iconic predator

Most shark length records are estimates, and the larger estimates are often disputed. However, mature males are 11 to 13 feet (3.4 to 4 m) long, according to the Smithsonian National Museum of Natural History in Washington, D.C. That range means Contender is about 9 inches (23 cm) longer than a typical large male of this species.

Female great white sharks grow to around 20 feet (6.1 m) long — much larger than males — so Contender is far from the biggest member of its species on record. The biggest reliably measured great white shark was 19 feet, 9 inches (6 m), according to the Massachusetts Division of Marine Fisheries. However, there are unconfirmed reports of great whites growing to around 23 feet long (7 m), according to the Florida Museum of Natural History.

Newton said that because they don't encounter adult size white sharks of either sex very frequently, Contender was an important find. OCEARCH has been trying to better understand the lives of white sharks in the North Atlantic to help inform conservation efforts to protect them.

"The elusiveness of the adult animals for researchers may simply reflect that they spend their time in deeper waters/further offshore from sites where active tagging efforts are being performed," Newton said.

The team used a smart position and temperature transmitting (SPOT) tag to monitor the animal. A SPOT tag, which is fixed to the shark's first dorsal fin, sends a signal to a satellite each time the shark breaks the surface of the water, according to the World Wildlife Fund (WWF). The tag transmits the shark's position while also recording depth and temperature data.

Contender has traveled about 290 miles (470 kilometers) since he was tagged on Jan. 17, according to OCEARCH's shark tracking website, where they describe him as "the ultimate ocean warrior." The latest ping from his tag, recorded on Monday (Feb. 10), revealed he was out at sea east of Merritt Island, near Orlando, in Florida.

Shark quiz: How much do you know about these iconic ocean superstars?

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An enormous great white shark recently killed on a drumline in Queensland, Australia, will be used to help researchers discover more about the species. The gigantic female was only slightly smaller than the largest great white ever caught.

The 18.4-foot-long (5.6 meters) female white shark (Carcharodon carcharias) was found dead by the Queensland Shark Control Program at Tannum Sands, off the Queensland coast, on Aug. 10. She was pregnant with four pups when she died.

"This is the largest white shark caught in the Queensland Shark Control Program since its commencement in 1962," Tracey Scott-Holland, a spokesperson for the Queensland Department of Agriculture and Fisheries told Live Science in an email.

Reliable, verified records of large white sharks are lacking, and many historical records of behemoth sharks over 21 feet turned out to be exaggerations. The biggest white shark with a reliable measurement was caught off the coast of Massachusetts and measured 19.9 feet (6 m).

A drumline is a fishing method that uses a baited hook that's attached to a buoy and floats, with a chain anchoring it to the seafloor. The Queensland Shark Control Program uses drumlines to reduce the risk of shark bites. If a bull, tiger or great white shark — or other species associated with unprovoked bites —is caught in the Great Barrier Reef Marine Park, it is tagged, relocated and released as long as it is possible and safe to do so. Those caught outside the Marine Park are euthanized.

In Queensland, the authorities have been trialing catch alert drumlines, which send a satellite alert to a response team when a shark is caught so they can quickly tag and release the animal. But in the case of the pregnant great white shark, the team didn’t get to her in time.

"It is a shame to lose a big, reproductive animal like that," Bob Hueter, shark expert and chief scientist at OCEARCH, told Live Science in an email. "Normally, the workers are able to get out to the caught shark within a half-hour or so to tag and release the animal."

Related: 'One of the holy grails of shark science': Watch 1st ever footage of baby great white shark moments after birth

As apex predators, sharks keep the ocean's food web balanced and healthy, so a decline in their populations has a knock-on impact on many other animals. Globally, a third of sharks, rays and chimaeras are threatened with extinction.

Great white sharks are listed as vulnerable on the IUCN Red List of Threatened Species and face threats including overfishing and being caught as bycatch. The eastern Australasian population has around 750 breeding adults left.

White sharks reach sexual maturity at around 20 or 30 years old and carry between two and 17 pups every two or three years. This slow reproduction makes it difficult for the species to recover from threats.

The untimely death of a breeding female can have a significant impact on the local population. "Losing this very large, pregnant female along with her four pups is a setback for the [population's] genetic diversity and rebuilding capacity," Hueter said.

Leonardo Guida, shark conservation lead at the Australian Marine Conservation Society, told Live Science in an email that "a mixed wave of awe and sadness washed over [him]" when he heard the news.

Based on her size, "It's plausible she was born in the late 90s, when white sharks first became a protected species in Australia," he said.

But this loss could help scientists learn more about the species. "Samples were taken for research purposes, and we are collaborating with researchers from New South Wales and South Australia on several projects," Scott-Holland said. The shark's body will be used to help researchers find out more about the species' biology, genetics and populations.

Hueter — who is not involved in the analysis — is excited by what could be discovered. "Because it is exceedingly rare to be able to examine a pregnant white shark anywhere in the world, this particular shark could be very valuable for white shark science," he said.

Analyzing samples from a dead shark can provide data on the animal's feeding habits, contaminants in its waters and more.

"We're not even sure how long gestation takes in this species, and how often the females get pregnant, so examination of this 'mega momma' could help fill in some critical gaps in our knowledge," Hueter said.

New footage captures a lone orca killing and eating a great white shark in just 2 minutes, revealing they do not need to hunt in packs to take down one of the ocean's most formidable predators.

In the video, the shark desperately attempts to flee as the orca follows close behind, before disappearing beneath the surface. Shortly after, the orca is seen swimming away carrying a liver in its jaws. 

In a study published March 1 in the African Journal of Marine Science, scientists confirmed this case was the first ever record of a lone orca (Orcinus orca) hunting and consuming a great white shark (Carcharodon carcharias) without the help of its podmates. 

The incident took place in June 2023 when researchers on a tourist boat saw two orcas — known as Port and Starboard because of their collapsed dorsal fins — south of Seal Island, South Africa. The two orcas already have a reputation for attacking great whites and feasting on their nutrient-rich livers — a new behavior that has led great whites to abandon a popular hunting ground.

After approaching the orcas, the researchers noticed an oily substance floating on the surface, birds diving into the water and "the distinct smell of shark liver," according to the study. The researchers speculated that the pair of orcas may have already killed a shark before the boat arrived.

"Once you've smelled it, you'd recognize it again," lead author Alison Towner, a marine biologist at Rhodes University, told Live Science in an email. She explained that shark liver smells rich, fatty and not altogether unpleasant, but very hard to describe. 

Nearly an hour later, the boat saw an 8-foot-long (2.5 meters) juvenile white shark at the surface with Starboard chasing behind. "The killer whale pushed the shark forward by its pectoral fin while it thrashed on the surface," Towner said. 

By grabbing the shark's pectoral fin and shaking it, Starboard tore the shark open in precisely the right spot to remove its liver. 

Related: Great white shark ripped in 2 was 'loaded' with orca DNA, scientists say

A few minutes later, a shark cage diving boat that happened to be nearby saw Starboard swim past "with a bloody piece of peach-coloured liver in its mouth," according to the study. Port stayed around 330 feet (100 m) away throughout and was not involved in the predation.

"The moment Starboard rapidly preyed on my favorite shark species was both devastating and intensely powerful," Esther Jacobs, the founder of shark conservation initiative Keep Fin Alive, who saw the attack, said in a statement.

Although the onlookers didn't see the moment Starboard removed the shark's liver, as this happened underwater, Towner believes the shark would've been killed instantly. 

The exact mechanism of how orcas shaking a shark can tear it open is still unclear, but more clues arrived the next day when the carcass of a different great white shark — this one measuring 11.5 feet (3.5 m) — washed up nearby. "The interesting stretch marks on its flank may suggest torsion induced by thrashing," Towner said. 

Orcas target sharks' fatty livers because of their high nutritional value. "Shark livers are packed with rich, oily lipids, making up to one third of their body mass in some species," Towner said. 

Sometimes known as the wolves of the sea, orcas have strong social bonds and usually hunt in groups. While they have been known to hunt other species alone — including seals, porpoises, and penguins — this is the first record of a single orca killing a great white. In previous accounts, attacks have involved between two and six orcas. 

This finding may have important conservation implications. "Altering the top predator balance has cascading impacts," Towner said. "With most sharks already facing various man-made pressures, orca predation adds further strain and could be a tipping point in some regions for some species."

A huge shark bit the head off a stranded pygmy sperm whale in New Zealand as a person standing in waist-high water attempted to get the whale back out to sea. The shark, likely a great white (Carcharodon carcharias), returned 30 seconds later to eat the rest of the whale, witnesses said.

The incident took place  in northern Hawke's Bay on the Māhia Peninsula on Sunday (Feb. 25) after a pygmy sperm whale (Kogia breviceps) and her calf got stranded on the beach, Hawke's Bay Today reported.

Chad Prentice, Māhia sole charge police officer, told the newspaper that a witness said the shark was more than 16 feet (5 meters) long and killed the whale instantly.

Related: In rare attack, great white shark decapitates diver in Mexico. But why?

"I am told when the shark hit the whale the first time … it came out of the water and took its whole head off. There are not many sharks that can do that." Prentice said.

The slain whale was 10 feet (3 m) long, according to witnesses. As the rescuer fled for shore unharmed, the shark took away its prey.

"The water was red and about 30 seconds later the shark came back and hit the whole thing and took it out to sea — there is not even an ounce of remains left," Prentice said.

The sperm whale's calf, still stranded after the attack and left without a mother, was later euthanized and will be studied for further insights into what might have caused the stranding, according to Hawke’s Bay Today.

New Zealand is well known for marine mammal strandings. Usually, just one or two animals get stuck in shallow waters, but sometimes big groups strand simultaneously. The largest mass stranding in the country's history occurred in 1918 and involved around 1,000 pilot whales, according to the New Zealand Department of Conservation (DOC).

Many marine mammals are sick when they strand, but there may be multiple factors behind any given event, and researchers still have a lot to learn about the phenomenon.

The DOC warned of the potential for increased shark activity around the Māhia Peninsula in January after about 45 false killer whales and bottlenose dolphins were stranded and euthanized.

"Several shark species feed on whale[s] and dolphins, including their carcasses, and can be attracted to the site of whale strandings. These include sevengill sharks, blue sharks, tiger sharks, and great white sharks," Clinton Duffy, the DOC marine technical advisor, said in a statement at the time.

Daren Grover, the general manager of New Zealand marine mammal charity Project Jonah, told Hawke's Bay Today it's normal for sharks to prey on sick animals and said they are "opportunistic predators."

A mutilated great white shark that washed up in Australia in October was mauled by orcas and "loaded" with its attackers' DNA, scientists have confirmed.

Only the shark's head and spine remained when it appeared on a beach in Portland, Victoria, fueling speculation that orcas disemboweled the great white shark (Carcharodon carcharias) to feast on its liver — similar to attacks that have been recorded off the coast of South Africa for several years. 

A necropsy has now revealed orcas (Orcinus orca), also known as killer whales, were indeed responsible for the gruesome attack.

"Inspection of the shark [showed] really characteristic bite marks right in the pectoral girdle, so right between those fins under the belly, that are quite typical of killer whales where they effectively suck out the liver," Adam Miller, an associate professor in aquatic ecology and biodiversity at Deakin University in Victoria who led the analysis, told the Australian broadcaster ABC Radio Melbourne.

Related: Big, healthy great white shark washes up dead on Canada beach in latest of string of mystery strandings

The shark — which scientists estimate measured over 16 feet (4.9 meters) long when alive — provides the first evidence of orcas predating on a great white off Australia's coast.

Orcas in these waters are known to kill blue sharks (Prionace glauca) and shortfin mako sharks (Isurus oxyrinchus) to eat their livers, Miller said. Researchers suspected that some great whites may have met the same fate due to several aggressive interactions recorded off Kangaroo Island and the Neptune Islands in southern Australia, but it had never been confirmed.

Miller and his colleagues worked in partnership with First Nations groups and government authorities to acquire the carcass, enabling them to analyze genetic samples and swabs of the shark's bite wound. "We were able to confirm that those bite wounds were just loaded with killer whale DNA, so it's a bit of a smoking gun," he said.

A group of around seven orcas was sighted in nearby Bridgewater Bay a couple of days before the great white shark washed up in Portland, Miller said.

Two orca pods are known to live in Australian waters, he said, and they "have quite distinctive feeding behaviors and predation behaviors." But behaviors are sometimes learned and shared between pods, Miller added. "Their communication is pretty amazing," he said. "Behaviors are picked up by one pod [from] the neighboring pod through direct communication." 

It's unclear which pod is responsible for attacking the great white shark and whether the behavior is widespread in these waters. Frequent predation by orcas could spell trouble for the Australian population of great whites, which is already down to a "critically low number of breeding individuals," Miller said.

"From a conservation point of view it's significant, but we don't know how frequently it's happening so we'll keep an eye on things," he added.

Large marine predators including great white sharks regularly spend time in the ocean's twilight and midnight zones, far beneath the depths at which they feed, in a discovery that has mystified scientists. 

In a new study, data from 12 species of large predatory fish, including sharks, billfish and tunas showed they regularly spent time in the mesopelagic zone  — also known as the twilight zone —. which stretches between the depths of 656 and 3,280 feet (200 to 1,000 meters). They were also seen in the midnight zone, 3,280 to 9,800 feet (1,000 to 3,000 m) beneath the ocean surface. 

"How, when, where they access the deep ocean certainly varies, but the clear anecdotal answer is that the deep ocean seems like an important habitat — regardless of the predator species," Camrin Braun, study lead and an assistant scientist at the Woods Hole Oceanographic Institution (WHOI), told Live Science. "It's clear there are good reasons for these animals to dive deep, otherwise why would they all do it? 

As part of the study, published Nov. 6 in the journal PNAS, researchers matched the diving patterns of 344 electronically tagged predatory fish, including great white sharks (Carcharodon carcharias), tiger sharks (Galeocerdo cuvier), whale sharks (Rhincodon typus), yellowfin tuna (Thunnus albacares) and swordfish (Xiphias gladius) with shipboard sonar over a cumulative period of 46,659 days to identify which species regularly deep dive to the twilight and midnight zones. 

Related: Watch great white shark get mobbed by gang of seals in 'incredible and surprising' footage 

Their findings showed a correlation between dives and the location of the deep scattering layer (DSL). This ocean layer is so densely packed with small fish and other marine organisms it is sometimes mistaken for the seafloor. Creatures of the DSL rise up to the surface at night to feed, then sink back down to the twilight zone in the day. 

This suggests marine predators feed on animals in the DSL. However, the team also discovered many dive far deeper than the DSL extends, for reasons unknown. Great white sharks dive as deep as 3,700 feet (1,128 m), whale sharks to 6,300 feet (1,912 m) and swordfish as far as 6,500 feet (2,000 m).

"There's good evidence for some species/situations in which diving deep is clearly for foraging," Braun said. "So that supported our expectation. However, we also find several cases where we can pretty definitively say the use of the deep ocean is not for feeding — or if it is it represents a totally different kind of predator-prey interaction or mysterious prey resource."

The evidence also suggests the twilight zone has been overlooked as a critical habitat for large predator species, the researchers said. Many of the species inhabiting the twilight zone are fished commercially, and steps need to be taken to understand and protect this potentially critical ecosystem.

"If it turns out that there is indeed more biomass in the twilight zone than in all current marine capture fisheries combined then it's possible to imagine a kind of mesopelagic 'gold rush' to catch and use this biomass," Braun said. "There are many 'ifs' in this chain and many issues in making mesopelagic fishing feasible BUT it seems that biomass may be important for predators. Therefore, we really need to better quantify those links between predators and mesopelagic biomass before we can sustainably harvest/use those resources.”

A large, healthy-looking great white shark that washed up dead on a beach in Canada is the latest in a string of mystery strandings in the region.

The 14-foot-long (4.3 meters) male adult shark was seen thrashing in the water near North Bay Wharf in Nova Scotia before stranding on Broad Cove Beach in Cape Breton on Oct. 5. The carcass then washed back out to sea, but a team with the animal conservation organization Marine Animal Response Society (MARS) managed to recover it a week later for analysis.

Pathologists performed a necropsy on the great white shark (Carcharodon carcharias), but the examination yielded no clues about the cause of death.

"Right now it does not look nutritional (the liver was large and full of lipids), nor does it look like trauma," Laura Bourque, a wildlife pathologist with the Canadian Wildlife Health Cooperative who conducted the necropsy, told Live Science in an email.

Related: Orcas attacked a great white shark to gorge on its liver in Australia, shredded carcass suggests

While the shark's dorsal fin was missing a chunk, the necropsy revealed this was the result of an old, healed injury and probably didn't contribute to the animal's death. The shark was otherwise "in good overall body condition," MARS staff wrote in a Facebook post.

The stranding is the latest in a series of similar incidents that have left scientists floundering. The shark is the fifth great white found beached on the Canadian coast and registered with MARS since last October — a record number when compared to the last 20 years, which saw just one or two such strandings in total, Live Science previously reported.

Scientists haven't got to the bottom of the previous four strandings yet, but they are "in the process of finalizing those cases," Bourque said.

Adult great white sharks rarely wash ashore, Tonya Wimmer, the executive director of MARS, told Live Science in an email. Three of the five dead sharks were juveniles. "This last year has been an anomaly in terms of the number of white sharks reported to us in distress or dead," Wimmer said. 

Very little is known about what causes sharks to become stranded, Wimmer said. While marine mammals can wash up for various reasons — including ingestion of plastics, entanglement in fishing gear, vessel strikes, disease and injury — it's unclear whether the same factors are at play with sharks, she added.

Scientists kept samples of the shark's tissues and are performing additional tests, as "any infectious, toxic or metabolic disease may potentially not be apparent at necropsy," Bourque said.

The team also collected additional samples in the hope they might "support several research projects on these magnificent animals," the Facebook post said.

The carcass of a torn-up great white shark has washed up on a beach in Australia, fueling speculation that orcas attacked it to gorge on its liver — a first in these waters.

Residents found the 10-foot-long (3 meters), disemboweled shark near Cape Bridgewater, about 200 miles (320 kilometers) west of Melbourne in the state of Victoria. Nothing much remained of the animal's body except its head and tail, prompting witnesses and researchers to think orcas ripped the great white shark (Carcharodon carcharias) apart.

"I have never seen anything like that before," said Ben Johnstone, a local fisher and manager of the bait shop Portland Bait and Tackle who received a tip-off and went to inspect the carcass on Tuesday (Oct. 17). "The only other creature that could've caused it would be an even bigger white shark," he told Live Science in a message on social media.

Residents notified authorities, who came to collect the shark's body and sent samples to government agencies and academics for analysis, Australian Broadcasting Corporation (ABC) News reported.

Related: Watch orca tear open whale shark and feast on its liver in extremely rare footage

Orcas (Orcinus orca), also known as killer whales even though they are in the dolphin family, have attacked great white sharks before. But cases so far have mostly been confined to waters off the coast of South Africa, where two orcas nicknamed Port and Starboard have been feasting on shark livers for several years.

"We're not actually sure why killer whales are such picky eaters," Lauren Meyer, a research fellow in biological sciences at Flinders University in Australia, told ABC News. "We certainly see that they prefer the liver of white sharks, mako sharks, bronze whalers and sevengills, and even tiger sharks."

Orcas may target shark livers because this organ is nutritious, with large amounts of fat and vitamins. Once a shark is killed, its liver, which is large and buoyant, floats to the surface, making it easy to eat. While it isn't "100% clear" that orcas attacked the beached great white, it's possible a pod ganged up on the shark to "slurp out" its liver, Meyer said.

A pod of orcas was seen circling in the bay near Cape Bridgewater two days before the shark washed up, ABC news reported.

"We know there are white sharks that go through that area and use it as an important corridor," Meyer said. "We also know that it's a place for killer whales where they hunt a number of different prey items."

Nine interactions between orcas and great white sharks were previously recorded in waters off the coasts of Australia and New Zealand, but this is the first time a disemboweled great white has washed up.

Scientists in Australia have called for swimming advice to be updated to reflect new information about one of the most dangerous shark species. The call came after researchers tracked the movements of bull sharks off the coast of New South Wales and found the times when the largest individuals are most active.

Currently, advice states that swimming and surfing should be avoided at "dawn" and "dusk" as this is when visibility is poorest and when sharks are more active — both factors that increase the risk of attacks.

However, researchers from the New South Wales Department of Primary Industries and Macquarie University argue swimmers should avoid the water during the afternoon and low-light conditions as well.

Amy Smoothey, scientific officer and shark biologist at the New South Wales Department of Primary Industries, and one of the lead investigators in the study published in the journal Biology on Aug. 31, said the team tracked 233 tagged bull sharks (Carcharhinus leucas) along 21 coastal beaches in New South Wales between 2017 and 2023 to find out when they are closest to shorelines.

Related: Great white sharks have almost no interest in eating humans, study confirms

"We found that the presence of large bull sharks was greatest from midday through to 4 a.m.," she told Live Science in an email, adding there was an increased probability of the sharks being near the shore between 6 p.m. and 1 a.m.

The researchers found there are certain conditions that increase the chances of encountering a large bull shark. These include when the water temperature is higher than 68 degrees Fahrenheit (20 degrees Celsius), after heavy rain or when the water is murky.

"These conditions are favourable for ambush predators like bull sharks," Smoothey said. "Be aware during periods of low-light levels, as these are times when bull sharks are typically more active and you may not be able to see the approaching shark."

Bull sharks are one of the three species involved in most fatal attacks in Australia, along with great white sharks (Carcharodon carcharias) and tiger sharks (Galeocerdo cuvier). Bull sharks, which can grow to around 11 feet (3.4 meters) long, are generally considered to be particularly dangerous as they have a preference for warm coastal waters and can travel up rivers. The most recent fatal attack by a bull shark in Australia occurred in February this year, when 16-year-old Stella Berry was attacked in a river in Perth.

However, the researchers highlighted that unprovoked shark bites are rare. According to the University of Florida's International Shark Attack File, there were a total of 57 unprovoked bites by all species of sharks globally in 2022, most of which occurred in the United States and Australia. Of these, five attacks were fatal.

Smoothey said that the researchers recommend an update to advice about shark safety, but that current guidelines are still important. "We concur with the current shark smart advice that nocturnal swimming and surfing, especially in warm waters and when water visibility is poor, should be avoided for many reasons, not the least of which being the presence of bull sharks," she said.

Editor's note: The original image on this article was of a sand tiger shark (Carcharias taurus). The image has been updated with to show a bull shark.

South Africa is renowned for having one of the world's biggest populations of great white sharks (Carcharodon carcharias). Substantial declines have been observed, however, in places where the sharks normally gather on the coast of the Western Cape province. Sharks congregate at these locations to feed, interact socially, or rest.

In Cape Town, skilled "shark spotters" documented a peak of over 300 great white shark sightings across eight beaches in 2011, but have recorded no sightings since 2019. These declines have sparked concerns about the overall conservation status of the species.

Conserving great white sharks is vital because they have a pivotal role in marine ecosystems. As top predators, they help maintain the health and balance of marine food webs. Their presence influences the behavior of other marine animals, affecting the entire ecosystem's structure and stability.

Marine biologists like us needed to know whether the decline in shark numbers in the Western Cape indicated changes in the whole South African population or whether the sharks had moved to a different location.

To investigate this problem, we undertook an extensive study using data collected by scientists, tour operators and shore anglers. We examined the trends over time in abundance and shifts in distribution across the sharks' South African range.

Our investigation revealed significant differences in the abundance at primary gathering sites. There were declines at some locations; others showed increases or stability. Overall, there appears to be a stable trend. This suggests that white shark numbers have remained constant since they were given protection in 1991.

Looking at the potential change in the distribution of sharks between locations, we discovered a shift in human-shark interactions from the Western Cape to the Eastern Cape. More research is required to be sure whether the sharks that vanished from the Western Cape are the same sharks documented along the Eastern Cape.

The stable population of white sharks is reassuring, but the distribution shift introduces its own challenges, such as the risk posed by fisheries, and the need for beach management. So there is a need for better monitoring of where the sharks are.

Factors influencing shark movements

We recorded the biggest changes between 2015 and 2020. For example, at Seal Island, False Bay (Western Cape), shark sightings declined from 2.5 sightings per hour in 2005 to 0.6 in 2017. Shifting eastward to Algoa Bay, in 2013, shore anglers caught only six individual sharks. By 2019, this figure had risen to 59.

The changes at each site are complex, however. Understanding the patterns remains challenging.

These predators can live for more than 70 years. Each life stage comes with distinct behaviors: juveniles, especially males, tend to stay close to the coastline, while sub-adults and adults, particularly females, venture offshore.

Environmental factors like water temperature, lunar phase, season and food availability further influence their movement patterns.

Changes in the climate and ocean over extended periods might also come into play.

As adaptable predators, they target a wide range of prey and thrive in a broad range of temperatures, with a preference for 57 to 75 degrees Fahrenheit (14 to 24 degrees Celsius). Their migratory nature allows them to seek optimal conditions when faced with unfavorable environments.

Predation of sharks by killer whales

The movement complexity deepens with the involvement of specialist killer whales with a taste for shark livers. Recently, these apex predators have been observed preying on white, sevengill and bronze whaler sharks.

Cases were first documented in 2015 along the South African coast, coinciding with significant behavioral shifts in white sharks within Gansbaai and False Bay.

Although a direct cause-and-effect link is not firmly established, observations and tracking data support the notion of a distinct flight response among white sharks following confirmed predation incidents.

More recently, it was clear that in Mossel Bay, when a killer whale pod killed at least three white sharks, the remaining sharks were prompted to leave the area.

Survival and conservation of sharks

The risk landscape for white sharks is complex. A study published in 2022 showed a notable overlap of white sharks with longline and gillnet fisheries, extending across 25% of South Africa's Exclusive Economic Zone. The sharks spent 15% of their time exposed to these fisheries.

The highest white shark catches were reported in KwaZulu-Natal, averaging around 32 per year. This emphasized the need to combine shark movement with reliable catch records to assess risks to shark populations.

As shark movement patterns shift eastward, the potential change in risk must be considered. Increased overlap between white sharks, shark nets, drumlines (baited hooks) and gillnets might increase the likelihood of captures.

Beach safety and management adaptation

Although shark bites remain a low risk, changing shark movements could also influence beach safety. The presence of sharks can influence human activities, particularly in popular swimming and water sports areas. Adjusting existing shark management strategies might be necessary as distributions change.

Increased signage, temporary beach closures, or improved education about shark behavior might be needed.

In Cape Town, for example, shark spotters have adjusted their efforts on specific beaches. Following two fatal shark incidents in 2022, their program expanded to Plettenberg Bay. Anecdotal evidence highlights additional Eastern Cape locations where surfers and divers encounter more white sharks than before.

Enhanced monitoring and long-term programs

Further research is required to understand the factors behind the movements of sharks and their impact on distribution over space and time. Our study underscores the importance of standardizing data collection methods to generate reliable abundance statistics across their entire range. Other countries suffer from the same problem.

Additionally, we propose establishing long-term monitoring programs along the Eastern Cape and continuing work to reduce the number of shark deaths.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Cape Cod in Massachusetts is home to one of the world's biggest hotspots of great white sharks, new research finds. Between 2015 to 2018, an estimated 800 great white sharks visited the area, according to a study published July 27 in the journal Marine Ecology Progress Series. 

This is the first estimate of abundance for great white sharks (Carcharodon carcharias) in the western North Atlantic Ocean, the researchers said. The finding "suggests that Cape Cod is among the larger aggregation sites worldwide," the authors wrote. 

So why are these apex predators gathering off Cape Cod's coasts? Because that's where their favorite meal resides, explained study co-author Megan Winton. 

"Over the course of the past 10 years, white sharks have come back to Cape Cod to feed on the recovering seal population," Winton, a marine researcher and member of the nonprofit organization Atlantic White Shark Conservancy, told The Inertia. 

Related: Great white sharks have almost no interest in eating humans, study confirms

Humans hunted gray and harbor seals to the brink of extinction in the 1960s, but their populations have dramatically increased since 1972 when the U.S. Marine Mammal Protection Act was passed, which makes it illegal to catch or kill marine mammals without a permit. Now, there are roughly 30,000 to 50,000 gray and harbor seals in southeastern Massachusetts, according to a 2016 estimate. As a result, the number of great white sharks in this area has also been steadily rising, the new study found. 

To track their numbers, the researchers identified individual sharks by analyzing tagging data and recording their unique coloration patterns using underwater GoPro cameras. After more than 130 research trips over three years, they identified 393 individual great white sharks from 2015 to 2018. 

However, the researchers also wanted to account for the sharks' migratory behavior, so they developed a model to calculate how many sharks were moving in and out of the area, and estimated that roughly 800 sharks aggregated in this region over the three-year period. 

In the 1980s, great white shark populations in the Atlantic Ocean were just 27% of what they were in 1961. But they have made a widespread comeback along the western North Atlantic coast in recent years, according to the National Oceanic and Atmospheric Administration. This study confirms that trend in Cape Cod. 

"What I find most amazing is the speed at which the population recovered," Chris Lowe, director of the Shark Lab at California State University, Long Beach, told Outside. 

Most of the great white sharks visited Cape Cod during late summer and early fall, when ocean temperatures there are at their highest, before migrating out of the area in early winter. 

"Their movements are very dynamic, they trickle in and out," study co-author Greg Skomal, recreational fisheries program manager at the Massachusetts Division of Marine Fisheries, told the Boston Herald. "Some white sharks simply stop by on their way north while others spend more time along the Cape, likely because they have success feeding on seals."

Though Cape Cod is a hotspot for great white sharks, there has not been a reported attack on humans since 2018, and the risk posed to recreational swimmers remains low, the study's authors wrote. 

"They are very cautious predators," Winton told New Hampshire Public Radio Station (NHPR). "But the increased presence and number of white sharks off the Cape really drives home the need for ongoing research."

Great white sharks were once rare in northern waters but are becoming an increasingly common sight. Until 2006, there had been just 32 recorded sightings of great white sharks off Canada's east coast, but the apex predators are now showing up there almost daily.  To highlight the sharks' intriguing move, "Shark Below Zero," a new program from National Geographic, explores the factors that are driving these animals into frigid northern waters.

As great white sharks (Carcharodon carcharias) spread north, shark attacks there are also increasing, albeit minutely. 

In general, great white shark attacks are extremely uncommon; a study published earlier this month revealed that great whites have almost no interest in eating humans. In the North Atlantic, these attacks are even rarer. But in 2020, 63-year-old Julie Dimperio Holowach was swimming off the coast of Bailey Island, Maine, when she was bitten by what is believed to be a great white, due to a tooth fragment the shark left behind. This was the state's first documented fatal shark attack. 

The following year, a 21-year-old woman was bitten off the coast of Cape Breton, Canada, but survived. This was the first time anyone had been attacked by a great white shark off Canada's coast since the 1800s, according to the Canadian Shark Attack Registry. 

Related: Watch a great white shark devour a seal off the coast of Cape Cod, shocking nearby whale watchers

"What are these white sharks doing here? Greg Skomal, senior fisheries biologist at Massachusetts Marine Fisheries, said in a clip from "Shark Below Zero." "What's drawing them?"

The apex predators are being attracted to the frigid waters by an abundance of their favorite prey — seals. The seal population in the region has exploded in the last 60 years thanks to conservation efforts such as the 1972 U.S. Marine Mammal Protection Act, going from around 2,300 individuals in 1960 to 380,000 in 2017. 

"A lot of folks think white sharks in the waters off New England and Canada are a new phenomenon, but there are some great accounts of white sharks from fishermen in the early to mid-1900s — and earlier — in that region before shark populations coast-wide took a nosedive," Megan Winton, staff scientist at the Atlantic White Shark Conservancy, told Live Science in an email. Winton is in the team investigating the shift to northern waters among great whites in the film, which is part of NatGeo's SharkFest season — a four week event celebrating sharks. Check out our how to watch Shark Fest 2023 guide if you want to see more. 

The increased sightings in the area is down to an abundance of prey and an increase in shark numbers, she added. In the 20th century, the great white population was decimated, falling by around 80%. To stop the decline, various U.S. laws protecting white sharks were introduced, and numbers are returning to healthy levels. 

"What we're seeing right now is the species recolonizing its historic range as it recovers and as populations of seals, one of their favorite foods, rebound following protections that were put into place for marine mammals in the 1970s," Winton said. "But because their numbers were so low and they were so hard to study in the region for so long, we know next to nothing about white shark behavior in the northern extent of their range, which is why this expedition was so exciting to be a part of." 

And Winton said the shifts we are seeing now are just the start. Great white sharks are partially warm blooded, so while they can survive in cold water, their preferred temperature range is between 50 and 80 degrees Fahrenheit (10 to 26.5 degrees Celsius). Water temperatures off Nova Scotia, for example, generally only exceed the lower range there for about four months of the year.  

But climate change is altering ocean temperatures across the globe — and a warming ocean is likely to change the geographic range of white sharks. "The waters off the northeastern U.S. and Canada are among the fastest warming ocean regions on the planet," Winton said. "Scientists are already documenting northward shifts in other species, and white sharks and their prey are likely to be no exception. 

"As the ocean continues to warm, white sharks are likely to move further north and stay in northern waters for longer. There's no doubt that climate change is going to have a major impact on all life in the ocean, and the shifts we're seeing now are likely just the beginning," Winton added.

"Shark Below Zero" premieres on Disney+ and Hulu on July 2, and National Geographic on July 5.

Martin Richardson was swimming in the Red Sea in Egypt when he was attacked by a mako shark (Isurus oxyrinchus). He was bitten approximately five times and was waiting to die when something unusual happened. 

"There was no reason for the shark to stop," he said in "Saved from a Shark," a new show from National Geographic. "I had lost approximately 5 pints [2.8 liters] of blood. You only have 8 to 9 [pints, or 4.5 to 5 L] in your body. I was waiting for a feeding frenzy… I knew it was circling me… I turned away and looked at the mountains. I gave up."

At this moment, a group of dolphins appeared just behind Richardson, and the attack stopped. He was then pulled onto a boat that had been racing to get to him before the shark did and rushed to hospital, where needed more than 300 stitches. "I firmly believe the dolphins saved my life," he said. 

Related: Great whites are dining on other sharks instead of seals, researchers discover in NatGeo show

Do whales and dolphins really protect humans from sharks? "Saved from a Shark" — part of NatGeo's SharkFest — looks closely at four cases where people were seemingly protected from the predators in the water."Being saved by another animal is certainly a very romantic notion," Tom Hird, marine biologist and shark conservationist, said in the program. 

But it's not so clear that's what's actually going on in most cases. 

Mike Heithaus, professor in the department of biological sciences at Florida International University, said it's unlikely dolphins were intentionally saving Richardson's life. 

"The dolphins see a big cloud of blood, they know a shark is in the area." If they had young, they'd want to scare the shark away from the young. "They may not have been trying to save Martin," he said in the show. 

In another case explored in the film, Nan Hauser, director of the Cook Islands Whale Research, revisited the moment in 2017 when a humpback whale (Megaptera novaeangliae) she was diving with saved her from a huge tiger shark (Galeocerdo cuvier) that was stalking her. In footage shot during the encounter, Hauser is approached by the whale, pushed and then lifted onto its snout. 

"[The whale is] looking at me and I know he's got something to tell me," she said in the program. "I do not understand. He wants me to understand. I look down into the deep blue. And I then I see [the tiger shark] right below me.

"I know — and the whale knows — this is a serious situation and I want to get out of the water. Then all of a sudden I was swooped up by the whale… now he's got me right on the front of his face."

The footage captured shows the whale engaging in a behavior similar to what it would do to protect a calf, Heithaus said.

Howether, Heithaus said the most unusual case was when a group of lifeguards swimming off the coast of New Zealand were encircled by a group of dolphins. Unbeknownst to the group, a great white shark (Carcharodon carcharias) was stalking them. "I'm used to having dolphins swimming alongside me, but this was totally different," Rob Howes, one of the lifeguards in the water, said in the program. 

One of the larger male dolphins charged towards him, and he then realized it was targeting the approaching shark. "Everything built to a big crescendo. Then everything went calm. The shark disappeared very quickly. It was bizarre."

Heithaus said in most cases, whales and dolphins are probably not protecting humans for altruistic reasons — more likely they are trying to protect themselves or their young. But with the lifeguards in New Zealand, "this is one case where it really seemed like the dolphins were protecting people," he told Live Science in an email. 

"Saved From a Shark" premieres on Disney+, Hulu, and National Geographic on July 2. Check out our how to watch Shark Fest 2023 guide if you want to catch up on all the shark-centric shows dropping in July.

Great white sharks off the coast of South Africa are feasting on other sharks — with these fish making up a larger proportion of their diet than seals, researchers have discovered. The great whites in Mossel Bay, known for their aerial attacks on prey and deadly clashes with orcas, appear to be hunting at the mouths of rivers, where smaller sharks congregate to breed. 

The Mossel Bay coastline is a great white shark (Carcharodon carcharias) hotspot, with an estimated 40 to 60 individuals stalking the waters at any one point. Researchers originally thought the big fish were drawn to the area by an abundance of their favorite prey: cape fur seals (Arctocephalus pusillus). Seal Island — a small rocky landmass about 2,000 feet (610 meters) from the shore of Mossel Bay that is home to around 4,000 seals. 

But something didn't add up. In "Shark Eat Shark," a new program that's part of  National Geographic's SharkFest, researchers explained that if seals were the sharks' main source of prey, around 1,500 seals would be killed per hunting season. Yet only 150 end up in these predators' bellies. 

Related: How to watch Shark Fest 2023: National Geographic's month of shark-centric programming is back

So what are they eating the rest of the time? "Our hunch is that they are spending more time hunting other sharks than seals," Lacey Williams, head field specialist at Oceans Research, said in the film. 

To find out, Williams and Enrico Gennari, a shark scientist who specializes in the study of great whites, used tracking data to see where the sharks were going during seal breeding season, a period when fewer seals enter the water, making them far less abundant as a source of prey. 

Related: 2 orcas slaughter 19 sharks in a single day in South Africa, eating their livers and leaving them to rot

They realized the sharks were gathering around three river mouths where lots of other, smaller shark species live, breed and feed, so the researchers deployed underwater cameras to see what was happening beneath the surface. 

The team captured dramatic footage of a catshark swimming along the seafloor, but when great white appears and the catshark freezes. "The catshark appears to play dead," Neil Hammerschlag, director of the shark research and conservation program at the University of Miami, said in the program. "What's super cool is it's not even breathing, it's holding its breath, by doing that it's not pumping water out of gills that would otherwise be generating a weak electric field the great white shark would pick up… I've never seen footage of this kind ever before," he added.

"When you actually look at the behavior of the sharks on the videos, they act like they're scared of great white sharks. And you know what runs from white sharks? White shark food."

The researchers then turned their attention to the species they think great white sharks are dining on — smooth-hound sharks (Mustelus mustelus), which grow to about 6 feet (1.8 meters) in length. After fitting 20 smooth-hounds with tags that emit a different signal if the shark is eaten, the researchers watched as the smooth-hounds were gobbled up one by one. "They are in the stomach of something much bigger," Gennari said, adding that "70% of tagged sharks have been eaten."

To confirm what was predating on the tagged smooth-hounds, the team gathered muscle tissue from great whites. Fatty acids in their food leaves a signature in this tissue that shows what the predator has been eating — and findings show their diets are dominated by other sharks. 

"We knew that white sharks eat other sharks, but this study is revealing the extent may be greater than previously appreciated, even in white sharks living near seal colonies," Hammerschlag told Live Science in an email. 

"I think our view of white shark feeding is biased, because the places where humans can easily find and observe white sharks are at seal colonies. It's actually not that easy to catch a seal; seals are smart and aggressive — with large canines and claws that can injure white sharks. Many white sharks bear wounds from encounters with seals. Catching and eating other sharks is probably easier and safer."

"Shark Eat Shark" premieres on National Geographic on July 2. 

Humans and juvenile great white sharks swim in the same waters nearly every single day along some beaches in southern California, a new study has found. Yet bites remain rare.

“I think what we've finally done is put a nail in the coffin for the old myth that if you're in the water with a white shark, it's going to attack you,” study co-author Chris Lowe, a marine biologist at California State University, Long Beach, told Live Science. The researchers published their findings on June 2 in the journal PLOS ONE.

Shark attacks are extremely rare. In 2022, there were 41 unprovoked bites and one fatality reported in the U.S., according to the University of Florida’s International Shark Attack File. Yet perceived risk among the public is high, the study authors said. Part of the problem, they said, is there is very little data showing how often sharks and humans come into close proximity. 

To find out, the researcher flew a drone over beaches in southern California every month for two years, noting where in the water they spotted people and great white sharks (Carcharodon carcharias).

Most of the juvenile great white sharks they spotted were at two locations: Carpinteria, which is just south of Santa Barbara; and Del Mar, just north of San Diego. Along those beaches, the research team spotted a human-shark interaction on 97% of the days they took the drone out.

The sharks were all located on the far side of the wave break — the line where the waves start to crest — but so were plenty of people. While waders and bodyboarders tended to stay on the beach side of the wave break, swimmers, surfers and paddle boarders were frequently spotted past the wave break — often bringing them close to white sharks.

Yet over the course of the study, there was just one unofficial report of a white shark bite along these beaches, Lowe said. A few months afterward, there was one additional record of a shark bite, he added.

The young white sharks are probably more focused on eating animals like stingrays, which live on the ocean floor, Lowe said. And even though these young sharks can still grow to about 9 feet (2.7 meters) long before they reach adulthood, they might be afraid of humans, he added.

The researchers are still trying to understand why the juvenile white sharks were congregating around Carpinteria and Del Mar. One reason might be an abundance of food, Lowe said. But these young sharks might also hang around the coast because there aren’t that many adult white sharks nearby to threaten them.

Adult white sharks, which can reach up to 20 feet (6 m) long, tend to live closer to the offshore islands and further north where they can find more seals and sea lions, Lowe said, adding that while he’d definitely want to be more careful going into these waters, bites from adult white sharks are still rare. 

But with the juveniles off southern California, the findings show that shark encounters are extremely common and not particularly dangerous. It's possible for someone to swim near one of these juvenile white sharks without ever knowing it — Lowe said they’d often spot sharks right next to, or even underneath someone who appeared completely unaware of the giant, predatory fish.

“For years, we've been saying we really don't think sharks are as dangerous to people as people think or as they've been taught to believe,” Lowe said. “And what this research shows, for the first time, is that that’s true.”

A shark in Australia has attacked and likely killed a man after repeatedly biting the victim and dragging him underwater. Eyewitnesses reported that the shark returned to the victim three times — an atypical behavior in what was already a rare attack. 

Simon Baccanello, a 46-year-old teacher, was surfing off the coast of South Australia on May 14 when he vanished. He was one of a dozen surfers in the water at the time. One bystander, Jaiden Miller, who witnessed the attack, told the Adelaide Advertiser, “I saw his board tombstoning, which means he's underwater and his board's getting dragged under … trying to fight his way back up to the surface.

"He [Baccanello] was gone. [We] saw the shark just thrashing around out the back. The shark's obviously let go and come back and got him for a third time."

Related: In rare attack, great white shark decapitates diver in Mexico. But why?

In a statement released May 15, South Australia Police said the victim was presumed dead after emergency services failed to find his body but recovered a piece of wetsuit and pieces of white polystyrene believed to be surfboard material. 

Fatal shark attacks are extremely rare. Globally there were five known fatal attacks in 2022, according to Florida Museum's International Shark Attack File. 

Most shark attacks are the result of mistaken identity. From below, swimmers and surfers are almost indistinguishable from seals — sharks' favorite prey — research published in 2021 highlighted. In most cases, a shark will realize a person is not food and swim away. Blood loss after an attack is the main cause of fatalities. 

Gavin Naylor, director of the Florida Program for Shark Research at the Florida Museum, said a shark carrying out repeated attacks on one person is "atypical, but not unheard of."  

"If the bite is motivated by predation or territoriality they can deliver an initial bite and then return to bite again," he told Live Science in an email. The reason for returning to a victim depends on the species involved, which in the recent incident is currently unknown. 

"White sharks [Carcharodon carcharias], for example, often ambush seals with an initial 'surprise' bite from below and then wait for the animal to bleed and become weakened before going back (seals are formidable animals and can injure the sharks attacking them, so white sharks are prudent to keep out of their way until they become weaker)," Naylor said. 

The emotional state of the animal will also affect how aggressive it is and whether it returns to bite again. "If a shark is excited and has been feeding where there are other sharks competing for limited food they may get 'amped up' and be more persistent/aggressive," Naylor added.

Baccanello would be the second person to be killed by sharks in Australia this year. Sixteen-year-old Stella Berry was killed by a bull shark (Carcharhinus leucas) in Swan River, Western Australia, after jumping into the water to swim on Feb. 4. 

A great white shark washed up on South Carolina's Myrtle Beach earlier this month in a rare and unusual stranding — and the reason behind the beaching remains a mystery. 

The 10-foot-long (3 meters) female was alive when locals saw it in the shallows on April 3. "There were multiple attempts to get the shark back in the ocean but it kept washing back ashore and eventually stopped breathing," Crystal Alden, a local who participated in the rescue effort, wrote in a post on Facebook.

In a series of pictures attached to the social media post, the shark appears to be stuck in a shallow pool. Its dorsal fin, eyes and gills are clearly visible, white the rest of its body is submerged. More photos show the shark lying in the back of a pickup truck with scratches to the underside of its mouth and sharp teeth exposed between protruded jaws. In the final picture posted by Alden, the young female hangs from a digger by its tail.

Biologists from the South Carolina Department of Natural Resources (SCDNP) and visiting scientists from Georgia Aquarium and Ripley's Aquariums, in Toronto, Canada, conducted a necropsy on the great white (Carcharodon carcharias) — but they could not determine the cause of death.

"A necropsy revealed nodules on the shark’s spleen but no conclusive cause of illness; our biologists are sending off tissue samples for further analysis to hopefully learn more," SCDNR representatives wrote in a Facebook post on April 6. 

Related: Photo shows 'massive' great white shark scarred after rare battle with 2 serial killer orcas

The investigation could take several months. "We’ve sent the tissues to a lab that has experience performing pathological analysis on white shark tissue samples," an SCDNR spokesperson told Live Science in an email. "We have not received results yet and think it may take one or two months before a report is completed."

The beaching is a very rare event, according to the SCDNP’s Facebook post. "While it’s not uncommon for large coastal sharks, whales, dolphins and sea turtles to become stranded on the shore when ill/injured, a white shark stranding in South Carolina is unusual," the SCDNR wrote. "White sharks are typically only winter visitors to South Carolina waters."

Great white sharks along the East Coast tend to spend the summer and fall in northern waters, feeding on high-calorie prey like seals. They migrate south in the winter months to the warmer waters off the more southerly states.

Employees with the SCDNR said they did not recognize the young shark as it had not been tagged, and that it would not have been a danger for beach-goers.

The stranding is a rare opportunity to collect data on great white sharks, according to the SCDNR. "We can’t confirm with certainty the last time a white shark was stranded on a South Carolina beach," the spokesperson told Live Science. "The last time the S.C. Department of Natural Resources was able to conduct a necropsy on a white shark was about 15 years ago on a shark stranded on Morris Island. That necropsy was done in the field, which limited our ability to collect tissue samples."

A fisher was recently decapitated by a 19-foot-long (5.8 meters) great white shark while diving for ax tripe, a scallop-like mollusk in Mexico. The tragic event made headlines because of the unusual nature of the attack. 

Manuel Nieblas López, who was in his 50s, was attacked Jan. 5 in Tobari Bay along the Gulf of California off Mexico. At the time of the attack, López was collecting the shellfish at a depth of between 36 and 59 feet (11 and 18 m) using a surface-supplied air source — a scuba-like apparatus that connects the diver to a compressed air source on a boat through a series of pipes,  according to Trackingsharks.com, a website that records all global shark attacks. Two other fishermen, who were on a support boat when the attack happened, witnessed the shark "impressively ripping off his head and biting both shoulders," said Jose Bernal, who spoke for the surviving fishers, according to Trackingsharks.com. 

Sharks rarely bite people. When they do, they typically grab the legs or torso after mistaking the person for prey, such as a seal, then release the victim after realizing the mistake. But a shark biting a person's head or shoulders is extremely rare, experts told Live Science.

This type of attack is so rare that Greg Skomal, a marine biologist at the University of Boston and head of the shark program at Massachusetts Marine Fisheries, has never heard of it occurring. "As rare as shark bites on humans can be, decapitation is even more rare," added Chris Lowe, the director of the Shark Lab at California State University, Long Beach. 

So what could have caused this unusual type of attack?

Related: Grisly new footage shows orcas attacking a great white shark and eating its liver 

As with almost all shark attacks, "mistaken identity" is likely the main reason why the shark attacked López, the experts said. 

"If sharks are excited and hungry, they make rash decisions and bite what — in the heat of the moment — they consider a potential prey item," said Gavin Naylor, a marine biologist at the University of Florida who runs the International Shark Attack Files (ISAF) at the Florida Museum of Natural History. "Remember that predators have to think quickly," he added, and if they hesitate it "can leave them hungry." 

Sharks don't have great vision, which makes it hard for them to distinguish between prey and humans. Because of this, around 60% of shark attacks recorded by the ISAF occurred in murky waters with reduced visibility, Naylor said. (There is no mention of the water quality in any reports of the most recent attack, so it is not possible to know for sure if this played a role.)

The Sun reported that López may have avoided the attack if he had been wearing a brightly colored wetsuit to help him stand out from seals, which had been advised by local authorities. But the experts are unconvinced by these claims. 

"It is a difficult hypothesis to test," Skomal said. "Since most wetsuits are black or darkly colored there is no way to tell statistically whether there is a trend there or not," Lowe added. 

However, the diver's fishing activity likely played a role in misleading the shark into thinking he was a prey animal, the experts said. 

The smell of the shellfish concentrated around the diver "could have lured the shark to the area," Lowe said. "Any time someone is fishing — whether for fishes or invertebrates like scallops or lobster — sharks are drawn to the smells in the water and the vibrations of struggling animals," Naylor added.

"It is also possible that [due to his position on the seafloor] he resembled a sea lion foraging," Skomal said.

Fishers like López had been warned to avoid fishing in the area due to an increase in shark activity during December and January, when pregnant female sharks enter the area, Newsweek reported. In December 218, another fisher was killed after being attacked by a great white shark shortly after jumping in the water, according to Trackingsharks.com.

Related: Spiraling vortex of 60 sharks rips apart a dead humpback whale in mesmerizing new video

López's position on the seafloor may explain why the shark attacked his head and shoulders.

"It was the most accessible part of the person's anatomy," Naylor said. Most scallopers essentially "walk along the bottom" so the shark could not have approached the victim from underneath and approaching from the side would have likely left the shark open to a potential counterattack from its prey, he added. Lowe agreed that "the person's orientation in the water relative to that of the shark" plays a key role in where they are bitten. 

It is also possible that the shark deliberately went for the head "to quickly incapacitate the perceived prey," which has been suggested by some shark attacks on seals, Skomal said. 

However, it is hard to say what happened in this case with any certainty.

"In most cases, we just don't know" why a shark attacks someone, Lowe said. "As you can imagine, it is very difficult to discern the motivation of the shark without detailed information of the situation prior to the bite."

For at least five years, a pair of serial killer whales in South Africa has been slaughtering great white sharks and eating their livers. (No fava beans or chianti necessary). Now, researchers have shared the world's first video footage of one such orca-on-shark attack.

In June, researchers reported that the two male orcas (Orcinus orca) — who go by the aliases Port and Starboard — had attacked at least eight great white sharks (Carcharodon carcharias) near South Africa's Gansbaai coast since they were first spotted in 2017. Known for their distinctively floppy dorsal fins (one droops to the left, or port side, while the other droops to the right, or starboard side), the killer whale duo is just two orcas among many that are thought to be terrorizing the great whites of Gansbaai.

The new footage, shot during an hour-long hunt via drone and helicopter, reveals that the orca known as Starboard helped several pod-mates attack a great white, then gobbled up several chunks of white meat that appear to be the shark's fatty liver.

This is the first time that an orca has been seen in action attacking a great white, according to the authors of a new study published Oct. 3 in the journal Ecology; all previous whale-on-shark attacks in the region were just inferred from mutilated shark carcasses that washed up on the Gansbaii coast.

"This behavior has never been witnessed in detail before, and certainly never from the air," lead study author Alison Towner, a senior shark scientist at Marine Dynamics Academy in Gansbaai, South Africa, said in a statement.

The newly released footage also reveals some of the evasive tactics employed by great whites when being stalked by the menacing orcas. 

On two occasions, an orca hunter slowly approached a great white with the intent to kill; the shark, rather than fleeing, stayed close to the orca and kept it in sight while circling through the water — a defensive strategy that seals and turtles use when evading sharks, according to the researchers. However, the team added, this strategy likely isn't very effective against orcas, who are social animals that hunt in groups.

Around the world, orcas have been observed killing everything from little fish to fearsome sharks, sea lions and even blue whales. But rarely has one pod of easily identifiable orcas had such a clear and immediate impact on their habitat, the researchers wrote in the African Journal of Marine Science in June.

Attacks from Port, Starboard and their gang have inspired the great white sharks of Gansbaai to adopt "large-scale avoidance strategies," Towner said, with individual sharks disappearing from the region for weeks to months at a time after sightings of Port and Starboard. Historically, the area has been dominated by great whites — not orcas — the researchers added.

These long-term shark migrations have already had downstream effects on the ecosystem. Most notably, a new mid-level predator called the bronze whaler shark (Carcharhinus brachyurus) has moved into the area to take over the niche that great whites previously filled, according to the researchers. Bronze whalers are often preyed upon by great whites, but with the big guys away, bronze whaler sightings have increased significantly at Gansbaai. This shift could ripple down the entire food chain, putting negative pressure on the whole ecosystem, the team added.

Great white sharks, (Carcharodon carcharias), also known as white sharks, are the largest predatory fish in the world. They belong to a partially "warm-blooded" family of sharks called Lamnidae, or mackerel sharks, that are able to maintain an internal body temperature that's warmer than their external environment — unlike other "cold-blooded" sharks, which can't, according to the Florida Museum of Natural History.

Great white sharks are the only living members of the genus Carcharodon — inspired by the Greek words "karcharos," which means sharpen, and "odous," which means teeth. This name is well-chosen, as great white sharks have rows of up to 300 serrated, triangular teeth. These sharks have bullet-shaped bodies, gray skin and white bellies.

Despite being one of the best-known shark species thanks to movies such as "Jaws" (1975), great white sharks live a secretive lifestyle, and scientists still have much to learn about these iconic predators. 

Size

Great whites are not the biggest sharks in the world. That title goes to whale sharks (Rhincodon typus), which are filter-feeders and usually grow up to 33 feet (10 m) long and weigh around 42,000 pounds (19,000 kg). The biggest shark species ever was the now-extinct megalodon (Carcharocles megalodon), which may have grown up to 60 feet long (18 m) or more, although scientists are still debating its exact size. 

Related: Scientists discover great white shark 'queen of the ocean'

Habitat

Great white sharks are migratory and undertake long-distance journeys across the open ocean, possibly for food and breeding. A 2002 study published in the journal Nature found that one great white shark swam 2,360 miles (3,800 kilometers) from the coast of central California to the Hawaiian island of Kahoolawe. In 2005, researchers tracked a great white shark swimming almost 6,900 miles (11,100 km) from the coast of South Africa to Australia, before later heading back again, Mongabay reported. To have enough energy for such long journeys, great white sharks store energy in their oil-rich livers, according to the Monterey Bay Aquarium.

Related: Great white shark population off California's coast is growing

Behavior

When sharks do bite humans, it's likely to be a mistake. A 2021 study published in the Journal of the Royal Society Interface found that to a juvenile great white shark, the shape and motion of humans swimming or paddling on surfboards looks the same as seals — one of their main sources of food. This suggests attacks could be a case of mistaken identity, at least for juveniles. 

"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, lead author of the 2021 study and a postdoctoral researcher at Macquarie University in Australia, previously told Live Science.

When someone has been bitten by a shark, experts often find it difficult to establish which shark species was involved. Sharks don't hang around for identification, and victims can struggle to make an accurate observation of the shark in the heat of the moment. Many shark species also create similar-looking wounds. Shark attack data is therefore skewed towards easily identified species such as great white sharks, according to the Florida Museum of Natural History's International Shark Attack Files (ISAF). The ISAF data show there have been 354 unprovoked great white shark attacks, including 57 fatal encounters, recorded since 1580 — more than any other shark species.

Related: Man survives attack by great white shark off California beach

Diet

By hunting prey, great white sharks and other sharks play an important role in the ocean. They keep prey populations healthy by catching weak and sick individuals and prevent those populations from growing too large for a habitat's resources to support, Live Science previously reported. Great white sharks can also be prey themselves, but their risk of predation drops as they get older and larger. The only things that eat adult great white sharks are larger adult great whites and killer whales (Orcinus orca), which may hunt great whites for their energy-rich livers. 

Related: Video captures great white shark's gruesome attack on a seal near Cape Cod

Mating

Scientists have studied shark specimens, such as accidentally caught pregnant females, and know that great white sharks don't lay eggs. Fertilized eggs hatch inside a female's body and develop there until the female gives birth. A 2016 study published in the journal Biology Open found that embryos probably feed on uterine fluid and undeveloped eggs between when they hatch inside the mother and when they are born. While in their mother's womb, young great whites also swallow their own teeth, according to the Florida Museum of Natural History. They may do this to reutilize calcium and other minerals.

Scientists assume that great white sharks give birth in warm temperate and tropical waters, but they have not identified specific shark nurseries. Gestation is thought to take about a year, after which a female gives birth to between two and 10 offspring called pups, according to the University of Michigan's Animal Diversity Web. Pups are more than 3 feet (1 m) long when they are born and are able to take care of themselves. 

A 2014 study published in the journal PLOS One estimated great white sharks' lifespan based on radiocarbon levels in their vertebrae tissue. The researchers suggested that the oldest female shark in the study was 40 years old and the oldest male was 73 years old. This suggests that males may live longer than females, but further research is needed to corroborate these findings. 

Related: Secret great white shark social club discovered off Mexican coast

Conservation status

Great white sharks are threatened globally as bycatch — animals caught by fishers that are not the intended target. Great white sharks are also deliberately killed by humans as part of beach-protection programs in Australia and South Africa, although sharks are sometimes captured and released alive. 

Additional resources

To learn more about why great white sharks are scarcely seen in captivity and how the Monterey Bay Aquarium was able to briefly display them, watch this short YouTube video by Vox. For more information about shark attacks and how to avoid them, check out the International Shark Attack Files website. For a general guide to the world's sharks, check out "Sharks of the World: A Complete Guide" (Princeton University Press, 2021), available to buy at Amazon. 

Bibliography

Boustany et al. "Expanded niche for white sharks," Nature, Volume 415, Jan. 3, 2002. https://www.nature.com/articles/415035b 

Chewning, D. and Hall, M. Animal Diversity Web, "Carcharodon carcharias," 2009. https://animaldiversity.org/accounts/Carcharodon_carcharias/

Florida Museum of Natural History, "Shark Biology," Aug. 9, 2021. https://www.floridamuseum.ufl.edu/discover-fish/sharks/shark-biology/ 

Hamady et al. "Vertebral bomb radiocarbon suggests extreme longevity in white sharks," PLOS One, Volume 9, Jan. 8, 2014. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0084006

International Shark Attack Files, Florida Museum of Natural History, "Species Implicated in Attacks," updated Jan. 25, 2022. https://www.floridamuseum.ufl.edu/shark-attacks/factors/species-implicated/

Martins, C. and Knickle, C. Florida Museum of Natural History, "Carcharodon carcharias," updated Oct. 18, 2018. https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/carcharodon-carcharias/

McGrouther, M., Australian Museum, "White Shark, Carcharodon carcharias (Linnaeus, 1758)," March 5, 2020. https://australian.museum/learn/animals/fishes/white-shark-carcharodon-carcharias-linnaeus-1758/

Monterey Bay Aquarium, "White shark." https://www.montereybayaquarium.org/animals/animals-a-to-z/white-shark

National Geographic, "Great white sharks." https://www.nationalgeographic.com/animals/fish/facts/great-white-shark

Pester, P., Live Science, "Great white sharks can't see a difference between humans and prey," Oct. 27, 2021. https://www.livescience.com/great-white-shark-mistaken-identity

Rigby et al. The IUCN Red List of Threatened Species, "Carcharodon carcharias," 2019. https://www.iucnredlist.org/species/3855/2878674

Ryan et al. "A shark's eye view: testing the 'mistaken identity theory' behind shark bites on humans," Journal of the Royal Society Interface, Volume 18, Oct. 27, 2021. https://royalsocietypublishing.org/rsif/doi/10.1098/rsif.2021.0533

Sato et al. "How great white sharks nourish their embryos to a large size: evidence of lipid histotrophy in lamnoid shark reproduction," Biology Open, Volume 5, Sep. 15, 2016. https://journals.biologists.com/bio/article/5/9/1211/1210/How-great-white-sharks-nourish-their-embryos-to-a

Smithsonian National Museum of Natural History, "How Big are Great White Sharks?" https://ocean.si.edu/ocean-life/sharks-rays/how-big-are-great-white-sharks

Weisberger, M., Live Science, "What If There Were No Sharks?" Sep. 9, 2019. https://www.livescience.com/what-if-no-sharks.html

Scientists have discovered a secret great white shark social club in the clear blue waters of Guadalupe Island, off the western coast of Mexico.

Dozens of sharks descend on the island's coastline to forage every fall and winter, but their Pacific holidays are hardly solitary getaways. According to new research published March 23 in the journal Biology Letters, a group of tagged great whites formed tight cliques during the 2017 and 2018 seasons. They preferred to patrol for food with close buddies or in same-sex pairs, sometimes spending more than an hour swimming around together.

One pair of sharks particularly astonished scientists by spending roughly 70 minutes swimming together — a far longer friend date than any of the other sharks shared.

"Seventy minutes is a long time to be swimming around with another white shark," lead study author Yannis Papastamatiou, a marine scientist at Florida International University, said in a statement.

Lengthy interactions like these are likely to be "social associations" and not just random interactions, Papastamatiou added — think of it like the shark version of having a hunting buddy.

For their new study, the researchers tagged six great white sharks (three male, three female) near Guadalupe Island between October 2017 and December 2018. Dubbed "super social tags," the monitors tracked each shark's swimming speed, depth and direction, and also alerted researchers anytime a tagged shark came into close proximity with another tagged shark. Each tag, which also contained a small video camera, popped off the shark's dorsal fin after about five days.

More than 30 great white sharks at the island had already been tagged by previous research expeditions, giving researchers plenty of opportunities to see their super social tags in action. The team recorded hundreds of social interactions between the great whites — some short, some much longer.

In general, male sharks preferred to hang out with other male sharks, and female sharks preferred the company of other females. But the social behavior of each shark varied wildly. One shark interacted with a dozen others in a 30-hour span before shaking loose its tag, while another shark kept its tag on for five days and associated with only two other sharks.

Many of the great white interactions occurred near a seal breeding ground, suggesting that perhaps the sharks spend more time with each other when prey is near, in order for one shark to take advantage of another's hunting success, the researchers said.

"They aren't working together but being social could be a way to share information," Papastamatiou said. 

Given the study's small sample size, the scientists concluded that more observations are needed to draw any firm conclusions about the great white social networks of Guadalupe Island.

Originally published on Live Science.

Unnerving images of a mummified shark that looks like a zombie, as well as other dead and decaying sea creatures, have been captured in eerie new footage of an abandoned aquarium.

The spooky viral video was taken by a pair of "urban explorers" who broke into the unnamed aquarium in Spain. The video was posted to YouTube by one of the explorers, a French woman who goes by the name of Juj' Urbex, along with several shorter clips on her TikTok. 

The video shows the rotting remains of a small reef shark inside a broken display case. The size of the glass box suggests that the shark was already dead when it was originally put on display. The body, therefore, had likely been treated with chemicals and kept in an airtight case to preserve it, but after the case broke and the shark was exposed, it started to slowly decay, giving it a zombie-like appearance. When the aquarium was damaged and subsequently evacuated, all living animals were transferred to new aquariums, but the shark corpse may have been less of a priority and thus left behind, Juj' Urbex speculated in the video. 

Related: The 12 weirdest animal discoveries 

Discovering the dried-out remains of the shark "made me feel a lot of sorrow for this beast" even though it was already dead, Juj' Urbex said in the video translated into English. 

The explorers also found the decomposed remains of an octopus and squid inside separate shattered glass jars. Like the shark, these animals were likely already dead when the aquarium closed its doors, and after their jars, which likely contained formaldehyde, were smashed, the cephalopods started to rot. The pair also found two sea stars that had been left behind, but unlike the other animals, these invertebrates had not begun to decay because they had been completely dried out before being put on display. 

Another standout discovery was a massive lifelike replica of a giant squid made from foam, which probably used to hang from the ceiling but has since fallen to the floor. The aquarium used to display actual giant squid specimens, but they were removed before the building was condemned, Juj' Urbex said in the video.

The explorers have not disclosed the location of the aquarium, to prevent copycat explorers from visiting the site and to avoid being caught (urban exploring is a form of trespassing), Juj' Urbex said in the video. However, she did reveal that the aquarium was somewhere in Spain and was closed in 2014 after a 43-foot (13 meters) wave damaged the building. In January 2014, a freak wave of this size did hit Spain's northwest coast, causing significant damage, according to Spanish news site The Local, hinting that the aquarium is likely in that region. 

In 2018, another urban explorer, Luke Mcpherson, discovered a 16-foot (5 m) mummified great white shark, later nicknamed Rosie, suspended in an enormous formaldehyde tank at an abandoned wildlife park in Australia, according to the Daily Mail.   

Originally published on Live Science.

In mid-August, a team of Massachusetts-based marine biologists set out on the waters of Stellwagen Bank National Marine Sanctuary, just east of Boston. Their mission: to tag some basking sharks — the second-biggest shark species on Earth, and a predator still considered highly mysterious to scientists. But soon after the team hit open water, another marine mammoth caught their attention: A young humpback whale, floating dead on the ocean's surface.

Then, the sharks came.

"Eight or more great white sharks had found the carcass," and were tearing its blubber to bits, David Wiley, a research ecologist at Stellwagen Bank, told Live Science.

It was an "unimaginable" spectacle, Wiley said, crowned with thousands of hungry seabirds swooping down to snatch bits of whale tissue out of the bloody water — and you can see the havoc for yourself in a new video (above) by Stellwagen Bank and the National Oceanic and Atmospheric Administration (NOAA).

"It was nature in action," Wiley said. "Everything dies for something else to consume. Nothing goes to waste."

Humpback whales, which can grow to be about the size of a school bus, roam all over the world, and are frequently seen at high-latitude feeding grounds like Stellwagen Bank in summertime. Unfortunately, that can put them in the path of large boats and fishing nets — the two main threats facing humpbacks in the wild, Wiley said. One of those threats is likely the cause of death here.

One of the biologists at the scene in Stellwagen looked at the fingerprint-like pattern under the dead humpback's fluke (or tail fin), and identified it as the 1-year-old calf of a known mother whale named Venom. (Wiley could not say whether the mother's name was a Spider-Man reference). Given the dead whale's young age, it's likely that the calf fell victim to some sort of human interaction, Wiley said. However, by the time the researchers arrived, the body had been so badly chewed up by sharks it was impossible to find any clear indications of what had killed it.

While the sight of the dead calf was a somber one, the researcher also knew that the ensuing feeding frenzy was an extremely uncommon sight, and a rare chance to see great whites at the top of the water. The team took the opportunity to tag five of the feasting sharks with special acoustic sensors, which will help NOAA scientists track the movement and behavior of the enigmatic predators as they cruise around Stellwagen, and eventually south to their wintering grounds.

The whale, meanwhile, may still play a major role in revealing the secret lives of the sanctuary's underwater residents.

"As soon as the sharks eat away the blubber, the carcass will become negatively buoyant and drop," Wiley said. "Whale falls can feed hundreds of animals for years to come."

The researchers were unable to tag the whale before it fell, and the carcass is likely at the bottom of the sea by now, Wiley said, so it will take some searching to locate the body's final resting place. But if researchers can find it, this will be the first whale fall ever seen at Stellwagen Bank, Wiley said. Studying it could reveal multitudes about the ecology of the area — and give the deceased calf of Venom a scientific legacy that few whales can claim.

Originally published on Live Science.

Sharks are a diverse group of fish that have been prowling our oceans for hundreds of millions of years. The group includes several large, food chain-topping predators from the extinct Helicoprion, which had a jaw like a circular saw, to modern-day great white sharks that accelerate through water like a bullet as they hunt down their prey. 

Giant sharks have evolved and gone extinct throughout Earth's history and plenty of behemoths still lurk in the ocean today 一 though not all are ferocious predators. Here are eight of the biggest sharks from past and present. 

8. Megamouth shark

Megamouth sharks (Megachasma pelagios) are filter feeders and eat vast quantities of tiny shrimplike crustaceans and plankton, rather than hunting larger prey. The sharks feed by taking big gulps of seawater and then pushing the water out through their gills, leaving their mouth full of tasty little critters. Megamouth sharks can grow to about 16 feet (5 meters) long and weigh 1,650 pounds (750 kilograms), according to the University of Michigan's Animal Diversity Web (ADW).

The species was first discovered off the coast of Hawaii in 1976 when a megamouth shark was struck and became entangled in the anchor of a Navy ship, Live Science previously reported. Megamouth sharks spend their days deep in the ocean but ascend to surface waters at night as they follow their food source. They live in all major oceans around the world but their exact distribution remains poorly understood by scientists, according to the International Union for Conservation of Nature (IUCN). 

7. Thresher shark

One look at a common thresher shark (Alopias vulpinus) and it's easy to see where the bulk of its size comes from — their long, sickle-shaped tails make up half their total body length, according to the National Oceanic and Atmospheric Administration (NOAA). Thresher sharks swipe their enormous tails like a whip to stun fish, smacking them directly and with the powerful waves generated by the swipes, making their prey easier to catch, Live Science previously reported. 

The sharks often grow to 20 feet (6.1 m) long. The largest thresher shark ever recorded was 24.9 feet (7.6 m) long, and the heaviest weighed more than 750 pounds (340 kg), according to the Florida Museum of Natural History. Thresher sharks live in tropical and cold sea waters worldwide and mostly eat small, schooling fish such as herring.

Related: Whodunit solved when 'sword' is found embedded in thresher shark 

6. Greenland shark

Greenland sharks (Somniosus microcephalus) are peculiar animals that inhabit deep, cold waters in the Arctic and North Atlantic oceans. Ocean parasites often attach themselves to the eyes of Greenland sharks, which can render them partially blind. But that doesn't seem to bother these sharks much, as they use their other senses to catch prey, according to ADW. Greenland sharks eat fish and marine mammals such as seals. They grow slowly but can reach lengths of 24 feet (7.3 m) and weigh up to 2,645 pounds (1,200 kg), according to the St. Lawrence Shark Observatory in Canada.

Related: No, scientists haven't found a 512-year-old Greenland shark

A 2016 study of Greenland shark eye tissue published in the journal Science estimated that these sharks don't even reach sexual maturity until they are about 156 years old, Live Science previously reported. The study also suggested that the maximum lifespan of a Greenland shark is at least 272 years, with the oldest shark in the study estimated to have been about 392 years old. 

"It's important to keep in mind there's some uncertainty with this estimate," Julius Nielsen, co-author of the 2016 paper previously told Live Science. "But even the lowest part of the age range — at least 272 years — still makes Greenland sharks the longest-living vertebrate known to science."

5. Great white shark

Great white sharks (Carcharodon carcharias) are perhaps the best-known predators in the ocean and the largest living sharks that don't filter feed. The biggest great white sharks are estimated to grow to 20 feet (6 m) long but there are unconfirmed reports of these sharks reaching lengths of 23 feet (7 m), according to the Florida Museum of Natural History. They can also weigh up to 7,000 pounds (more than 3,000 kg), according to the World Wildlife Fund (WWF). 

As juveniles, great white sharks spend most of their time hunting fish and other small prey on and near the seafloor, Live Science previously reported. When they grow up, the sharks hunt down marine mammals such as sea lions and dolphins. Great white sharks have a wide geographic range but are most common in temperate waters, such as off the west coast of the U.S. in the Pacific Ocean, according to the IUCN.  

4. Helicoprion

There are a handful of extinct sharks that would comfortably meet and surpass the size of modern great white sharks and Greenland sharks, but the Helicoprion is perhaps the most bizarre example. This ancient ratfish relative is nicknamed the "buzz saw shark" as it had a whorl jaw with a spiral set of teeth. Fossilized Helicoprion jaws, which resemble spiky ammonites, indicate these sharks may have grown up to 25 feet (7.7 m) long, making them the largest predator on Earth when they lived nearly 270 million years ago, Live Science previously reported. 

Related: Toothy spiral jaw gave ancient sea predator an edge 

3. Basking shark

Great white sharks may be the largest predatory shark alive today but they seem almost quaint next to the biggest filter-feeding sharks. Although basking sharks (Cetorhinus maximus) only eat plankton, they can reach up to 40 feet (12.2 m) in length and weigh more than 5 tons (4.5 metric tons), according to the Florida Museum of Natural History. These behemoths are most commonly found in the Atlantic and Pacific Oceans, according to the IUCN. 

Basking sharks are often regarded as slow, gentle giants but they are capable of rocketing out of the water at speeds of 11 mph (18 km/h) and jumping 4 feet (1.2 m) in the air to breach, Live Science previously reported. This breaching behavior may be used to communicate with other basking sharks or to rid themselves of parasites. 

2. Whale shark

Whale sharks (Rhincodon typus) are the biggest filter-feeding sharks and the biggest fish in the world. They usually grow to between 18 and 33 feet (5 to 10 m) long and weigh around 21 tons (19 metric tons). However, the largest whale shark ever recorded was a whopping 66 feet (20 m) long and weighed 46 tons (42 metric tons), according to the Zoological Society of London. Whale sharks live in tropical and warm temperate oceans around the world, except for the Mediterranean Sea.

Whale sharks are categorized as an endangered species by the IUCN and are threatened with extinction due to fishing, boat strikes and other human activity.  

1. Megalodon

The undisputed king of predatory sharks is the megalodon (Carcharocles megalodon). Members of this extinct species are the largest sharks to have ever lived and the biggest fish known to science. The exact size of megalodon is debated within the scientific community but they may have been up to about 60 feet (18 m) long based on teeth fossils, and perhaps even 80 feet (24 m) long. That's three to four times the length of the biggest great white sharks. They may also have weighed up to 50 tons (45.4 metric tons), according to the Smithsonian National Museum of Natural History.

Related: Megalodon shark mamas had human-size cannibal babies

Most megalodon fossils are dated to between the middle Miocene epoch and the Pliocene epoch (15.9 million to 2.6 million years ago) and there is no record of them existing after this period. Megalodon have been resurrected on the big screen, such as in the 2018 science fiction thriller "The Meg," but the real megalodons are long gone.

About 3,000 years ago, a shark fatally mauled a man in waters near western Japan. The encounter left a map of horrific scars spread across the man's skeleton, and parts of his body were never recovered.

Analysis of the person's bones, which were excavated from a communal burial ground at the Tsukumo archaeological site in Okayama prefecture, documented 790 traumatic injuries, such as cuts, punctures, fractures from blunt force and deep, crisscrossing gouges with "sharp, V-shaped edges," the researchers wrote in a new study. Such wounds match those left by sharks, making this the world’s oldest recorded instance of a shark attack on a human — about 1,000 years older than the previous record-holder. 

Related: In photos: Seeing sharks up close

"This find not only provides a new perspective on ancient Japan, but is also a rare example of archaeologists being able to reconstruct a dramatic episode in the life of a prehistoric community," study co-author Mark Hudson, an archaeologist with the Max Planck Institute for the Science of Human History in Jena, Germany, said in a statement.

The man's injuries were so numerous that he probably didn't survive, and he would have died from blood loss and shock, the study authors wrote. He likely was alive when attacked, as the distribution of skeletal damage differed from damage patterns left by sharks on scavenged corpses. The widespread trauma to the skeleton also suggests "that the victim remained in the sea for some period of time sufficient to allow the shark to feed on the body after death," the scientists reported in the August 2021 issue of the Journal of Archaeological Science: Reports.

Torn apart

Construction workers uncovered the Tsukumo site in 1860, and the first archaeological excavations took place in 1915. Since then, archaeologists have found more than 170 human remains buried there. But only one skeleton, an adult male known as Tsukumo No. 24, had such serious and extensive injuries. The remains of the man, who died between 1370 B.C. and 1010 B.C., showed traumatic lesions scarring the majority of his skeleton, with most of the damage on his pelvis, left leg, shoulders and arms. He was also missing his left hand and right leg, and his left leg had been arranged upside-down in the grave, according to the study.

The authors scanned the bones with X-ray computed tomography (CT) and built a 3D model of Tsukumo No. 24 so they could visualize and map his injuries. Nearly all of the ribs had been bitten and fractured, and "the chest cavity and abdomen may have been eviscerated," the scientists wrote. Wounds were heavily concentrated around the left hip and leg, hinting that the man may have lost his left hand while trying to defend that part of his body. Long bones in the arms and legs showed bites from numerous directions, suggesting that the shark continued circling and tearing at the corpse after the man was dead.

What type of shark attacked him so long ago? Tiger sharks (Galeocerdo cuvier) and great white sharks (Carcharodon carcharias) are the most likely candidates, as both are commonly found in Japan's Seto Inland Sea near the site where the body was buried; both species have also been known to attack humans, according to the study. However, such attacks are rare, and most sharks don't attack people without provocation, the researchers added.

"Humans have a long, shared history with sharks," the scientists reported. "This is one of the relatively rare instances when humans were on their menu, and not the reverse." 

Originally published on Live Science.

One of the largest great white sharks ever tagged was just spotted swimming south of Miami, Florida, according to NBC Miami. 

Unama'ki "pinged" at 5:46 a.m. ET off of Key Largo, south of Miami on Thursday (Nov. 5) , which means that its dorsal fin broke the surface of the water, sending a signal to a satellite, alerting researchers of its whereabouts, according to a previous article from Florida Today. 

Unama'ki was first tagged in Nova Scotia in September; in the indigenous language of the Mi'kmaq people, her name means "land of the fog." With a length of 15 feet and 5 inches (4.7 meters) and a weight of 2,076 pounds (942 kilograms), she is the second largest white shark ever tagged by Ocearch, a nonprofit organization that tags and tracks large marine animals. 

Related: Image gallery: Great White sharks

But she's not the only impressive beast out there. Great white sharks are the largest predatory fish on the planet and grow to an average of 15 feet (4.6 m), according to National Geographic. Some have been found to weigh up to 5,000 Ibs. (2,268 kg) and to grow to more than 20 feet (6 m).

Over a month ago, researchers with Ocearch also discovered and tagged a 17-foot-long (5 m) heavy female great white shark — weighing 3,541 lbs. (1,606 kg) — off the coast of Nova Scotia that they called the "queen of the ocean," according to a previous Live Science report. She was officially named Nukumi, after a legendary wise grandmother figure from the indigenous Mi'kmaq people.

Great whites are classified as "vulnerable" by the International Union for Conservation of Nature. As top predators of the ocean, "great white sharks are central to the functioning of ecosystems and the maintenance of biodiversity," according to Ocearch. 

Researchers hope that Unama'ki will lead them to a site where she gives birth and thereby reveal a previously unknown white shark nursery, according to Ocearch. 

But great white shark whereabouts aren't always clear. The majestic sea creatures can only be tracked once they break the surface, and each shark tends to spend a different amount of time at the surface, according to Ocearch.

You can track Unama'ki's whereabouts, or at least every time she breaks the surface, here. 

Originally published on Live Science.

A fatal great white shark attack in Maine on Monday (July 27) was only the state's second recorded shark attack ever. But white sharks have long been in the waters of the Gulf of Maine. 

Great white sharks (Carcharodon carcharias) range as far north as the Bay of Fundy and Newfoundland, in Canadian waters, said Gregory Skomal, a senior fisheries scientist at the Massachusetts Division of Marine Fisheries. These same sharks can be found as far south as the Gulf of Mexico in cooler months.

"We've got over 200 tags out on white sharks, and those sharks move seamlessly all the way to Canada," Skomal told Live Science. 

Related: The 10 coolest shark stories

Fatal attack

Despite the long-running presence of sharks in Maine waters, scientists know about only two recorded attacks on humans. The first was an attack of a commercial diver by a porbeagle shark in 2010; the diver was not injured according to CBC News.

The second was this Monday's attack, with a far more tragic outcome. According to CNN, Julie Dimperio Holowach, 63, of New York City, was swimming with her daughter when she was attacked and killed. A tooth fragment left behind indicated that the attacker was a great white shark.

It's likely that the shark mistook Holowach, who was wearing a wetsuit, for a seal, said Bob Hueter, a senior scientist at Mote Marine Laboratory and also chief scientist for the marine research organization OCEARCH. Seals are common along the coastline of the Gulf of Maine, he told Live Science.

"Where there are seals in the summertime up in New England, there are white sharks, you can bank on that," Hueter said. 

Traveling great whites

Great whites are an elusive species, but advances in tagging and tracking technologies have begun to reveal their secrets. Using both satellite tags and acoustic tags that ping networks of underwater sensors along the Eastern Seaboard, researchers have found that white sharks probably give birth off the coast of Long Island, in an area called the New York Bight. In the fall, the sharks flee chilly waters and head south to the Carolinas, Florida and Gulf of Mexico. As the waters warm in the spring and summer, they head back north.

"It's kind of like opening the restaurant for them," Skomal said. "It allows the opportunities to feed on the pinniped [seal] species" that live in the Northeast and off the Canadian coast. 

Scientists have begun to understand these movements in the last decade. In 2017, Skomal and his colleagues published a study in the journal Marine Ecology Progress Series showing the wide distribution of white sharks and the timing of their movements. This month, Hueter and his colleagues published research in the Canadian Journal of Fisheries and Aquatic Sciences revealing a consistent and common great white shark presence in the Canadian Atlantic.

A segment of the mature females also heads out into the open ocean, past Bermuda as far as the mid-Atlantic ridge, Hueter said. Researchers aren't yet sure, but they suspect that these are pregnant females, who may be breaking away from the main shark population while they gestate, "probably because they don't want to be harassed by any more males," Hueter said.

No one knows precisely how many great white sharks live off the U.S. East Coast, Skomal said, though he and his team hope to provide some of the first data-driven estimates later this year or early next year. However, the population has likely been growing and stabilizing since protections were put in place for them in the 1990s, Skomal said. Before that, they were overfished, and their populations plummeted. 

This restoration is good news for the ocean ecosystem. As apex predators, sharks play an important role in keeping their prey species in check, keeping the food web in balance, Hueter said. However, during the decades that great white shark populations were in decline, human recreation in the ocean exploded, Skomal said. People became accustomed to an ocean artificially deprived of great whites. The sharks still probably aren't back to their original numbers, Skomal said, but more people and more sharks in the water means more opportunities for clashes. Part of the goal of shark-tracking projects is to understand where and when sharks hunt in a very detailed way, he said. 

"If we can understand where and when a white shark is most likely to attempt to attack a seal, we can also share that information with beach managers and the general public," Skomal said. "Those might be the areas or the times to avoid conducting your activities on the water."

Originally published in Live Science.

Great white sharks (Carcharodon carcharias) are often imagined hunting large prey. But apparently they spend more of their time ⁠— at least as juveniles ⁠— nosing around on the seafloor for little morsels of food.

Between 2008 and 2019, researchers studied the stomach contents of 40 juvenile great white sharks captured off the coast of eastern Australia. That information, combined with data from studies elsewhere in the world, painted a surprising picture of how these young sharks feed. The sharks' main food was a large fish: Australian salmon (Arripis trutta), representing about one-third of what they ate. But more than a fifth of their diet was made up of critters that swim just above the ocean bottom, live in reefs, or bury themselves in the sand.

Related: Image gallery: great white sharks

Here's a breakdown of the shark diets, according to the paper, which was published June 7 in the journal Frontiers in Marine Science:

• Mid-water swimming fish, like Australian salmon: 32.2%
• Bottom-dwelling fish, such as stargazers, sole or flathead: 17.4%
• Reef fish, such as eastern blue gropers: 5.0%
• "Batoid" fish, a group of flat-bodied fish like stingrays: 14.9%
• Unidentified or unusual prey: 30.5%

"This evidence matches data we have from tagging white sharks [with electronic trackers] that shows them spending a lot of time many meters below the surface," Richard Grainger, lead author of the study and a researcher at the University of Sydney, said in a statement. "The hunting of bigger prey, including other sharks and marine mammals such as dolphin, is not likely to happen until the sharks reach about 2.2 meters [7.2 feet] in length," Grainger said.

There was also some evidence that the male sharks went after stingrays and their cousins more often than female sharks did; but the researchers noted that there was a fairly small sample size from which to make this claim.

Great white sharks are well-understood compared with other shark species, said Catherine Macdonald, director of the Field School (a marine biology education program) and a conservation biologist at the University of Miami in Florida, who was not involved in the new study.

But there's still a lot to learn about how white sharks behave.

"These results align well with what scientists know about white shark diet and how target prey species change as individual sharks increase in size," Macdonald told Live Science. "From a scientific perspective, that's great news, because it helps confirm the results of previous studies done using different techniques, and suggests we already have a pretty good general picture of white shark diet at different life stages."

It's important to understand that these results represent a snapshot of how these sharks lived in a particular place and time, Macdonald added. Sharks eat many things, and it's likely that their choices are constantly in flux as the world around them changes. These predators likely instinctively weigh factors like their risk of injury or encountering another predator, their odds of catching the prey, how nutritious the prey is and how hungry they are in choosing what to hunt, she said.

"Humans are having unprecedented impacts on marine ecosystems, and so what [they are] measuring isn't really 'what white sharks eat' ⁠— it's 'what white sharks are currently eating based on all of the effects human actions have already had on their ecosystems,'" she said. "The paper identifies eastern Australian salmon (A. trutta) as an important food item ⁠— but fishing pressure, changes in ocean temperature and availability of their prey means that populations of A. trutta look quite different today than they have historically."

• In photos: glow-in-the-dark sharks
• 8 weird facts about sharks
• In photos: baby sharks show off amazing ability

Originally published on Live Science.

An astonishing underwater photo of a shark looks uncannily similar to the iconic poster for the 1975 film "Jaws."

In that poster, an enormous great white shark (Carcharodon carcharias) barrels upward through the water toward an unsuspecting swimmer, the shark's gaping mouth crammed with layers of teeth.

Remarkably, British photographer Euan Rannachan captured a nearly identical view of a real great white in waters off the western coast of Mexico, The Sun reported yesterday (May 7). [In Photos: Great White Sharks Attack]

Rannachan took the photo while diving in a shark cage near Guadalupe Island. At the time he snapped the picture, he was just a few feet away from the shark — a female measuring 17 feet (5 meters) long, nicknamed "Squirrel" by the divers, according to The Sun.

The image captured an unusual perspective; the shark is perpendicular to the camera, angled toward the surface with its underside and fearsome maw on display, just like the shark in the movie poster.

Rannachan originally shared the photo on Instagram in November 2018, calling it "Jaws in real life."

Rannachan told The Sun that during dives like these, "shark wranglers" on a boat toss chunks of fish into the water to draw the sharks close to the surface, so photographers in the cage can get better pictures. Sometimes, when the wranglers don't drop the bait quickly enough, a shark will dive deep under the boat and then rocket upward to snatch the fish, Rannachan said.

And that's exactly what Squirrel was doing when Rannachan snapped the photo.

"I just happened to be in the right spot seeing her coming up," he said.

Female great whites, which are slightly larger than males as adults, can grow to be 20 feet (6 meters) long and weigh up to 4,200 lbs (1,905 kilograms). The shark that appeared in "Jaws" was significantly bigger — about 25 feet (8 m) long, with a head weighing 400 pounds (181 kg) and jaws that spanned 5 feet (2 m); according to The Hollywood Reporter.

However, the movie shark wasn't real. It was a mechanical model nicknamed "Bruce" after Bruce Ramer — director Steven Spielberg's lawyer, NPR reported.

• Image Gallery: Great White Sharks
• In Photos: Seeing Sharks Up Close
• In Photos: Baby Sharks Show Off Amazing Ability

Originally published on Live Science.

For a multitude of reasons, great white sharks should be considered nature's ocean-dwelling superheroes — they're big and strong, live long lives, can heal their wounds remarkably fast, and it's even likely that they rarely get cancer. But how is it possible that these ancient giants have so many superhero-like traits? Scientists have now taken a major step toward answering that question by decoding the entire genome of the great white shark.

An international team of researchers led by scientists at the Save Our Seas Foundation Shark Research Center and the Guy Harvey Research Institute at Nova Southeastern University in Florida sequenced the genome of the great white shark (Carcharodon carcharias) and compared it with the genomes of several other vertebrate species. The team discovered a wealth of unusual genetic characteristics that might explain why white sharks are the superheroes (or supervillains, if you're a plump sea lion) of the sea. Their study was published online on Monday (Feb. 18) in the journal Proceedings of the National Academy of Sciences.

Genetic stability is key

Sequencing the great white shark genome was no small task — the genome consisted of 4.63 billion base pairs (the nitrogen-containing molecules that make up the "rungs" of the DNA ladder), which is about 1.5 times the size of the human genome. "It's quite an impressive effort," said Dovi Kacev, a marine molecular ecologist and researcher at the National Marine Fisheries Services Southwest Fisheries Science Center in California, who was not involved with the study. [Image Gallery: Great White Sharks]

Nearly 60 percent of the white shark genome consisted of repeated genetic sequences, which is similar to what's seen in the human genome. What's special about the white shark genome was that many of those repeated regions are codes for a special group of genes known as LINEs.

"These [LINEs] make copies of themselves and then reinsert randomly in various locations in the genome, and in the process they make double-stranded breaks in the DNA that need to be repaired," said Michael Stanhope, an evolutionary biologist at Cornell University in New York. Stanhope co-led the study with Nicholas Marra and Mahmood Shivji, conservation biologists at Nova Southeastern University.

Those frequent breaks in the DNA make the genome unstable, which typically leads to a higher risk of problem-causing genetic mutations that can eventually lead to cancer. But white sharks seem to have evolved a way to avoid such genomic instability.

The researchers found that the white shark genome contained a lot of genes responsible for maintaining genetic stability — things like DNA-repair genes and tumor-suppressing genes. And when the researchers compared the white shark's stability genes with analogous genes in other vertebrates, they found small changes in the gene sequence that suggest a specific pattern of evolutionary adaptation for these genes in white sharks.

"Think of it as fine-tuning the role of these genes in maintaining genome stability in the white shark," Stanhope said.

People have speculated that sharks have a much lower rate of cancer than other animals, but "there's not a lot of real data to say that with certainty," Kacev said. Nonetheless, the abundant presence of specially adapted stability genes could explain the potential cancer resistance.

"If you want to prevent cancer, you need to maintain the stability of your genome," Stanhope said, which means avoiding genetic mutations. An accumulation of excess mutations leads to cancer, but the shark genome seems specifically designed to prevent that. "These are things we would have to test in the lab, though, to really know," he said.

Stanhope also cautioned that while white sharks might have a genetic adaptation to prevent them from getting cancer, that does not mean that consuming shark products could prevent a human from getting cancer, despite what proponents of "alternative medicine" may claim.

And their other special abilities …

Genetics may also explain another one of the white shark's superpowers: the ability to heal quickly. The team discovered several white shark genes that are known to play important roles in vertebrate wound-healing processes. And, similar to the stability genes, the wound-healing genes in the white shark were under the same kind of positive evolutionary selection pressures, meaning there's a tendency for the number of these beneficial traits to increase.

"We also found an enrichment of genes for both wound healing and genome stability genes in the white shark compared to other vertebrates," Stanhope said. In other words, the white shark genome has a higher proportion of these types of genes compared with what's seen in other vertebrate genomes.

While the team discovered a number of genes that may be responsible for many of the great white's super-shark abilities, there was one characteristic that wasn't clearly accounted for by the genome: the shark's sensitive sniffer.

Sharks are known for having a keen sense of smell, so the researchers expected to find numerous olfactory receptor (OR) genes, which are the genes responsible for the effective schnozes of other vertebrates. But the white shark genome contained exceptionally few of these genes. What the researchers found instead was another category of genes, called vomeronasal genes. These genes can also be involved in the perception of smell, but they aren't normally as abundant as OR genes, Stanhope said. In the white shark genome, however, there are more than dozen vomeronasal genes, so the researchers suggested that maybe those genes drive smell perception in the white shark.

"We're still at a point here where we're scratching the surface, but having this genome sequence gives us a starting point for addressing these questions in more detail," Kacev said. This research will undoubtedly help answer questions about other species, too, he added. "Understanding the genome of the white shark is not only important for the white shark, but it's a scaffold, or jumping-off point to understand related species."

Great white sharks are one of the world's most well-recognized marine creatures, but their populations are struggling as people continue to hunt them out of fear and greed. "People have these images of [white sharks] that are depicted in movies and TV shows as being these killing machines," Kacev said. Yet, the reality is that humans kill far more sharks than sharks kill humans.

"Humans kill many, many millions of sharks every year across the world for silly, fake medicine reasons; for shark fin soup and all sorts of reasons that are just tragic, really," Stanhope said. The researchers hope their study helps more people realize how special these ancient vertebrates are.

"I hope that people recognize the remarkable, biological adaptations of these animals and as a consequence, have a greater appreciation for them," Stanhope said.

• In Photos: Glow-in-the-Dark Sharks
• 8 Weird Facts About Sharks
• In Photos: Baby Sharks Show Off Amazing Ability

Originally published on Live Science.

The great white shark (Carcharodon carcharias) may have wiped out the giant megalodon (Otodus megalodon).

Millions of years before human beings emerged, a type of shark that grew up to 60 feet (18 meters) long prowled the oceans. Based on the fossil record, scientists suspect that O. megalodon died off about 2.6 million years ago, around the time a lot of other marine species went extinct. (Researchers even recently suggested that the mass die-off may have been the result of a nearby supernova.) [These Bizarre Sea Monsters Once Ruled the Ocean]

But scientists may have miscalculated megalodon's time of death by about 1 million years.

For a paper published today (Feb. 13) in the journal PeerJ, researchers re-examined the fossil record of megalodons in California and Baja California, Mexico, where many examples of the huge fish have been found.

There's clear evidence that up until about 3.6 million years ago, megalodons were alive in the ocean. But after that, things get dodgy. Fossils dated to between 2.6 million and 3.6 million years ago tended to have issues. Many of the fossils seemed to have shifted within the surrounding rock in ways that complicate the dating methods scientists use.

But if megalodons died out 3.6 million years ago, they weren't part of that mass marine extinction. So, what killed them?

The researchers in the new study suggested that the huge sharks were outcompeted by a smaller, savvier predator.

Great whites arrived in the oceans about 4 million years ago, just 400,000 years before megalodon's revised death date.

"We propose that this short overlap (3.6 to 4 million years ago) was sufficient time for great white sharks to spread worldwide and outcompete O. megalodon throughout its range, driving it to extinction," College of Charleston paleontologist Robert Boessenecker, an author of the study, said in a statement.

Boessenecker also suggested that the whole idea of a sudden marine die-off 2.6 million years ago may be an artifact of gaps in the fossil record, rather than the result of some "cataclysm" like a supernova.

As for the great whites, if they know what killed the giant megalodon, they aren't telling.

• Image Gallery: 25 Amazing Ancient Beasts
• The 10 Weirdest Sea Monsters
• Ancient Sharks and 'Sea Monsters' Inspired Mayan Mythology

Originally published on Live Science.

Each winter, an open ocean void in the deep sea of the mid-Pacific Ocean attracts large crowds of great white sharks (Carcharodon carcharias) that make the monthlong swim from the coasts of California and Mexico. Scientists followed the sharks to their mysterious ocean lair and discovered a few potential reasons why the fearsome predators might be attracted to the area, the Monterey Bay Aquarium Research Institute reported.

The sharks, known as the northeastern Pacific whites, feed on elephant seals and other marine mammals along the coast of California from about August to December, according to the Schmidt Ocean Institute. Then in December, the sharks swim to their meeting spot in the middle of the ocean, about halfway to Hawaii, where they spend their winter and spring before returning to California. Satellite images suggested the area was an oceanic desert, so scientists were stumped as to why these prolific predators would leave the food-rich waters off California.

Barbara Block, a marine scientist at Stanford University's Hopkins Marine Station, discovered the area more than a decade ago when she tracked tagged sharks to the area. She dubbed the spot the "White Shark Café," although she wasn't yet sure why the sharks were going there. [Image Gallery: Great White Sharks]

When Block and her colleagues at Stanford University and the Monterey Bay Aquarium ventured out to the mysterious shark-gathering zone this spring aboard the Schmidt Ocean Institute's research vessel Falkor, they were met with a surprise: a playland of sorts for jellyfish, phytoplankton, squid and fish — perfect ingredients for a great white shark buffet, the San Francisco Chronicle reported.

This group of specialized open-ocean marine life migrate up and down the water column each day, through what's called the midwater range — the zone just below where sunlight penetrates the ocean depths. During daylight hours, the creatures sink to the depths and then return to shallower waters at night.

Electronic tag data retrieved from 10 sharks revealed the predators were following a similar pattern — making several dives down to nearly 1,500 feet (450 meters) during the day and down to about 650 feet (200 m) at night. In April, the male sharks increased their dive activity, making up to 140 dives in a day, while the diving habits of female sharks remained unchanged, the San Francisco Chronicle reported.  

"The story of the white shark tells you that this area is vitally important in ways we never knew about," Salvador Jorgensen, a marine scientist at the Monterey Bay Aquarium and one of the expedition leaders, told the San Francisco Chronicle. "They are telling us this incredible story about the mid-water, and there is this whole secret life that we need to know about."

But the difference between male and female shark diving behavior in April is still a mystery.

"Either they are eating something different or this is related in some way to their mating," Jorgensen told the San Francisco Chronicle.

The team is continuing to analyze data from this year's cruise with hopes of answering more questions about the biological significance of the White Shark Café. They plan to publish their results in the coming months, Jorgensen told Live Science.

Original article on Live Science. 

When one of the ocean's top predators washes up dead on a beach, it's likely that something fishy must have happened. On Sunday (June 17), beachgoers found a juvenile male great white shark (Carcharodon carcharias), weighing 500 lbs. (225 kilograms) and reaching 8 feet (2.4 meters) long, on Beer Can Beach in Aptos, California, near Santa Cruz, reported KION.

But authorities aren't disclosing the shark's cause of death, and it's now the subject of a law enforcement investigation by the California Department of Fish and Wildlife (CDFW).

KION reported the male shark appeared healthy besides a few relatively minor lacerations, possibly caused by sea lions. But it's unclear if those scratches caused the creature's death, KION reported.  

Researchers from CDFW collected the shark on Sunday afternoon and performed a necropsy at the Long Marine Lab in Santa Cruz on Tuesday (June 19), but they aren't revealing what they found. "Upon receiving the lab's necropsy results, the CDFW's Law Enforcement Division is now taking up the investigation," a representative from CDFW told Live Science in an email. The representative declined to comment further. [See Photos of the Great White Shark on Beer Can Beach]

It's not a frequent occurrence for great white sharks to wash ashore, although one washed up in the same area last year. "The white shark population has been essentially booming off the California coast," said David Ebert, a shark scientist and the director of the Pacific Shark Research Center at Moss Landing Marine Laboratory in Moss Landing, California. "It wouldn't be unexpected that occasionally one would wash up," he said.

Great white sharks are classified as vulnerable by the International Union for Conservation of Nature. But great white shark populations have been making a comeback since about 1972, when the Marine Mammal Protection Act was passed, said George Burgess, a marine biologist and director emeritus of the Florida Program for Shark Research at the University of Florida. The act made it illegal to harm any marine mammal, including seals and sea lions, that makes up the great white shark's main food source. And, because they're classified as vulnerable, great whites are illegal to catch without a special permit.

What could kill such a beast?

Great white sharks don't usually have predators, except for occasional attacks by killer whales (Orcinus orca), Burgess said. "Killer whales tend to go for the belly and eviscerate the white shark," Burgess told Live Science. But the midsection of this great white shark was intact, and there were no major lacerations apparent in photos. [Photos: Orcas Are Chowing Down on Great-White-Shark Organs]

The great white that washed up dead in the same area last year had a bacterial brain infection that also affects salmon sharks (Lamna ditropis) and thresher sharks (Alopias species), Ebert said. It's unclear how the sharks get infected with brain bacteria, but it's a significant cause of death in salmon sharks along the California and Oregon coasts, scientists reported in a 2012 study in the journal Veterinary Pathology.

Humans are capable of killing a great white shark, but that's infrequent, Ebert said. "They're not taken often in fisheries," he said. "It's a good size animal, so it's not the kind of thing that someone's likely to try to catch." There is an allowance for accidentally catching a white shark that gets entangled in a fishing net, he said, but it's illegal to target them.

Some fishermen might be tempted to catch a great white shark, though, because shark fins are a delicacy in Chinese culture and elsewhere. "Those fins are worth a great deal of money, and, if they were sold on the black market, they could have made a real pretty penny," Burgess said. This shark still had all its fins,  so Burgess wonders if it was caught accidently in a fishing net and then thrown back in the water by someone who didn't know what else to do. 

Ebert said he's "not aware of any other instances in California where a white shark washing up has led to a criminal investigation."

Neither of the experienced shark researchers has any clue as to why the CDFW's Law Enforcement Division is investigating the shark's death. But, Burgess said, "If this was a result of human interaction, it had to be illegal."

Original article on Live Science.

"Didn't your mother ever tell you not to swim with your mouth full?"

Not this female great white shark. The predator, with a partially eaten seal carcass hanging from her teeth, was caught on video by biologist Greg Skomal of the Massachusetts Division of Marine Fisheries (MA DMF), working with the Atlantic White Shark Conservancy (AWSC).

Measuring an estimated 11 feet (3.4 meters) in length, the shark — and its gruesome mouthful — was spied in Atlantic waters near Massachusetts, approximately 300 yards from the Monomoy National Wildlife Refuge. Researchers are currently conducting a five-year shark population study in the area, AWSC representatives wrote in a Facebook post describing the video.

Skomal used an underwater GoPro to capture the grisly sight, which AWSC representatives posted to their Facebook page on June 20. The shark cruises past the video camera with a portion of partly consumed seal torso dangling from her lower jaw, offering a rare glimpse of the large predator's feeding behavior. [In Photos: Great White Sharks Attack]

It is especially unusual to capture photos or video of sharks preying on seals in northwest Atlantic waters, though their deadly feeding strikes are well-documented from interactions off the African coast, an AWSC representative said in a comment on Facebook.

However, this wasn't the first time that AWSC video recorded a shark nomming a mouthful of pinniped. In 2014, one of their research teams filmed another great white shark, dubbed Salty, devouring a seal in waters near Chatham, Massachusetts.

Great white sharks' hunting strategies are a subject of great interest to marine biologists, who face enormous challenges when investigating the day-to-day behavior of ocean animals like sharks that live in the open sea, according to Gavin Naylor, a biology professor at the College of Charleston.

Naylor told Live Science in 2015 that observing great white sharks can be difficult because they are hard to raise in captivity, and studying them in their ocean home comes with hazards to divers.

When it comes to great whites, "there's a lot we still don't know," Naylor said. The Cape Cod area has come to be recognized as a location where great white sharks gather, offering AWSC researchers a unique opportunity to learn about their habits, Skomal said in a statement. 

This particular great white shark's video debut was the first time during the MA DMF survey that she was seen by the scientists, and she was assigned the catchy name "WS 16-02," the AWSC reported on Facebook.

Original article on Live Science.

A great white shark famously saved last month by Cape Cod beachgoers is likely still alive and swimming, said a shark expert.

The shark was rescued after it became stranded on a beach on July 13. Before it was released, experts pinned an acoustic tag to the shark's dorsal fin, which is on its back. A system of acoustic receivers — located about 3 miles (4.8 kilometers) south of where researchers released the shark — picked up the animal's unique signal within two weeks of the rescue, said Gregory Skomal, afisheries biologist with the Massachusetts Division of Marine Fisheries, who helped save the shark.

"It's very encouraging that the shark was alive," he told Live Science. "If I had to guess, if it survived for a couple days, it's going to survive [in the long term]." [Jaws Gallery: See Amazing Photos of Great White Sharks]

The young great white's tale is a miraculous one. The shark, a male juvenile, almost died after the retreating tide left it stranded on a Cape Cod beach in Massachusetts. Beachgoers saw the shark flopping around on the sand, and poured water over its gills to help it breathe and stay cool.

Videos taken of the rescue show the shark's underside turning red, likely because of capillaries bursting under the weight of its organs that were no longer supported by the buoyant water, experts said. Moreover, the heat and lack of oxygen likely strained the shark's body.

An organized effort involving the Chatham Harbormaster's office, the Atlantic White Shark Conservancy and state officials helped the shark survive. As soon as shark experts arrived on the scene, they tied a rope around the shark's tail and used a motorboat to drag the animal into the water.

Once waterborne, the shark got some new bling: an acoustic tag.

"It's a little dart that goes underneath the skin, into the muscle at the base of the dorsal fin," Skomal said.

The tag emits a high-frequency sound that can't be heard by people or sharks, but is recognized by receivers stationed around Cape Cod, Skomal said. When a tagged shark swims within several hundred feet of a receiver, the device detects the unique ping and records the time and date, Skomal said.

Each tag lasts up to eight years, he added.

The researchers don't get the data in real time. Instead, they have to visit each receiver, pull it out of the water and download its data via Bluetooth, Skomal said.

The last time the researchers saw the young male shark, it was alertly swimming away from their motor boat off the cape. Great white sharks typically hang around the area because it's filled with grey seals, one of the predator's preferred foods. However, great whites also eat fish, and are known to feed on whale carcasses and sometimes even turtles, Skomal said.

Researchers will continue to monitor the rescued shark's movements, as well as 40 other tagged sharks with acoustic transmitters in the area, he said. But sharks often leave the area, leaving nary a clue about their whereabouts.

That's not always a bad thing, Skomal said.

"If we don't hear from it at all for the rest of the summer, it's even more encouraging because that means the shark swam away to a different area," he said. "They move around quite a bit."

Follow Laura Geggel on Twitter @LauraGeggel. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

A young, great white shark had a near-death experience when the retreating tide left it stranded on a beach in Cape Cod on Monday afternoon (July 13). Beachgoers spotted the giant fish writhing on the sand, and threw water on its gills to help it breathe.

State officials arrived soon after, and dragged the shark into the water using a long rope attached to a motorboat, as seen on video of the shark rescue. At first, the shark looked limp and lifeless. But, it came to after the officials held it close to the moving boat, allowing water to flow over its gills.

It was a rare event, and not just because people saved the life of a vilified marine creature, shark experts told Live Science. Great whites rarely wash up on beaches because they typically live in the open water, far away from the coast, said George Burgess, a shark expert at the Florida Museum of Natural History at the University of Florida in Gainesville. Fortunately, beachgoers reacted in time, though shark scientists who viewed the video suspect the great white didn't come out unscathed, as the heat and lack of oxygen likely taxed the animal's body. [Jaws Gallery: See Amazing Photos of Great White Sharks]

Great whites get confused

Although there's no exact count of great whites beaching themselves, "these guys sometimes come ashore very much alive," Burgess said. "They've spent their lives in the open sea, and they get confused a bit" when they encounter the coast's tides, rocky walls and sandy floors.

When great white sharks and other pelagic, or open-ocean, sharks do get "beached," they're usually inexperienced juveniles, Burgess said.

"Perhaps they're a little more naive than their older kinfolk, who have probably encountered [beaches] at some point and figured it all out," he told Live Science.

Sharks that live close to shore, like the requiem shark family, which includes spinner and blacktip sharks, are better-equipped to understand the intricacies of the surf zone and realize that it has a bottom, he added.

Hopefully, the rescued shark learned its lesson to steer clear of beaches, but its future is far from certain, the experts said.

Gregory Skomal, a fisheries biologist with the Massachusetts Division of Marine Fisheries, put an acoustic tag on the rescued great white that will ping receivers in the area as the shark swims around. Biologists check the various receivers about once or twice a week to track animal movement, Skomal said. But the technology isn't always reliable, as batteries can die and trackers can fall off animals, experts said.

"If you hear from it you know it's alive, and if you don't hear from it, you don't know anything," Skomal said. 

Beach prison

Video recordings show how the rescue saved the shark's life. But the 7.5-foot-long (2.3 meters) juvenile was likely injured while it waited for help, said Daniel Abel, a professor of marine science at Coastal Carolina University in Conway, South Carolina.

Like any other fish out of water, sharks have trouble breathing on land.

"Air has considerably more oxygen than water does, but gills are not designed to function in air and so they collapse on each other," Abel said. "As long as they're moist, they'll get some oxygen in there … enough to probably survive."

Furthermore, a beached shark doesn't have buoyant water to support its weight. This may explain why one of the recordings shows "a little bit of blushing, or reddening, on its underside," Abel said. "That means that some of the blood is pooling and breaking some of the little capillaries on the bottom." [On the Brink: A Gallery of Wild Sharks]

Being on a hot beach can also lead to overheating. Great white sharks and their relatives are warm-bodied animals, meaning they can maintain a body temperature that is warmer than the surrounding water, Abel said. A fast metabolism lets sharks act as top predators. Their muscles contract faster and they can collect sensory information better than animals that aren't warm-blooded, he said.

But once they're out of the cool water, sharks easily overheat, Abel said. He commended the beachgoers for throwing water on the stranded shark, which likely not only helped it breathe but also let it cool down, he said.

It's possible the public will see more great white sharks stranded on beaches in the future. Their populations are gradually increasing along the east and west coasts of the United States, according to two 2014 studies conducted by Burgess and his colleagues.

Perhaps their numbers are increasing because they have more food to eat, including seals and sea lions, which are now protected under the Marine Mammal Protection Act of 1972, he said.

As more great whites munch on seals near the coast, people will inevitably see more strandings, as well as shark sightings, Burgess said. "And unfortunately, at some level, there's going to be some more interactions that are bites," he said.

Awareness and caution can help prevent shark bites, experts said.

"Quite apart from fearing predators, we should celebrate them," Abel said. "An ocean needs its food web, and sharks are essential at several different levels of that."

Follow Laura Geggel on Twitter @LauraGeggel. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

With an underwater camera attached to his head, a diver captured a spooky encounter with a great white shark off the shores of Florida.

Earlier this month, the diver, Jimmy Roseman, of West Melbourne, Florida, was swimming in the murky waters around Bethel Shoal, off the coast of Vero Beach, when a great white shark approached him and kept circling back.

"In the video, it did look like it was kind of far away," Roseman told local TV station Fox 35. "But the whole time, it was about 6 to 7 [feet] (1.8 to 2.1 meters) away from me."

Roseman poked the shark with his spear gun until it left. [See the shark video]

Great white sharks (Carcharodon carcharias), which get their name from their pale underbellies, can be found in most oceans around the globe, though they prefer to swim in temperate coastal areas. They are the largest predatory fish in the sea, sometimes growing to be longer than 20 feet (6 meters) and weighing up to 5,000 lbs. (2,268 kilograms). The creatures are known to have 300 teeth, arranged in up to seven rows.

Shark attacks on humans are relatively uncommon and are very rarely fatal. Last year, 72 unprovoked shark attacks were reported worldwide, and 10 of those were deadly, according to the International Shark Attack File, compiled by biologists at the University of Florida (UF). Forty-seven of those attacks occurred off U.S. shores, with eight reported in Florida's Volusia County, a hotspot for shark attacks. There was just one shark-related death in the United States in 2013, in Hawaii.

The number of shark attacks around the world has climbed since 1900, but this likely reflects the increasing amount of time humans spend in the sea, boosting the chances of such encounters, UF researchers said.

Shark attacks inevitably get more attention than the conservation problems the big fish face. Though illegal fishing makes it difficult to assess the total number of shark deaths, a study last year estimates that humans kill 100 million sharks annually, largely to feed an appetite for shark fin soup.

Follow Megan Gannon on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

A massive great white shark has been spotted swimming close to an Australian beach, scaring the locals and forcing the beach to close, according to news reports.

The female shark, nicknamed "Joan of Shark"by local fisherman, is more than 16 feet (5 meters) long and weighs about 1.8 tons (1.6 metric tons), The Telegraph reported. Signals from a satellite tag on the shark alerted authorities to its location, and city officials warned residents of Albany, Western Australia, to stay out of the water.

Joan was the largest of her kind to be electronically tagged. Fisheries protection officers injected an external tracking device in the shark and tracked her for three weeks. They captured the shark again a week later and placed a more sophisticated tag in her stomach that will enable the officers to track her for at least a decade, The Telegraph reported. A network of more than 300 monitors on the seabed can pinpoint the shark's movements, sending signals via satellite to warn authorities of her whereabouts. [Image Gallery: Great White Shark Pictures]

The shark may have smelled a dying humpback whale that was beached in the area, a spokesman for the state department of fisheries said, according to The Telegraph.

Great white sharks are the largest predatory fishes on the planet. They can reach up to 20 feet (6 m) in length and weigh up to 2.5 tons (2.3 metric tons).

They are highly intelligent and curious creatures, with well-developed senses. They can swim at speeds of up to 15 mph (24 km/h), and can leap completely out of the water when hunting prey. They attack quickly, from below, and pack a powerful, sometimes deadly, bite.

These massive sharks have 300 teeth, arranged in up to seven rows. Young great whites feed on fish, rays and other small sharks. Adults hunt harbor seals, sea lions and elephant seals, or scavenge whale carcasses for the blubber.

Great whites have been known to attack humans, but not eat them. Great white sharks have killed a number of swimmers and divers off the coast of Western Australia in the past four years.

Follow Tanya Lewis on Twitter and Google+. Follow us @livescience, Facebook & Google+.

It's a battle of shark versus shark dating back over a century: Which species set the stage for modern great white sharks, the biggest carnivorous fish to roam the seas today?

In one corner are "megatooth" sharks, which include the largest sharks ever to have lived. In the other is the smaller-but-plenty-toothy mako shark. Now, researchers say they have new evidence pointing to the mako shark as the great white's ancestor.  

Great white sharks (Carcharodon carcharias) are the biggest meat-eating shark in the world, with some reaching more than 20 feet (6 meters) long and weighing more than 5,000 pounds (2,250 kilograms). They hunt in more of the world's seas than any other sharks, ranging across the Atlantic, Pacific and Indian oceans, from the cold waters near the Antarctic to the tropical waters near the equator, cruising up to 43 miles per hour (70 kilometers per hour) in pursuit of prey.

Their numbers are rapidly declining worldwide, however, mostly because of accidental entanglement in fishing nets.

The evolutionary history of the great white has been contested by paleontologists for 150 years. They were originally classified as direct relatives of megatooth sharks such as the extinct Carcharocles megalodon, the largest carnivorous shark that ever lived.

Fossils of a newfound species of shark, Carcharodon hubbelli, suggest the modern great white actually may have descended from broad-toothed mako sharks. Researchers say the newfound species represents a possible midway point in the evolution from one to the other.

"We can look at white sharks today a little bit differently ecologically if we know that they come from a mako shark ancestor," said researcher Dana Ehret, a vertebrate paleontologist at Monmouth University in New Jersey. [Images: Great White Sharks]

Jaws, in fossil form

Most ancient shark species are known only from teeth, but an analysis of C. hubbelli, also known as Hubbell's white shark, was based on a complete set of jaws with 222 intact teeth and 45 vertebrae.

"This specimen that we describe is almost unbelievable for a fossil shark found during the Cenozoic — that is, the last 65 million years," Ehret told LiveScience. "You just really don't get fossil sharks preserved this nicely anywhere in the world except for these places in Peru and Chile where this was found."

This specimen was once about 16 feet (4.8 m) long. The species was named after Gordon Hubbell of Gainesville, Fla., a collector who recovered the fossils from a farmer who discovered them in the Pisco Formation of southern Peru in 1988. Hubbell donated the fossils to the Florida Museum of Natural History in 2009.

"Naming the shark in his honor is a small tip of the hat to all the great things he has done to advance paleontology," Ehret said.

Based on Hubbell's hand-drawn maps and descriptions of the landscape, the researchers ventured to the site where the shark fossils had been discovered. Their quest earned them one close call.

"We decided to leave the field a day early, and as it turned out, we left the area just a few hours before the magnitude-7.9 quake that hit Pisco in Peru in 2007," Ehret recalled.

An ancient shark

By analyzing the ages of mollusk shells there, the researchers estimate the shark dates back to the late Miocene (about 6.5 million years ago) rather than the early Pliocene (about 4.5 million years ago) as had been thought. [25 Amazing Ancient Beasts]

"That 2-million-year pushback is pretty significant because in the evolutionary history of white sharks, that puts this species in a more appropriate time category to be ancestral or kind of an intermediate form of white shark," Ehret said.

Analysis of the shapes of the fossil teeth revealed this ancient intermediate form of the white shark was related to ancient broad-toothed mako sharks. While modern white sharks have serrations on their teeth to help devour marine mammals, mako sharks lack these serrations because they primarily feed on fish. Hubbell's white shark has coarse serrations, suggesting a transition from broad-toothed mako sharks to modern white sharks.

"Some people might jump to the conclusion that this is a smoking gun, that the debate is over," Ehret said. "I don't think the debate will be over. It's difficult to work with fossil sharks, since we typically only find isolated teeth and different paleontologists will interpret the fossils in different ways. I completely understand that — I value the opinions and conclusions that other paleontologists draw.

"While I personally think we make a very strong case that white sharks evolved from mako shark ancestors, I know some people out there will continue to investigate the relationships between the giant shark Megaladon and modern white sharks," Ehret said. "That's how science has to work: You have to put out hypotheses and also test them, see if they stand up to scientific research."

Scientists continue to collect shark fossils at sites including the Calvert Cliffs of Maryland, the Lee Creek Mine in North Carolina, and areas in Panama, Chile and Peru.

"I think we'll find all kinds of interesting new fossils to flesh out this story a bit more," Ehret said.

Ehret and his colleagues detailed their findings in the November issue of the journal Palaeontology.

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Great white sharks tend to patrol specific neighborhoods for weeks on end, a new study finds.

And despite their ability to migrate thousands of miles, great whites in the Pacific were found to be a distinct genetic group compared with great whites elsewhere.

Sharks tagged with acoustic devices often spent up to 107 days at four key sites along the central and northern California coast where seals and sea lions are abundant: Southeast Farallon Island, Tomales Point, Año Nuevo Island and Point Reyes.

"The sharks were detected frequently at their chosen site," said Salvador Jorgensen, a postdoctoral researcher at Stanford University. This means "they are patrolling around there nearly constantly, for long periods of time. They will occasionally visit one of the adjacent sites, but they always come back."

The findings were published online Nov. 3 by the Proceedings of the Royal Society B.

Acoustic receivers detected five white sharks beneath the Golden Gate Bridge. There are no data to indicate how far the sharks crossed into the bay or why, but the researchers say it's likely they were hunting seals and sea lions in the region.

More broadly, the study revealed great whites spend the majority of their time in three areas of the Pacific: the North American shelf waters of California; the slope and offshore waters around Hawaii; and an area called the White Shark Café," in the open ocean about halfway between the Baja Peninsula and the Hawaiian Islands.

"The thing we've learned about white sharks," said study co-author Scot Anderson, a marine biologist with the National Park Service, "is that they're not swimming around aimlessly — they are very selective predators."

The northeastern Pacific population may have been founded by a relatively small number of sharks in the late Pleistocene — within the last 200,000 years or so, genetic research shows. Other distinct other populations of white sharks are concentrated near Australia and South Africa.

"If you had asked us a few years ago, we would have said white sharks found in California probably migrated throughout the Pacific," said molecular geneticist Carol Reeb, a research associate at Stanford.

"Now, even though we know they travel great distances, their paths are surprisingly constrained to specific routes," Reeb said in a statement. "This explains how a highly migratory marine species becomes a genetically isolated population. This also makes it much easier to appreciate how vulnerable the northeastern Pacific white shark population could become if too many individuals were taken as either catch or bycatch, since these sharks do not appear to interbreed with other shark populations."

• Gallery: Great White Sharks
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A digital rendering of a great white shark's maw could lead to the first accurate estimate of the power behind a full-force bite.

The shark's ability to inflict killer damage on anything it grabs, however, probably is due to saw-like teeth and not the amount of bite force, the study researchers say. Once a great white clamps down on a prey with its razor-sharp teeth, the shark often shakes the catch from side to side to initiate a sawing action.

Daniel Huber, a biologist at the University of Tampa in Florida, examined an eight-foot (2.4-meter) great white shark that had died after becoming entangled in nets off the coast of Australia. Huber and his colleagues dissected the shark's head and took several measurements, including the size and placement of the jaw muscles.

"We are figuring out in three dimensions the leverage of all of these jaw muscles," Huber told LiveScience. The jaws work like a set of pliers, where pliers with long handles would let you grab an item with more force than pliers with short handles.

From this data, the researchers are developing a 3-D digital recreation of the shark and a computer simulation of a full-force bite. They will compare the final force estimate with those from tiger and bull sharks, which, along with the great white, are responsible for most shark attacks on humans.

“The white has the narrowest head of the three, so it has less space for jaw muscles,” Huber said. “Consequently, we’re expecting that it will have a lower bite force on a pound-for-pound basis.”

But great whites would still top the charts as savviest hunters and most adept at capturing prey.

“Much of the damage inflicted by white sharks is due to their teeth, and not necessarily to the force,” Huber said.

The research is being sponsored by the University of New South Wales, University of Tampa, University of Newcastle in Australia and the Computational Biomechanics Research Group.

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Millions of years ago the oceans were ruled by a bus-sized, whale-eating shark with teeth as big as your hand.

Scientists have long believed that the prehistoric megalodon shark evolved into today's scariest sea predator, the great white. However, a new study comparing teeth suggests that the great white is more closely related to the smaller, but equally vicious mako shark.

"Most scientists would probably say the great whites evolved from the megalodon line, which existed from two to twenty million years ago," said Chuck Ciampaglio, a geologist and paleontologist at Wright State University. "However, our research, which is based on analyzing fossils of several hundred shark teeth, shows that the great white shares more similarities with the mako shark."

Reconstructing prehistoric sharks is difficult. A shark's skeleton is made of cartilage, which decomposes quicker than bone. Researchers have only recovered a few fossilized megalodon vertebrae.

"Teeth are the thing to go on," Ciampaglio told LiveScience.

Sharks replace their teeth regular, so they can be found on the seafloor. Fossils of megalodon teeth are collected on ancient seabeds now exposed. Ciampaglio digitized hundreds of teeth -- upper, lower, front, and back teeth from the three species, and analyzed their sizes and shapes.

The analysis showed great whites and makos have very similar tooth and root structure. "The great whites and makos lay right on top of each other," Ciampaglio said. They also have very similar growth trajectories - how a tooth changes in size and shape as the shark grows to its adult size.

The great white and megalodon, however, shared none of these characteristics. Serration is their only common trait, said Ciampaglio, but the other characteristics are more important.

This evidence "strongly supports the theory that the great white is descended from the prehistoric mako group," Ciampaglio said. The megalodon was probably the end of a run of giant sharks that died out 2-3 million years ago, he said.

Recently, a few fossil species was found off South America that look like an intermediate between the great white and mako, Ciampaglio said. This further strengthens his theory on great white evolution.

While great whites typically grow up to 20 or 25 feet in length, the megalodon was twice as long and had a gaping maw that a human could climb into, should someone so desire.

"They were huge sharks, approximately the length of a Greyhound bus and possessing teeth that were up to six inches long," said Ciampaglio.

In Greek, megalodon means "big tooth." Thanks to those teeth, scientists have been able to estimate the size of the megalodon to have been at least 40 feet in length. Many researchers suspect they were 50 feet or larger, and some have speculated they were much bigger.

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For the first time, great white sharks in New Zealand waters have been outfitted with satellite tags, researchers said today. The devices will help scientists learn where and how deep the creatures go.

Four sharks were tagged in the project with devices that collect detailed information about the depth, temperature, and light levels of water through which they travel. After a few months, the tags will detach from the sharks on pre-determined dates and float to the surface, where they'll broadcast data back to ground stations via satellite.

Researchers will combine the data with genetic information to study whether New Zealand's great whites are interrelated to other populations. The project will also help scientists better understand threats to the sharks.

"An important first step in the conservation and management of any species is to identify critical habitats and migration routes," said Clinton Duffy of the New Zealand Department of Conservation. "White sharks are difficult to study due to their naturally low abundance, large size and mobility. This technology provides us with a window into their lives for the first time."

Scientists have tagged great whites off South Africa, Australia and elsewhere in recent years. Last month, a great white that killed two other aquarium sharks in California was tagged and released back into the ocean.

Great whites can reach 21 feet (6.5 meters) in length. Their reputation as a maneater is undeserved, scientists say. Most attacks occur when the sharks confuse humans with their preferred prey, including sea lions and seals.

Game fishing and commercial fin harvesting have put the great white's survival at risk, experts believe, though there are no exact figures on regional or worldwide populations of the beasts.

The new project is supported by the U.S.-based Wildlife Conservation Society (WCS).

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Image Gallery

Shark Attacks on Humans

Just a dozen shark attacks occurred in Florida in 2004, compared to 30 in 2003, 29 in 2002, 34 in 2001, and 37 in 2000. The deadly series of four hurricanes in the 2004 summer meant fewer people were in the water, but sharks are known to head for deep water when a hurricane approaches.

Globally, there were 61 unprovoked shark attacks in 2004, according to The International Shark Attack File at the Florida Museum of Natural History. Seven people died. There were also 15 provoked attacks (typically a diver bit after grabbing a shark or a fisherman bit while removing a shark from a net) and 12 cases of sharks biting boats. The global total was down slightly from recent years but still part of an upward trend overall.

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