Tag Archives: great white shark

Great White sharks may mistake humans for seals, explaining attacks

Shark attacks are exceedingly rare when you consider the sheer number of beachgoers that cross paths with these apex predators. Every year, there are no more than a couple dozen unprovoked shark attacks with an annual average of just four unprovoked fatalities. While every death is a tragedy, it’s worth bearing in mind that three times more people are killed by vending machines and about 30 times more are killed by falling coconuts than sharks.

What’s more, on the very rare occasion that sharks attack people, it may all be due to a case of mistaken identity. According to researchers from Australia, sharks can’t see very well, so they may not be able to distinguish swimmers at the water’s surface from their natural prey. In other words, sometimes humans just happen to look like their usual food.

Mistaken identity

This insight was gained after researchers looked at various silhouettes from the shark’s point of view. They recorded and compared video footage of swimmers, people paddling surfboards, and seals as a shark would see them from right below the water, with sunlight in the background.

“Surfers are the highest-risk group for fatal shark bites, especially by juvenile white sharks,” says lead author Dr. Laura Ryan, a post-doctoral researcher in animal sensory systems at Macquarie University’s Neurobiology Lab.

In order to truly put themselves in the sharks’ fins, the researchers employed their knowledge of the great whites’ retinal structure and brain visual systems to estimate their visual acuity. The focus was on the retina of great white juveniles, which are responsible for the majority of attacks on humans. These young sharks tend to have poorer vision than adults and are also more likely to venture inside habitats frequented by humans.

The footage was fed into modeling programs to simulate the way a paddling human or swimming seal might look through the eyes of a shark. “I didn’t realize being a scientist would involve quite so much coding,” Ryan said, which reminds us that modern science is becoming increasingly interdisciplinary and coding has become a must-have skill in any researchers’ toolkit, regardless of their field.

The analysis suggests that sharks, which are believed to be color blind, are ill-equipped to tell apart the silhouette shapes of humans or their motion cues from those of seals. As the sharks grow larger, their retinas also improve. Experience may also help adults better tell apart seals from humans, learning what’s good or bad to eat as they age, the researchers claim in their study published in the journal Royal Society Interface.

“We found that surfers, swimmers and pinnipeds (seals and sea-lions) on the surface of the ocean will look the same to a white shark looking up from below, because these sharks can’t see fine details or colors,” Ryan said.

It’s not sharks’ fault we look like food

These findings confirm a long-standing theory that great whites and other sharks responsible for rare attacks on humans do not actively seek us as prey.

Unfortunately for sharks, they have a bad rep due to their fierce appearance and skewed portrayals in popular media (i.e. Jaws films). Meanwhile, humans kill millions of sharks every year for their fins, cartilage, and oil. And our fear of sharks has also led to the widespread installation of shark nets and drumlines, which further threaten sharks, as well as other marine life. Great whites are now classed as endangered.

Great white sharks hunt for meals in unexpected places

We tend to picture them as majestic hunters hunting unsuspecting prey near the surface, but great white sharks might be spending more time foraging on the ocean floor for small morsels, according to a new study.

Credit: Flickr.

Great whites are the largest predatory fish on Earth, capable of growing to an average of 15 feet (4.5 meters) in length. They are usually found in cool, coastal waters throughout the world and their numbers are decreasing due to overfishing and accidental catching. Great white sharks are currently considered a vulnerable species, although population estimates are often unreliable.

Between 2008 and 2009, Australian researchers analyzed the stomach contents of 40 juvenile great white sharks captured off the coast of eastern Australia. That information plus data from studies from other parts of the world helped to get a better picture of the diets of these young sharks.

“Within the sharks’ stomachs we found remains from a variety of fish species that typically live on the seafloor or buried in the sand. This indicates the sharks must spend a good portion of their time foraging just above the seabed,” said lead author Richard Grainger. “The stereotype of a shark’s dorsal fin above the surface as it hunts is probably not a very accurate picture.”

The study showed that, on average, the shark diets consisted of 32% mid-water ocean swimming fish such as Australian salmon, 17.4% bottom-dwelling fish such as stargazers, 14.9% batoid fish that lurk on the seafloor such as stingrays, and 5% reef fish such as eastern blue gropers.

Meanwhile, the rest of the stomach contents was made up of unidentified or less abundant groups of fish. The findings show that marine mammals, cuttlefish and squids also are part of the diet of the juvenile great white shark, but only occasionally and far from being the main element of the diet.

“We discovered that although mid-water fish, especially eastern Australian salmon, were the predominant prey for juvenile white sharks in NSW, stomach contents highlighted that these sharks also feed at or near the seabed,” said in a statement Dr Vic Peddemors, co-author of the study.

As they get older, sharks tend to move around more and take on board more fat in their diet to help power longer journeys. The study showed that they are unlikely to begin hunting larger prey such as dolphins or other sharks until they reach around 2.2 m in length (7.2 feet).

While the study covered only a small sample, it is consistent with tagging programs that show white sharks spend much of their time swimming far beneath the surface. In Australia, tracking data showed sharks migrate from Queensland to Tasmania and that the range of movement expands as they get older.

Looking ahead, the researchers called for more work to be done to analyze the exact nutritional composition of shark diets — not just the calorific content — in order to understand the relationship between their physiology, behavior, and ecology.

“This will give insights into what drives human-shark conflict and how we can best protect this species,” said co-author Gabriel Machovsky-Capuska.

The study was published in the journal Frontiers in Marine Science.

Credit: Wikimedia Commons.

Great white shark genome might teach us how to heal faster or stave off cancer

Credit: Wikimedia Commons.

Credit: Wikimedia Commons.

Great whites are some of the most recognizable marine species. Our fascination for these majestic, but also fearsome creatures deepens now that scientists have completed the first genome sequencing of the iconic apex predator.

Scientists sink their teeth in the great white’s genome

The great white’s genome was decoded by an international team of researchers, including those at the Nova Southeastern University’s (NSU) Save Our Seas Foundation Shark Research Center, Guy Harvey Research Institute (GHRI), Cornell University College of Veterinary Medicine, and Monterey Bay Aquarium.

“Decoding the white shark genome is providing science with a new set of keys to unlock lingering mysteries about these feared and misunderstood predators – why sharks have thrived for some 500 million years, longer than almost any vertebrate on earth” said Dr. Salvador Jorgensen, a Senior Research Scientist at the Monterey Bay Aquarium, who co-authored the study.

According to the results, the great white genome contains one-a-half times more information than the human genome. That was not surprising to learn, given that they have 41 pairs of chromosomes, whereas humans have only 23.

There’s no doubt that great whites (Carcharodon carcharias) have experienced tremendous evolutionary success. They’re found throughout most of the world’s oceans, grow up to half the length of a bus, have more than 300 razor-sharp, triangular teeth arranged in seven rows, can detect a seal from two miles away, and are the top of the food chain. Their only threat is humans, whose overfishing and illegal hunting have caused the great white shark to be listed as a vulnerable species on the IUCN Red List.

Not only can great white grow to a large size, but they also have a long lifespan, easily reaching 70 years in the wild. But, despite their size and lifespan, the predators rarely get cancer. Previously, research had established a linear relationship between an animal’s body size and the incidence of cancer, but the great white seems to be one of those rare exceptions. The new study suggests that this is partly due to the great white’s genome stability — genetic adaptations which help preserve its genome.

Another remarkable feature of great whites is their extraordinary ability to regenerate quickly. Researchers have tracked back this ability to certain genes that are tied to fundamental pathways involved in wound healing, including a key blood clotting gene.

“Not only were there a surprisingly high number of genome stability genes that contained these adaptive changes, but there was also an enrichment of several of these genes, highlighting the importance of this genetic fine-tuning in the white shark,” said Mahmood Shivji, who is the director of NSU’s Save Our Seas Foundation Shark Research Center.

“Genome instability is a very important issue in many serious human diseases; now we find that nature has developed clever strategies to maintain the stability of genomes in these large-bodied, long-lived sharks,” said Shivji. “There’s still tons to be learned from these evolutionary marvels, including information that will potentially be useful to fight cancer and age-related diseases, and improve wound healing treatments in humans, as we uncover how these animals do it.”

Decoding the white shark’s genome is a great breakthrough that will help conserve the species. For instance, the genome data could be used to better assess white population dynamics. The insight gained from the great white’s genome might also lead to novel cancer drugs in the future.

The findings were reported in the journal PNAS. 

Juvenile Great White Shark Gets Stranded on the Sand, Rescued by Beachgoers

We’re more used to whales washing up ashore, but sharks also do it sometimes. This juvenile shark was apparently trying to hunt some seagulls and ventured out of the water too much for its own good. However, after struggles and apparent dehydration, the shark was saved by beachgoers.

Initially, we see the two meter shark (7 feet) struggling as people on the beach just watch. However, animal rescuers and the harbor master arrive shortly, throwing buckets of water on the shark to rejuvenate it. After a few tense moments, the shark starts to move again, to the applause of by-standers. The shark is then tied up and dragged by boat to the water, something which might seem violent but is completely harmless to the animal. Furthermore, the creature is also checked for injuries before being released once more to the water.

The video was uploaded by Mike Bartel this week (July 13), who said, “Thanks to the harbor master and beach-goers, this shark was saved.”

Despite its fearsome appearance, the great white shark almost never attacks humans – contrary to popular belief it doesn’t mistake humans for seals and it doesn’t seem to like how we taste. According to the International Shark Attack File (ISAF), between 1580 and 2013 there were 2,667 confirmed unprovoked shark attacks around the world, of which 495 were fatal – and that’s almost five centuries. This doesn’t mean that sharks aren’t dangerous or they can’t attack humans, just that this happens extremely rarely. It’s actually us that are threatening sharks, not the other way around: The great white shark is listed as vulnerable by the IUCN Red List, but it is on the cusp of being labeled endangered due to overfishing.

Several groups are seeking to have the great white shark declared an endangered species by the federal government. (Al Seib, Los Angeles Times )

Petition calls for California’s great white sharks listing as endangered

Several groups are seeking to have the great white shark declared an endangered species by the federal government. (Al Seib, Los Angeles Times )

Several groups are seeking to have the great white shark declared an endangered species by the federal government. (Al Seib, Los Angeles Times )

An U.S.conservation group has pushed a petition to the government requesting that California’s great white sharks should be federally protected as an endangered species. The organization has presented a number of studies and claims, backed by other independent organizations, and argues that California’s white sharks are a genetically distinct species. With a mere 340 adults remaining, it might already be doomed.

“Anywhere in that range presents a very high extinction risk,” says Geoff Shester, the California program director of Oceana, one of the organizations that filed the petition. “It’s well below most other species that are currently listed as endangered.”

Great white sharks have already been listed as vulnerable by the International Union for Conservation of Nature (IUCN), among some other 50 species in the same situation, however the petition filed with the National Marine Fisheries Service says that California’s great whites, which typically dwell in the northeastern Pacific, is a genetically distinct species.

“They’re genetically and behaviorally distinct from other white sharks,” Shester said. “While they are capable of making long-distance migrations, they tend to just go back and forth between the same offshore and coastal sites from year to year. There has been a theory for a while that this population was distinct, but it wasn’t until new science came forward in the last two years that it showed no mixing between this population and the other main ones.”

[RELATED] Americans are eating endangered shark soup

Worldwide, great whites numbers are dwindling year after year due to a number of factors, from shark finning, to commercial fishing, to bycatch. Pollution is one other major factor which has helped lower the numbers – and in California, at least, great whites were found to be contaminated with high levels of mercury, DDT and PCBs, and no one has figured out why. They’re the most contaminated sharks in the world, according to scientists.

While the ultimate goal of these petitions is to reduce shark mortality, Shester says the first step is to simply gather more data about these little-understood sharks.

“One of the primary outcomes with other Endangered Species Act listings is additional prioritization and funding for research,” he says. “And we really need to understand the trends for this population. We still don’t know some basic biological information.”

Hollywood portrays great whites as vicious, blood thirsty killers, in reality the roles may actually be reversed.

“While we humans tend to be scared of these sharks, these sharks are our allies in the sense that, as top predators, they keep the oceans healthy,” he says. “Just as wolves keep deer populations in check, these white sharks are playing an important ecological role, and they need us to protect them and help them recover.”

via MNN

The Shark Men crew as they work had to keep the 18 feet great white shark nicknamed Apache alive on board their boat.

Biggest white shark caught so far – released back in wild [PHOTO]

The Shark Men crew as they work had to keep the 18 feet great white shark nicknamed Apache alive on board their boat.

The Shark Men crew as they work had to keep the 18 feet great white shark nicknamed Apache alive on board their boat.

Shark Men: Biggest and Baddest, is a new TV show set to premier on National Geographic Channel tomorrow night, which chronicles the work of a team of scientists and professional fishermen who go after great whites in an effort to figure out where the mysterious giants breed and give birth.

During one of their stints in the Pacific Ocean, the team caught what’s been attested to be the biggest great white shark so far caught. The capture was made off Mexico’s Guadalupe Island in the fall of 2009, as the crew battled to get the great white predator on the deck, where they measured and weighed it, while trying to keep it alive at the same time.

The specimen was a male measuring 7.9-foot-long (5.5-meter-long), which breaks the team’s previous record of 16.8 feet (5.1 meters), set when they caught a female great white named Kimel. The article’s center piece has a name as well – Apache, after the dog of Brett McBride, boat captain on the National Geographic Channel show Shark Men.

The capture was no trip down the park, as the two-ton Apache put up quite a fight – at one point breaking free from his barbless hook, said expedition leader Chris Fischer.

“The battle with Apache was like nothing we’ve ever dealt with,” Fischer said.
“He was all scarred up and had big marks all over him—you could tell he was just a bad-ass shark,” Fischer said.
“It was so impressive and so humbling to be near him.”

Once on board, scientists tagged the shark with a satellite tracking system and took a blood sample, before releasing him back into the wild.

Biggest white shark is not that big

What’s remarkable is that most of the marine scientists around the world aren’t too impressed by the find. When great white sharks are concerned, the female is generally larger than the male, because they need more girth to carry their young. So, the probability of some other great white of larger dimensions swimming freely through the ocean is very big.

“That is one big shark, [but] I have no doubt that this isn’t the largest white shark in the wild,” John O’Sullivan, head of the Monterey Bay Aquarium’s White Shark Program, said by email.

Shark expert Kenneth J. Goldman added, “I don’t see anything overtly magnificent about it being so large. It’s just another adult male they’ve tagged.”

Size isn’t important for researchers

Size apart, Apache will prove to be a valuable asset for researchers towards their goal of understanding great white shark behavior. The first thing they’re trying to find out is how great whites plot their migration paths, still very vaguely known. One theory says great whites gather in specific spots near the coasts—including the Guadalupe Island site— and then travel to a feeding spot in the middle of the ocean to feed. The animals often return to the same aggregation sites after feeding.

Overall, tagging sharks to figure out where they migrate and congregate may help conservationists protect the species, Fischer added. Great whites are considered vulnerable by the International Union for Conservation of Nature.

Meanwhile, Apache lives on, he said, as a “giant male shark out there doing his great white thing.”

Shark Men—Biggest and Baddest premieres at 10 p.m. ET/PT on Sunday, May 8, on the National Geographic Channel.

Census finds just 219 white sharks near California

Sharks are some of the most fascinating creatures to ever have “walked” the face of the planet; the best argument for this claim would be that they stand alons on the top of the food chain, with no natural enemy, other than humans, of course. Among the species of sharks, a few stand out as true silent killers of the deep, and among these, one of the most interesting ones is the great white shark.

A first of its kind census regarding the number of these toothed animals revealed startlingly low numbers; as it turns out, there are only 219 adult and young adults in all the entire northeast Pacific Ocean.

“Once we went out and noticed that we were seeing the same sharks every year, it started to dawn on us that this population isn’t huge,” UC Davis doctoral student Taylor Chapple, the study’s lead author, told FoxNews.

“This low number was a real surprise,” Chapple said. “It’s lower than we expected, and also substantially smaller than populations of other large marine predators, such as killer whales and polar bears.”

Sadly, the image of these underwater predators has been greatly distorted by the media, thanks to ‘Jaws’, and a multitude of other movies in the same line. Sharks are nature’s ultimate killing machine, and it breaks my heart to see such admirable animals face such a fate, which they cannot escape.