12 Facts About Great White Sharks

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iStock

In 1974, Peter Benchley released Jaws, a horror novel that sold 20 million copies, spawned an iconic film—and catapulted the great white shark (Carcharodon carcharias) to infamy. Although the book brought him fame and fortune, Benchley came to rethink its negative portrayal of great whites: The author-turned-conservationist said in 1995 that if he was writing his book then, “The shark … could not be the villain; it would have to be written as the victim.” The great white is now classified as a vulnerable species. Read on to find out why the truth about Carcharodon carcharias is often stranger—and always more compelling—than the fiction that obscures it.

1. EYE-ROLLING IS A DEFENSE MECHANISM.

Many sharks protect their eyeballs with a pair of clear lid structures called nictitating membranes, which act like protective, transparent eyelids. But not great whites—they don't have the membranes. Instead, their eyeballs roll backwards into the skull reflexively when a shark bites into a thrashing victim [PDF]. This exposes the sclerotic coat, a fibrous tissue that surrounds the eye.

2. SOME REPORTS ON THEIR SIZE ARE KIND OF FISHY.

The great white is a huge fish, no question—but some claims about its maximum size are probably exaggerated. In 1870, one zoologist measured the disembodied jaws of a large adult and estimated that the whole shark must have been 36.5 feet long. But a modern reevaluation—in which the jaws were compared to those from other dead sharks—showed that the creature’s actual length was probably about 16.5 feet, and the reports of the giant shark were likely a printer’s error.

And then there's the Cojímar specimen, a great white captured and killed near Cuba in the early 1940s. Those who saw it in person said the fish was 21 feet long and weighed 7100 pounds. Since then, the claim has been disputed by fish experts who, using an available photo, calculated that the animal’s real length was also in the ballpark of 16 feet. According to biologist Jose Castro’s book The Sharks of North America, the largest great white “believed to have been measured reliably” stretched 19.6 feet long. When it comes to weight, big males have been measured weighing up to 2819 pounds while the largest female weighed 4343 pounds.

3. GREAT WHITES ARE CLOSELY RELATED TO MAKOS.

According to a 2016 paper, there are 509 species of shark divided into nine orders and 34 families. Great whites belong to the lamnidae family, which contains only four other species: the porbeagle, the salmon shark, the longfin mako, and the shortfin mako. All five sharks have conical snouts, eyes that look solid black, and lengthy gill openings. They share a couple of other things as well—including a method for trapping body heat.

4. THEY CAN STAY WARM IN FRIGID WATER.

Most shark species have no direct control over their body temperatures; they're about as hot or cold as the water they’re swimming in. But there are a handful of species—the entire lamnidae family included—that are endothermic, meaning they can consistently maintain high body temperatures even in cold water.

The great white and its relatives have their powerful muscles to thank for this talent. The muscles naturally produce heat as they contract, warming up blood in that area, which is then redistributed to other parts of the body. This allows great whites to keep their core body temperature as high as 25 degrees (Fahrenheit) warmer than the ambient water, which means they can thrive in bitterly cold places. And when muscles are kept warm, they work more efficiently, so great whites can swim faster and farther than many other sharks. On the flip side, great whites need to consume a huge amount of calories in order to keep their body temperatures up.

5. NOT ALL GREAT WHITES GO AFTER THE SAME FOODS.

Great whites have varied diets and not all individuals share the same food preferences. But in general, younger sharks mostly eat fish and squids while older, larger sharks tend to go after big targets like marine mammals. Catching small fish and biting into fatty seals are, of course, two very different tasks. This explains why juvenile white sharks have narrower teeth than adults do—the better to pierce the skins of slippery fish. Living sharks of every species possess multiple tooth rows and are constantly replacing old chompers with brand new ones. As a great white matures, its incoming teeth become broader, serrated, and triangle-shaped, allowing great white adults to tear large chunks of meat off their victims.

6. GREAT WHITES CAN GET AIRBORNE.

Fatty, calorie-rich pinnipeds like seals and sea lions are common prey for large great whites, which typically attack from below in an explosive burst. The top speed of a great white is over 20 miles per hour, and during seal hunts, they can burst completely out of the water—a feat known as breaching—which leads to the successful capture of a pinniped 40 to 55 percent of the time, depending on lighting and other variables.

7. THEY DINE ON THE WORLD’S BIGGEST FISH.

In the 1960s, a 14.7-foot great white shark was captured near an Australian whaling station and, when it was dissected, two mysterious bones were found in its stomach. They were later identified as vertebrae belonging to an adult whale shark that was estimated to be 28 feet long. These filter feeders can grow to be 40 feet long and weigh at least 7 tons; experts now think that great whites are scavenging on floating whale shark carcasses rather than hunting the fish.

8. ATTEMPTS TO PUT THEM IN CAPTIVITY HAVEN’T GONE WELL.

Certain sharks thrive in aquariums; great whites don’t. Every single great white that’s been placed in captivity has either died or been released after a brief stay. The Okinawa Aquarium, Sea World San Diego, and the now-defunct Marineland of the Pacific are among the facilities which experimented with captive white sharks at some point or other. At the Monterey Bay Aquarium, one specimen spent a record-breaking six months living in a million-gallon tank. Once she began stalking other display fish, however, she was set free. Several different factors make great whites ill-suited for captivity. To breathe, the animals must be in constant motion to push water over their gills, and aquariums don’t always offer enough space for this. Other issues include the species’ famously large appetite and its tendency to run into glass walls.

9. DESPITE MYTHS TO THE CONTRARY, GREAT WHITES CAN GET CANCER.

There’s a myth that great whites and other sharks are immune to cancer, which has had some unfortunate real-world consequences. Assertions that shark cartilage is an edible cancer cure has led to mass harvesting of the vulnerable fish.

For the record, clinical tests have shown that ingesting shark cartilage in no way treats any form of cancer. Cancer has been documented in more than 20 shark species, including the great white: The first reported instance of a tumor-plagued great white was announced in 2015.

10. THEY TRAVEL VAST DISTANCES.

The great white inhabits many of the world's oceans, but they're most often found in waters with surface temperatures from 59°F to 72°F. The species also migrates seasonally. Some travel from South Africa to Australia and back every year. Other great whites cross the Atlantic, making long treks between Cape Cod, Massachusetts and the Azores, 2300 miles away. And each winter, scores of them leave Californian waters for a point researchers have nicknamed “the white shark café.” Located halfway between Hawaii and Mexico, this region doesn’t appear to offer much in the way of food, but the sharks remain there from April to July. Data from tagged great whites tells us that the males go on rapid, deep dives multiple times per day while hanging out in this area. Nobody knows why the white shark café is such a hot destination—but it might be a place where the fish gather to breed.

11. ORCAS PREY ON THEM.

When great whites get knocked upside-down, they freeze up and exhibit “tonic immobility,” a state of semi-consciousness. There’s at least one animal that can exploit the vulnerability. On October 4, 1997, an orca was seen barreling towards a great white shark (which measured 9 to 13 feet long) near one of California’s Farallon Islands. A human onlooker filmed the orca dragging the stunned fish around on its backside. Eventually, it let go [PDF], and then ate the dead shark's liver.

Between May and the end of June 2017, the bodies of four white sharks—all missing their livers—washed onto South African beaches. All four deaths have been attributed to orcas. A great white’s liver is high in fat and loaded with nutrients, which may account for the orcas’ interest in singling it out for consumption. One of the sharks had its testicles and stomach missing as well.

12. DO THEY REALLY MISTAKE PEOPLE FOR SEALS? PERHAPS NOT.

Though shark-on-human attacks are rare, most of the time, when you do hear about an attack, a great white is behind it. Since 1580, Carcharodon carcharias has been positively identified in at least 314 unprovoked attacks on humans (80 of them fatal). No other shark species is credited with even half as many.

According to one common explanation, great whites attack humans because they mistake them for pinnipeds. The argument goes that, when viewed from below, a person on a surf board projects a seal-like silhouette.

While this is a popular idea, it leaves some critical things unexplained. First of all, great whites have proportionally large eyes by shark standards—and acute vision to boot. Also, the big fish strike seals with tremendous force at great speed; by comparison, the sharks usually move at a slow, deliberate pace when approaching people. And in the vast majority of attack incidents, a great white will deliver a single bite and then leave without consuming the victim. In fact, nearly three out of every four humans who get bitten by white sharks survive the encounter.

Biologists have proposed that when the animals bite people, they do so out of curiosity (at least, in most cases). “Great whites are curious and investigative animals. That’s what most people don’t understand,” marine biologist R. Aidan Martin told National Geographic. “When great whites bite something unfamiliar to them, whether a person or a crab pot, they’re looking for tactile evidence about what it is.”

The sharks often go out of their way to nibble on inanimate objects—such as underwater cameras—before losing interest and moving on. So maybe, when they decide to bite people, they're not looking for a snack.

YouTube Star Coyote Peterson Brings 'Misunderstood' Animals to His New Animal Planet Series

Animal Planet
Animal Planet

As host of the popular YouTube series Brave Wilderness, Coyote Peterson is no stranger to going face-to-face with creatures many deem terrifying—think great white sharks and pit vipers—but that he says are simply "misunderstood."

Animals have always been a big part of Peterson's life, even before he made a career out of being stung and bitten by ferocious critters. The Ohio native studied video production and directing at Ohio State University, and then decided to combine his two passions—film and all things wild—to teach viewers about wildlife and the importance of conservation. His YouTube channel currently has more than 15 million subscribers.

Now Peterson is embarking on a new adventure with Animal Planet in the show Brave the Wild. He'll travel all over the world with wildlife biologist Mario Aldecoa and his crew, sharing creatures that aren't often in the spotlight and that viewers may find a little frightening. He recently chatted with Mental Floss about the importance of conservation, his thing for snapping turtles, and his close encounter with a jaguar and her three cubs.

You’ve said your love of animals started with snapping turtles. Can you talk about the first time you saw one and what about them fascinated you so much?

The first snapping turtle I caught was when I was only 8 years old. I was always fascinated with turtles, because at first glance they look prehistoric, almost dinosaur-like. Growing up in Ohio, I never got to see any "exotic" animals. My favorite thing to watch on TV was Steve Irwin. Watching him wrestle crocs is what inspired me to catch my first snapping turtle, the most dangerous animal Ohio has to offer.

Coyote Peterson with a gigantic snapping turtle
Animal Planet

In Brave the Wild, you introduce animals that are often feared or misunderstood. What's the importance in exposing viewers to these creatures?

One of my goals through this series was to inspire people to overcome their fears of these seemingly dangerous animals and learn to admire them from a safe distance. The more you understand these creatures, the less you are afraid of them. One of the messages I try to convey in every episode is the importance of conservation.

What’s the most "misunderstood" creature you've encountered?

The most misunderstood creature that comes to mind is the carpet shark, which we filmed in season one. As I always say, people’s biggest fears are the three S’s (sharks, snakes and spiders). The carpet shark is found off the coast of Australia. They only bite humans in the case of mistaken identity. To some of these sharks a person’s foot might look like a fish. Any time you enter a new environment you need to be aware of what you need to look for, not only to keep yourself safe, but the animal as well.

What goes into preparing for each encounter to make sure you and the animals come out alive?

With any new expedition, you need to come into the environment knowing exactly what to expect. When encountering a new animal, I try to stay as calm as I can and have no hesitation. If I stay calm, the animal stays calm, [and] I'm creating a safer interaction for myself. I use different tactics when I encounter different animals. It also depends on whether the environment is land or in water.

How do you keep your composure on camera when you're in a potentially dangerous situation?

Any situation I find myself in, I look at it as my job. For example, I would be afraid operating a crane, because that is something I don't do. If it's part of your job, it's something that you get used to. When I do my job, I make sure I'm focused and never hesitate. Before I encounter any animal, I know what I'm going to say to the camera. I say that, for the best show, we always need to have the camera rolling so the audience can see what is happening.

Coyote Peterson with a kangaroo
Animal Planet

You were in Australia filming Brave the Wild during bushfire season. What was that like?

Visiting Australia was one of the best experiences I had filming the show. Australia is a fascinating country that has so many unique environments. We spent over 50 days in Australia and encountered more than 35 different species. We were there right before all these devastating fires started, and we got to witness the severity of the drought and all the different animals it impacted.

What was your favorite animal encounter in upcoming series?

Each encounter I have in the wild is special. I would have to say that the most exciting moment for me was when we were filming in Brazil and I saw a jaguar and three of her cubs up close. Not only did I get to see this in real life, but my amazing team was able to capture this special moment on tape. It is just so amazing seeing these animals survive and thrive in the wild while dealing with not only the dangers of the wild but human encroachment as well. Hands down, this was my favorite episode that we got to film.

Catch new episodes of Brave the Wild on Animal Planet, Sundays at 9 p.m. ET/PT.

10 Secrets of Seeing Eye Dog Trainers

Seeing Eye instructors with the dogs they are training.
Seeing Eye instructors with the dogs they are training.
The Seeing Eye

Founded in 1929, The Seeing Eye is a nonprofit in Morristown, New Jersey, that trains guide dogs to help their blind owners navigate the world safely. In order to make sure each dog is ready for all the obstacles and challenges that come with leading the visually impaired, instructors train them in both real-world settings and simulations at The Seeing Eye's campus. It's a system that has worked for over 90 years.

“It’s the oldest guide dog school, and we’ve been honing this very specific process of training a dog to do very specific tasks,” Brian O’Neal, a guide dog mobility instructor with The Seeing Eye for nine years, tells Mental Floss. “We have a road map.”

Seeing Eye dogs are venerated; in January 2020, New Jersey proclaimed them the official state dog. And legally, no guide dog can even be called a "Seeing Eye dog" unless it graduated from the school itself. Though the dogs that come out of the school have garnered plenty of attention, the dedicated instructors who prepare them for working life are less well-known. We spoke with three trainers from The Seeing Eye about why certain breeds make great guide dogs, how they keep their owner’s safe from low-hanging branches, and whether or not they can read cross signals (spoilers: They can’t).

1. It takes years of apprentice work to become a Seeing Eye Instructor.

Being a Seeing Eye instructor isn't a volunteer position anyone can sign up for—it's a full-time job. If you meet the basic requirements, such as having a four-year Bachelor’s degree, you can apply to become an instructor. Once you make it through the application process, you go through a three-year apprenticeship program in order to become an official trainer. The apprenticeship includes classes and exams, as well as hands-on training with dogs and students, The Seeing Eye’s name for blind people preparing to become guide dog owners.

The work doesn’t become any less intense when apprentices graduate to full-fledged instructors. From 7:45 a.m. to 4:30 p.m., they train, exercise, and care for eight dogs total—four in the morning and four in the afternoon. If you aren’t ready to commit to working for The Seeing Eye full-time, you can volunteer to be a puppy raiser and foster future guide dogs in your own home.

2. Seeing Eye dog instructors also train the dog owners.

The dogs and their trainers aren’t the only ones working hard at The Seeing Eye. Before a blind person can take a guide dog home, they must live on the campus and go through weeks of training to learn all the intricacies of working with their dog, including navigation and bonding.

“A student is someone who’s applied to our school and [has] been accepted to our program, and we’ve flown them here or provided travel to come here,” O’Neal explains. “We match them with a dog, and over 27 days, we teach them how to safely and effectively work with this dog and vice versa. Once they’ve completed the program, they become graduates.” But to get there, the instructors, students, and their dogs have to put in long hours.

“Class is emotionally and physically exhausting," Sarah Indano, who's been in the apprenticeship program for two and a half years, tells Mental Floss. "It's like boot camp to really train these people for everything they need in a limited amount of time."

3. The Seeing Eye instructors only work with dogs bred by the organization.

The Seeing Eye in Morristown, New Jersey.
A photo of The Seeing Eye campus in Morristown, New Jersey.
The Seeing Eye

The Seeing Eye breeds all its own dogs at a center in Chester, New Jersey, and each must meet a strict set of requirements to become a part of the breeding program. “All the dogs are medically tested and their temperaments are also tested,” Ruthanne Dewey, a guide dog mobility instructor at The Seeing Eye for more than six years, tells Mental Floss. “The best of the best are selected to go into that breeding program.”

Even with the proper pedigree, not every dog the organization breeds is fit to be a guide animal. At 7 weeks old, dogs are sent to live with volunteers called puppy raisers who provide them with care and teach them basic commands. When the dogs are about 14 months old, they receive medical testing to determine if they’re fit enough to train to be guide dogs. From there, the training, which O'Neal says involves a lot of "repetition and consistency," lasts four months.

4. Instructors typically work with a handful of choice breeds.

Seeing Eye instructor with a yellow Lab.
Seeing Eye instructor Ruthanne Dewy with a yellow Lab she trained.
Seeing Eye/Ruthanne Dewy

Seeing Eye dogs almost always belong to the following groups: Labrador retrievers, golden retrievers, German shepherds, or any mix of those breeds. Both physically and personality-wise, these breeds produce the best dogs for the job. “They are working breeds,” O’Neal says. “They have a long history of work and working alongside humans in varying capacities. So it comes down to their drive to work as well as their incredible temperament.”

This drive to work often translates to a desire to please their humans. As O’Neal states, trainers can only teach dogs so much, and an animal’s need to keep their owner happy is what ultimately allows them to do their job well. “They want to get the praise from that person. They want to figure out, ‘what does this person want me to do? Because I’ll do it.’”

These breeds also fit the physical requirements for a guide animal: They’re big enough to lead a person down the street or block them from traffic, but at the same time, small enough to fit on public transportation or beneath an office desk.

5. Praise is crucial during the training process.

Seeing Eye dogs may not know the directions to the supermarket, but they're trained to learn other tasks that enable their owners to move through their environments with confidence and security. These include stopping short of curbs, moving around objects, and blocking people from walking in front of vehicles. Dogs learn these skills through positive reinforcement—as much as it takes to make the behaviors second-nature.

“When the dog does something right, we’re showering it with love and affection telling it did a great job, and if it didn’t do a great job, we’re telling it ‘no, we don’t do it that way,’ and we’ll always go back and give them the chance to be successful,” O’Neal explains. “That’s important, because if we just said 'no' and moved on, I could see animals being discouraged by that."

6. Seeing Eye instructors can’t teach dogs to read street signs.

Seeing Eye instructor with a black Lab.
Seeing Eye instructor Brian O'Neal with a black Lab he trained.
Seeing Eye/Brian O'Neal

A Seeing Eye dog can navigate obstacles on a sidewalk, or stop a person from stumbling off a curb, but Seeing Eye instructors can't train them to replace a GPS. “I get asked all the time how the dog can read the stop light and know that green means go and red means stop,” Dewey says. “I always explain to people that it is not the dog that decides when to cross the street. The dog doesn’t know how to get to the grocery store. All that falls on the person. The blind person has to be able to cross the street safely.”

7. The Seeing Eye has escalators and Priuses on campus to simulate real-world obstacles.

The more advanced stages of Seeing Eye dog training take place in urban areas, starting in the center of Morristown and culminating in trips to New York City. But before the dogs are ready to enter the real world, trainers find ways to recreate those environments on the campus.

“We have our own maintenance department and mechanic that is in charge of our own fleet of vehicles,” O'Neal says. These cars are used to prepare dogs for the type of traffic they'll encounter when guiding their owners in public. “We also have Priuses so we can make sure the dogs are learning to steer clear of cars that are silent as well.”

The campus also has plenty of indoor obstacles designed for training, like staircases and an escalator that's housed on the grounds.

8. Some obstacles require some surprising training equipment.

Training a dog to look out for objects in front of it—like cars or pedestrians—is fairly straightforward. Making sure they’re aware of obstacles above ground-level poses more of a challenge to instructors. For these lessons, trainers use some unexpected equipment. “We have an obstacle course with overhead pool noodles that stick out to make sure the dogs are watching out for the top part of the person, too,” O'Neal says.

Instructors don’t know what size a dog’s owner will be during the training process, but that hasn't been a problem so far. Incredibly, the dogs are able to figure out the height and width of their humans on their own. “If you’re an instructor that’s really short, but that dog goes to a person that’s really tall, that dog quickly learns and adapts that they have to look out for [obstacles] that are much higher,” O'Neal says. “To me that’s one of the most amazing parts of the job; how much the dogs adapt and do on their own that we don’t teach them and can’t teach them.”

9. Seeing Eye apprentices take classes on the human eye to learn more about visual impairments.

Every instructor’s apprenticeship includes courses on dogs and dog training, but they also take classes to learn about the vision issues faced by the students. “I’m currently studying for my second exam, which is on the human eye and diseases and disorders of the eye and optic nerve,” Indano says, likening these classes to a college course. “It gives us the basis of the language we use to communicate with our students. We’re reminded that not only do our students see us as dog professionals, but they also see us as vision professionals, as well.”

This level of understanding is made even greater during Blindfold Week—which exactly what it sounds like. “We wear a completely dark blindfold for one week, and we live with the students for the first week of class,” Indano says. “We’re given some prep on how to effectively use a cane for travel for the first two days of class, and are taught how to cross streets, how to judge traffic, and keep ourselves safe."

The apprentices are even paired with a dog during Blindfold Week, effectively putting them through the same training as the students. "It gives you a lot of insight into what these students are going through," Indano says.

10. Seeing Eye instructors don't prepare dogs to work 24/7.

Seeing Eye instructor with a black Lab.
Seeing Eye instructor Sarah Indano with a black Lab she trained.
Seeing Eye/Sarah Indano

Seeing Eye dogs don’t have the time to chase squirrels, accept pets from strangers, or sniff trash cans when they’re on the job, but that doesn’t mean they never get to enjoy being a regular dog.

“People think these dogs don’t ever get a break,” Indano says. “They put on their business suits, which for them is their harness, and they’re at work. When they go home, their business suit comes off, and they get to be a dog that their person can snuggle and give pets to and play fetch with ... They live and love to work for their owners, and they get to go home and get even more love.”

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