SHORTLY AFTER DAWN ON JUNE 17, 2017, MARY LEE DISAPPEARED off the coast of Beach Haven, New Jersey, a sleepy beach community 20 miles northeast of Atlantic City.
Concern quickly spread among Mary Lee’s 130,000 Twitter followers, a modest but loyal fan base most likely amassed during her numerous high-profile travels around the world: winters in Palm Beach, summers in the Hamptons, and, in between, the occasional jaunt to Bermuda, where she splashed around in the island’s cerulean surf. Wherever Mary Lee Went, people followed her every move. Curious beachcombers and paparazzi checked their iPhones for news of her whereabouts and speculated about Mary Lee’s real age, her sudden fluctuations in weight, and even the rumored father of her reported pregnancy.
So when Mary Lee suddenly vanished, people naturally feared the worst. Dropping off the map wasn’t like her. It certainly wasn’t the kind of behavior expected by her growing legion of fans or her handlers. Either she had decided to go offline for a few weeks or—as seemed more likely as June turned to July—Mary Lee wasn’t ever coming back.
I first heard about Mary Lee, and the growing frenzy surrounding her, from Greg Skomal, a senior fisheries biologist at the Massachusetts Division of Marine Fisheries and head of the Massachusetts Shark Research Program. Skomal, who’s been studying great white sharks in Cape Cod since the Reagan administration, couldn’t stop talking about her. I can’t say I blamed him. As he made abundantly clear over the course of our conversations, it isn’t every day you get to track in real time a 16-foot, 3,456-pound great white, certainly not in the waters of the Atlantic.
“The great white shark is still really an open book,” Skomal told me in his office at the Shark Research Program, where he and his team examine the migratory patterns and social behavior of great whites. “When you turn on the television and see white sharks doing incredible things, typically it’s filmed in the Pacific and Indian Oceans. Scientists for decades have been studying this species in those areas. White sharks in the Atlantic have always lagged behind in terms of what we know about its biology, its natural history, its ecology. We didn’t have any of the white shark hot spots you see in other oceans.”
That all changed around 2004, according to Skomal, when the Northeast’s previously imperiled seal population started to flourish three decades after the Marine Mammal Protection Act of 1972 prohibited local fishermen from killing them to protect fish stocks. Once the seals returned to Cape Cod, so did the white shark, the seals’ natural predator. The return of white sharks provided scientists like Skomal with an unprecedented opportunity to study them. For the first time, they had regular access to white sharks in the Atlantic Ocean. “If you can find the species you’re trying to study,” Skomal said, “you can study it.”
And if you can study the species, you can start to figure out its biology, its behavior, and, over time, the size of its population—previously unknown data sets that help scientists get a better understanding of the species’ overall health and, as Skomal and others are starting to figure out, how the health of the Atlantic is directly related to the well-being of white sharks in its waters.
Skomal was part of the team that caught Mary Lee off the coast of Cape Cod in September 2012. Under the direction of OCEARCH founder Chris Fischer, the former Emmy Award–winning host of ESPN’s Offshore Adventures program, Skomal and a group of researchers tagged Mary Lee’s dorsal fin—the great white’s telltale peak—with a Smart Position and Temperature Transmitting Tag. SPOT, as the tag is also known, allowed OCEARCH to track Mary Lee’s movements and, in a technological twist, broadcast her whereabouts to the general public in real time across Twitter, Facebook, and the organization’s other social media platforms.
Because collecting data from free-swimming sharks is next to impossible, the catch-and-release work of OCEARCH is helpful. If scientists are ever going to understand these apex predators and their role in maintaining the world’s oceans, they need to examine them up close. Watching the operation unfold is a thing of beauty. In the video OCEARCH released of Mary Lee’s capture, Fischer spots the shark while chumming the waters in a skiff. Once he and his crew catch it, Fischer radios ahead to Skomal, who’s waiting a few miles away on the OCEARCH, a floating at-sea laboratory. “We are all green here,” Fischer tells him, calm and collected amid the growing excitement. “We are a full go. Big, big, big mature female shark. Definitely a five-plus-meter fish.”1
Towing the shark, Fischer steers the skiff toward the OCEARCH and docks the shark into a floating pen, a 75,000-pound capacity hydraulic platform that is slowly raised out of the water, until the pen looks like a wood-paneled pool deck extending off the massive vessel. Then, with the precision of a NASCAR pit crew, Fischer and his team get to work. To lessen the shark’s nervousness, one man covers the shark’s head with a large towel. He then inserts a large hose into the shark’s mouth, providing the captured shark with a continuous flow of fresh seawater so it can breathe in the open air. While that man caters to the shark, others frantically start tagging her, measuring and sexing, drawing blood samples, and performing a quick muscle biopsy to identify reproductive habits and, according to the OCEARCH website, assess organic and inorganic contaminants. One man, who I assume drew the short straw, scraped bacteria and other marine parasites from the shark’s teeth. Before releasing the shark safely back into the sea, Fischer christened his great white Mary Lee, after his mother. “I didn’t know if I was ever going to have the opportunity to name another shark,” he later admitted during a press conference.2
The entire operation—catch, tag, and release—took less than fifteen minutes, but those fifteen minutes ultimately produced more than five years’ worth of new research about great whites, the ocean’s most mysterious and most misunderstood inhabitant.
“What we’ve done, for the first time in history, is establish a proven method of capturing the ocean’s giants and releasing them alive,” said Fischer. “And, in between, giving the leading scientists fifteen minutes of access to use all of the latest technology and to do all of the research projects they’ve ever dreamed of.”3
To achieve Fischer’s stated goal of providing a brighter future for the white sharks, OCEARCH and their collaborators first need to learn the fundamental pieces of the white sharks’ life. If scientists are to preserve the great whites, they need to understand their behavior, biology, reproduction, and range movements. This list is by no means exhaustive. One important place to start is with the population size and the health status of the great whites on the East Coast. Another important area to explore is where the sharks mate, give birth, and grow up as juveniles. To this day, no one has ever witnessed a great white giving birth. If a scientist can determine exactly where white sharks mate and mature, for instance, they can petition the government to protect those maritime areas.
OCEARCH has worked with scientists from different organizations, and their ongoing tagging program has catalogued hundreds of sharks, which are added to OCEARCH’s open-source database to aid researchers in their work.
Still, as we enter this golden age of shark research, Skomal was quick to remind me, “There’s a lot for us to learn.”
Fischer told the Associated Press in 2013 that he expected Mary Lee to be more of an offshore fish, taking advantage of the Atlantic’s bountiful schools and, potentially, hanging out in the North Atlantic right whale’s birthing habitat off the Carolinas. Instead, Mary Lee hugged the East Coast, traveling from Cape Cod to Charleston, then up and down the Southeast, swimming between Jacksonville, Florida, and Wilmington, North Carolina, before heading around Cape Hatteras, toward New York, a few miles offshore from Times Square. While Mary Lee didn’t pinpoint potential birthing sites, her path did help to confirm what scientists knew about the distribution of white sharks off the eastern coast of the country. Before she could spill any more secrets, however, Mary Lee went offline. The loss of Mary Lee was a setback, but the best approach as far as Fischer, Skomal, and everyone else was concerned was to keep tagging as many white sharks as they could and, as a result, uncover as many of the species’s hidden secrets as possible.
On a subsequent expedition, Skomal and his team pinned another white shark—this one named Luci—with a sophisticated pop-up satellite archival transmitting tag, which over time collected data about the shark, including the depths of its dives. Figuring out a shark’s migratory pattern was useful, but piecing together a shark’s movements as it ventures nearly a mile below the surface of the ocean would help scientists figure out how deep a shark can dive and, once it’s down there, what sharks might do at those depths. After preserving via satellite luci’s data, Skomal and his team team were able to piece together, meter by meter, one of Luci’s most spectacular dives as she cruised along the East Coast of the United States. Skomal established her position at 600 feet below the ocean’s surface. While there is plenty of sunlight at the surface, light quickly fades as the depth slowly absorbs it. Continuing the descent, Luci freely exited the sunlit zone, speeding through the enveloping darkness past 660 feet, where only 1 percent of the light penetrates the increasing density.
In 2014, a scuba diver named Ahmed Abdel Gabr, a former member of the Egyptian army, set the Guinness World Record for the deepest scuba dive. Having spent four years training, he successfully dove 1,000 feet under the Red Sea, proving that humans—or at least one with seventeen years’ experience as a diving instructor, three canisters of oxygen strapped to his back, and a support team in tow—could survive a deep-sea immersion. Abdel Gabr’s descent took twelve full minutes, while Luci blew past this depth in a matter of seconds.
Past 1,000 feet, water pressure begins to reach staggering proportions. One atmosphere at sea level equals 14.6 pounds of pressure per square inch, the same as the weight of the earth’s atmosphere. This means that, on land, each square inch of your body is subjected to a force of 14.6 pounds. Water pressure increases about 1 atmosphere every 33 feet of depth, which at 1,000 feet, translates to 30 atmospheres, or roughly the equivalent of one large, 450-pound, adult pig squatting on every square inch of your body. To withstand water pressure at this depth, German engineers reinforced the hulls of U-boats, which allowed them to dive beyond 1,000 feet, but even these engineering marvels couldn’t survive a dive beyond 1,200 feet. Like early explorers venturing across the Atlantic and Pacific Oceans, Skomal and his team were discovering something entirely new, something truly groundbreaking, a high point in shark research.
A deep dive creates problems for many animals. For humans, high blood nitrogen pressures can exert a narcotic effect, known as “nitrogen narcosis,” which during ascent may lead to nitrogen bubble formation, a phenomenon known as “the bends.” Great whites avoid this problem at this depth because they don’t have lungs or swim bladders.
Well beneath the sunlit zone, which ends at 660 feet, Luci breached the middle of the twilight zone at 1,750 feet. This bewitching area of the ocean (660 to 3,300 feet) is too dark for photosynthesis. Many underwater creatures live in the dim light here during the day but travel up the water column to hunt at night in the sunlit zone. Sharks are highly suited to this area because, like lions, they can see in the dark, thanks to the tapetum lucidum, a layer of tissue behind the retina that reflects light through the retina a second time, increasing the light available to the eye’s photoreceptors. Because Luci’s eyes can take in light even in near darkness, she would have still been able to attack unsuspecting prey, if she were so inclined. But she wasn’t finished diving. Luci easily beat the maximum depth of a nuclear-powered submarine (1,750 feet) and, 950 feet later, eclipsed the height of the Burj Khalifa in Dubai, the world’s tallest building.
At 3,000 feet, Luci entered the ocean’s dark zone. No light can penetrate this depth. No plants can grow there. The only source of food is the “snow” of waste from above. To the surprise—and celebration—of Skomal and his team, Luci bottomed out at 3,700 feet, where she was surrounded by total darkness except for the occasional bioluminescence of nearby fish, jellyfish, and crustaceans, which flashed in the water like lightning in the pitch-black sky.4
Luci is not the only shark star with such diving capabilities. In New Zealand, the National Institute of Water and Atmospheric Research (NIWA) tagged a 16-foot-long shark they named Shack, which set the world’s record for the deepest known dive by a great white shark at 3,900 feet. According to NIWA, Shack “regularly . . . deep dives between 3,200 and 3,900 feet while crossing the Pacific Ocean.”5
Nature has designed great whites like Luci, Shack, and others to routinely dive to great depths around the world. They inhabit one of the most inhospitable places on the planet. The pressure at this level is staggering, roughly the weight of a grand piano on every square inch of a great white’s body. At this depth, Luci was the only living thing with solid mass; every other creature was gelatinous and had strange, translucent appendages. Temperatures at 3,700 feet are equally unfriendly at 35° to 39°F, which Luci combated by generating her own body heat. While Skomal and his team studied the mechanisms of Luci’s singular descent, they remained mystified about the reason for the dive. The Marine Conservation Science Institute’s Michael Domeier has theorized that, at these depths, sharks like Luci are likely hunting a giant squid, a mysterious, deep-ocean dweller. Most squid live at the surface and are only 2 feet long, but at 3,000 feet, they grow twenty times bigger. At these depths, squid, worms, and sea crabs grow to monstrous sizes because of a phenomenon known as “abyssal gigantism,” a condition scientists link to either the deep-sea environment’s higher atmospheric pressure or its colder temperatures. For years, people doubted giant squid really existed. Then some began washing up on beaches around the world. A squid measuring 30 feet in length beached in Galicia, Spain, while other recent discoveries proved that female and male giant squid can grow as long as 43 and 33 feet, respectively. Before Skomal confirmed great whites can dive to this depth, the only known predators of giant squid were sperm whales. But as Luci bottomed out, it wasn’t too hard to imagine great whites and giant squid waging epic battles at the bottom of the ocean floor.
ONE OF THE GREATEST IRONIES ABOUT WHITE SHARKS IS THAT they aren’t white—or at least not entirely. Only their underbelly is white. This design is shrewd, because in deep-sea water the shark’s blue-white countershading camouflages them when pursuing prey.
Great whites are one of the largest carnivorous sharks in the ocean; however, they are only sixth in overall size compared to other sharks, a fact that belies the notion of the great white as a killing leviathan. The largest sharks, which are harmless to humans, belong to the filter feeder category—the whale, the basking, and the megamouth sharks, all of whom are larger than the great white. Like great whites, the Pacific sleeper and Greenland sharks are carnivorous but larger, according to Greg Skomal. Unlike many species, where males are bigger than females, female white sharks like Mary Lee are larger than their male counterparts, which on average measure between 11 and 13 feet and weigh between 1,500 and 1,700 pounds. Mature females grow to 15 or 16 feet and can weigh up to 2,500 pounds. While males can easily reach 17 feet, it is not unusual for a female shark to grow to 20 feet in length and weigh 4,300 pounds, equal to the length and weight of an adult giraffe, as difficult as that is to imagine. A white shark caught in Cuba in 1945 measured 21 feet in length and weighed a staggering 7,300 pounds, or 3.5 tons, a weight equal to six adult grizzly bears. The reason female white sharks are larger than males is simple: as Skomal told me, females need considerable strength and abdominal space to carry their pups during the white shark’s long gestation period, all while continuing to hunt. It takes longer for a white shark to develop in utero than it does a human, mainly because once they are born, shark pups are on their own. Unlike dolphins and orca whales, which protect their babies, white sharks leave their pups to fend for themselves. The great white pups eat what they can catch, which in their infancy is fish. As white sharks mature, they start hunting seals and other larger mammals.
“[Pregnant white sharks] are older animals,” Skomal explained. “They’re in their twenties and thirties when they reproduce. And they’re not capable of reproducing until they hit those sizes and those ages. When an angler removes a young, or small, great white shark from the ocean, it has a significant impact on the population because that shark probably hasn’t lived long enough to breed.” The population replacement rate for the white shark is extremely low, which makes the species vulnerable to exploitation. “They’re maturing at a late age and only giving birth to a handful of young, most likely, every two to three years. We have to be particularly conscious of this when it comes to sustainability, conservation, and management of the species.”
While there is still no reliable data about the world’s total great white population, scientists believe that the total number is dropping, largely because of overfishing and other environmental factors. White sharks are currently listed as vulnerable, a tick above endangered, on the International Union for Conservation of Nature’s Red List of Threatened Species.
The white shark’s vulnerability belies the popular misconception of the species as bloodthirsty man-eaters. “When people think of white sharks,” Skomal told me, “they think all kinds of things. Most of them are fairly negative, which came out of Jaws. Hollywood has done a very good job of scaring the hell out of people.”
The nearly five-decade-long counterattack against sharks is not just the result of the cultural impact of Jaws. It is also the result of the rapid expansion of the commercial fishing industry during the 1980s. These developments endanger the species and, in the process, upset the delicate balance of the marine ecosystem.
A fear of sharks has led people to seek the thrill of catching them. But what I have found out about the great white is extraordinary. In sharks and in life, fear is often the absence of knowledge. “The more people know about these animals,” Skomal said, “the more likely they are to revere them as opposed to fear them. The more we’re learning about sharks, the more we’re learning that they’re an integral part of the marine ecosystem.” Fischer and Skomal and an entire generation of marine biologists and conservationists have dedicated their careers to trying to change the public’s perception of sharks, specifically great whites, as underwater monsters.
Like most teenagers of his generation, Skomal discovered marine life from TV shows like The Undersea World of Jacques Cousteau and National Geographic, which brought color images of sharks and other underwater wonders to living rooms around the world for the very first time. But what really impacted Skomal were his family vacations to the Caribbean, where he fell in love with the ocean, mesmerized at an impressionable age by coral reefs and the variegated fish species he saw scuttling about their natural environment.
“When I was, like, twelve, thirteen years old, I wanted to study sharks, but I figured by the time I got old enough to do it, it would all be done,” he said. “How naive was I?”
Later, after resolving to learn everything he could about the ocean, Skomal enrolled at the University of Rhode Island, where he earned his bachelor’s and master’s degrees. He later returned to school to earn his PhD at Boston University. While searching for a full-time researching job, he volunteered at a federal laboratory. Surrounded by field scientists with years of experience, Skomal conducted scientific investigations, developing in the process an unshakable passion for great whites. In 1987, he landed a full-time job as a senior fisheries biologist at the Massachusetts Division of Marine Fisheries, where he quickly realized that most of the scientific knowledge about great whites emerged from hot spots in the Pacific and Indian Oceans. Fortunately, his career coincided with the return of great whites to the northeastern Atlantic Ocean, once the seal population returned. “I was at the right place at the right time,” Skomal told me. The entire Atlantic Ocean was suddenly his to explore and research, uncontested. “Many white sharks come up to Cape Cod in the summertime, and simply move in the wintertime down to the coasts of Florida and Georgia and South Carolina. But then we have a component of the population that wanders the Atlantic, and those are most intriguing to me. You know, not just the coastal migratory pattern, but the ones moving out into the central part of the Atlantic, where they’re diving to great depths.”
Like Fischer, Skomal has a nose for finding great whites. To date, he and his team have tagged and tracked more than 150 great whites and have identified approximately 350. In a 26-foot skiff, he regularly patrols the waters off Cape Cod’s Monomoy Island, an 8-mile-long run of sand extending southwest from Chatham. The island is a popular congregating spot for seals. Often, Skomal films these encounters. From his boat, he looks out for the great white’s unmistakable shadow underwater: a dark mass moving through the green water. When he sees a shark, he approaches the prow and plunges a tag into the base of the passing shark’s dorsal fin. No worse for wear, the shark swims on, unbothered.
As Skomal described it, hunting for sharks sounds routine and uneventful, like swimming laps in a pool. But it isn’t always this easy or stress-free. Once, trying to get a close-up of the shark’s face to help identify it, he attached his GoPro on a pole and plunged it into the water. He had done this scores of times but on this occasion, an 11-foot female went right for the camera. “It kept coming and then opened its mouth and bit it,” he said, calling the shark’s action exploratory, rather than predatory. If it had been the latter, he reminded me, the shark would have destroyed the camera and, in all probability, pulled Skomal into the water during their brief tug-of-war.
Skomal added that this shark was not one of the 150 sharks in the area that were already tagged by his team for research. He and his team will now review the video to look at her markings and determine if she’s brand new to the area or if she is one of the 350 sharks his team has tracked previously. These experiences and the research information that come out of this tagging program have helped to answer a number of questions about great whites, including their life expectancy, which has confounded scientists for years.
Previous studies concluded that great whites live into their twenties and thirties. However, as scientists continue to collect more information, such estimates are proving problematic. Schoolchildren know that as trees grow, they lay down rings on an annual basis. Each ring represents a year. Sharks similarly lay down band pairs of rings on their vertebrae which is thought to be on an annual basis. While this trait was known in small to medium-large white sharks in the northwestern Atlantic, what was not known was that, after maturity, the largest sharks may experience a change in the rate of vertebral material deposition. Another difficulty scientists encountered while trying to determine a shark’s age was that some bands become too thin to read accurately.
The best scientific method to determine the life expectancy of great whites is radiocarbon dating. This well-known method uses the properties of radiocarbon (carbon-14), a radioactive isotope of carbon, to determine the age of an object. But where could scientists find the white sharks for the test? It just so happened that a lab in Narragansett, Rhode Island, contained the largest collection of vertebrae samples from white sharks caught in the northwestern Atlantic Ocean from 1967 to 2010. Using this material and the National Ocean Sciences Accelerator Mass Spectrometry facility at Woods Hole Oceanographic Institution, scientists were able to determine that great white sharks can live to over seventy years,6 which means that great whites are alive today that, as pups, heard the sound of US depth charges attacking Nazi submarines in World War II. Based on the data they collected from Mary Lee, Skomal estimated that she is in her early thirties, a woman in her prime. Because she likely has another forty years in her, if she were still online, she would have helped scientists identify her preferred breeding ground and pup nursery, which could have provided Skomal and other scientists with invaluable insights to assist with management of the species.
Tagged great whites appear to give birth in certain areas, although this process is not fully understood. Further complicating the issue is the fact that white sharks are found all over the world, which multiplies potential nursery sites exponentially. Based on tagging programs and circumstantial evidence, however, scientists are beginning to zero in on a few nurseries. Some are believed to be located off Taiwan and Japan. Another possible location is the Sea of Cortez off Mexico, because several tagged females went there from April through August, though scientists were unable to prove this hypothesis.7 Montauk, Long Island, is likely home to a nursery, 100 miles east of Manhattan. Some organizations have tagged numerous juvenile great white sharks in this area. Given the proximity to the Long Island Sound, this site offers great white pups plenty of baitfish. When Mary Lee was pinging off near Montauk, rumors abounded that she was about to give birth.
The behavior of white sharks, however, is far from predictable. According to Skomal, there is no such thing as a typical day in the life of a great white. “When I tried to come up with the average day in the life of a white shark, I found that it’s really difficult to do,” he explained. “Now, we’ve tagged one hundred and fifty-one white sharks in the last ten years . . . a fairly respectable sample size for that species. It’s an elusive shark; we don’t believe its population size is very big. So, our database should give me a nice snapshot of what they’re doing. And what we’re finding out is they’re doing whatever they want. Some white sharks will hang around Cape Cod for the whole summer, and they get into a routine of just basically moving up and down the coastline over the period of three or four months. Other sharks may stop by Cape Cod before moving on up into the Gulf of Maine; other animals might only be there for just a couple of hours before heading off deep into the Atlantic Ocean. Every shark seems to be very different. And I’m not getting any real patterns that tell me what the average day in the life of a white shark is really like.”
I asked Skomal how close sharks get to shore. “We’ve tagged white sharks, literally, within feet of the shoreline . . . almost touching the sand of the beach itself. They are hunting in that very shallow water for seals. So there’s no doubt in my mind that they’re moving within close proximity of humans, quite possibly routinely, and they have been doing that for hundreds of years.”
So much for the great white’s reputation as an insatiable underwater assailant hell-bent on killing unsuspecting beachgoers. In fact, a great white’s proximity to land makes it more vulnerable to humans. While great whites are classified by the US government as a “prohibited species,” commercial and recreational fishermen alike can still catch white sharks as long as they don’t keep them. Usually, when a recreational fisherman encounters a white shark, the shark is feasting on a dead whale. Most recreational fishermen are content to film and photograph a great white in action, because they are a difficult and dangerous species to capture. However, some recreational fishermen do target them. White sharks are hardy animals, but if one is hooked deeply or in its gill, or banged against the side of the boat, the damage can prove lethal. Longline commercial fisheries, on the other hand, inadvertently capture white sharks as bycatch, which for the time being is simply the cost of doing business in the open seas. Because they are prohibited from keeping or selling great whites, they let them go—sometimes after the sharks are already dead. Skomal described this act as “cryptic mortality.” “The species is unquestionably vulnerable to directed exploitation,” he said. “Unfortunately, it’s unclear how great whites are faring.” And there is always the situation where fishermen can get away with murder.
When a great white shark washed up on a beach in Aptos, California, the question became, how did this shark die? The nine-foot-long shark appeared healthy. As the Department of Fish and Wildlife inspected the fish, they noticed three bullet holes from a .22 caliber rifle. The case was solved only through an anonymous tipster who revealed that the shooter was a commercial fisherman, Vinh Pham. Upon questioning, he said that the shark “was disturbing his fishing activity.” The punishment for the crime of murdering a great white in cold blood—$5,000 fine and no jail time. He did not even lose his fishing license.8 As long as our society values one of the world’s great apex predators as worth nothing more than a small fine, the killing of great whites will continue.
Aerial surveys suggest that great whites are rebounding off the northeast coast of the United States, and Skomal’s work conducting surveys in these waters since 2009 bears this out. In his first year, he spotted only five sharks in the Cape Cod area. Seven years later, in 2016, he spotted approximately 150. Still, the exact population of great whites in the United States remains unknown. Similarly, the International Union for Conservation of Nature (IUCN) can’t accurately estimate the total population of great whites around the world, even though it can tabulate the populations of other vulnerable and endangered species, including snow leopards (5,000), tigers (3,000), and black rhinos (4,800). The absence of hard numbers is troubling, because without them, conservationists are unable to come up with a plan to help protect the world’s disappearing white shark population. And that population becomes increasingly vulnerable as individual sharks traverse the oceanic hemispheres; great whites like Mary Lee and Luci aren’t only record-setting divers, they’re also marathon travelers. A look into the past can explain how they became such great swimmers.
The age of the fish began about 530 million years ago, during the Cambrian explosion. Nature kept coming up with new designs, and 450 million years ago during the Silurian period, nature developed the relative to our modern sharks. For the next 150 million years, nature tinkered with, developed, and improved the sharks; evolution adjusted the jaws, molded and rounded the head, and experimented with new shark species. For example, the Helicoprion shark grew a table saw–like set of teeth on its lower jaw in the Permian period, 280 million years ago, though it became clear that this variation on the species didn’t work. During the Carboniferous period, 300 million years ago, sharks dominated the oceans and split into subgroups like skates and rays. By the Jurassic period, 200 million years ago, the predecessors of today’s sharks appeared. New species kept appearing through the ages, like Hybodus, which had horns but then went extinct. By 60 million years ago, nature had developed the sharks we recognize today. One of nature’s most enduring creatures, the shark’s design was extraordinary, allowing it to survive and rule the seas for literally millions of years as one of the world’s top apex predators.
The previous blueprint for fish required bones, along with supporting vertebrae, scales for protection from the water, and swim bladders that gave fish their remarkable buoyancy. Because all fish had to do to escape danger was to use its vertebrae to flick its tail for a quick getaway, fish brains were small. Over time, however, nature threw away this blueprint and started all over with the shark. The bones were discarded in favor of cartilage, which offered the shark structure and support, and a new material called dermal denticles replaced scales. Denticles turbocharged the shark’s speed in the ocean since they reduced resistance. While fish were good at escaping, sharks developed a brain to help become supreme hunters. Numerous popular articles have described the brain of a white shark as being the size of a walnut, a misleading comparison. The brain of an adult white shark is shaped like a Y, and from the scent-detecting bulbs to the brain stem, a shark’s brain is bigger and more complex than previously believed. In comparison, the brain of a human comprises two wizened hemispheres, roughly the size of a head of lettuce. Of course, because large animals tend to have larger brains, a more meaningful comparison is between brain weight versus body weight. The brain of a 1,000-pound great white shark can weigh 35 grams, or about 0.008 percent of its total body weight. In comparison, the human brain weighs 1,400 grams, or 1.9 percent of our total body weight. Relative to the body weight of birds and marsupials, however, the great white’s brain is large.9
An astonishing structure, the brain of a great white shark is composed of millions of neurons, or nerve cells, which contain supporting structures. The brain coordinates the shark’s many movements, from clenching and opening jaws that can either rip prey apart or, if the situation calls for it, delicately grasp an object, to lashing its tail to scare off a competitor. The shark’s brain is arranged in a linear fashion. Specialized regions line up like a jeweled necklace, from the brain stem to the posterior cranial nerves, which are responsible for conveying information from the shark’s inner ear, lateral line, and electrosensory systems. Moving toward the top of the brain, next is the cerebellum, where sensory inputs come together to help generate movement. A white shark’s cerebellum is well developed, which can explain the shark’s speed and reflexes. In the shark’s midbrain are the optic lobes, which process what the shark sees. A special vessel arrangement near their eyes warms them and the brain for faster processing. Another advantage of this capability is that it helps the shark travel through waters where the temperature changes very quickly.
After the midbrain is the cerebrum, where the shark thinks. In this area of the brain, home-ranging and social behavior occur. Great whites use this part of the brain to identify and track prey, process environmental markers for food sources, and recognize potential mates, to name just a few items. The cerebrum is also where the shark’s brain splits into the two cerebral hemispheres, a unique feature among vertebrates. At the top of this Y are the olfactory tracks that the shark uses to smell.10 Because some 70 percent of the shark’s brain is dedicated to this sense, the shark is perpetually enshrouded in a world of scents. The reality is that great whites are intelligent and are endowed with a brain superior to that of the other fish.11 For instance, salmon have a fraction of the cerebral endowment of a great white.
Denticles, which replaced the scales of fish, became the new skin for the shark. Denticles are essentially modified teeth with an inner core made up of tissue and blood covered by a hard outer layer of calcium carbonate. Each one has its own unique shape, but the basic structure is similar. Think of the design like a bicycle helmet with a round front and three main ridges flowing from front to back. Each ridge tapers into points at the tail end. The denticles are crammed together like overlapping shingles on a roof, covering the shark. If you rub your finger over a shark from head to tail, the denticles feel smooth, but run your finger in the opposite direction, and the skin is rough.
Inspired by the shark’s denticles, engineers at Harvard’s School of Engineering and Applied Sciences have been studying and testing ways to improve the aerodynamic performance of airfoils, or wings. The engineers took a smooth airfoil and arranged 3-D printed shark denticle devices on its upper surface and investigated the effect on aerodynamic performance. Using a complex software program, engineers performed tests in water tanks and made computational analyses of fluid dynamics. They discovered that the airfoil with the attached shark denticles resulted in the formation of vortices behind the attachment. A short separation bubble appeared in its wake. The denticle is essentially a vortex generator, and these vortices are responsible for up to a 10 percent reduction in drag.12 The Harvard engineers also discovered that the denticles enhanced lift and even helped to maintain lift at higher angles of attack. Therefore, the shark’s denticles simultaneously enhance lift and reduce drag, resulting in large lift-to-drag ratios.13
As this explains the shark’s lightning speed in the water, engineers are looking into copying the shark’s design and applying it to any wing on a plane, helicopter, or other aircraft. Engineers can also use the design on wind turbines to enhance their performance. In coming years, different wing shapes may appear with improved performance, and if so, society will need to thank the sharks for providing the design’s inspiration.
Besides the brain and denticles, nature made other improvements to the shark, and a significant one was the liver, which holds an oil reserve that helps sharks stay afloat and traverse long distances. Through evolution, fish came to rely on a swim bladder for buoyancy, which prevents them from wasting too much energy. A fish’s swim bladder is usually two gas-filled sacs located in its dorsal portion. However, without a swim bladder, sharks still required something to ensure buoyancy. Working double duty, an oil reserve in the shark’s liver solved the flotation problem and provided sharks with the energy to propel themselves through the water for long distances.
But other developments beyond the shark’s internal oil reserve made long-distance travel possible. The shark has pectoral fins that stick out from its side like wings on a plane. The shark uses its tail to move forward but uses its pectoral fins to pitch up or down. Although the oil in its liver allows for buoyancy, most sharks have a negative buoyancy, which means that because their bodies are denser than the fluid they replace, they have a natural tendency to sink if they’re not moving forward. The great white, however, turned this seeming disadvantage into an advantage. When great whites begin their trip with a slight downward orientation of the pectoral fins and the tail for propulsion, the negative buoyancy allows the shark to simply glide downward with minimal effort. After reaching a certain depth, the shark makes an upward adjustment with its pectoral fins and, as its tail powers the shark along, it can once again ascend. This type of swimming is known as “drift diving,” which makes the shark very effective at traveling long distances, since drift diving requires far less energy—sometimes 50 percent less than the energy required for swimming forward at a specific depth.14
Mary Lee, Luci, and their fellow great whites make staggeringly long voyages around the world this way. Great whites have been tracked going from Mexico to the Hawaiian Islands and back again. As any car owner knows, a trip of this length would require a lot of stops at the gas station. In fact, a typical car would have to stop and fill up the gas tank thirty-seven times for a comparable journey. Where can the sharks pull over and refuel? As it turns out, the sharks don’t hunt on these migrations, so they rely on internal stores of energy. Unlike whales and terrestrial animals that can draw from energy stored in blubber or fat during long-distance migrations, sharks don’t carry blubber; they bulge with muscles, like Olympic swimmers. To travel long distances, sharks rely on their body oil, which is held in the liver like a giant storage tank. A shark’s liver, which sits in the abdominal cavity, is huge, extending roughly from the shark’s esophagus to its pelvic fin. Oil in the liver accounts for a quarter of the weight of a great white, which means a 2,000-pound great white is carrying 500 pounds of oil, or roughly 60 gallons of oil, more than twice the fuel-tank capacity in a Cadillac Escalade.
Before NIWA started tagging sharks in 2012, they thought that great white sharks lived in cold water only. But after five years of diligent work, they now know that great whites in New Zealand migrate to tropical waters in winter, abandoning the area between April and September for warmer temperatures in the north. In migrating these distances, Shack and other great whites confirm they are remarkable travelers and superb at long-distance migrations that can match the travels of whale species like the grays and humpbacks. The maximum distance one New Zealand shark migrated in winter was 2,000 miles. The tag data reveal that great whites routinely travel 100 miles a day, whereas humans walk an average of 2.5 miles a day.
Now that science can track where the sharks travel, the information can be of great importance in helping protect and manage shark populations. Perhaps the best way to understand this is through the life-and-death experiences of whales in the Stellwagen Bank National Marine Sanctuary, 25 miles east of Boston, between Cape Ann and Cape Cod in Massachusetts Bay. This 842-square-mile federally protected marine sanctuary is a safe haven for whales and other marine species. When scientists were tracking humpback and right whales in the sanctuary, however, they discovered that the whales’ path crossed against ships entering and leaving Boston Harbor. As a result, whales were being killed by ship strikes. Authorities changed the shipping lanes, increasing shipping costs but dramatically reducing whale fatalities. The same analogy applies here to the sharks. By knowing the migrations of tagged sharks, we can use emerging information about mating and breeding areas to protect the species.
A similar rush to understand great whites and their migrations is underway in the Pacific, where great whites feast on a rich diet of blubbery elephant seals and sea lions along California’s central coast. For reasons that remain unclear, however, great whites make a strange migration in the spring. Like sailors following a siren call, the sharks leave behind the coast’s rich cornucopia of blubber for a patch of territory more than 1,000 miles away, halfway between the Baja Peninsula and Hawaii.15 Nicknamed the White Shark Café, this area, which is approximately the size of the state of Colorado, hosts what some people have started to refer to as Burning Man for sharks. One plausible explanation for the sharks’ mysterious journey is sex. In some species, females visit an area to find a mate in what is called “lekking.” (A “lek” is an aggregation of males.) In the Café, where the Pacific’s chlorophyll-low waters offer great clarity, female white sharks check out male sharks, specifically their fins and muscle tone. To show off, male sharks execute rapid oscillating diving patterns known as “bounce dives,” which require great strength and stamina. The shark will dive at night 500 feet straight down before returning back to the surface, creating a birdlike V-shaped pattern in the water. During the day, sharks increase these dives to 1,500 feet below the surface. One industrious male completed ninety-six dives in a single twenty-four-hour period, and the males keep up this behavior for three months inside the Café. The females watch this behavior and select the most prepossessing male. At the same time, the males might be moving at various depths to find the female pheromones, which they can track to their source and make a display of beautiful dives to woo the female.
Like most other reasons for doing something, if it isn’t for sex, it’s probably for food. It’s entirely possible female white sharks headed there as culinary tourists, innocently engaging in foraging behavior, until the males showed up and turned the Café into a pickup bar. Still, scientists point out that the females do not make the same bounce dives as the males, and though humans have explored only 5 percent of the world’s oceans, the proponents of the sex theory are confident that the Café isn’t home to a unique food resource that would draw females back and forth from California, an exhausting round trip totaling 5,000 miles, approximately 700 miles farther than the wildebeest’s annual grass-munching trek across eastern Africa. At this stage in the research, no definitive conclusion has been reached.16 Foraging, mating, and—like their Burning Man counterparts—communing as one species all remain under consideration. Perhaps it’s all three at once.
To better understand the sharks in this area—and to protect great whites on the high seas—scientists have descended on this site with an armada of ships and tools. Reflecting the importance of this area, a 2016 UNESCO/IUCN report identified the White Shark Café as a potential World Heritage Site.17 If this site is approved, great whites will have an area protected from fishing vessels, which will give the species a better chance for survival. Of course, as we’ll learn later, fishing fleets from around the world want to exploit this area of the Pacific. Given the increased vulnerability of the great white, it would be a double tragedy if fishing activities in protected areas interfered with the mating of the species. Like the work in the Atlantic with Mary Lee, the more knowledge society has about great whites, the greater the likelihood that the proposed fishing regulations will be effective. The race is on between the industrial fishing fleets of the world and the scientists to unravel the mysteries in order to implement the optimum regulatory fishing decisions.
In the meantime, scientists like Greg Skomal continue to tag and track great whites to gather as much information as they can, hoping a currently unknown shark, just waiting to be discovered, can offer unimagined insights—just as Mary Lee did before she went offline.
MARY LEE’S DISAPPEARANCE REMAINS A MYSTERY, AND IT ALWAYS will, though Chris Fischer doesn’t believe a commercial fishing vessel got her. Nor does he worry about a recreational angler cosplaying Quint from Jaws. Neither scenario is likely, he said. “Mary Lee’s the queen of the ocean. She’s a mature white shark that absolutely dominates wherever she goes.” Fischer and Skomal both believe that, after five years, the battery in Mary Lee’s tag simply ran out of juice. Like them, I often imagine Mary Lee is still out there. Perhaps she found a mate and delivered another litter of pups, somewhere off Montauk—close to the likes of Julianne Moore, Robert De Niro, and other A-list celebrities in the Hamptons, who are likely unaware of the royalty swimming in the waters nearby: the great white whose secrets revealed to scientists how to start safeguarding the ocean and its underwater denizens for future generations.