Emperors of the Deep

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.

CHAPTER 2

MAKOS, THE F-35 OF SHARKS

THE WOODS HOLE OCEANOGRAPHIC INSTITUTION (WHOI) is the largest independent oceanographic research institution in the United States, with more than a thousand staff members. Established in 1930 in Woods Hole, Massachusetts, WHOI operates ships around the world, where scientists and engineers work to understand the ocean and its relationship to the rest of the planet. I went there to meet Jelle Atema, an expert in shark sense.

Born in the Netherlands, Atema whittled flutes out of wood as a boy and observed animals in the nearby woods, developing at an early age a love of music and nature, neither of which he’s been able to shake. Later, he studied biology at Utrecht University, one of the oldest universities in the Netherlands, before earning his PhD at the University of Michigan, Ann Arbor, in 1970. Four years later, he joined the faculty at Boston University’s Department of Biology and Marine Program, where he matured into a tenured professor, internationally renowned biologist, and, in his spare time, a world-class flutist, performing at venues throughout the United States, Europe, and Asia. It’s no wonder, then, that Atema now goes by the nickname “The Original,” a sobriquet he picked up in 2017, when attendees at an annual ocean conference noted that Atema was the only researcher present who had attended the inaugural conference forty years earlier.

Atema has published 175 papers at the WHOI—all of which have focused on how aquatic animals employ their underwater senses. Through the years, sharks have proved to be a particular interest of his, mostly because the species is constantly in search of prey, which makes their individual senses an invaluable source of information. Like most animals, sharks rely on their acute senses of scent and sight, taste and hearing, to move about. But unlike other animals, sharks are equipped with something called “flow detection,” a keen ability to track trace odors left in the wake of a prey. Though it’s long been rumored that a shark can detect a single drop of blood a mile away, Atema told me this overstates the powers of a shark’s olfactory system—not to mention the primary laws of physics. For the odor of a single drop of blood to reach a shark, it would have to remain intact. Anyone who’s ever cut themselves shaving knows that blood quickly dissolves in water. Still, Atema told me, “if a lot of blood gets into the water, and a moderately diluted drop of it reaches the shark a mile away, the shark can probably locate the source” by following the flow patterns across 5,280 feet underwater. Odor alone, though, isn’t enough for a predator to locate its prey, because odors can’t indicate the direction of their origin. However, as animals move through the water, they leave behind an odor trail, inadvertently scenting the water in much the same way humans and other animals coat the air with their respective odors when they move across land. Called “odor plumes,” these flavor-scented eddies are complex three-dimensional structures that attach to water particles. Picture the oily residue in the wake of a moving boat. Many sea animals use these swirling eddies of water to locate prey, potential mates, and, when they’re ready to call it a day, the location of their homes. Because odor reaches each nostril at different times, sharks and other aquatic animals can determine the location of the plume and thus which direction to swim toward.