Emperors of the Deep

In addition to their noses, sharks use their skin to find prey. A shark’s lateral line, a racing stripe of an organ that runs the length of a shark’s body and across its head, has evolved with breathtaking accuracy. One can make out the thin lines in profile photos of sharks. With exquisite sensitivity, the lines can detect movement, vibration, and pressure gradients in the surrounding seawater. Filled with fluid, the canal-like lateral lines are sheathed with epithelial cells with short hairs called “cilia” that sway within the fluid when they come in contact with water motion. Sharks can detect vibrations as low as 1 hertz. The number of hertz equals the number of cycles per second. The human hearing organ operates in a higher bandwidth at roughly 20 to 20,000 hertz and peaks in the 300 hertz range while sharks have greater sensitivity and can operate at a lower bandwidth. Another way of stating this capability is that sharks can detect motion as minuscule as the width of an atom. Lateral lines convert the movement of the cilia into electrical impulses. The shark’s brain processes this information to give directional information.

To test the accuracy of lateral lines, a German experimenter manufactured a trail in a swimming pool using a toy boat and set a trained seal after it. (While seals lack a lateral line, they do have whiskers, and lateral lines and whiskers work in a similar manner.) The manufactured trail featured a 90-degree angle—a hard right-hand turn. In a burst of creativity, the experimenter blindfolded the seal, hypothesizing that, even hunting blind, the seal would stay locked on to the turbulence of the trail through the turn. It did.[1] Like the inspired experimenter, Atema has spent years conducting original research about the uncanny underwater sensing abilities of aquatic animals. He started with sharks and then moved on to lobsters and other aquatic animals. In his shark research over the past fifteen years, he has focused his work at WHOI and Boston University, trying to figure out exactly how sharks employ lateral lines to sense and locate prey, eventually proving that sharks rely on the deadly one-two punch of their lateral lines and olfactory senses to hunt. He published his findings in a seminal 2014 paper, which included a schematic of how shark senses operate, separately and in tandem, during a hunt.[2]

Atema was able to piece together why sharks make mistakes and on rare occasions accidentally bite humans. A shark will make visual contact with its prey before striking. Underwater, visibility is limited and varies considerably based on conditions. On sunny days, for instance, when the water is clear, a shark can see the length of a football field. Conversely, on cloudy days, when the water is churned and murky, a shark might only be able to see a few feet in front of its nose. Under these conditions, a shark may not be able to know precisely what it is attacking, which explains why sharks sometimes mistake surfers for seals.

Sharks have the ability to sense small changes in electrical fields in the water. This sense, called “electroreception,” is vital to understanding sharks’ remarkable hunting skills. Electroreception occurs in organs called the “ampullae of Lorenzini,” a series of dark pores leading to canals (ampullae) that are scattered under the skin across a shark’s head. They allow the shark to sense electrical pulses of fish. Named after Stefano Lorenzini, an Italian physician and noted ichthyologist who examined shark cadavers in seventeenth-century Florence, these pores reminded Lorenzini of canals (ampullae in Latin), hence the name. Lorenzini speculated that they may be chemoreceptive, but Atema’s mentor in the Netherlands, a man named Adrianus Kalmijn, demonstrated their electrical function in the 1960s. At the same time, Kalmijn, Atema, and other students determined the sensitivity of the shark’s lateral line to water motion. Sharks typically have thousands of electro pores, a number that remains fixed throughout the shark’s life.[3] The scalloped hammerhead shark, for example, has more than three thousand electro pores. The exact arrangement of the canals varies from shark species to shark species.

Part of the excitement about these discoveries is that the new information is overthrowing old assumptions about sharks. For instance, it was once believed that when an animal’s muscle contracted, it created a low-power electrical field, which the shark picked up. Scientists then discovered that all living tissue generates a tiny electrical field in seawater. The electrical resistance of an object is a measure of its opposition to the flow of the electrical current. Because the skin of a fish or a sea lion offers substantial electrical resistance, the internal electrical field flows out of the mouth and anus, two low-resistance areas, creating a dipole field that sharks can detect, though that field is minuscule. Muscles and nerves also generate electrical fields, but these are not the main source of detection.[4] A shark’s ability to pick up extremely low voltages is extraordinary: the threshold of sensitivity is as low as 15 billionths of a volt.[5] A shark, whose tissue is only flesh and blood, matches humankind’s most technologically advanced instruments for detecting electric fields. Injured or sick fish produce stronger electrical fields, but even these fields are faint. Besides predation, this system is also believed to help sharks navigate by sensing the earth’s electromagnetic fields.

A shark’s bite must be exquisitely timed, and the ampullae are key to this timing. Many attacks between hunter and hunted end in failure. If the bite is off a millisecond, the predator will miss its prey. The ampullae, which are only effective at distances of 3 feet or less, are used in the final stages of the attack. Atema’s 2014 paper demonstrated that, regardless of species, virtually all sharks hunt the same way—from the relatively small dogfish shark to the mako, one of the top apex hunters in the ocean.

Spanning the globe, makos are found everywhere, from Montauk to Mumbai, patrolling tropical and temperate waters alike. The mako is one of the most remarkable and unique sharks in the ocean. The word “mako” is a Maori word, though no one can say with any certainty what it means. Though many believe it’s a corruption of “mackerel,” it’s more likely simply the name for the shark. The mako has a dramatic contrast between the vibrant ultramarine color on its dorsal surface and its snowy white underbelly, which camouflages the mako from prey above and below. Between the two, alongside the shark’s body, runs a band of reflective silver.

The mako’s countenance is severe, and its eyes are black with purpose. Its teeth, which flash like a dagger upon coming into view, are not serrated like the teeth of the great white and other sharks. They are designed to grab and hold prey, not to tear flesh into pieces. Sharks do not chew their food. The teeth of most sharks are slanted inward when the mouth is closed, but they straighten when the jaw opens. The mako’s teeth, however, remain upright in the bottom jaw, readying them for action.

Three characteristics define mako sharks: intelligence, speed, and toughness. As a species, a mako is basically a fearless, seagoing linebacker on a Fulbright scholarship.

The mako has one of the largest brain-to-body ratios of all the fish in the ocean, which has prompted several international tests to determine a mako’s intelligence and ability to identify objects. A New Zealand scientist demonstrated that the mako can differentiate items and recognize shapes. Perhaps more telling, the sharks involved in the study, after initial caution, started to recognize the scientists as nonthreatening coinhabitants of the water. They allowed scientists to restrain them briefly, and even touch them.[6]

A second defining characteristic of the mako is its speed. Makos can grow to weigh more than 1,000 pounds. Despite its significant weight, the mako is the fastest shark in the ocean. Researchers have clocked the great white at 30 miles per hour, but the shortfin mako can achieve extended bursts of 45 miles per hour. Some people claim makos can reach 60 miles per hour, although scientists consider these estimates excessive. (While the mako beats out all other sharks, the sailfish is the fastest fish in the ocean, clocking 65 miles per hour, the speed limit on the New Jersey Turnpike.) The mako’s speed is a product of its shape: a perfectly proportioned cylinder that reduces resistance. The mako’s head narrows to a single point, creating a sharp snout that helps the shark slice through the water.

The mako also generates speed across long distances because of its unique tail and musculature. Although the tail of every shark species is vertical—as opposed to the horizontally aligned tails of dolphins—each shark features a distinctive tail, or caudal, fin. In most sharks, the caudal fin’s upper lobe is longer than the fin’s lower lobe. This is true of the thresher shark. The mako, however, is armed with upper and lower lobes equal in length. At the same time, the mako’s red muscles, which process the transportation of hemoglobin through red blood cells, run up and down both sides of its body. While red muscles help sharks swim continuously, the location of the mako’s red muscles is a significant distinction. Among sharks, only the great white shares a similar location of red muscles. Like a strong core in humans, the red muscles help steady the body, limiting wasted lateral movements. Various motion studies show that the body of a mako remains fairly stable when it swims. This lack of lateral movement preserves kinetic energy. The mako uses this excess energy to swing the equal lobes of its caudal tail side to side in wider, more efficient arcs than other species. Together, the mako’s symmetrical caudal fin and the location of its red muscles allow the mako to generate and sustain such high speeds over long distances.

Another boost to speed comes from the mako’s massive gills, which, if laid out flat, would cover a surface area of 56 square feet, and are nearly three times larger than the gills of a blue shark. These massive gills filter and process large quantities of oxygen-rich seawater to power the muscles. And, because makos are endothermic, they can increase their body temperature—sometimes to as much as 20°F warmer than the surrounding water. Thanks to an internal network of blood vessels, the warm blood coming from their large swimming muscles symbiotically transfer heat to the cold blood operating the gills, which in turn delivers some much-needed oxygen back to the swimming muscles. Unlike most cold-blooded animals, including most fish, which dissipate heat out of the gills, the warm-blooded mako holds on to most of this heat, circulating it back through the body. The additional heat makes their muscles more effective—a 20°F increase in body temperature allows a threefold increase in muscle power[7]—rivaling only great whites in this ability.

Atema pointed out another advantage to being warm-blooded: “It increases sensory perception and brain function.” The mako is nearly unmatched in its dominion.

The mako’s speed allows it to prey on a wide diet: mackerel, billfish, and even other sharks. However, in deep waters, makos turn to tuna, a much more difficult prey. Catching tuna, which swim like underwater silver bullets through the blue netherworld, presents a unique challenge for makos and, for humans, a fascinating glimpse into the wonders of evolution. To catch tuna, makos had to develop speed, which in turn put pressure on tuna to respond. Like the gazelle and the cheetah, tuna and makos battled back and forth for supremacy and the edge for survival. Evolution worked to develop the adaptations for each species to survive, but instead of diverging, the two converged. Remarkably, tuna and mako morphed into near replicas of each other, as if the gazelle grew the limbs of a cheetah. They have similarly shaped tails, where the upper and lower lobes are the same size. Both have horizontal keels that act like small fins; these are shaped in a way that complements both species’ speed with stop-on-a-dime levels of maneuverability.[8] Both developed the ability to warm their blood.

The third characteristic that defines makos is their toughness. They have the strength for sprints and the stamina to sustain the 6,000-mile round trip across the Atlantic between the United States and Britain. More important, they fight like a prize fighter and have the heart to fight to the death. Hooked by fishermen, makos jump completely out of the water, an act of athleticism rivaled only by great whites. To exit the water, the mako needs a starting velocity of 22 miles per hour. As its speed hits 45 miles an hour, the mako can jump 15 to 20 feet, exceeding Michael Jordan’s vertical jump of 48 inches.

The sensors jammed into a mako shark’s head resemble the cockpit of the F-35 fighter jet. The mako’s sensors are equal in sophistication to the fighter jet’s advanced systems except they are bundled in nerves, flesh, and blood.

Combined, these three characteristics—intelligence, speed, and toughness—make makos one of the world’s greatest apex predators.

Here is a true story of the battle between a mako and a sea lion, one of the largest mammals in the ocean. The story is informed by Atema’s detailed, scientific explanation, based on his decades of studying the underwater-sensing abilities of these sharks.

Off Los Angeles, an angler landed the largest mako ever caught, a record shortfin weighing in at 1,323 pounds and measuring 12 feet long. The angler donated the shark to the National Oceanic and Atmospheric Administration (NOAA), which in turn autopsied it. When NOAA scientists examined its stomach contents, they found in the shark’s belly a California sea lion,[9] swallowed whole a week earlier. It takes time to fully digest such prey. The sea lion’s head, with its eyeballs, whiskers, and teeth, was still clearly discernible. Its winged flippers and dog-like head were pocked with wounds from the shark’s pointed teeth. The shark’s stomach juices had eaten away most, but not all, of the sea lion’s skin. The seal’s rib cage and other bones were still intact, waiting for the shark to slowly dissolve them.

To catch the sea lion, this mako required all of its skill, cunning, and strength. Endowed with incredible strength and world-class speed, sea lions are also armed with razor-sharp teeth and ferocious, powerful jaws. Sea lions can weigh as much as 800 pounds and can travel at speeds of 25 to 30 miles per hour. With a short turning radius and powerful muscles, they can catch up to 50 pounds of fish a day, including species as large and fast as tuna. Sea lions are a worthy match for makos.

Here is a dramatic reconstruction of the battle. This mako usually patrolled far out at sea, but on this day it stayed close to the Los Angeles shoreline for some reason. In the vicinity, a large sea lion, hugging the coast, was making its daily rounds for fish not far from south Los Angeles’s Huntington Beach. The sea lion broke the surface for air and dove back down. This sound did not attract the mako. Instead, it was the sea lion’s odor, which the mako detected about a third of a mile away. Gliding along the coast, the mako followed the odor plume, cutting west when the sea lion cut west, unaware that the ocean’s most deadly and relentless hunter was tracking it for a kill. When the sea lion broke the surface again for a gulp of air, the shark followed, its dorsal fin breaching the surface in the same place for a brief moment before submerging again in pursuit of the sea lion among the shadows of the green kelp beds. Without any visual clues, the mako closed the distance from half a mile to less than a quarter of a mile, using its sense of smell and its lateral lines to track its unsuspecting prey.

After half an hour, the shark finally gained a visual of the sea lion, which meant that the mako was near enough for the sea lion to recognize it. Fear released power, and, fighting for its life, the sea lion soared like a rocket, flipping and undulating to evade the mako. Though the sea lion likely reached speeds as high as 30 miles per hour, the mako was able to keep pace, using its secondary dorsal fin to turn in tandem with the sea lion and pull within 3 feet of it. Like an F-35 pilot with a missile guidance system, the mako’s ampullae sensed the sea lion’s electrical field, its large brain ablaze with the signals it received from its muscles and pectoral and caudal fins. With one last lunge, the ampullae-directed jaws tore into the sea lion’s rib cage. Red blood swirled in the blue water. The sea lion lashed back at the shark and, in a futile attempt to break free, tried to bite the shark with its formidable teeth, though it couldn’t penetrate the denticles of the mako’s rough skin. Finally, after twenty minutes and a half mile, the mako swallowed the sea lion whole.

In this attack, all the mako’s senses came into play, from the moment it sensed the odor to the moment of the final bite. The mako was just too strong and quick for the sea lion, an epic battle between species that has been waging for eons, since the Silurian period—prey and predator battling for survival and evolving over millions of years to create even a small edge that might mean the difference between life and death. In the evolutionary process, nature has created a dazzling array of species, each with its own remarkable adaptations. Equally important, nature maintains an exquisite balance among species, which keeps the system intact, a dynamic equilibrium within an ecosystem in which the diversity and population of animals remain relatively stable. If too many sea lions survive, they feast on too many fish, disrupting the balance of the surrounding ecosystem. The makos maintain this delicate balance as apex predators.

To humans, it may seem cruel for the sea lion to be eaten alive, but that is nature’s way. An efficient and quick death is perhaps better than suffering. When the sea lion disappeared into the mako’s cavernous maw, it should have been forever, but it wasn’t. A week later, another apex predator entered that same area. A sports fisherman, chartering a boat with state-of-the-art electronics, a large bait capacity, and powerful twin diesel engines, let out his fishing line just outside the Los Angeles Harbor and hooked the mako. As soon as the mako clamped down on the hook, it realized its mistake and made a run for it. The reel sang as the line tore through the rod’s tip and into the water. The shark took out a quarter of a mile of fishing line. As the struggle continued, the shark, in an attempt to spit out the hook, leaped over 20 feet out of the water, fighting for its life. Over the next hour, as the fisherman struggled to reel in the mako, it executed five leaps.

Finally, after two and a half hours, the fisherman hauled the exhausted mako close to the boat, and one of the crew yanked the shark aboard with a large gaff hook. The crew, captain, and fisherman all gasped in shock at the size of the mako. Large makos are typically 8 or 9 feet long, but this one was 12 feet. Impressed with his catch, the captain took the mako to a special weigh yard, where a certified weighmaster registered it at 1,323 pounds, 102 pounds heavier than the previous world record for a shortfin mako shark caught off the coast of Chatham, Massachusetts.

According to California law, a sports fisherman cannot sell shark meat. He or she can consume it, however, for him- or herself, or donate the shark for research. At the NOAA Southwest Fisheries Science Center, the mako sat on a table, waiting to be autopsied. The specialist came in, sliced the mako to get to the stomach contents, and removed the sea lion from the shark’s belly. A week after the epic battle, hunted and hunter both were dead.

Anglers pursue makos because their dreams of an epic battle with the big shark can turn into reality. Makos charge boats, sometimes jumping right into them. In mako fishing, you might lose not only your fish but also your rod or even your arm. This big game fishing carries a real element of personal danger.

For anglers, the mako is the prize shark to catch; the fight it puts up is legendary. History is replete with epic battles like the one between an angler and a mako off Nantucket. The mako flew out of the water and into the boat and whacked the fisherman across the ribs and stomach. Thrown almost the entire length of his 13-foot boat, the fisherman found himself forced against the cabin door, the wind knocked out of him. Gathering himself, he looked down; 8 inches from his left foot was the gaping mouth of a 286-pound mako, its rows of razor-sharp teeth exposed. The shark, it seemed to the stunned fisherman, was eyeballing him, trying to gauge whether he was predator or prey. Suddenly, the shark came to life and, for the most terrifying two to three minutes of the fisherman’s life, started chasing him around the cramped cockpit. The fisherman grabbed a baseball bat and struck the mako, which only emboldened the shark. Finally, after six blows, the fisherman killed the mako, though not without first enduring a litany of injuries, including three fractured ribs and a lacerated elbow.[10]

Here is another story from one of the most famous shark fishermen of all time, Frank Mundus, the inspiration for the Quint character in Peter Benchley’s Jaws. His story takes place on a fishing trip in Brielle, New Jersey.

As the mako zoomed through the air toward our boat on a parabolic trajectory, he came down squarely across one of the rods. Down the rod slid the shark’s bulk shearing off the rod guides as it went. The startled fisherman, seeing a few hundred pounds of mako about to be deposited in his lap, had the presence of mind to get the hell out of there. He jumped out of the fishing chair, going over backward, and landed on his head on the deck, almost breaking his neck. The mako slid into the cockpit and promptly took over.

Pandemonium broke loose. The shark went berserk. Bouncing and twisting violently, he slammed his way from gunnel to gunnel. He smashed fishing chairs; he sent chum cans flying to spew the contents all over the place. All hands beat a hasty retreat to the cabin and barricaded themselves behind the companionway door. Seconds later the mako crashed against the door knocking its knob out by the roots.[11]

In my travels, I heard a more recent—and much more sinister—take on a familiar tale. In 2017, three men—Michael Wenzel, 21, Robert Lee Benac, 28, and Spencer Heintz, 23—gassed up a high-speed boat and headed out to fish. Along with a case of beer, they took along a revolver and 50 feet of rope, hell-bent on catching a mako in Tampa Bay.

It wasn’t long before the three men caught a mako. As they reeled it in, they brought it alongside the boat. Exhausted after its struggle, the shark was moving slowly, like a punch-drunk boxer in the fifteenth round. Wenzel went over to the boat’s helm and removed the gun from a small cabinet. Aiming the muzzle at the shark, he pulled the trigger. A bullet ripped through the shark’s sandpaper-like skin, lodging in its liver. Because sharks are powerful animals, a single gunshot isn’t always enough to kill them, at least not right away, which gave the men some time for “fun.” It was time to teach this shark a lesson.

Next, they pulled out the rope and tied one end around the tail of the shark and the other around a cleat at the stern. Wenzel returned to the helm and gunned the engine, dragging the shark at 40 knots in the wake of the boat for more than five minutes.

The three men took a video of the ordeal. In the video, Wenzel, Benac, and Heintz are laughing and smiling as the shark struggles in the water. The ordeal and gunshot wound are too much for the shark, and it ultimately dies under this torture. The men hold up what is left of the carcass to the camera: a heap of blood and tissue and, because most of the shark’s skin was torn apart, exposed cartilage.

The men were proud of what they had done. To show off, they sent the video to Mark Quartiano, a legendary charter fisherman in Miami known as Mark the Shark. Quartiano takes people out specifically to catch sharks, and by his own account he has killed hundreds of them. Yet after viewing the video, he was filled with outrage. “I was horrified,” Quartiano told CNN. “I’ve been shark fishing for fifty years, and I’ve never seen a disrespect for an animal my entire career that was that evil.”[12] Quartiano said he decided to publish the video to Instagram, so the fishermen could be identified and caught. Under the hashtags #sowrong and #notcool, the video racked up thousands of views. It attracted the attention of Florida wildlife officials, who began an investigation. Working with the Florida Fish and Wildlife Conservation Commission, the Hillsborough County State Attorney’s Office charged two of the men, Wenzel and Benac, with two separate charges of aggravated animal cruelty, a third-degree felony, and a misdemeanor charge of using an illegal method to take a shark. In his police photo, Wenzel is smiling.[13] Florida governor Rick Scott said he wanted laws to prevent “such inhumane acts.”[14] (As of this writing, there has been no court decision regarding guilt or innocence.) The men who tortured the shark were shocked that Quartiano had, in their eyes, betrayed them. In disgust, they hurled at him what they considered the ultimate insult; they called him “a PETA-lover.”