AT SHARK-CON, AN ANNUAL EVENT HELD IN TAMPA BAY, I met a friendly man named Duncan Brake, who travels the world filming sharks and other marine wildlife. His work has taken him everywhere, from the Falklands to Antarctica. He told me excitedly about a project he was working on in the mangroves of the Bahamas, where scientists are finding out all sorts of things about the social behavior of lemon sharks. I asked Brake to put me in touch with these scientists, so he introduced me to Tristan Guttridge, executive director of the Bimini Biological Field Station, otherwise known as Sharklab. The lab houses a number of scientists conducting experiments and exploring shark behavior. Populated with various shark species, Bimini is an ideal place to conduct shark research because it’s located 45 miles east of Fort Lauderdale, and relatively untouched—far from the interests of tourists or developers.
Young and energetic, Guttridge strikes an interesting picture: with his wavy brown hair, impish smile, and two-day growth on his handsome face, he projects a vibe that’s more beach bum than shark expert. During our conversations, though, his seriousness and passion for sharks revealed the accomplished scientist and postdoc lurking under his casual exterior.
As far back as Guttridge can remember, he has been mesmerized by sharks. His grandfather, a Navy veteran of World War II, introduced him to the world of nature, regaling him with stories. In one of them, he described his run-in with a shark after his aircraft was shot down off the coast of Malaysia. Guttridge’s grandfather and another survivor exited the plane before it sank, and they made a mad dash for the beach. “I saw a dorsal fin as big as a block of flats,” his grandfather said. The shark circled them and, despite showing great curiosity in the two airmen, allowed them to reach the beach without incident. The story stuck with Guttridge, who cultivated his love of nature.
Like a young Indiana Jones, Guttridge traveled, at the age of eighteen, to Madagascar, where he conducted coral reef surveys, working amid a school of barracudas. Once he finished the six-month survey, he moved on to Tanzania to participate in a terrestrial biodiversity project. While in Tanzania, he was stung by a scorpion and, after accidentally stepping on an ant trail, had his legs and genitals overrun by them. He also climbed Mount Kilimanjaro. Following these adventures around the world, he returned home to the United States to volunteer at Sharklab, investigating the social organization and behavior of lemon sharks, which congregate in mangroves and shallow subtropical waters. In 2010, he earned his PhD at the University of Leeds. There Guttridge worked with another scientist, Culum Brown, a professor of biological sciences at Macquarie University in Australia, coeditor of the book Fish Cognition and Behavior, and editor of the journal Animal Behavior. With Brown, Guttridge uncovered new information about the traveling patterns of lemon sharks.
In a groundbreaking study, Guttridge proved that sharks—in this case, lemon sharks—are not the solitary animals that popular opinion assumes they are. None of the shark books I scooped up as a child, for instance, ever touched on the idea that sharks exhibit social behavior, only instincts. As it turns out, though, they are social animals, just like humans. Eager to prove this point, Guttridge set up an experiment with sharks in long pens separated by a plastic mesh. The sharks could see each other, but they couldn’t come in contact with one another. Guttridge and his team installed a single shark in the middle pen (zone 2) and two to four sharks in the far pen (zone 3). They kept the nearest pen (zone 1) empty. In each test, the solitary shark in zone 2 preferred to spend time near zone 3, where its fellow sharks congregated, demonstrating an active preference to socialize. Without food or any other potential motivator, it was clear that the sharks were seeking a connection with their fellow sharks. Guttridge was excited. He realized he had come upon a new area in shark research, every biological scientist’s dream. His study proved that sharks clearly demonstrate sociality and cognition, something heretofore never considered in the species. “When given the choice,” Guttridge said, “sharks had an active preference to be social.”
Guttridge did more than design and execute his study. He started spending time in the mangroves to observe lemon sharks up close as a kind of subtropical Jane Goodall. Mangroves are a key habitat for lemons because they offer juvenile sharks cover while they develop hunting and other survival skills. In the open ocean, juvenile sharks are defenseless against larger predators. Mangroves are also important ecosystems for sea life. Mangrove trees, which have thick, multiple roots anchored in the mud, provide a hiding place for a cornucopia of animals. The thicket of branches, densely packed with small green leaves above the roots, can extend 100 feet in the air. These branches are rookeries, or nesting areas, for coastal birds like herons and egrets. Kingfishers, with their translucent blue plumage, camp along the branches of the black mangroves, where they wait to spear small fish with their sharp beaks.
Guttridge set up a watchtower under the blazing sun in the Bahamian mangroves. In this Eden, far from the intrusions of humans, he studied the sharks, surrounded only by natural wildlife. From his tower, he watched the sharks and other indigenous sea creatures swimming and twirling around the mangrove trees’ horizontal brown roots. While music and news from his transistor radio played in the background, he took copious notes, sometimes watching for days at a time. Eventually, the days turned into months, which somehow added up to three years in the mangroves. This time was well spent, because Guttridge discovered that the sharks were doing more than simply aggregating in the mangroves. They were establishing social bonds with one another that extended beyond hunting assistance and mate selection. He observed sharks spending time with their compatriots, sharks of similar size and age, like boys and girls do in school. In addition, Guttridge witnessed juvenile lemon sharks regularly traveling together through the mangroves in a sort of carpool, tucked closely together as a single unit.
What struck Guttridge most was how lemon sharks behaved during high tide, a dangerous time in the mangroves. Because the incoming tide raises the water level, predators can move freely into the fringes of the mangroves, seizing vulnerable prey like juvenile lemon sharks. The gimlet-eyed barracuda, for example, which is pocked with black, is known to steal into the shallows to nab unsuspecting lemon sharks. Remarkably, Guttridge observed lemon sharks seeking shelter from barracudas and other opportunistic predators in pairs, partners in survival. Once the juveniles knew they were safe—when high tide was over and the water level drifted back down—the sharks would disperse.
When juvenile lemon sharks weren’t working together, they played together, which allowed Guttridge and his team to note that individual sharks exhibit distinct and diverse personalities. Some sharks, according to Guttridge, like to explore and cover broad territories, while other sharks prefer to stay closer to select sites. To document this behavior, he teamed up with Duncan Brake, who set about capturing it on film. Because the underwater roots and the tall branches of the mangrove trees blocked his desired shot, Brake sent a drone over the top of the forest. He was astonished at what he saw. Wide and deep canals thread their way through the mangroves, serving as a kind of underwater highway for the sharks. The sand at the bottom of the canals and the shallow water allowed the scientists to see the sharks clearly in the light-green water and film them as they traveled freely through the canals. In a typical video, two lemon sharks, each about 3 feet long, swim as a pair. Sometimes they meander along, and sometimes they speed up and, with a few flicks of their tails, dive together in and around the mangrove roots. Sometimes one ventures across an underwater branch, its cartilaginous friend in hot pursuit. The scientists sometimes saw half a dozen lemon sharks circling each other in congregations. Because Brake didn’t observe the lemon sharks hunting or feeding, he was sure their behavior was strictly social, a theory Guttridge backed up.
The lemon sharks’ ability to socialize prompts an obvious question: If they interact so freely, can they learn from one another? Since these young sharks need to learn how to hunt, for example, is it possible that other lemon sharks could teach them? How animals learn to hunt has been extensively studied in other species, but no such studies have been done on sharks, until now.
To investigate the social learning capabilities of juvenile lemon sharks, Guttridge designed another experiment, creating a novel, but simple, food task. Sharks entered a start zone, where they came in contact with a target that dispensed a food reward. Sharks were trained to get the reward, and then they acted as “demonstrators” who knew how to get the food. Guttridge paired these sharks with untrained juveniles. To control the experiment, he also allowed untrained juveniles to interact with “sham demonstrators,” sharks that had no previous experience with the task. Guttridge recorded both groups and then compared the results. The sharks working with the “demonstrators” learned the correct steps to get the reward, while the sharks paired with “sham demonstrators” failed. By observing other sharks in their group, the juvenile lemon sharks learned new tasks, which proved to Guttridge and his team that juvenile lemon sharks can apply socially derived information to their environment. Guttridge’s mentor and coauthor, Culum Brown, summed up the research’s conclusion: “I personally work on spatial learning in fishes quite a bit, and I think it is fair to say that sharks’ abilities in this area are just as good as any vertebrate.”
Brown and Guttridge also discovered that lemon sharks in Bimini have a strong site fidelity, or preference, for this island. If one were to encounter a lemon shark 5 feet in length or seven years of age, there is a 50 percent chance it was born in Bimini.
What Guttridge recorded has changed how science looks at sharks. Darwin said that humans and other animals share the same attributes, the only difference being the degree of those attributes. Humans are clearly the most sophisticated species in terms of creating connections with others. However, this feature does not take away from the connections formed by other species, like sharks. We must now view sharks in a new way: as creatures that share our attributes, specifically intelligence and sociability.
BECAUSE GUTTRIDGE WORKED WITH CULUM BROWN ON THE STUDY, I wanted to learn about Brown’s shark research in Australia, on the other side of the globe. I called his university office in Sydney. Our conversation focused on Port Jackson sharks, a bottom-dwelling species found only in Australia. Port Jacksons have a high forehead and a gray camouflage color with black lines scattered across their top. They have strong jaws and back teeth that can crush hard-shelled animals like mussels and sea urchins. Stocky and built like miniature tanks, they grow to about 5 feet in length and are, by far, the most common shark in Australian waters. These qualities, in addition to their relative passivity, make Port Jacksons an easy species to tag and release.
Brown and his team captured sharks and attached tags to their dorsal fins. They then made a small incision on the underside of each shark and inserted an acoustic tag designed to send out a ping whenever the Port Jackson shark came within a third of a mile of an underwater receiver or within 30 feet of another tagged shark. Each ping was time-stamped. Using these proximity-tagging methods, Brown was able to track the sharks on a map, and the scientists could identify each shark individually and, therefore, monitor interactions among the sharks. In other words, Brown and his team could determine which sharks hung out together.
Brown released the tagged sharks in Jervis Bay on the New South Wales coast, 90 miles south of Sydney, an ideal spot to study their behavior because it hosts several seasonal Port Jackson mating aggregations. He followed the migrations of those small sharks south from Jervis Bay to Tasmania, a trip of approximately 600 miles. Several findings came out of the study. Some sharks returned from their 1,200-mile round-trip journey each winter for five consecutive years, and they returned to the same location—not just the same bay or body of water but also the same reef from which they started. These migrations showed the incredible accuracy of the shark’s homing ability.
Brown also observed sharks spending most of their total aggregation time with sharks in their own social network. Like the lemon sharks in Bimini, the Port Jackson sharks liked to stay with sharks of the same size and sex. Some were recorded staying with the same sharks over a couple of years. “Large groups of sharks formed in the breeding season is not just a random collection of individuals,” Brown said. “The sharks preferred to hang out with other individuals who were similar to them.” Brown’s coauthor, Jo Day, a researcher at the Taronga Zoo, said, “The sharks established long-term relationships over many years.” One researcher compared the paper’s findings to Marlin’s and Dory’s behavior in Finding Dory.
Later, Brown told me that the intelligence of sharks is underrated. Their navigation skills are superb and they learn survival skills from one another. If they have all these remarkable senses combined with intelligence, then the next logical step is to conclude that sharks—and other fish—feel pain. A human’s physical ability to feel pain is a trait inherited from a fishlike ancestor. The nerves endings and related structures are identical. The perception of pain, and the associated psychological response, evolved to protect animals from harm. “It would be impossible for fish to survive as the cognitively and behaviorally complex animals they are without a capacity to feel pain,” Brown told HuffPost.1
If Brown is correct, sharks suffer a great deal of pain when they’re caught, gaffed, and finned. Death does not come easy to sharks. When they are finned alive, they slowly suffocate to death, which can take anywhere from ten to twenty minutes. Brown believes that a review of the evidence for pain perception strongly suggests that fish experience pain in a manner similar to the rest of the vertebrates. Although no one can provide a definitive answer on the level of fish or shark consciousness, the extensive evidence of fish cognitive sophistication and pain perception suggests that the best practice would be to lend fish like sharks some level of protection against cruelty, as society would to any other vertebrate.2
THE CURTAIN IS SLOWLY BEING DRAWN BACK TO REVEAL AN unappreciated aspect of sharks. The study of sharks is just now beginning to uncover real breakthroughs. It wasn’t until the turn of the twenty-first century that scientists realized that several species of sharks aggregated for mating and predation-avoidance purposes. A 2004 aerial study proved to researchers that basking sharks aggregate,3 while a 2013 study using active and passive telemetry showed leopard sharks engaged in the same aggregating behavior.4
In the years since, scientists like Guttridge and Brown have expanded our knowledge of sharks, including the misunderstood species’ long-overlooked ability to engage in social behavior and establish lasting, meaningful relationships with one another. With a high brain-to-body-mass ratio compared to that of other fish, sharks have the intelligence to engage in complex social behaviors, such as forming dominance hierarchies and creating social bonds.5 Of course, different shark species vary in social abilities, but even “solitary” sharks like the great white and the hammerhead might in fact integrate some aspect of social interaction into their behavior.
The sociability of all animals lies on a continuum from highly social on one end to completely solitary on the other. And on this continuum, the common perception of sharks has held that they are strictly solitary creatures. Of course, where sharks land on the spectrum depends on the species. Because great whites and tigers are strong and savvy enough to survive on their own, they remain fiercely independent hunters. Many smaller shark species, on the other hand, are social creatures. At least two species, lemon and Port Jackson sharks, enjoy the benefits of being in social groups.
As I traveled on my journey, I came across evidence in other shark species that supports Guttridge’s conclusions about the social behavior of lemon sharks. Whale sharks, for example, have been seen aggregating in the Gulf of Mexico during the summer months, as well as off the coast of Kenya. Scientists have recorded basking sharks, which are large filter feeder sharks, near Newfoundland and swimming in large groups of more than a thousand individuals. The extent of the social interactions during these aggregations has not been fully studied, but is it possible that some socialization is taking place?
Some research also points to blue sharks hunting together in small packs. Researchers have observed blue sharks working together to feast on schools of anchovies. One group of blues drives the anchovies into “bait balls,” and then the other blues take turns lunging at the fish, although more studies are necessary to draw definitive conclusions.
All creatures have to learn from birth how to hunt in a challenging world. Science has revealed the dynamism of the shark species in that there is no “one size fits all” behavior. Sharks’ great strength is their flexibility to alter behavior among the species to survive. I learned along my journey that great whites are autodidacts, learning on their own how to hunt fish and later seals. In South Africa, great whites soar out of the ocean depths to catch seals, demonstrating that, by the time they mature, they master their self-taught lessons. Now I have discovered that some smaller shark species developed another approach to learning how to hunt, the ultimate life-survival skill. Through evolution, smaller sharks developed an adaptation to learn from one another. Unlike any other species, the shark’s remarkable adaptability has allowed them to flourish.
This relatively new discovery of the shark’s ability to communicate requires a reassessment of shark intelligence. The fact that some sharks have the ability to learn from other sharks shows that they must have the intelligence to communicate and absorb complex information. This intelligence to connect with their fellow creatures should not come as a surprise: apex predators have to be intelligent to survive. When the lemon sharks leave the mangroves as adults, they can literally thank their peers. Each new generation of lemon sharks moving out from the mangroves into the open ocean is a tribute to a dynamic and malleable species that has withstood countless upheavals over 450 million years to rule the seas.