On the Hunt! How Sharks Find and Catch Their Food
SHOW NOTES
Dr Yannis Papastamatiou has spent decades studying shark behaviour – how they hunt, feed and live together – but he still remembers a moment in French Polynesia vividly [6.11]. During a night dive for his research into reef shark behaviour, Yannis recalls seeing hundreds of grey reef sharks slicing through the darkness, illuminated only by the beam of his torch. “It’s a location where you have about 300 grey reef sharks in a small channel, and at night they’re just going ballistic, just destroying reef fish. Doing those dives at night was probably what I consider the best dive I’ve ever done.” The first few minutes of that dive were nerve-wracking. “But after the first five minutes, the nerves passed away, and it just became a spectacular experience,” Yannis recalls.
Raised in London and half Greek, Yannis’s love for the ocean began far from the tropical reefs he studies now [8.01]. “I was born and raised in London,” he explains, “so I wasn’t exactly in a place exposed to sharks. But every summer, he would visit Greece with his family, spending long days in the sea. “Again, not too many sharks you’re going to see in Greece,” he laughs, “but my love of the sea started there.”
Two key moments set him on his path to shark science [9.22]. The first was watching Jaws. “I loved Jaws,” he says, “and I thought the character of Hooper was really great — the scientist — and that definitely left an impression on me.” The second was a National Geographic documentary from the 1980s featuring pioneers like Valerie Taylor and Eugenie Clark. “I had that documentary on VHS,” Yannis remembers, “and I just used to watch it again and again. That really had a big impact on me.” By the time he was five, he knew what he wanted to do: study sharks.
But it wasn’t until his teens that he finally saw one. “The very first shark I ever saw was in the UK off Chesil Beach – it would have been a little catshark. I remember seeing it and being ecstatic. Shortly after, I went to the Red Sea and saw silver tip and white tip reef sharks — my first tropical reef sharks.”
Today, Yannis is a behavioural ecologist who uses cutting-edge technology to explore how sharks move, forage, and interact with one another [14.11]. “One of my main areas of interest is understanding the ecological role of these animals, which I think gets oversimplified. What is their role as predators? What is their role as competitors? What is their role as prey? And what would happen if these animals were gone?” Yannis is particularly fascinated by the idea that sharks are not solitary drifters, but social animals with complex interactions. “We now know, at least for some species, that they are social,” he says. “The big question now is why — what drives these social associations?”
But before diving into that, Yannis explains the fundamentals of how sharks find food in the vast, three-dimensional space of the ocean [20.00]. First is their incredible sensory abilities, and how they behave to use those senses. The longest-range sense is hearing, because sound travels great distances underwater. Sharks are actually very good at detecting low-frequency sounds, which they may be able to hear from about a kilometre away! Next is smell, which can work over hundreds of metres, “then vision plays a role when they’re within tens of metres,” explains Yannis. “And finally, electroreception — their ability to detect electric fields — is only effective within tens of centimetres.”
With all these senses, sharks navigate the ocean like living instruments, constantly sampling their environment [21.05]. “They’re living in a three-dimensional world,” Yannis says, “so we see them doing what’s called ‘yo-yo diving,’ bouncing up and down the water column. It’s probably a way of sampling vertically, because for sharks, what’s above and below matters just as much as what’s around them.”
But sensing is only part of the story. How they move — and why — depends on what kind of prey they’re after [23.33]. Sometimes, the shark might not know exactly where their prey is, meaning they have to do a sort of random search to find it. “We call this a random walk,” explains Yannis. “It’s not that they’re lost — it just means they don’t know exactly where the prey is, so they have to search.” But, in places like coral reefs where food is plentiful, sharks might move more predictably within a small range. “We see this especially with reef sharks,” Yannis notes. “During the day they stay in a certain area, and at night they move over a larger area, then return to the same spot. It’s not random — it’s very structured.”
That pattern — leaving a home base to hunt and returning to it later — is known as central place foraging, and it forms one of the foundations of Yannis’s research [26.45]. “It’s similar to seabirds,” he explains. “They have a nest, they go out to forage, and they come back. Reef sharks don’t have nests, but they have preferred parts of the reef. They go out, forage, and return the next day.” Through long-term tracking at Palmyra Atoll in Micronesia, Yannis and his colleagues discovered that grey reef sharks were fiercely loyal to particular areas: “If you lived on the southwest part of the atoll, you only went back there. If you were from the north, you stayed in the north. They just keep going back to the same places.”
Even more fascinating, those sharks weren’t moving randomly — they were forming social groups [30.29]. “We found they were forming associations, hanging out with the same individuals again and again,” Yannis says. “It raised the question: why? What’s the benefit of being social if you’re a shark?” He thinks the answer lies in the sharing of information. “It might be that by hanging out together, they can learn where food is,” he explains. “If I find a patch of prey and you see me go there, you can benefit too. It’s not cooperation — it’s information sharing. And that might be a big advantage.”
This idea — that sharks learn from one another, intentionally or not — could explain why certain species return to the same spots day after day. “That central place might be a meeting point,” Yannis says. “Even though they split up at night, it allows them to regroup the next day, to find the same individuals they associate with.”
There are also many different hunting strategies across shark families [34.15]. Some, like the angel sharks, are ambush predators, lying hidden in wait for prey to cross their paths. Others actively pursue their prey, outswimming them with bursts of speed. Some can switch between these two strategies. Great white sharks are an example: “they patrol, but they can also wait for hours in one spot, using what we call an area-restricted search,” says Yannis. “They’re patient hunters”.
White sharks also seem to engage in social foraging – hunting near one another, not necessarily cooperatively, but to share opportunities [42.42]. Yannis and colleagues have studied this behaviour in the species off Guadalupe Island, in Mexico. “Some individuals were staying close together for hours,” he recalls. “It’s not cooperative hunting, but it makes sense — if one catches a sea lion, there’s going to be leftovers. Staying close could mean you get a meal too.” He pauses, amused. “It’s not teamwork,” he smiles, “it’s just smart.”
Still, not all sharks hunt in groups [45.31]. Many are loners with extraordinary adaptations. None, perhaps, as audacious as the cookiecutter shark — a tiny, 50-centimetre-long predator that takes circular bites out of whales, dolphins, and even submarines. “You’ve got to be impressed with a shark that’s 40 centimetres long and willing to go after an orca.” Yannis laughs. Scientists still don’t know exactly how cookiecutters feed, but Yannis has studied the telltale wounds they leave behind. “They have a special jaw, almost like an ice cream scoop, and they generate suction before taking a perfect, spherical bite.” Humans have been bitten too — long-distance swimmers crossing channels at night. “You have to be a special kind of person to get bitten by a cookiecutter shark,” he says, laughing. “Just don’t swim in the open ocean at night, and you’ll be fine.”
For Yannis, these quirks — from sharks that glow in the dark to ones that steal bites from giants — are what make sharks and the ocean endlessly captivating [52.41]. “The deep sea is like a desert,” he says, “food is sparse, and these animals have evolved incredible adaptations to survive.” Some light up their fin spines as a potential warning. Others may even use light to communicate. His fascination, though, always circles back to behaviour and how sharks are able to navigate such a complex, three-dimensional world. We often think of sharks as mindless hunters, but as Yannis’ research shows, there’s strategy and intelligence there: “The more we learn, the more we realise just how sophisticated they are.”
ABOUT OUR GUEST
Born and raised in London, England, Dr. Yannis Papastamatiou spent his early years snorkelling in the warm waters of Greece. He obtained an undergraduate degree from the University of Southampton, before moving to the United States of America to get his Masters from California State University Long Beach, and Ph.D. from the University of Hawaii. He is currently an Assistant Professor at Florida International University where his lab researches the physiological and behavioral ecology of sharks and other predators. His shark research has taken him all over the world including Japan, Mexico, Bahamas, Pacific Islands, Alaska, and Belize resulting in nearly 60 publications in the scientific literature. He is also very interested in the study and exploration of deep (> 50 m) coral reefs. In 2017 he became part of the research team of Pelagios Kakunjá, to collaborate in several projects, particularly in Cabo Pulmo, Revillagigedo Archipelago and Guadalupe Island.
Florida International University
Research papers referenced in this episode:
Papastamatiou, Y.P., Mourier, J., TinHan, T., Luongo, S., Hosoki, S., Santana-Morales, O. and Hoyos-Padilla, M., 2022. Social dynamics and individual hunting tactics of white sharks revealed by biologging. Biology Letters, 18(3), p.20210599. <
Papastamatiou, Y.P., Friedlander, A.M., Caselle, J.E. and Lowe, C.G., 2010. Long-term movement patterns and trophic ecology of blacktip reef sharks (Carcharhinus melanopterus) at Palmyra Atoll. Journal of Experimental Marine Biology and Ecology, 386(1-2), pp.94-102.
