Dolphins may have an elite tolerance to spices

This article was originally published in Hakai Magazine.

Fishermen around the world are desperate for a reliable way to prevent dolphins from plundering their catch. Robbery of dolphin nets – known as depredation – costs fishermen income and also puts dolphins at risk of injury and entanglement. Proposed solutions, such as the use of noisemakers, have had mixed results. So Greek researchers went back to the drawing board in search of the perfect deterrent: something so nasty it would keep dolphins away and keep them away. They imagined fishing nets coated in a resin mixed with capsaicin, the chemical compound that gives peppers their characteristic heat.

Giving predators a spicy surprise may seem like a far-fetched solution, but capsaicin deterrents have been proven on land with other mammals such as deer, squirrels, and rodents.

Yet after five months of fishing trials with capsaicin-coated nets, the research team, co-led by Maria Garagouni, a marine biologist at the Aristotle University of Thessaloniki, Greece, came to a difficult realization: their idea did not work. The bottlenose dolphins interacting with their nets were completely unfazed.

Despite the disappointing result, Garagouni says she was impressed with the dolphins’ ability to fly through their nets. Garagouni began collaborating with fishermen ten years ago to study depredation in the Aegean Sea; even so, the animals’ prowess surprised her. When dolphins come for a meal in the nets, she explains, it’s more than a job of breaking and grabbing: in many cases, the animals perform methodical missions in the nets until they have eaten their fill.

“The initial shock for me was seeing it happen in real time,” says Garagouni. The first time the dolphins interacted with the hot sauce-tipped nets, two individuals spent no more than 15 minutes ripping 217 holes in the contraption.

“And then the Victory Towers!” said Garagouni. “The next room, when there were young calves in the group – after filling up on fish, the youngsters would go off and do some leaps in the air, almost as if to burn off all that new fuel. If that was our livelihood, I think that would be the most infuriating thing to watch. But for me, obviously, it was amazing.

Does this mean the dolphins could swallow Da Bomb Beyond Insanity en route to The hottest glory? Aurélie Célérier, a neuroscientist at the University of Montpellier, France, who specializes in communication between marine mammals and was not involved in the study, says it’s too early to make that call. Although many cetaceans, including bottlenose dolphins, are known to lack four of the five primary tastes – they can only sense saltiness – spiciness is registered by a different set of sensory cells through chemistry. This process, which signals sensations such as pain and heat, is little studied in the species. Other toothed whales seem to have the hardware to detect capsaicin, Célérier notes, but there’s still a lot to learn.

There could be something else at stake in the dolphins’ triumph over spice: cetacean supersmarts. From herding fish with plumes of slime to tenderizing tough prey by tossing it high into the sky, dolphins are known for a wide variety of clever feeding strategies. Their propensity to innovate, combined with the fact that they are notoriously undemanding eaters, helps them survive, but it’s also part of what puts them in increasing conflict with anglers. The dolphins may have just found a way to get into the spicy fillets without too much contact.

The capsaicin coating did not deter the dolphins, but oddly enough it seemed to affect another animal. An unidentified predator, possibly a sea turtle, seal or shark, tore large holes in the scientists’ simple control nets, but not in the spicy ones.

The research team is putting a pin on their searing research for now, but Garagouni hopes it will serve as a springboard for others in their quest to outsmart the dolphins. Even a study that fails, she says, offers helpful clues and leads to new questions.

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