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A call for help sounds to ensure survival of a 140-year-old fishing partnership pairing cetaceans and humans

People in Laguna proudly refer to their southern Brazilian city as the “national capital of fish-herding dolphins.” For at least 140 years, artisanal fishers and bottlenose dolphins have worked together in careful synchrony to catch mullet in a lagoon there. The spectacle of nets flying through the air while dolphins dive into the murky water has become a popular attraction for tourists and is recognized by local authorities as an intangible cultural heritage.

Before 1998 no one knew for sure whether humans and the cetaceans were really working together or just appeared to do so—or whether one species was benefiting but not the other. It was then that scientists confirmed that this renowned example of human-wildlife cooperation does aid at least one of the participating parties: the fishers who enjoy larger catches when they join forces with dolphins. Most people believed that the dolphins were reaping rewards, too, but this hypothesis was more difficult to put to the test.

Now scientists have finally confirmed that the benefits are indeed mutual. An exhaustive new study published in the Proceedings of the National Academy of Sciences USA on January 30 shows that dolphins who team up with fishers gain more food and have an edge in survival, compared with those that hunt without bipedal partners.

The resident population of up to 60 dolphins use their echolocation to find schools of mullet that humans otherwise would not be able to detect beneath the opaque water. Then the cetaceans herd the school toward the fishers, who are usually standing in the shallow water just offshore. The dolphins give a behavioral cue, such as a sudden deep dive, to let the fishers know when to cast their nets. The net casting benefits the dolphins by breaking up the school of speedy fish and making it easier for them to capture individual mullet. “Each brings a new skill to the table that increases their mutual success,” says the study’s lead author Mauricio Cantor, a behavioral ecologist at Oregon State University.

These celebrated interspecies hunts are in danger of going extinct, however, according to findings reported in the paper. “Our data suggest this interaction is becoming rarer over time,” Cantor says. “If things continue the way they are, these interactions might disappear in the next 50 to 60 years.”

Laguna’s cooperative fishers and dolphins are one of the few remaining examples of a millennia-old tradition that has occurred all around the world. Fossil evidence from Europe indicates that humans and wolvesmight have collaborated to hunt prey as early as 32,000 years ago. One of the first clear records of human-wildlife cooperation dates back to the first century C.E., when Pliny the Elder mentioned fishers working with dolphins in modern-day southern France. Since then cooperativelike interactions with people have been recorded in at least 16 species—mostly cetaceans but also some birds—in countries as varied as Australia, Myanmar, Mauritania and Japan.

Many of these collaborations have disappeared, however. And those that remain are almost all in decline thanks to pollution, overfishing and habitat loss, combined with the general disconnection of humans from the natural environment. “Today most interactions we have with wildlife tend to be antagonistic and not mutually beneficial,” Cantor says. “So it’s really important to understand how these things happen and what we can do to safeguard this unique biological phenomenon.”

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Continue reading: A Famed Dolphin-Human Fishing Partnership Is in Danger of Disappearing

Rachel Nuwer is a freelance science journalist and author who regularly contributes to Scientific American, the New York Times and National Geographic, among other publications. Follow Nuwer on Twitter @RachelNuwer Credit: Nick Higgins