The people of Laguna proudly refer to this southern Brazilian city as the “capital of the dolphin colony.” For at least 140 years, artisanal fishermen and bottlenose dolphins have worked together to catch mullet in the lagoon. The spectacle of flying nets and dolphins diving into murky water has become a popular tourist attraction and has been recognized as an intangible cultural heritage by local authorities.
Before 1998, were humans and cetaceans really cooperating, or were they just appearing to be doing so, or were some species benefiting and others not? , no one knew for sure. Scientists have confirmed that this famous example of human-wildlife cooperation helped at least one of the participants. This hypothesis was more difficult to test.
Now scientists have finally confirmed that these benefits are indeed mutual.An in-depth new study published in Proceedings of the National Academy of Sciences January 30th Dolphins that team up with fishermen gain more food and have shown a survival advantage compared to dolphins that hunt without a bipedal partner.
A resident population of up to 60 dolphins uses echolocation to locate pods of mullet that humans cannot otherwise detect under opaque water. The cetaceans then swarm and shoal toward fishermen standing in shallow water offshore. Dolphins give behavioral cues, such as a sudden deep dive, to let fishermen know when to cast their nets. Net casting benefits dolphins by breaking up schools of fast fish and making individual mullet easier to catch. Mauricio Cantor, author and behavioral ecologist at Oregon State University, says:
However, according to the findings reported in the paper, these famous interspecific hunts are in danger of extinction. “Our data show that this interaction is becoming rarer over time,” says Cantor. “If this continues, these interactions may disappear in the next 50 to 60 years.”
Laguna’s communal fishermen and dolphins are one of the few examples of a millennia-old tradition around the world. Fossil evidence from Europe indicates that he may have been 32,000 years old when humans and wolves cooperated to hunt prey. One of the first clear records of human-wildlife cooperation dates back to the first century AD. At this time, Pliny the Elder mentioned fishermen who deal with dolphins in modern-day southern France. Since then, he has documented cooperative interactions with people in at least 16 species of cetaceans and some birds in countries as diverse as Australia, Myanmar, Mauritania and Japan.
However, many of these collaborations have disappeared. And what remains is almost all declining due to pollution, overfishing and habitat loss, plus the general disconnection of humans from their natural environment. Most interactions tend to be adversarial and not mutually beneficial,” says Cantor. “It is therefore very important to understand how these things happen and what can be done to protect this unique biological phenomenon.”
Kanter and his colleagues used a variety of approaches to better understand the complexities of human-dolphin cooperation in Laguna. They collected data using drones, underwater microphones, sonar cameras, GPS, and interviews with fishermen. The study’s lead author, Fabio Daura Jorge of the Federal University of Santa Catarina, Brazil, also shared his 15 years of survey responses from fishermen and his 10 of dolphin behavioral records as well as photographs of both individual animals and groups. Brought to the table for over a year.
Putting all this data together, the researchers found that both dolphins and humans caught more fish when they teamed up. The fisherman found that he was 17 times more successful when working with dolphins than when he was alone, and dolphins were also more successful in these partnerships (researchers quantify dolphin benefits are working on). Dolphins who partnered with fishermen had a 13% higher survival rate compared to uncooperative dolphins. In nearby areas, some fishermen use illegal driftnets to drown dolphins as bycatch. “By avoiding these encounters, cooperative dolphins are more likely to survive,” says Canter.
These findings “support the long-held hypothesis that these dolphins have higher prey capture rates when interacting with fishermen,” said Jessica van der, a behavioral ecologist at the University of Cape Town in South Africa. Wal said. He was not involved in this research. “I applaud the authors for their comprehensive and creative angles to better understand the natural history of animals. [this] complex cooperation. “
The researchers also built models to simulate interactions between fishermen and dolphins and predict how they might change over time. A decline in cooperative hunting over the past 15 years has already been reported anecdotally by fishermen, and models predict this trend will continue in the future, suggesting that cooperation between humans and dolphins in Laguna may be extinct. are in danger of The authors found that the main causes of its decline were declining mullet populations caused by overfishing and climate change, and changes in livelihoods of artisanal fishing communities.
The authors suggest some solutions to avoid this expected loss. For example, fishermen may be encouraged to continue working with dolphins if catch buyers are willing to pay a premium for the fish. This, says Cantor, “will be more rewarding for fishermen financially, even if catches decline over time.”
Protecting dolphins from bycatch also helps. The government could invest in policing the area to remove illegal nets and arrest violators.
Raising awareness about human-wildlife cooperation is also an important piece of this conservation puzzle. “Getting people excited about these rare phenomena is a way to add more value to these kinds of cultural practices that seem to be disappearing,” says Kanter. Conservation has been shown to help maintain biodiversity as well.”
Stephanie King, a behavioral biologist at the University of Bristol in England, who was not involved in the study, agrees on the importance of preserving the few remaining examples of human-wildlife cooperation. “Humans are famous for the way they work together, but even more remarkable is that two distantly related species with vastly different evolutionary histories are working together to achieve a common goal,” she says. says.
“Exemplary” new research not only sheds light on how human-wildlife cooperation is coordinated and achieved, but also how it can be protected in the face of large-scale environmental protection. is also “very important,” continues King. A social challenge that affects both fishermen and dolphins. “
