On the coast of the municipality of Laguna in southwestern Brazil, a curious collaboration has been going on for at least a hundred years: predators of two different species cooperate and synchronize. The goal of this strategy is for humans and bottlenose dolphins to collectively capture greater prey than either would achieve on their own. And they succeed, according to a study that analyzed this behavior. In the inland lake that forms along Brazil’s Atlantic coast, the region’s artisanal fishermen know that when wild dolphins dive into the water after making their signature clicks, they must cast their nets at an interval of no more than 20 seconds . This aquatic “grazing” fulfills a classic objective of military strategy: when the school of fish splits to escape the threat, they fall into each other’s clutches and vice versa.
“The school of fish that coordinates and moves in a group is impassable,” explains lead author of a new study, Mauricio Cantor, of the University of Oregon in the United States. With practice, this “co-learning,” as the biologist calls it, has allowed both groups to understand that the catch will be larger if the dolphins drive the fish onto the beach and the fishermen cast their nets practically together, both predators . It’s a balance between local fishermen and a pod of 50-60 dolphins that has remained constant for at least 100 years. Work to document it has taken nearly two decades and features the details of the phenomenon today in PNAS Magazine.
Two fishermen follow the behavior of a dolphin in Laguna.Damien Farine
Scientists have observed that “dolphins dive longer and change their behavior” when foraging with fishermen. And most importantly, dolphins that cooperate with humans increase their chance of survival by 13%, “a sign of long-term benefit” because they reduce the risk of accidentally dying in the nets of large ships when they go out to sea for food, “The older ones Fishermen give them names, they can recognize them, and the staff think they’re the good dolphins,” jokes the researcher.
Cantor highlights the synchronization dynamics between both species when hunting. From an evolutionary point of view, these cooperative practices are “a rare phenomenon,” explains the ecologist, who is also a biologist. Another case of cooperation between humans and birds is known for extracting honey in Africa, which will be his next field of work. Because it is such a rare phenomenon, the authors devote the final section of their publication to presenting possible conservation scenarios in which traditional fishing practices can continue, with a stable dolphin population in balance with their environment.
Dolphins dive longer and change their behavior, cooperative ones survive longer, a long-term benefit
Mauricio Cantor, researcher at the University of Oregon
This collaboration between species has prompted the research team to develop an entire multiplatform system to record what is happening on the sea shore. The study measures the phenomenon on land, sea and in the air: drone images from the air, scientists on the ground taking data, underwater headphones to detect the echolocation clicks of dolphins and the sound of submerging nets. The goal: to record in detail how both species learned to coexist and interact for the same price without destroying each other.
Cultural transmission between dolphins, according to Adrián González, director of marine mammal care at Oceanogràfic de Valencia, who did not take part in this research, is what sets the study apart because it is so well documented. “There is learning from parents to children, which means that the culture brings long-term benefits for the dolphins,” explains the specialist, emphasizing: “The work shows that the specimens that eat the most survive, in this case fish, and less energy wastage it presupposes”. Regarding conservation in the region, researcher González suggests that since Brazil is not a very whaling country, the local population of the lagoon probably has a lot to do with the peaceful coordination between two predatory species, facilitating smoother cooperation with the dolphins.
José Zamorano-Abramson of the Evolutionary Psychobiology Group at Complutense University believes that the “synchronized collaboration strategy” is the “great contribution of the work” as “it shows synchronicity between different species to achieve an external goal “. . The professor, who did not take part in this study, reports that there have been reports of fishermen using the help of whales to catch fish on the Mediterranean coast since the time of the naturalist Pliny the Elder more than 2,000 years ago. The researcher points out that today there are also encounters between humans and bottlenose dolphins in Australia and India, as in Brazil Researcher, psychologist who defines it as cooperative hunting.
Professor Zamorano-Abramson calls the new study one of the “few examples” measuring “social learning over time between species, a shared culture”. For this reason, the researcher, in agreement with the authors, emphasizes the importance of keeping this practice alive for the benefit of all.
The principal investigator admits to having a “bittersweet feeling” in his experience studying the final stages of a unique collaboration in history that is likely doomed to extinction because of the threat of intense fishing catching the dolphins that kill the Lagoon leaving towards the open sea Atlantic. That’s why Cantor emphasizes that exploring the area requires “securing one of the last instances of human-wildlife collaboration.”
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