Southeast Brazil’s native fishermen wait patiently with their nets in hand as their cetacean friends move the fish towards the beach. They know when to cast their nets based on the dolphins’ cues, which are typically deep dives.
Over the course of more than a century, this fishing relationship has been passed down through the generations. Researchers were able to demonstrate that humans benefited from this coupling, but they were unable to confirm whether dolphins did as well.
According to a recent study that was published in Proceedings of the National Academy of Sciences, cetaceans that hunt alongside people have higher survival rates than those who don’t.
“We found that when wild dolphins and artisanal net-casting fishers work together in synchronizing their fishing effort, both species increase their hunting success. This rare case of human-wildlife cooperation also provides survival benefits for the dolphins and socioeconomic benefits for the humble fishing community,” Mauricio Cantor, a biologist at Oregon State University and an author of the paper, told the Daily News Egypt.
He added: “This is a cultural practice that has been around in that area for over a century but is now in decline.”
If environmental and behavioural changes continue to happen, the researchers’ best models and best data suggest that one of the last cases of human-wildlife cooperation can flip into another human-wildlife conflict and be extinct in the next decades.
The authors used three approaches to reach the findings. With a multi-platform tracking system, combining drones, sonar cameras, videos, acoustics and photography, they tracked the interactions of dolphins and fishers above and underwater simultaneously. These data revealed the fine-scale mechanics of their cooperation.
“Then we used long-term boat-based surveys and interviews to monitor the population and social dynamics of dolphins and fishers, respectively. These data revealed how both of them gain long-term benefits with this cultural fishing practice.”
In the end, the team used empirical insights to build numerical models that predict the fate of the cultural practice in face of various scenarios of cultural and environmental change.
Cantor explained that this study is the first to show how human-dolphin cooperation works, what each species gain from interacting and the positive impacts this practice can have on the population dynamics of humans and wild animals.