Off the southern Brazilian coast, dolphins actively influence their behavior to cooperate with fishermen in catching fish. This is reported by the Max Planck Institute for Behavioral Biology in Konstanz, Germany, which was involved in a similar study. Not only humans, but also marine mammals benefit from communal hunting.
However, the fishing tradition that has existed for more than a century is under threat, on the one hand due to the decline of animals, but also due to the declining interest in sustainable fishing. Dolphins – so-called bottlenose dolphins – still float swarms of mullet off the Brazilian coast of the city of Laguna. This increases the number of fish in the water for a short time and signals the fishermen standing in the water where to cast their nets. The researchers have now been able to demonstrate that the dolphins actively direct this behaviour.
Observed fishermen and dolphins for 15 years
“Fishermen were known to observe the behavior of dolphins to determine when to cast their nets,” explained Fabio Daura-Jorge, a researcher at the University of Santa Catarina, Brazil. “But we didn’t know that the dolphins are actively coordinating their behavior with the fishermen.”
For the study, researchers from Brazil and their colleagues at the Max Planck Institute observed the behavior of fishermen and dolphins for about 15 years. They also used drones and underwater photography to gain new insights into the hunting behavior of dolphins and humans.
Animals and people benefit from the hunting tradition
Both dolphins and humans benefit from this hunting tradition, which has existed for some 140 years. The researchers found that the dolphins benefit from a 13 percent higher survival rate compared to their solitary hunting counterparts. The fishermen, in turn, catch about four times more fish than without the marine mammals.
The researchers emphasized that the dolphins’ cooperative behavior is not genetically determined. It is rather a peculiarity of the dolphin population in Laguna. Both marine mammals and humans would pass on their knowledge to future generations.
Researcher: Collaboration is at risk
However, model calculations show that cooperation between dolphins and humans is under threat. The number of fish in the region has declined sharply in recent years. The coastal population is also less interested in learning the special hunting technique.
“Our calculations show that if current developments continue, the cooperation could become uninteresting for the dolphins or the fishermen,” explains Daura-Jorge. To preserve them, it is necessary to better understand the reasons for the decline of mullets and to promote sustainable fishing.
Source: Krone
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