Wild dolphins assist fishermen in Brazil

In Laguna, Brazil there are about 200 local fisherman who make their living from catching the mullet fish which is a local source of food for the community. Nothing too unusual about that except for the fact that the fisherman get a little help from a group of about 20 bottlenose dolphins everytime they fish. These 20 dolphins are a part of a larger group of dolphins who do not assist the fisherman. Researchers are trying to find out what is the difference between the two groups. The "cooperative" dolphins tended to spend more time together, even when not assisting humans.

When assisting the fishermen these dolphins work together to herd groups of the mullet fish toward a line of fishermen in boats or knee-deep water. The dolphins then signal with specialized head or tail slaps when and where the fishermen should throw their nets. The cooperation is helpful to both parties, researchers said. The two wouldn't survive without each other. The effort is not entirely charitable on the part of the dolphins because the fish that escape the nets often swim right into the mouths of the dolphins.

Researcher Daura-Jorge has said "The fishermen have names for the cooperative dolphins — particular stars in this cooperation are 'Scooby' and 'Caroba,' that cooperate for more than 15 years."

Scientists have concluded that this cooperation seems to be a learned or inherited behavioral trait. It seems that the social interaction is what drives the foraging behavior of the dolphins to assist in the fishing. This cooperation behavior may be passed down from mother dolphin to her calves through social learning. This is exactly how the trait is passed on in the human half of the equation. The elders in the community teach the younger fishermen how to work with the dolphins.

Researcher Daura-Jorge and his team have tested out this idea by studying the genetics of the Laguna dolphins. It is possible that certain dolphins are inheriting their human teamwork skills, with teaching mothers reinforcing the behaviors. Their study of this will be published in the May 2 issue of the journal Biology Letters.

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The effort is not entirely charitable on the part of the dolphins. Fish that escape the nets often swim right into the mouths of the dolphins, which have learned to wait for that fulfilling moment.

Daura-Jorge and his team conducted boat surveys over a two-year period, collecting photo identification data and other information on the dolphins. Any that teamed up with humans for fishing was classified as "cooperative." The others were classified as "non-cooperative."

The researchers next used computer modeling to identify social relationships among the dolphins. "Cooperative" dolphins turned out to spend more time together, even when not assisting humans. They appeared to have their own social network within the larger local population of bottlenose dolphins.

The scientists suspect that "ecology, genetics and social learning" could be driving and maintaining the wild dolphin subset's unique relationship with humans. Interestingly, the phenomenon seems to mirror how the Brazilian fishermen learn their trade.

"The human side of this dolphin-fishermen interaction is maintained through inter-generational information transfer, that is, teaching by elders, and it is likely that a similar process is used to transmit complex behavioral traits between generations of dolphins, as found in other localized behaviors, such as 'sponging' in Shark Bay, Western Australia," they wrote. (Source)

WATCH VIDEO: Dolphins invent a new way to hunt fish.

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