Off the coast of Brazil, dolphins and humans have been working together to snare mullet since 1847. Ed Yong reports at Discover Magazine:
The dolphins drive the mullet towards the fishermen, who stand waist-deep in water holding nets. The humans cannot see the fish through the turbid water. They must wait for their accomplices.
As the fish approach, the dolphins signal to the humans by rolling at the surface, or slapping the water with their heads or tails. The nets are cast, and the mullet are snared. Some manage to escape, but in breaking formation, they are easy prey for the dolphins.
About half of the dolphins who chill out in this area are in on this scheme. And the dolphins who ally with humans hang out together, while the dolphins who think that’s totally lame have their own scene. The mullet just know that they are dead.