Dolphins Are Amazing, Part 5,423: They Help These Fishermen Catch Fish

A small group of dolphins in Brazil have learned to steer fish into humans' nets, but no one knows why.

Let's cut to the chase here: although whales are majestic, dolphins are the best. I love that they work in teams and that they develop something like "culture," in which specific groups of dolphins behave idiosyncratically in ways that are intelligent.

Here's the latest case-in-point. Down in Brazil, a group of dolphins aid the local fishermen! This has been going on for generations, despite unclear benefits for the marine mammals. Researchers looked at the practice in a new paper in the journal Biology Letters entitled, "The structure of a bottlenose dolphin society is coupled to a unique foraging cooperation with artisanal fishermen."

For the record, this seems like the ultimate hipster foodie trump card: "My fish was caught by artisanal Brazilian fishermen with the help of a unique group of... intelligent dolphins." Here's how ScienceNow describes the situation:

Every autumn, lucky visitors to Laguna, Brazil, which is situated around a narrow lagoon on the Atlantic Ocean, catch an odd sight. Here, resident bottlenose dolphins (Tursiops truncatus) frequently turn sheepdog, herding schools of small, silver fish called mullets toward the shore--and, it turns out, toward lines of wading fishers. As soon as the dolphins get close to their human companions, they give the signal, slapping their heads or tails against the surf. In an instant, the fishers cast their nets, catching dozens of frenzied mullet.

Even more intriguingly, only a subgroup of the 50 or so dolphins have picked up the human habit. A third help out, while the rest steer clear of the people. Why do some dolphins help out? And why do others avoid the behavior?

To figure that out, the researchers spent two years watching the dolphins in the water, seeing which animals hung out together and for how long. They found that the animals that the social network of dolphins that help humans spends more time together and more tightly associated than the other animals. They still don't know why this is or how precisely younger dolphins figure out what to do, but the fact that there are identifiable characteristics to the human-helping social network is fascinating. In the graph below, the human helpers are the white circles.