Where humans and dolphins cooperate for mutual survival

Fishermen and dolphins in Brazil have a mutually beneficial partnership that spans the course of almost a century and a half

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Cooperation and competition are the two forces that determine outcomes throughout so much of nature. In general, when different animal species pursue the same food source, competition results. But, in the area of Laguna, Brazil, we find an exception to this rule.

For at least 140 years, fishermen and dolphins in the area have been cooperating with one another when fishing for mullet.

Now, researchers have been studying the interaction for a decade, and they published their results on January 30 in the article, Foraging synchrony drives resilience in human–dolphin mutualism. In the article, Mauricio Cantor, Damien Farine, and Fábio Gonçalves Daura-Jorge describe their use of drones and underwater photography in order to investigate the partnership.

The team reports that fishermen use dolphin sightings near shore to decide where and when to cast their nets, and that fishermen who followed the dolphins were 17 times as likely to catch fish as those who didn't. These fishermen also caught four times as much in their nets.

So, it's easy to see what the humans get from the partnership. The dolphins drive the fish into shore, and the fishermen get a bigger haul. It's less obvious, however, to see what the dolphins get from the relationship. Because the behavior persists, the scientists reasoned that the dolphins must benefit from it, and they set about determining how.

It turns out that when the fisherman cast their nets, the dolphins increase their echolocation and dive for longer. This led the researchers to conclude that something about the nets in the water disrupts the school of mullet in a way that makes it easier for the dolphins to catch strays. Additionally, the dolphins often snatch the mullet straight out of the fishermen's nets.

The team concluded that dolphins who engage in this cooperative fishing activity are 13 times more likely to survive than the ones that don't.

Here's a YouTube Video that describes the research.

I've actually seen something similar to this, first hand, when fishing for blue fish as a teenager at the New Jersey shore. We used to watch the seagulls. When there was a "run of blue fish", the school of blue fish would drive the anchovies to the surface of the water, causing them to leap out of the water. That, in turn, would attract the seagulls. When the fishermen saw the seagulls flocking and hitting the water, we would grab our rods and start running towards the spot. But, in that case, it's not clear whether the gulls benefitted in any way by signaling the humans to come running. It seemed to be more of a 1-way relationship. Perhaps there was a similar sort of mutualism going on in the pincher between the blue fish and the seagulls, however?

Humans do have a long history of cooperating with animal species like dogs and cats through domestication, but cooperation with wild species is less common. In addition to these Brazilian fisherman, human whalers teamed up with Killer Whales in 19^th and 20^th century Australia, and there are also stories of human/dolphin cooperation from Aboriginal Australians.

While the humans and the dolphins derive economic and survival benefits from this cooperative activity, I'm not so sure whether the mullet are very happy about the partnership. ;-)

For more information, see:

• An Incredible Thing Happens When Dolphins And Humans Team Up
• Dolphins and humans team up to catch fish in Brazil
• Dolphins and Humans Work Together to Catch Fish in Brazil
• When wild dolphins help humans fish, both benefit

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Thank you for your time and attention.

As a general rule, I up-vote comments that demonstrate "proof of reading".

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Steve Palmer is an IT professional with three decades of professional experience in data communications and information systems. He holds a bachelor's degree in mathematics, a master's degree in computer science, and a master's degree in information systems and technology management. He has been awarded 3 US patents.

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^{Pixabay license, source}

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