Dolphins Learn How To Trap Fish Inside Shells From Their Peers

Dolphins can use shells to trap fish, but how do they learn this behavior? Sonja Wild - Dolphin Innovation Project

Rachael Funnell 25 Jun 2020, 16:00

A new study published in the journal Current Biology reveals how dolphins learn new foraging behaviors from their peers. The research focused on “shelling” and was the first to discover that dolphins don’t just learn such foraging techniques from their mothers but also from other dolphins in the pod.

"Our study shows that the foraging behavior 'shelling' – where dolphins trap fish inside empty seashells – spreads through social learning among close associates," said Sonja Wild in a statement, who conducted the research for her doctorate at the University of Leeds. "This is surprising, as dolphins and other toothed whales tend to follow a 'do-as-mother-does' strategy for learning foraging behavior."

Shelling is one of two examples of tool use ever to be witnessed in dolphins, the other being a group of dolphins in Shark Bay, Western Australia, who use marine sponges when trying to catch prey. They discovered shelling while carrying out boat surveys in Shark Bay and of the 5,300 encounters they recorded between 2007 and 2018, 42 of them involved shelling.

"During shelling, dolphins chase their prey – usually a fish – into empty shells of giant gastropods, insert their beak into the shell, bring it to the water surface and then shake it about to drain the water out of the shell, so that the fish falls into their open mouth," Wild explained

They identified 19 individuals carrying out the foraging behavior but hypothesize there are likely many more practicing the technique, which would be easy for observers to miss given how quickly it’s over. But how had the dolphins learned this technique? To find out, the researchers carried out a social network analysis and concluded that the shelling behavior had spread primarily through social groups rather than generations, showing dolphins were learning from their peers, not just their mothers.

"The fact that shelling is socially transmitted among associates, rather than between mother and offspring, highlights the similarities between cetaceans [the group including dolphins, whales, and porpoises] and great apes in the way cultural behaviors are passed on," said Michael Krützen, University of Zurich, who initiated the study.

"Indeed, despite having divergent evolutionary histories and occupying different environments, there are striking similarities between cetaceans and great apes: both are long-lived, large-brained mammals with high capacities for innovation and cultural transmission of behaviors.”

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