ARI SHAPIRO, HOST:
Wild dolphins forage for food in all kinds of creative ways. Now researchers have studied exactly how dolphins learn one unusual method for catching fish. And as NPR's Nell Greenfieldboyce reports, this is one trick that they don't learn from their mothers.
NELL GREENFIELDBOYCE, BYLINE: Young dolphins spend years with their mothers learning how to take care of themselves and find food.
SONJA WILD: Most of these foraging behaviors are learned and passed on from mother to offspring.
GREENFIELDBOYCE: Sonja Wild is a researcher at the University of Konstanz in Germany. She's studied dolphins at Shark Bay in Western Australia. Their scientists have spent decades following over a thousand individual dolphins. Some of these dolphins search for food with the help of tools like sponges.
WILD: Dolphins wear these conically shaped sponges on their beaks as kind of a protective glove from when they go dig into sand for buried prey.
GREENFIELDBOYCE: Previous work has revealed that dolphins will only use sponges in this way if their mothers do it. It looks like at some point, one female dolphin figured out this strategy. Since then, it's been passed down from mother to child. But recently, Wild and her colleagues got interested in another food-finding technique. This one involves the use of shells, big empty shells left behind by sea snails. Wild says a dolphin will chase a fish into one of these shells.
WILD: And then they insert their beak into the shell, bring the whole thing up to the surface and then shake up above the water surface to drain the water out of the shell until the fish basically falls into their open mouth.
GREENFIELDBOYCE: This method became a lot more popular with the dolphins about a decade ago. That's when a heat wave killed off a lot of sea snails and left a lot of empty shells lying around.
WILD: It's a very remarkable behavior also given the fact that dolphins need to do this with their beaks. They don't have any hands to use, so seeing it is really mind-blowing.
GREENFIELDBOYCE: Wild and her co-workers tracked how this behavior spread through the dolphin population, who was doing it first and who followed over time.
WILD: And we figured out that the shelling behavior doesn't spread between mother and offspring but spreads between peers. So basically, dolphins that spend a lot of time with shelling individuals are more likely to learn that behavior themselves.
GREENFIELDBOYCE: These findings appear in the journal Current Biology. Diana Reiss is a dolphin researcher at Hunter College in New York who wasn't part of the research team. She says this discovery is exciting because of what it tells us about social learning among wild dolphins.
DIANA REISS: When they're out there, they seem to be observing others, watching what they're doing and acquiring it from others in their social group.
GREENFIELDBOYCE: This is similar to what humans and great apes can do, and it could help dolphins survive in a changing environment. Wild points out that a mother-knows-best approach can make a lot of sense when conditions are stable.
WILD: Because the knowledge of those previous generations is tested and stable and adapted to the current environmental conditions.
GREENFIELDBOYCE: But when those conditions become unstable, there's real advantages to being able to follow a pal who's come up with a bright new idea.
Nell Greenfieldboyce, NPR News.
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