Dolphins off the coast of Western Australia are teaching each other how to use empty seashells to trap and eat fish, according to a new study published in the journal Current Biology. The technique, called “conching” or “shelling”, involves dolphins chasing hard-to-catch fish into an empty seashell and then ferrying the shell to the surface where the dolphin uses its beak to jostle the prey into its mouth.
Lead author of the study, Sonja Wild, a behavioral ecologist at the University of Konstanz and the Max Planck Institute of Animal Behavior in Germany, said, “seeing it for the first time was just a ‘wow’ moment because you do not expect a shell popping up right next to the boat that is being carried by a dolphin. You kind of, like, drop everything.”
The study documents how conching has spread through dolphin populations as the intelligent creatures teach each other how to do it. Scientists have observed instances of conching going back at least 10 years, though it has always been a rare sight.
Wild says there was a major uptick in sightings in Shark Bay, off the coast of Western Australia, after a 2011 marine heatwave killed off a large number of sea snails, leaving their shells ripe for the picking. Wild and her colleagues have been observing the Shark Bay dolphins for years, mapping their social and genetic relationships.
Between 2007 and 2018, they identified 1,000 individual dolphins and saw 19 of them engage in conching 42 times. While conching still appears to be quite rare, Wild says all the dolphins who do it know each other.
While analyzing their population data, the researchers found that conching spreads horizontally within dolphin generations, meaning from peer to peer, as opposed to vertically, from mother to calf. “That is indeed quite special because dolphins normally rely very much on their mothers for foraging behavior,” Wild said. “And we’re now showing for the first time that they are, indeed, capable of learning foraging behavior outside of the mother-calf bond.”
Janet Mann, a dolphin researcher at Georgetown University who wasn’t involved in the study, told the New York Times it’s impossible to say definitively that peer imitation is the only way dolphins learn about conching, noting we’ve “barely scratched the water’s surface” when it comes to understanding the behavior.
Wild agrees. “It is very much possible that some dolphins may have learned this by themselves, by just interacting with their shells and then by accident kind of lifting them above the surface,” she said. She says it’s possible, too, that some dolphins are passing the skill down to their young. But her team’s models “clearly show that the majority have learned from their peers.”