Researchers including from the University of Western Australia have been studying the dolphins of Shark Bay, Western Australia, for more than 35 years and in the mid-1990s recorded the first instances of a new foraging technique called "shelling".

Research fellow in UWA's School of Biological Sciences and Oceans Institute Dr Simon Allen said shelling was a tactic used by dolphins to target prey that hid inside large empty shells of giant sea snails found in Shark Bay.

"The dolphins chase the fish into these shells, then insert their beaks into the opening and lift the shells to the surface, shaking it all about until the trapped prey falls into their mouths," he said.

In a collaborative project led by the University of Zurich, the team conducted boat-based surveys in the western gulf of Shark Bay between 2007 and 2018 to quantify how shelling behaviour spread across the population.

A total of 42 shelling events were documented, performed by 19 individual dolphins.

Dr Allen said foraging techniques in Shark Bay were typically passed on from dolphin mothers to their offspring in what researchers refer to as vertical social transmission.

"This transmission between generations was considered the primary way in which young dolphins learned foraging methods," he said.

But the new study, published in the journal Current Biology, demonstrates that some of Shark Bay's dolphins have actually learned this foraging method outside the mother-calf bond.

It suggests that these dolphins observed their close associates shelling and then adopted the technique themselves, which researchers refer to as horizontal social transmission.

These findings represent the first evidence of horizontal transmission of a foraging tactic in toothed whales, providing further evidence of cultural similarities between dolphins and great apes.

Chimpanzees, gorillas and humans, have also demonstrated a broad range of socially learned foraging behaviour outside the mother-calf bond.

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University of Konstanz postdoctoral researcher Dr Sonja Wild said the results were quite surprising as dolphins tended to be conservative, with calves normally following a 'do-as-mother-does' strategy for learning foraging behaviour.

"Our results show that dolphins are definitely capable, and in the case of shelling, also motivated to learn new foraging tactics outside the mother-calf bond," she said.

"This opens the door to a new understanding of how dolphins may be able to behaviourally adapt to changing environments, as learning from one's peers allows for a rapid spread of novel behaviour across populations."