Shelling out for dinner – dolphins learn foraging skills from peers

26 Jun 2020 | 3 mins

A new study by an international team of researchers including The University of Western Australia demonstrates for the first time that dolphins can learn foraging techniques outside the mother-calf bond – showing that they have a similar cultural nature to great apes.

The scientists have been studying the dolphins of Shark Bay, Western Australia, for more than 35 years and in the mid-1990s were able to record the first instances of an extraordinary new foraging technique called “shelling”.

Co-author Dr Simon Allen, Research Fellow in UWA’s School of Biological Sciences and Oceans Institute, 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,” Dr Allen 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.

From 5,278 dolphin group encounters they identified 1,035 different individuals. 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 – what researchers refer to as horizontal social transmission, that which can occur within generations.

These findings represent the first quantitative 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.

The study was led by Dr Sonja Wild, who conducted the research as a PhD candidate at the University of Leeds and is now a postdoctoral researcher based at the Centre for the Advanced Study of Collective Behaviour at the University of Konstanz in Germany.

Dr Wild said the results were quite surprising, as dolphins tended to be conservative, with calves following a ‘do-as-mother-does’ strategy for learning foraging behaviour.

“However, 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.

“For example, an unprecedented marine heatwave was responsible for wiping out Shark Bay’s critical seagrass habitat in 2011. There was a subsequent die-off of fish and invertebrates, including the gastropods that live in those giant shells.

“While we can only speculate as to whether this prey depletion gave the dolphins a boost to adopt new foraging behaviour from their associates, it seems quite possible that an abundance of dead giant gastropod shells may have increased learning opportunities for shelling behaviour.”

Media references

Dr Simon Allen (based at University of Bristol, UK)
Simone Hewett, UWA Media and PR Manager, 08 6488 3229 / 0432 637 716

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