Gotcha! (Image: Kathrin Bacher)

What do kerplunking, beaching, sponging and now conching have in common? They are all terms for the antics of dolphins in pursuit of a meal.

For many years researchers in Western Australia’s Shark Bay have noticed Indo-Pacific bottlenose dolphins hefting and shaking heavy conch shells out of the water for several minutes. What were they up to? Perhaps they were eating the mollusc inside, or using the conch as a toy or in socio-sexual display. Now a series of photographs have captured a dolphin manipulating a fish into its mouth from a conch.

Simon Allen, a behavioural ecologist at Murdoch University in Perth, Australia, was out on a routine survey when one of the dolphins surfaced “with a monstrous shell oriented skywards”. It shook the shell up and down, and left and right. After a few minutes it disappeared underwater and re-surfaced with five other dolphins encircling it. “This weird encounter we thought might be play or showing-off,” he told New Scientist. But that evening when they developed photos of the encounter, they spotted the dolphin slurping a fish from the shell.


The team speculates the dolphins may chase fish into the conch and then raise it above the surface, knocking the shell around to stun the fish before tipping it into their mouths. “That conching behaviour is really about foraging,” says Allen.

Conching dolphin

Michael Krűtzen, an evolutionary geneticist at the University of Zurich, Switzerland, notes that dolphins in Shark Bay employ many different foraging tactics, giving them access to prey others can’t reach. One of the conching dolphins, which they’ve called William the Concherer, has a different fatty acid profile than other dolphins suggesting these techniques give access to a novel food source.

However, Janet Mann, an ethologist at the University of Georgetown in Washington DC who has extensively studied the Shark Bay dolphins and witnessed conching herself, says the behaviour is so rare that it is hard to draw firm conclusions. “We still don’t know the full story with the conch,” she says.

Allen and his colleagues also suggest that conching is a rare behavioural trait. It appears to have cropped up in both East and West bay dolphins which don’t mix, suggesting that the dolphins have independently come up with this innovation rather than learned it from each other.

Foraging behaviours are often learned by daughters from their mothers, so it would be interesting to see whether conching is also passed on culturally, says Krűtzen.

Journal reference: Marine Mammal Science, DOI: 10.1111/j.1748-7692.2010.00409.x