A NEW TOOL
Sponging may not be the only way that dolphins in Shark Bay are being innovative with props for foraging.
In 2007 researchers began to spot them regularly in the western gulf of the bay doing something odd with the massive shells of Australian trumpet snails, which are the world’s biggest gastropods.
“We had no idea what was going on,” says Dr Simon Allen, a dolphin biologist at the University of Western Australia (UWA) in Perth, who works alongside Richard Connor (now Professor of Biology at the University of Massachusetts) as part of the Shark Bay Dolphin Research Alliance project. “A dolphin just appeared with a massive trumpet shell and was shaking it about. We wondered if it was playing or showing off to its mates. But then later that day, we looked at the photos and saw water falling out and then a fish, and realised this had the potential to be another very clever technique for obtaining food.”
In the past decade, Simon and his colleagues have since observed ‘shelling’ (see below) 30–35 times. It may be that the dolphins unintentionally chase fish into shells on the sea floor and have learnt to get the fish out by carrying the shells to the surface and draining them of water. A more exciting possibility is that they are intentionally chasing fish into shells and using them like traps, Janet says, as human hunters do. If that turns out to be the case, it will definitively count as an advanced form of tool use.