Western Australia bottlenose dolphins (Tursiops truncates) appear to be the most inventive when it comes to how they catch their food.
Unlike some animals that have similar foraging techniques within the same population, bottlenose dolphins of Shark Bay use a wide range of foraging techniques to catch their prey.
Murdoch University Cetacean Research Unit and the University of Zurich have discovered another technique that reflects the innovative nature of the population.
‘Conching’ or shelling is the method where a dolphin picks up a conch shell (Strombidae) that has a fish inside, brings it to the surface and shakes it until it’s free of water—until the fish falls out into the dolphin’s mouth.
Cetacean Unit Research Fellow Simon Allen says the fact that so many foraging specialisations are being recorded within one population shows how inventive Shark Bay bottlenose dolphins are.
“It’s a dense population and you need to be very cluey to work out how you can best exploit your environment to get enough food,” Mr Allen says.
Mr Allen says it’s unknown whether the dolphin purposefully overturns empty conch shells so that fish are more likely to hide in them.
“Obviously the shaking about of the shell and the manipulation of the object implies some degree of problem solving,” Mr Allen says.
“The dolphin has worked out it has to lift the shell up and shake it about so the water comes out and the fish falls into its mouth.”
Other foraging techniques of Shark Bay bottlenose dolphins include ‘kerplunking,’ where dolphins scare fish out of vegetative cover with a loud bubbly tail slap in shallow waters and ‘sponging,’ where marine sponges are used as protective shields over their rostra when foraging the sea floor.
The sponging technique is especially unique because it is passed down from generation to generation and only used by the same matriline of dolphins.
About 40 dolphins of the same matriline in Shark Bay’s eastern gulf and 60 of another matriline in the western gulf are known to use the sponging technique today.
The research team have sighted conching behaviour eight times over five years of study, with six of those sightings occurring this season.
Mr Allen believes conching could be catching on quickly and might be a learned behaviour that spreads horizontally through the population, as opposed to vertically as it does in the case of sponging.
Future research could involve filming dolphins underwater in order to find out how much planning is involved in conching.