Australia (Bernd F. Laeschke – October 2012): A group of female dolphins has been learning from their mothers to use sponges to help catch fish for at least 180 years, a University of New South Wales (UNSW) study has found. Dolphins in Shark Bay, Western Australia, were first sighted in 1984 carrying sponges on their snouts. It’s believed the sponge helps protect their sensitive noses as they forage along the rocky sea bed, dislodging fish and crustaceans.
Almost forty species of dolphin in 17 genera are found in oceans around the globe, mostly in the shallower waters of the continental shelves. They are one of Earth's most intelligent animals: Dolphins are social, living in pods of up to a dozen individuals, but sometimes exceeding 1,000 animals. Their diet consists mainly of fish and squid.
For decades it’s been a mystery why only about five per cent of dolphins in Shark Bay use sponges to forage, and why the behavior hasn’t spread into other dolphin populations or disappeared. Dr. Anna Kopps from the UNSW Evolution and Ecology Research Centre spent four years studying the dolphins of Shark Bay observing this unusual behavior. Interestingly, she says the cultural behavior seems to be passed down only along maternal lines – from mother dolphin to daughter dolphin. Male dolphins generally don’t do it, preferring to socialize in packs to hunt for fish.
“What they do is unique among dolphins,” Kopps said. “It appears that this technique of using a sponge has been passed on from mother to daughter dolphin for around eight generations. “We were interested in how long it has been passed on because it is rare for an animal species to pass learned tool use behavior through several generations.”
She used computer modeling of behavior and genetics to estimate how long the sponging behavior has been going on in Shark Bay. The study concludes that sponging among dolphins could have stemmed from one female dolphin that started doing it at least 180 years ago and passed the foraging technique down through her female descendants.