Dolphins Shown to Pass Down Skill

Dolphin mothers off Shark Bay in Western Australia teach their daughters how to slip sea sponges on their snouts to protect themselves while foraging for food -- strong evidence, researchers say, of a transmitted cultural element among marine mammals.

The researchers spent 14 years watching the dolphin group and observed mothers showing their daughters how to flip the conical sea sponges onto their snouts and use them to avoid getting stung by stonefish and other threats as they probe the sea floor.

Team leader Michael Kreutzen of the University of Zurich in Switzerland said a genetic analysis of tissue samples from 185 dolphins, 13 of them “spongers,” showed that it was highly unlikely that sponging was a heritable trait.

On land, chimpanzees and orangutans have been known to use tools such as sticks and stone hammers to gather food.

Dolphins have been seen coaxing moray eels out of crevices by using the spines of scorpion fish that they had killed to prod the eels into the right position.

The sponging in Shark Bay appears to be a novel twist on animal tool use in that the skill is taught almost exclusively by mothers to daughters, the researchers reported in the current issue of the Proceedings of the National Academy of Sciences.

But the study found that only some female dolphins taught their daughters to sponge.

Kreutzen is now studying whether dolphins that sponge have a higher survival rate.