This two-year old female’s grandmother was the first dolphin in Shark Bay to start carrying a sponge for foraging (Image: Janet Mann)

Dolphins in Australia have been observed using tools, and they seem to pass on their specialist knowledge to others. This is the first time cultural transmission has been confirmed in a marine mammal.

Lacking hands, dolphins are limited in what they can do with a tool, but some bottlenose dolphins in Shark Bay, Western Australia, have devised a way to break marine sponges off the seafloor and wear them over their snouts when foraging.

“We believe that they use sponges as a kind of glove to protect their sensitive rostrums when they probe for prey in the substrate,” says Michael Krützen, formerly of the University of New South Wales in Sydney, Australia, and now at the University of Zurich, Switzerland.


Most sponges are flat, but tool-using dolphins select conical ones that will not fall off their snouts. The majority of dolphin “spongers” are females.

To discover whether tool-use is a genetic trait, or one transmitted culturally, Krützen and colleagues analysed DNA from 13 of 15 spongers, only one of which was male, and 172 non-spongers. They found that most spongers were maternally related – sharing the same mitochondrial DNA, which is only transmitted through the female line.

Learning to sponge

A comparison of their nuclear DNA showed that the spongers were closely related, suggesting that spongers are descendants of a recent “Sponging Eve”. However, the pattern of sponging among the dolphins could not be explained by a “gene for sponging” – the trait’s pattern of inheritance just did not fit.

The researchers conclude that the behaviour is culturally transmitted, presumably by mothers teaching the skills to their sons and daughters, although they have not actually observed this feat in action.

Dolphins are well known for their exceptional learning abilities in captivity, and the songs of whales have been shown to be culturally influenced. This is the first example of tool use being passed on culturally in a marine mammal, an ability so far only seen in primates and perhaps some birds.

Krützen also has an idea about why males do not like using sponges. “Males are more interested in forming alliances with other males than sponging,” he says. “They have a different social life than females, and this might restrict them to invest too much time in sponging, which is quite a solitary activity.”

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0500232102)