Were sea otters using tools long before dolphins?

A new report suggests that sea otters in the Pacific north-west may have been using tools to unlock their prey from shells long before dolphins in other parts of the world learnt such skills.

Sea otters in some populations will sometimes be seen floating on their backs and using use rocks and other hard objects to open the shells of food such as marine snails where they form part of their diet. Indo-pacific dolphins in locations such as Shark Bay in western Australia have been recorded putting sponges on their snouts as they hunt for fish under the sand to avoid injury from hidden rocks or coral pieces.

A long-term study looking at the genes of otters off the coast of California revealed that otters in all three sub-species had the ability to use tools open the shells. Even young and orphaned otters appeared to have this skill without having learnt it, when presented with this food type. The researcher’s findings suggest that the behaviour may therefore go back many generations, possibly thousands or even millions of years. 

In comparison, the dolphin’s use of sponges was confined to more closely-related individuals within a population, and perhaps goes back just a few hundred years.

Mitogenomes and relatedness do not predict frequency of tool-use by sea otters
Katherine Ralls, Nancy Rotzel McInerney, Roderick B. Gagne, Holly B. Ernest, M. Tim Tinker, Jessica Fujii, Jesus Maldonado