Orcas' seaweed 'backscratchers'

ORCAS make seaweed tools in order to scratch each other's backs, a study has suggested. The animals, also known as killer whales, were observed detaching lengths of seaweed and massaging each other with it.

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The orcas bite off the end of a kelp stalk, position it between themselves and a partner, and roll the kelp between their bodies for prolonged periods, researchers said.

The study was led by the Centre for Whale Research (CWR), in collaboration with the University of Exeter. The paper, published in the journal Current Biology, is entitled: Wild killer whales manufacture and use allogrooming tools. Scientists spotted the behaviour in drone footage of southern resident orcas in the Salish Sea, in the inland waters of the US state of Washington.