Orcas scrub each other clean with bits of kelp

Drone footage has captured killer whales breaking off stalks of kelp and rubbing the pieces on other orcas, a rare case of tool use in marine animals

By Sofia Quaglia

23 June 2025

Groups of killer whales exhibit strong social behaviour

Shutterstock/Tory Kallman

Orcas off the west coast of North America are grooming each other with kelp, in a rare sighting of marine mammals manufacturing and using tools.

For several years, scientists have been keenly observing 80 endangered killer whales in the segment of the Pacific Ocean between British Columbia and Washington state. To get a bird’s eye view of the whales’ lives, the researchers also tracked them with drones.

Read more

Orcas have begun wearing salmon hats again – and we may soon know why

Advertisement

While poring over footage from summer 2024, they noticed that the orcas were manoeuvring strands of kelp in odd ways. It was “really weird”, says Rachel John at the Center for Whale Research in Washington state, “but the whales, they do weird things all the time”.

In the footage, the orcas can be spotted breaking off kelp stalks near where they meet the rock bed by grabbing them with their teeth and jerking their heads back and forth. The short, snapped-off segments were roughly equivalent in length to that of the whale’s beak-like face. Over and over again, the orcas appear to consistently target just that specific segment of the algae, not other random parts of kelp.

After breaking off a strand, a whale would then sandwich the kelp between their head and the bodies of other whales in the pod, rubbing and rolling it onto each other’s sides. They take turns cleaning each other with the kelp, sometimes grooming each other for up to 12 minutes.