Orcas Use Kelp as Grooming 'Tools,' Scientists Say

Researchers have observed a group of killer whales in the North Pacific using kelp to groom each other, a behavior reminiscent of tool use by primates.

The orcas cut pieces of bull kelp and place them between their bodies to rub against each other. Scientists believe this behavior, called allokelping, helps remove dead skin or parasites and strengthens social bonds.

This behavior was observed in the Salish Sea, on the US-Canada border, in a group of 73 whales that has been studied for decades. Michael Weiss, head of the research, said they initially thought it was an isolated behavior, but later found it to be widespread throughout the group.

The orcas participating in allokelping were usually related or of similar age, and several had visible skin peeling. Researchers believe that the use of kelp enhances contact and reduces stress, as it does in other social species.

The discovery was made using drones with high-definition cameras. Monika Wieland Shields, director of the Orca Behavior Institute, said the findings are impressive.

The future of this group of orcas is uncertain, as they do not interbreed with other populations and depend on Chinook salmon, whose populations have declined. In addition, bull kelp is threatened by ocean warming.