Orcas use kelp to groom each other, US researchers discover

Southern resident killer whales in the Salish Sea have been observed using detached pieces of seaweed to rub against each other, the first recorded instance of tool-making by marine mammals. This behavior, called "allokelping," may strengthen social bonds and contribute to skin health among the whales.

Researchers from the Center for Whale Research (CWR) and the University of Exeter documented the behavior using drone footage. Whales were seen biting off kelp stalks, positioning them between themselves and a partner, and rolling the kelp between their bodies for extended periods.

What they're saying:

"We were amazed when we first noticed this behavior," said Dr. Michael Weiss, CWR research director. He noted that bull kelp is "firm but flexible, like a filled garden hose, with a slippery outer surface," making it an ideal grooming tool.

Unlike general "kelping," moving kelp for play or to remove parasites, allokelping involves the deliberate creation and cooperative manipulation of a tool by two whales. Dr. Weiss highlighted that the behavior is widespread among all ages and pods of southern resident killer whales, suggesting it's an important part of their social lives.

Professor Darren Croft, of the University of Exeter and CWR's executive director, explained the significance of touch in animals, including humans, for moderating stress and building relationships. He suggested that using kelp could enhance this tactile experience and also benefit skin health.

Brown algaes like bull kelp also have antibacterial and anti-inflammatory properties that may offer additional benefits.

By the numbers:

As of CWR’s last census in July 2024, only 73 southern resident killer whales remain. Their numbers are critically low due to declining Chinook salmon populations (their primary food source), pollution, and noise from human activities.

Bull kelp forests, where the whales source their tools, are also declining due to rising ocean temperatures.

Big picture view:

Dr. Weiss expressed concern for the population's future.

"Under the status quo, all of our projections indicate the population will continue to decline," Dr. Weiss said. He emphasized that losing these whales means losing "a complex society and a deep, unique set of cultural traditions."

Professor Croft added that protecting kelp forests may be crucial for preserving this unique culture.

The study, titled "Wild killer whales manufacture and use allogrooming tools," was published in the journal Current Biology.

The Source: Information in this story came from the Center for Whale Research.

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