Scientists reveal how killer whales groom each other

By Stephen Beech

Killer whales "groom" each other using tools made from seaweed, reveals new research.

The "incredibly exciting" discovery is a very rare example of tool use by marine species, say American scientists.

Birds, elephants and primates are all known to make tools, but examples of tool use among marine animals are much more limited.

Now a team of whale experts has discovered "widespread" tool manufacture and usage in an endangered population of resident killer whales living in the Salish Sea - part of the Pacific Ocean between British Columbia and Washington State.

Their findings, published in the journal Current Biology, show that whales fashion tools from kelp and use them for grooming purposes.

Dr. Michael Weiss, of the Centre for Whale Research in Friday Harbor, Washington, said: “We found that southern resident killer whales regularly use lengths of bull kelp during social interactions, apparently as a tool to groom one another.

“To find that the whales were not just using but also manufacturing tools, and that these objects were being used in a way never before reported in marine mammals, was incredibly exciting.”

Dr. Weiss and his team discovered the unexpected whale activity while conducting aerial observations of southern resident killer whales, which are a "critically" endangered population with fewer than 80 individuals left in the Pacific Northwest.

The researchers have been monitoring the whales since 2018 to learn more about their foraging and social behavior.

Dr. Weiss said: “While there are other killer whales around the world, the southern residents represent a genetically, ecologically, and culturally distinct population."

Through the high-resolution footage collected by their aircraft, the research team found that the whales created tools by breaking off the ends of bull kelp stalks.

They then pressed pieces of kelp against a partner and rolled the kelp between their bodies for long periods of time.

The research team spotted the behavior in whales across all social groups - both sexes, and all age classes.

They found that whales were more likely to groom closely related whales or similarly aged partners.

They also saw some evidence that whales with more mounting or dead skin were more likely to engage in grooming, suggesting it may have a hygienic function.

Dr. Weiss said: “What I find most remarkable is that despite this apparently being a common behavior - we see it most days we fly our drone over these whales - it hadn’t yet been discovered in this population despite nearly 50 years of dedicated observation.

“To me, this demonstrates not just the power of new observation methods but also how much we still have to learn about these animals.”

He said it is unclear whether the grooming behavior is entirely unique to that whale population or more widespread among other pods and species.

But he says the discovery opens new avenues for understanding tool use in marine mammals and shows that tools can be used in a range of contexts.

Dr. Weiss added: “This finding highlights yet another way these whales’ society and culture is unique and the importance of recovering the southern resident killer whale population."