In this study, published this month in Current Biology, marine researchers reveal evidence of the widespread creation and utilization of grooming tools among the killer whale (Orcinus orca ater) population. I reside in the Salish Sea, part of the Pacific Ocean between British Columbia and Washington.

“We discovered that southern resident killer whales frequently utilize bull kelp during social interactions, seemingly as a tool for mutual grooming.”

“It was incredibly thrilling to observe not only the tool-making behavior of whales, but also the application of these objects in manners not previously documented in marine mammals.”

Dr. Weiss and his team identified this surprising behavior while conducting aerial observations of the southern resident killer whales, a population dwindling to fewer than 80 individuals in the Pacific Northwest.

Since 2018, they have been monitoring these whales to gain insights into their foraging and social habits.

“While other killer whale populations exist across the globe, the southern residents hold unique genetic, ecological, and cultural distinctions,” Dr. Weiss explained.

Using high-resolution video captured from aircraft, researchers discovered that the whales fashioned tools by breaking the edges of the kelp’s stems.

Subsequently, they applied the pieces of kelp to their companions and rolled it between their bodies for extended durations.

This behavior was noted among whales from all social groups, irrespective of gender or age.

They observed that whales were more inclined to groom closely-related companions or older partners.

Furthermore, there was some evidence suggesting that whales with more molting or damaged skin were more likely to engage in grooming, indicating potential hygienic benefits.

“What stands out is that despite this evidently common activity, it has only recently come to light, with drones frequently monitoring these whales for nearly 50 years,” said Dr. Weiss.

“This exemplifies not only the strength of new observational methods but also the many aspects of these creatures we have yet to uncover.”

“Although the whale population has been formally studied for five decades, it continues to yield significant new discoveries,” noted Rachel John, a student at the University of Exeter.

“Previous aerial footage lacked the quality needed to recognize ‘Allokelping’ (i.e., using kelp on another whale), but the recent video captures this behavior in remarkable detail.”

It is still uncertain whether this grooming behavior is exclusive to this population or if it is more commonly observed among other whale communities and species.

Regardless, this finding opens new pathways for understanding tool use in marine mammals and highlights the broader implications of such behaviors.

“We know tactile interactions are crucial,” remarked Professor Darren Croft, a researcher at the University of Exeter and the executive director of the Whale Research Center.

“In primates, including humans, these interactions can alleviate stress and strengthen social bonds.”

“Killer whales frequently make contact with other group members — touching their own bodies and fins — but employing kelp in this manner may enhance these experiences.”

“This behavior might also be vital for skin health. Whales and dolphins utilize various strategies to shed dead skin, and this could serve as an additional adaptation for that purpose.”

“Brown algae like bull kelp may possess antibacterial and anti-inflammatory properties that could offer extra benefits to the whales.”

“We are currently conducting further research to validate these initial findings and to investigate the social and skin health advantages of this behavior.”

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Michael N. Weiss et al. 2025. Manufacturing and use of similar tools by wild killer whales. Current Biology 35 (12): R599-R600; doi: 10.1016/j.cub.2025.04.021