KILLER WHALES CRAFT KELP TOOLS FOR SOCIAL GROOMING
In a remarkable discovery, researchers have documented wild Resident killer whale (Orcinus orca ater) manufacturing and using tools in a social context. Observed in the Salish Sea from April to July 2024, members of the endangered southern resident population were seen detaching short lengths of bull kelp (Nereocystis luetkeana) and using them during tactile interactions with a partner, a behavior the authors call allokelping. This behaviour differs from playful kelp draping commonly seen in cetaceans, whales in this study deliberately fashioned kelp segments using their teeth, positioned them between their bodies, and coordinated their movements to roll the kelp across one another’s skin.
This represents a potential case of tool-assisted allogrooming, a behaviour rarely documented in non-primates and never before in marine mammals. Statistical analyses suggest that allokelping may serve both hygienic and affiliative functions, being more common among close kin and individuals of similar age, and possibly linked to skin molting. The whales’ use of their entire bodies, rather than limbs, to manipulate the kelp, and the mutual benefit of the interaction, make this a unique form of tool use in the animal kingdom. If confirmed, it would expand our understanding of cetacean intelligence, culture, and the evolutionary roots of cooperation.
Photo: Orca grasps a bull kelp stalk by the holdfast end and detaches a short stipe segment for use in allokelping.
Reference (Open Access): Weiss et al., 2025. Manufacture and use of allogrooming tools by wild killer whales. Current Biology.
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