The practice of mutual grooming with an implement is not exclusive to monkeys. In the Salish Sea, which lies between British Columbia and the state of Washington, resident southern orcas (Orcinus orca ater) have been observed using kelp as a grooming tool. A study published in Current Biology in June 2025 describes how this population of orcas fabricates and uses these tools for grooming. This behavior, called alkelping, involves breaking off sections of bull kelp (Nereocystis luetkeana) and using them to rub against each other. This is the first known case of cetaceans—marine mammals such as whales and dolphins—using tools for personal hygiene. The process of allokelping is consistent and involves two orcas working together. One breaks off a piece of kelp and places it between themselves and their partner, then both roll the kelp along their bodies. This can take place for extended periods and is observed frequently among all social groups, both males and females, and across all age groups. Researchers from the Center for Whale Research, who have been monitoring this population for nearly 50 years, only recently discovered the behavior due to the limitations of earlier video technology. Drone footage collected since 2018 finally captured the detail needed to recognize the grooming behavior. Michael Weiss, research director at the Center for Whale Research, notes that the choice of bull kelp is significant. He describes the kelp as firm yet flexible, similar to a garden hose filled with water, and with a smooth outer surface. These characteristics make it an effective grooming tool, much like a back brush that works underwater. Rachel John, a co-author of the study from the University of Exeter, highlights the importance of the discovery, showing that even well-studied animals can still hold surprises. The study was conducted by Weiss and Darren Croft from the University of Exeter. While the use of tools is common among land animals, it is rare in marine species. Among cetaceans, previous examples of tool use were mainly related to feeding. This study marks the first known case of tool fabrication and use for grooming. However, the researchers acknowledge that other marine animals, such as sea otters, also use tools. The uniqueness of allokelping lies in the fact that the orcas both modify the tool and use it mutually. The exact purpose of the behavior is still unknown, with hypotheses ranging from skin maintenance to social bonding. The kelp itself has antibacterial and anti-inflammatory properties, which could contribute to the benefits of the behavior. Researchers are currently working to confirm these initial findings and explore the social and health impacts of allokelping. The future of this behavior, however, is uncertain. The bull kelp that orcas use is declining in the region due to rising temperatures, which could threaten the persistence of allokelping. The resident southern orca population, already critically endangered with fewer than 80 individuals, faces a "very bleak" outlook, according to Weiss, due to insufficient birth rates. The researchers suggest that allokelping may be a cultural behavior unique to this orca population and emphasize the importance of cultural continuity in conservation efforts. They also note that similar conservation measures are already in place for the rubbing behavior of resident northern orcas on beaches, and allokelping could justify similar actions to protect this newly discovered tradition.