Scientists have documented southern resident killer whales using tools fashioned from kelp to groom one another—a behavior never before observed in marine mammals. The study, published recently in the journal Current Biology, reveals that these orcas are not only using kelp but are actually manufacturing grooming tools from it.
Michael Weiss, research director at the Center for Whale Research in Friday Harbor, Washington, led the team that made the discovery. "We found that southern resident killer whales regularly use lengths of bull kelp (Nereocystis luetkeana) during social interactions, apparently as a tool to groom one another," Weiss said, according to Live Science. This behavior, termed allokelping, involves the whales tearing off pieces of bull kelp and rolling them between their bodies while swimming in pairs.
The researchers observed this behavior during aerial surveys conducted from April to July 2022, capturing high-resolution drone footage of the orcas in the Salish Sea, a body of water between British Columbia and Washington State. These southern resident killer whales, a critically endangered population of fewer than 80 individuals, are known for their complex social structures.
"We began using a new drone to observe the whales that allowed us to see the whales and their behavior in much greater detail," Weiss explained, according to Science Alert. "We began to see how individuals were systematically transporting pieces of kelp and rubbing them against each other." The team witnessed allokelping behavior on eight out of twelve days included in the study, observing this occurrence 30 times across different ages and pods.
"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," Weiss stated, according to Science Focus.
The researchers found that allokelping was more common between whales that were close in age or had higher maternal relatedness. This suggests that the behavior may play a role in reinforcing social bonds. "It certainly does appear to be a social activity, and might help reinforce social bonds like other forms of grooming," Weiss said. The behavior was observed across all social groups, both sexes, and all age classes, indicating its significance in the orcas' social life.
Beyond social bonding, the kelp-assisted grooming may have health benefits. The whales with greater coverage of dead, flaky skin were more likely to engage in kelp-related behaviors, suggesting that the kelp may help remove dead skin or alleviate discomfort from skin molting. "I suspect these properties make them an ideal grooming tool," the researchers wrote, as reported by The Independent. Bull kelp stalks are firm but flexible, similar to a filled garden hose with a smooth outer surface.
The southern resident killer whales are genetically, ecologically, and culturally distinct from other orca populations. They primarily feed on salmon and have behaviors not observed in other groups. "This finding highlights yet another way these whales' society and culture is unique and the importance of recovering the southern resident killer whale population," Weiss noted, according to a press realease published on EurekAlert.
The discovery underscores the importance of conservation efforts for these critically endangered whales. "If we lose those whales, it's not just 73 whales gone. It's a set of cultural traditions and a society that is unique. We might never see this behavior again," Weiss said. The use of kelp tools not only demonstrates their intelligence but also reveals the complexity of their social interactions.
The research team's use of drone technology was instrumental in making this observation. "We hadn't noticed allokelping before because the videos being collected from our previous aircraft weren't of high enough quality, but the footage we're getting now shows this behavior in great detail," said Rachel John, a co-author from the University of Exeter, according to Popular Science. This advancement in technology opens new pathways for understanding the behavior and culture of marine mammals.
As the southern resident killer whales face threats from declining salmon populations, habitat degradation, and pollution, studies like this provide insights into their lives. Preserving not only the whales but also the kelp forests they rely on could be vital for maintaining their behaviors. "Both the southern residents and the kelp they use for this behavior are in serious trouble. Preserving the whales and the materials they use to make tools is important if we want to keep this unique culture around," Weiss concluded.
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