How orcas make tools from seaweed to groom each other

Orcas often travel to great depths and great distances across the sea. When they cross paths with humans, it's a real stroke of luck . What is known about them is still limited. A new study in the journal Current Biology reveals another unexplored aspect of the largest of dolphins: they can make tools from seaweed for grooming. Another fact that strengthens our understanding of their intelligence and social complexity, hidden beneath the ocean's surface.

Michael Weiss, director of the Center for Whale Research in the United States, and his colleagues made this discovery while conducting drone observations of orcas belonging to a population of fewer than 80 individuals in the Salish Sea in the Pacific Northwest, between British Columbia (Canada) and Washington (USA). The research published this Monday indicates that orcas not only use tools, but also make them, and that these objects are used in a way never before recorded in marine mammals.

“These orcas manipulate and change the object in their environment rather than simply using an object in its current form,” Weiss said during a press conference last Thursday. Using high-resolution images captured by aircraft, researchers discovered that these robust, black-and-white-spotted whales created tools by breaking off the ends of kelp stems, a subgroup of large brown algae. They then pressed 60-cm pieces against a partner and rolled them between their bodies for extended periods. During contact, the orcas twisted and turned their bodies, often adopting an “ S- shaped” posture. This cultural behavior, as defined in the study, is “unique to southern resident killer whales.”

Researchers studied the behavior—which they dubbed allokelping —of 25 cetaceans of the species Orcinus orca ater together with scientists from the University of Exeter (England). The practice the authors describe was detected in both sexes, at all ages, and in all social groups. They found that orcas were more likely to groom other closely related individuals—siblings, for example—or pairs of similar age. They also noticed that whales with more shed skin or dead skin were more likely to groom themselves. Experts suggest this may have a hygienic function.

Bruno Díaz , founder of the Bottlenose Dolphin Research Institute , believes that while the study is a good starting point, more information is needed. “Confirming this type of behavior will require years of data,” says the expert, who was not involved in the discovery. Marine zoologist Carmen Arija, director of Sea Wolves , shares a similar assessment. “It's difficult to analyze wild populations. It would be necessary to verify whether it's something specific to this group of orcas or if it's widespread among others,” she says. Sometimes, when scientists approach a group of cetaceans to observe them, they end up invading their personal space, making it difficult to observe social affiliation behavior.

“Normally, when there are interactions with boats and the like, these behaviors aren't usually observed. This is normal because we're peeking into their privacy,” adds Arija, who was also not part of the research. Turbidity in the water is another factor that makes analyzing this marine animal difficult. “Most of my studies, for example, have been conducted on the Mediterranean coast , where water is clearer,” says Bruno Díaz.

In Australia, research has found that female and young dolphins use sponges to protect their snouts while feeding and to scratch their faces on coral. Additionally, observations in Australia show the use of shells to hunt prey . In the Mediterranean Sea, studies have shown that dolphins use objects such as nets to draw fish toward them and make them easier to catch. In primates, including humans, touch helps moderate stress and strengthen bonds.

In danger of extinction

Scientists have been monitoring these cetaceans since 2018 to better understand their diet and social behavior, making it a constantly evolving field of study. This group of orcas is critically endangered, according to data from the U.S. National Marine Fisheries Service (NOAA).

"They are highly threatened," says Carmen Arija. Among the factors that could explain this situation is habitat degradation, caused by underwater noise and persistently high levels of industrial chemicals. The decline in the quality and quantity of their prey—such as Chinook salmon, whose population has declined due to overfishing and climate change—is preventing population recovery.