Who knew that southern resident orcas use kelp to scratch each other’s backs?
In the first known toolmaking by a marine mammal, southern residents have been documented by drone photography detaching lengths of seaweed and using them to massage each other, the Center for Whale Research announced. The findings were published Monday in the journal Current Biology.
Here’s how it goes in the southern residents’ kelp spa: The whales bite off the end of a kelp stalk, position it between themselves and a partner, and roll the kelp between them for prolonged periods. Rubbing and scrubbing, whales of all ages in the pods do it, possibly to strengthen their social bonds, and likely because it just feels good, said Michael Weiss, research director for the center.
The southern residents’ kelp massage “may be the first example of tool use in a wild animal benefiting two individuals simultaneously, and the first case of non-human animals manipulating a tool with the core of their body rather than an appendage,” according to the paper.
Researchers call the behavior “allokelping.” You might also just call it fun.
In all, researchers documented 30 bouts of allokelping across all age and sex classes and all three pods. Everybody’s doing it. Sometimes, the whales bit off a chunk of an intact kelp stalk to get the party started. Other times, they harvested free-floating pieces from kelp beds.
The whale with the kelp would approach a partner, flip the length of kelp onto their head, then press their head and the kelp against their partner’s flank, the two maneuvering to keep the kelp snugly between them while rolling it across their bodies, the researchers reported.
Commenting on the possible reasons for allokelping, professor Darren Croft, of the University of Exeter and the Center for Whale Research’s executive director, said, “We know touch is really important.”
“In primates — including humans — touch moderates stress and helps to build relationships,” he said. “We know killer whales often make contact with other members of their group — touching with their bodies and fins — but using kelp like this might enhance this experience.”
Croft said it might also be important for skin health, for removing dead skin. Brown algae like bull kelp also have antibacterial and anti-inflammatory properties that may provide further benefits to the whales, he noted.
It took a while for the researchers to realize what they were seeing — which was only visible to them after getting a new drone with a powerful zoom lens, from which they observe the whales from at least 100 feet above the pods, Weiss said.
Allokelping is a tricky maneuver, requiring the whales to pump their flukes and swim pressed against one another to roll the kelp stick just how they want it, right where they want it. If the piece gets loose, they just retrieve it and keep right on rubbing.
Believed to be unique to the southern residents, the behavior is just one more aspect of southern resident culture that makes them distinct as a population, and so worth protecting, Weiss said. The southern residents also share greeting ceremonies, and have their own language, passed generation to generation.
The kelp spa treatment of course can’t be enjoyed by the southern residents without kelp, so it’s one more reason to protect and restore it. Kelp is declining in Puget Sound, possibly in part because of warming water caused by climate change.
The southern residents aren’t the only orcas known to enjoy a good back scratch and skin sloughing. Northern residents and some Alaskan resident killer whales rub their bodies over smooth beach stones, also probably as a social activity and because it feels good, Weiss said. But what the southern residents are up to is next-level, using an object in their environment as a tool they manipulate to do something they want.
“There is something special about manufacturing and directly manipulating an object that is detached that you are exercising control over,” Weiss said.
While tool use among terrestrial animals is well known, it is more rare in the marine environment, probably because the animals mostly are streamlined and don’t have grappling limbs. And underwater they are just harder to observe.
Researchers first noticed the behavior in April 2024 and made more observations through July of that year.
The first time they noticed an orca breaking off a bit of kelp and interacting with it with another pod member, the researchers thought: Hmm, interesting, make a note to maybe look into it later, Weiss said. The second time they thought: Hey, wait, is this a thing? The third time, noticing whales in J pod rubbing away together, they realized they were observing a behavior that had probably been happening in the pods for the 50-year duration of formal research on the southern residents. But no one had ever noticed.
“It makes you wonder, what else is going on?” Weiss said. “And that is among the most-studied whales in the world.
“What about the others?”
The southern residents are an ancient society of three family groups, the J, K and L pods, that specialize in eating salmon, mostly Chinook. Their home range takes them on foraging rounds all the way from B.C. to the Golden Gate Bridge.
They are an endangered species, threatened by a lack of adequate food, underwater noise and boat disturbances that make it harder for them to find food by echolocation, pollution and inbreeding.
There are only 73 southern residents left in the wild.
