Orcas filmed making tools out of kelp to give each other massages on the move

Australia Broadcast Center

23-06-2025

Humans will spend big bucks on a seaweed spa treatment, and why not? It's rejuvenating and relaxing: just ask a group of orcas.
Southern Resident orcas — an endangered coastal population that swims off North America's Pacific north-west — have been observed rubbing specially fashioned pieces of kelp between themselves to create what looks like a massage on the move.
Dr Weiss and his colleagues filmed these interactions via drone cameras in the Salish Sea, which is located in the Canadian province of British Colombia and the US state of Washington.
Their observations were reported today in Current Biology.
The orcas were filmed biting down on the kelp, jerking their heads and swimming downwards to separate a segment of the seaweed that sits between its base and leaf-like blades.
"It's like a garden hose full of water: it's flexible, but it is also tough," Dr Weiss said.
Other cetaceans, such as humpback whales and right whales, have been observed rubbing themselves in kelp and even wearing the seaweed like a hat.
This behaviour is called 'kelping', but it is very different to what the orcas were observed doing, explained Olaf Meynecke, who leads the whales and climate program at Griffith University.
Because the orcas are using the kelp collaboratively to massage each other, the behaviour has been named "allokelping" — allo being a term used in biology to signal "different" or "other".
Dr Meynecke, who was not involved in the study, described the way this group of orcas engaged with the kelp as "much more active" than what has been observed with other cetaceans.
"The orcas are grabbing it, they're moving it, they're actually putting it against another individual," he said.
"The humpback whales and [other] baleen whales haven't done that; they are just happily rolling in it."
Dr Weiss and his team recorded allokelping 30 times over eight (out of 12) days of filming in 2024.
While the orcas themselves cannot explain the allure of kelp roller massages, Dr Weiss said there were hints in the data that could explain why they might do it.
They found that individual orcas were more likely to allokelp with close relations along their maternal line and with individuals of similar ages, suggesting the behaviour served a social function.
"They live in these very complex potentially challenging social environments where they're having to track dozens of relationships," he said.
But the social benefits of this grooming behaviour may also have a element of skin care.
When orcas shed their skin, it looks greyish and "peely", Dr Weiss said, and there is some evidence that individuals are more likely to engage in allokelping when they look peely.
"We can't say for sure that it's actually removing the dead skin … it could be treating something about the discomfort related to dead skin," he said.
Dr Meynecke from Griffith University has previously hypothesised that humpback whales may gain pharmaceutical benefits from kelping, and the orca's increased enthusiasm for allokelping when they shed skin might support his idea.
Using an object to achieve a goal takes a bit of brain power, and it's a feat even more impressive when a species takes the extra step of making their tools, as these orcas have.
But they're not alone: California crows cut pandanus leaves to skewer grubs in tree holes, chimpanzees sharpen sticks to 'fish' for termites, and elephants have been filmed using hoses.
In 2008, bottle-nosed dolphins in Shark Bay, Western Australia were reported using sponges as tools to protect their noses while foraging on the sea floor.
Georgetown University researcher Janet Mann, who first recorded this behaviour, said the latest study was "exciting", but pointed to her observations of "sponging" to challenge the claim that this is the first time whales or dolphins have been observed making tools.
"It's a very delicate operation to detach a basket sponge from the sea floor without destroying the integrity of that basket," she said.
But, she agreed, the use of tool to mutually groom each other was "unusual".
"Chimpanzees will use leaves and sticks to groom themselves … but to mutually groom each other [with a tool] is unusual," she said.
Southern Resident orcas are culturally and genetically distinct from other orcas in their region and communicate in a separate dialect.
In the 1980s, they made headlines when they went through a fad of wearing dead salmon as hats — a trend that is rumoured to have returned.
Dr Weiss said it wasn't clear whether this socially learned behaviour is a new fad, or ancient part of orca culture.
Philippa Brakes, a cetacean ecology researcher at Massey University who was not involved in the study, said that the behaviours of this population made them unique.
To do this, Dr Brakes said reducing ocean noise was important, as cetaceans communicate and learn from each other using sound.She added that the bull kelp orcas use was under threat from warming waters, and emphasised that the kelp needed to be protected in order to protect the whales' culture.