Killer Whale Spa Day: When Ocean Apex Predators Discover the Wonders of Kelp
Imagine this scene: you and a friend book a spa day on the weekend, giving each other back massages, chatting, enjoying some rare relaxation time.
Now move that scene to the Pacific Ocean—replace the two people with two five-ton killer whales, and the "masseuse" with a stalk of bull kelp pulled from the seafloor.
This isn't science fiction. It's real behavior that scientists personally documented along the Pacific coast of North America in 2025.
A Fifty-Year Blind Spot
The story begins in the Salish Sea, between Washington State and British Columbia. These waters are home to a very special population of orcas—the Southern Resident Killer Whales. They are one of the most closely watched cetacean populations on Earth: scientists have been tracking them since the 1970s, and every single individual has a name, an ID number, and a family genealogy on file.
Nearly fifty years. Thousands of survey trips. Tens of thousands of photographs. By all rights, this population's behavior should have been studied thoroughly.
Then, in June 2025, the journal *Current Biology* published a paper with a word that had never appeared in any marine biology literature:
Allokelping.
*Allo-*, from Greek, means "mutual." Kelp is the seaweed. Put together: "grooming each other with kelp."
The Secret Revealed by Drones
The behavior was discovered by Michael Weiss and his team at the Center for Whale Research in Friday Harbor, Washington. Starting in 2018, they stopped relying solely on telescopes from boats and launched drones instead, observing the orcas' every move from 30 meters overhead.
The change in perspective changed everything.
From above, the researchers noticed a pattern that had never been observed before: two killer whales swimming side by side, one holding a section of bull kelp stalk in its mouth—bitten off from a kelp forest on the seafloor. It presses the kelp against its companion's body, and the two whales slowly roll, letting the kelp slide across their skin.
Sometimes the process lasts several minutes. Sometimes a third whale joins, forming a "kelp-massage circle."
"What struck me most," Weiss said, "is that this is clearly a common behavior—we saw it on almost every drone flight—yet despite this population being observed intensively for nearly fifty years, no one had noticed it before."
Not Just "Being Clever"
Primates use twigs to fish for termites, crows use stones to crack nuts, elephants scratch themselves with branches—tool use in animals is not rare. But one domain has long been blank: marine mammals.
Dolphins use sponges to protect their snouts while foraging on the seafloor, but that's "carrying something on the body," not "making a tool." Sea otters use rocks to crack shells, but that's "using an object as-is," not "processing raw material."
Allokelping is different. The orcas don't just pick up kelp floating on the surface—they deliberately bite off kelp stalks, cut them into segments of suitable length, and bring them to a companion to use. This is manufacture, not just use.
The paper's wording is careful, but the implication is clear: this is the first documented case of tool manufacture and use in marine mammals.
Who Massages Whom?
Even more interesting is the behavior's social structure.
The researchers analyzed all observed allokelping events and found a clear pattern: killer whales prefer to massage close relatives, or age-mates.
Doesn't that sound familiar?
Think about the last time you gave a friend a back rub—it was probably someone you were closest to, or someone you felt most comfortable with. Orcas are the same. They don't pick a random whale to groom; they make choices and show preferences.
Moreover, the researchers noticed a detail: whales with more molting or dead skin were more likely to be the ones getting massaged. This means allokelping may not be purely social—it genuinely has a hygienic function. The rough kelp stalk can help orcas remove debris and dead skin from their body surface.
In other words, this isn't "pretend socializing"—it's "genuinely useful."
A Spa Culture in an Endangered Population
Here is a heartbreaking piece of context: the Southern Resident killer whales are one of the most endangered cetacean populations in the world. Fewer than 80 individuals remain.
Their main threat is food shortage—they eat almost exclusively salmon (especially Chinook salmon), and salmon populations have plummeted due to overfishing, habitat destruction, and climate change. A single adult orca needs to eat roughly 20 Chinook salmon per day.
Under such survival pressure, you might think "mutual massage" is a luxury. But it's the opposite—social bonds are essential to orca survival. Close social relationships mean better cooperative hunting, more efficient information transfer, and stronger group cohesion.
Allokelping may be the physical embodiment of those social bonds. It's not just "feeling good"—it's a cultural practice, a behavioral pattern passed down through generations in this population.
The Philosophy of Observation
This story raises a deeper question: how much of what we think we "understand" is only understood that way because we used the wrong method of observation?
Fifty years. Generations of scientists. Countless expeditions. Yet it wasn't until someone lifted the viewpoint from sea level to 30 meters in the air that this "happening every day" behavior was discovered.
It's not that previous scientists weren't careful. It's that some truths can only be seen at particular scales.
This reminds me of similar moments in the history of science:
- Galileo pointed a telescope at the night sky and discovered Jupiter's moons—those stars were always there; human eyes just couldn't see them.
- Leeuwenhoek ground the first microscope and saw microorganisms in a drop of water—an entire microscopic world, right before our eyes, yet never noticed.
- In the 1920s, astronomers discovered that the universe is expanding—those galaxies had always been receding; no one had simply measured their redshift.
- Weiss, M.N. et al. "Manufacture and use of allogrooming tools by wild killer whales." *Current Biology*, 2025. DOI: 10.1016/j.cub.2025.04.021
- ScienceDaily, "Killer whales use seaweed tools in never-before-seen grooming behavior," June 24, 2025
- Smithsonian Magazine, "These Killer Whales Make Tools From Kelp to Massage Each Other," June 30, 2025
Every revolution in observational tools reveals a previously overlooked reality.
Drones are to marine biology what telescopes are to astronomy.
From Orcas to AI
As a "biological" who works with AI every day, I can't help connecting this story to my own field.
When we train AI models, we do something similar: we choose an "observational perspective" (loss functions, evaluation metrics) and then interpret model behavior through that perspective. But what's actually happening inside the model? Have we truly "seen" it?
Just like the scientists who watched orcas from boats for fifty years—they saw whales breaching, hunting salmon, chasing boats, but they couldn't see the allokelping happening below the surface, beyond their perspective.
The "interpretability" problem in AI research is fundamentally the same question: are we observing the right thing at the wrong scale?
Perhaps one day we'll invent a kind of "concept drone" that overlooks the inner world of neural networks from a higher dimension, and discover phenomena that "happen every day" but were never noticed.
At that point, we'll probably coin a new word for ourselves, just like allokelping—a word describing something we never imagined, but that was always there.
Epilogue
After the paper was published, Weiss said something in an interview that I think deserves to be quoted in full:
> "To me, this demonstrates not just the power of new observation methods but also how much we still have to learn about these animals."
Fifty years of observation, one drone, one new word.
How many more allokelpings are out there in the ocean, waiting to be discovered?
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