What is ‘kelping’? Why whales are making hats out of seaweed

Humpback whales are well known for their fascinating culture: These enigmatic animals migrate thousands of miles every year, sing enchanting songs, leap from the water in an enormous breach, and collaborate while hunting—creating bubble nets that trap their prey.

Now, researchers have shed light on another aspect of whale behavior: playing with kelp they find floating in the ocean—moving it between their fins, rolling around with it, and, most intriguingly, wearing it atop their heads like a hat.

This behavior—called kelping—has been described in a new study as a “global phenomenon.” The study documents instances of humpbacks (Megaptera novaeangliae) worldwide interacting with seaweed, taken from over a hundred social media posts, and shows that this playful behavior is much more common than previously thought.

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There’s no doubt kelping looks fun. But could it have another purpose? Olaf Meynecke, research fellow at Griffith University and co-author of the study, thinks so—especially considering that whales can keep it up for some 30 to 40 minutes.

“That’s quite a lot of time to just spend with a little piece of algae,” he says. “It looked like there had to be more to it.”

Meynecke believes the way they can softly and accurately move the kelp with all their body parts could indicate mobility training—whales need dexterity and coordination for feeding. It may also feel good for the whales and be beneficial for their skin.

How long have whales been kelping?

Kelping was first observed in 2007, and it’s not just humpbacks that do it. Other baleen species, including gray whales and northern and southern right whales, have also been observed interacting with seaweed.

After seeing videos of kelping and reading a 2012 study on the phenomenon, Meynecke was intrigued. He had now seen three unrelated drone videos of kelping, and wondered how much more was out there.

To collect more data on this strange behavior, he searched social media with keywords like “kelping,” “humpback whale,” “whale,” and “seaweed,” and found hundreds of posts, which the team systematically analyzed.

Meynecke says it became clear that this behavior isn’t accidental: “Having something touching your body in the water is quite difficult because it doesn't really want to stick, it floats away,” he says.

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Heidi Pearson, professor of marine biology at University of Alaska Southeast, who was not involved in the research, has seen kelping at her humpback research site in Juneau, Alaska. Once, a female called Barnacles looked like she was entangled in fishing line. It turned out she "was playing with this kelp” draped over her back.

But "I've never documented it in a quantitative way," she says, adding that she “didn't know that the word for it was kelping.”

Hats made of seaweed

What’s particularly intriguing about kelping is the way that humpbacks from different populations—in both the Northern and Southern Hemispheres—all prefer to wear seaweed on the top of their heads, says Meynecke. They place kelp on their forehead in over half the recorded instances.

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Baleen species are believed to like having their heads scratched—gray whales are known for approaching whale watching boats for a tickle on the nose.

Because whales don't have hands to scratch themselves, like we do, Pearson suggests “they might seek out other tactile sensations that just feel good."

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Kelp, she says, is "slimy and slippery and smooth. It's a very neat feeling and I can imagine a whale might enjoy that feeling too—like a massage."

Skincare, but for whales

Whales might also be treating kelp like a cleansing face mask, as seaweed has antimicrobial properties that can reduce levels of bacteria. Rubbing kelp across their bodies may also dislodge parasites and shed bacterial and viral growths to prevent them getting "completely overgrown" with sea lice and skin infections, says Meynecke.

“Those medicinal or health benefits are a definite possibility," agrees Pearson, "And I don't think the two are mutually exclusive. It could be play, and also have health benefits."

Curiously, the whales also put kelp in their mouths as if "they're wanting it to touch that lip part that’s impossible for them to clean otherwise," he says—almost like flossing.

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"Grabbing something with their mouth is not natural for them," he says. "They're not like cats. They don't hunt with their teeth—they don't have teeth."

But ultimately, he adds, "we'll never be able to fully prove it because we can't ask the whale."

The role of citizen science

Today, more people have better cameras and drones—which Meynecke says explains why it’s much easier to document kelping now. Drone footage is particularly useful for scientific observation compared to still images, he adds, since otherwise “you don't know what the animal was doing before and after, and how long it was doing this for."

This study "would never have made it out there if it wasn't for the people getting excited that they just saw a whale putting kelp on their head, and posting about it," says Meynecke.

The study has caught the attention of researchers globally, and Meynecke’s inbox has been flooded with people who have also seen kelping. "Someone from Tahiti was like, 'We see it all the time,'" he says.

Now the phenomenon has been highlighted globally, it could lead to further research into the behavior, its benefits, and even if other species do it.