While Paris buzzes with the glamour of Haute Couture Fashion Week, a very different kind of runway moment is unfolding in the wild. The trendsetters in question? Not models — but chimpanzees — sporting blades of grass placed with surprising precision.

The “fashion effect” describes how individuals mimic others’ behavior, even when it serves no practical purpose. Think of tying a scarf around your dog’s neck — charming, but not exactly necessary. Humans are wired for imitation, a fact that keeps influencers in business across social media.

But this time, the phenomenon wasn’t found in humans at all. Researchers from Utrecht University in the Netherlands and Durham University in the U.K. have documented it among chimpanzees.

Fun fact: a similar case of “wild fashion” has been observed in orcas, which began balancing dead salmon on their heads.

The first chimpanzee trend appeared in the 2010s at Zambia’s Chimfunshi Wildlife Orphanage. It started with a female named Julie, who tucked a blade of grass into her ear. Other chimps quickly copied her — and the habit persisted, even after Julie’s death.

A Trend That Spreads to a New Group

Now, researchers writing in Behaviour report that another group of chimpanzees at the same sanctuary — with no contact with the first — has independently picked up the habit of putting grass in their ears.

This time, led by a male named Juma, the group took things a step further: they began letting grass hang from their backsides. There was no obvious reason — not even a scratch to relieve. “I’m not concerned with why they do it,” said Edwin van Leeuwen of Utrecht University. “What fascinates me is how they copy one another.”

A deeper look revealed a funny twist. Both chimpanzee groups shared the same human caretakers — and those caretakers occasionally stick blades of grass or matchsticks in their ears while cleaning them, right in front of their curious observers.

A Hint of Cultural Evolution?

So far, this quirky behavior has only been observed in captivity. In the wild, chimps are far too busy hunting for food or watching for predators to dabble in style experiments. But wild apes are excellent at copying behaviors that help them survive — a sign of intelligence and adaptability.

Imitating others might also serve a social purpose — a way to show connection or affection, reinforcing bonds within a group, much like humans do.

These findings from the Chimfunshi Wildlife Orphanage could deepen the discussion on animal culture and evolution. Some scientists still argue that humans are the only species capable of cultural imitation, even when the behavior is meaningless.

“But our research shows chimpanzees can also copy small, seemingly pointless actions,” said Jake Brooker of Durham University. “That’s why we thought sharing these observations was so important.”

mayer-nathalie

Nathalie Mayer

Journalist

Born in Lorraine on a freezing winter night, storytelling has always inspired me, first through my grandmother’s tales and later Stephen King’s imagination. A physicist turned science communicator, I’ve collaborated with institutions like CEA, Total, Engie, and Futura. Today, I focus on unraveling Earth’s complex environmental and energy challenges, blending science with storytelling to illuminate solutions.