At a chimpanzee sanctuary in Zambia, keepers started noticing an odd accessory: blades of grass peeking out from unexpected places.
The scene could pass for a bizarre fashion shoot: young chimps lounging in the shade, grooming one another, some with thin green straws tucked in their ears, others flaunting them at the rear. Behind the laughs, scientists now see a serious clue about how culture, trends and even “style” might spread among our closest animal relatives.
From ear ornament to back-end statement
The story begins at Chimfunshi Wildlife Orphanage in northern Zambia, one of Africa’s largest chimpanzee sanctuaries. Behavioural researchers there had already documented an odd habit a decade ago: chimps casually inserting a blade of grass into one ear and leaving it sticking out, as if wearing a minimalist earring.
That first case, reported in a 2014 scientific paper, seemed like a quirky one-off. But a new study published in the journal Behaviour on 4 July 2025 suggests the “look” not only returned in another group – it evolved.
In the most recent observations, a core group of chimpanzees at Chimfunshi still use the classic ear-based grass accessory. Yet some individuals have added an eye‑watering twist: they also plant the grass between their buttocks, letting it stick out like a tiny green tail.
What started as a single chimp’s odd habit turned into a short-lived craze, spreading through the group in just days.
Researchers tracked the spread and found that one high‑status male appeared to kick off the trend. Within about a week, several others were copying him. Not every chimp joined in, but enough did to treat it as more than random behaviour.
Did humans accidentally inspire chimp fashion?
The strange custom raised an obvious question: where did the idea come from? Since the new trend emerged in a group with no contact with the chimps studied a decade earlier, direct copying between groups seemed unlikely.
Researchers considered sheer coincidence, but the parallels were too tight. Two separate communities, in the same sanctuary, both playing with ear grass? The puzzle pushed them to look beyond the chimps themselves.
Sanctuary staff became the missing piece. Some human keepers admitted they occasionally stick a piece of grass or even a matchstick into their own ear to scratch or clean it while working. Other keepers, in other enclosures, said they never do this.
➡️ Trend hairstyle 2026: This is what the mid-length feather cut looks like
➡️ What does it mean, according to psychology, when you help waiters clear the table at a restaurant?
➡️ This simple kitchen routine saves time every single day
➡️ This kitchen trick helps prevent unpleasant smells without chemical sprays
Where keepers routinely fiddled with grass in their ears, chimpanzees were more likely to copy the gesture and turn it into a group habit.
The scientists’ working idea is simple: chimps observe humans all day. A curious chimp notices a familiar keeper putting grass in an ear. The chimp experiments with the same action, and it feels interesting or at least safe. The behaviour gets repeated. Then other chimps, watching closely, join in.
The bottom placement appears to be a playful variation that chimps invented themselves. Once the basic idea of “body plus grass” took hold, one individual tried a new location. It drew attention, probably some social reactions, and quickly spread as a kind of inside joke shared by the group.
Is it fashion, tool use or just a joke?
For scientists, the grass trend sits at an awkward crossroads. It does not function like a tool. The chimps are not using the grass to reach food, dig for insects or clean wounds. Nor does it provide obvious health benefits.
Instead, it looks a lot like what humans would call a style choice or a playful signal, more about communication than survival. A chimp strolling past with grass in its ear is doing something visible, unnecessary and socially noticeable. That’s close to the human logic of wearing a distinctive hat or piercing.
- Tool? No clear practical use.
- Play? Likely part of social play and experimentation.
- Signal? Probably says “I’m part of this group” or “I’m paying attention to you”.
- Fashion? In a broad sense, yes: a shared, arbitrary style spreading through imitation.
Why captive chimps have time for trends
Sanctuary life gives chimps something they rarely have in the forest: spare time. Food is provided. Predators are absent. Fights still occur and hierarchies still matter, but daily survival takes less effort.
Lead researcher Edwin van Leeuwen, from Utrecht University, argues that this breathing room lets new traditions take root. With energy freed up, chimps can spend longer watching each other, grooming, experimenting and copying odd gestures that catch their eye.
More free time means more room for culture-like behaviours: local quirks, traditions and seemingly pointless but socially meaningful habits.
Placing grass in an ear or buttock becomes a low‑risk way to signal social interest. When a subordinate mimics a dominant male’s weird new move, it might be a way of saying “I see you, I respect you, and I want to be associated with you.” That shared habit then cements bonds.
Researchers note that imitation in chimps, as in humans, is rarely neutral. Who you copy, when and where carries social meaning. By echoing the behaviour of a popular individual, chimps may be quietly negotiating their place in the group.
Could wild chimpanzees do the same thing?
Field scientists who follow wild chimpanzees already describe cultural differences among groups. Some use stones to crack nuts, others don’t. Some use specific leaf gestures during grooming or courtship. These are local traditions, learned socially and passed between generations.
That said, no one expects wild chimps to start parading around with decorative grass in their backsides. The pressures of life in the forest leave less space for such pure play. Food searching, territory defence and vigilance take priority.
Sanctuary settings act as a kind of behavioural laboratory. Freed from constant danger, chimps can push their curiosity into quirky territories that might never surface in harsher conditions. The same cognitive machinery that supports complex tool use in the wild can, in a safer setting, support seemingly frivolous trends.
How scientists tell a ‘trend’ from a fluke
One key challenge is distinguishing an individual quirk from a genuine group pattern. Behavioural scientists tend to look for a few things:
| Criterion | What researchers look for |
|---|---|
| Spread | Does the behaviour move from one individual to several others? |
| Longevity | Does it last weeks or months rather than a single day? |
| Learning path | Do younger or lower‑rank chimps copy higher‑rank or older ones? |
| Lack of function | Is there no obvious survival advantage, suggesting a social role? |
The grass‑in‑ears and grass‑in‑bottoms behaviours tick several of these boxes. They spread through part of the group, persisted for a period and did not appear to bring extra food or safety.
What ‘culture’ means when talking about chimpanzees
When scientists use the word “culture” for animals, they do not mean art galleries or literature. They refer to traditions and behaviours that:
- are shared within a group
- vary between groups of the same species
- are learned socially rather than genetically fixed
By that standard, chimpanzees clearly have culture. Different communities show unique handshakes, grooming rituals, tool sets and foraging tricks. The grass trend at Chimfunshi slots neatly into this picture as a lightweight, visual tradition.
For humans, this matters because it narrows the gap we like to draw between “our” symbolic behaviours and those of other animals. Chimps do not run catwalks or design labels, but they do show a taste for arbitrary signals that only make sense within their social group.
What this means for anyone visiting or working with great apes
For sanctuary staff, zoo keepers and field researchers, the study carries a practical reminder: apes watch every move. A casual habit – scratching an ear with grass, tying a bright bandana, tapping on glass – can become raw material for new ape behaviours.
That raises ethical questions. Should humans deliberately model certain actions to enrich ape lives? Some programmes already teach apes simple gestures or object uses to stimulate their minds. At the same time, no one wants to introduce behaviours that could cause stress, injury or conflict.
A sensible approach involves structured enrichment: offering safe materials, rotating objects, and observing how apes choose to interact with them. Grass fashions are relatively harmless. Other copycat habits, like messing with enclosure locks or inserting objects into wounds, would need quick intervention.
If you ever see a grass‑wearing chimp
Visitors who notice odd adornments on chimps can treat them as tiny windows into complex minds. That ear full of grass is not a random accident. It carries a history of observation, curiosity and quiet imitation.
Behind that single blade, there might be a keeper’s unconscious gesture, a bold chimp’s experiment, and a web of shifting alliances as others decide whether to join the fad or ignore it. For a species so close to our own, even a joke accessory can say a lot about how culture grows.
Originally posted 2026-03-03 14:46:20.