“Captive chimps are sticking grass in their ears and butts, and researchers say it's a trend”
Plain restatementA group of captive chimpanzees has been observed inserting blades of grass or sticks into their ears and rectums, and researchers characterize this behavior as a socially learned trend.
This claim is accurate. A peer-reviewed study published in the journal *Behaviour* in 2025, led by researchers including Edwin van Leeuwen and Jake Brooker, documents that chimpanzees at the Chimfunshi Wildlife Orphanage Trust in Zambia have been inserting blades of grass or small sticks into their ears and rectums. The behavior started with a male chimp named Juma in 2023 and spread through his group within about a week, though it was not observed in other groups at the sanctuary. Researchers say the behavior serves no obvious physical or medical function and appears to be a socially learned fad, similar to human fashion trends. One nuance worth noting: this is one group of eight chimps at one sanctuary, not "captive chimps" in general, though a related ear-grass behavior was seen at the same site back in 2010.
Captive [drifted from the evidence:] chimps are sticking grass [drifted from the evidence:] in their ears and [drifted from the evidence:] butts, and researchers [drifted from the evidence:] say it's a trend
[added by the neutral restatement:] A group of captive [added by the neutral restatement:] chimpanzees has been observed inserting blades of grass [added by the neutral restatement:] or sticks into their ears and [added by the neutral restatement:] rectums, and researchers [added by the neutral restatement:] characterize this behavior as a [added by the neutral restatement:] socially learned trend.
Red-tinted words in the claim drifted from the evidence. Green-tinted words are what a neutral restatement needs.
The trace / claim to source
- Captive chimpanzees at a specific sanctuary in Zambia were observed inserting grass/sticks into their ears and rectums.
- Researchers, in a peer-reviewed 2025 study in the journal *Behaviour*, describe the behavior as socially learned and analogous to a "trend" or "fad."
- The behavior has no apparent instrumental (functional) purpose.
- It spread rapidly within one group after being initiated by a chimp named Juma.
- Nothing materially misleading in the headline claim. It is a light, informal framing ("trend," "butts") but accurately reflects the researchers' own language of "fashion" and "fad."
- Minor simplification: the claim implies "captive chimps" broadly; the behavior was actually documented in one group of eight at one sanctuary, not across captive chimps generally. Similar (though not identical) behavior was previously observed at the same sanctuary starting in 2010.
- The precise mechanism of social transmission (whether caregivers definitively originated the behavior) is inferred rather than proven.
- Whether the fad will persist long-term.
New research published in Behaviour (2025) documents how a small group of chimpanzees at the Chimfunshi Wildlife Orphanage Trust began participating in this strange fad. Five out of eight chimps were spotted wearing grass in their ears, while six put their own unique stamp on the trend, letting the blades dangle from their behinds. In August 2023, at the Chimfunshi Wildlife Orphanage Trust sanctuary in Zambia, a trendsetting chimp named Juma was seen sticking a piece of grass into his ear, deep enough to stay there on its own. The team traced the "new quirk" to a male chimp named Juma, who seems to have originated the grass-in-butt variation, and from there, the study shows, it spread rapidly to most of his groupmates within a week. The chimps (Pan troglodytes) insert a blade of grass or stick into their ear or rectum and then just let it hang there for a while, researchers reported. The behavior doesn't appear to have any physical or medical purpose, but spreads socially.
Complete reasoning
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Answers come only from the case file above; nothing is added.
Is this behavior really happening, or is it just an internet rumor?
It is real. A peer-reviewed study published in the journal Behaviour in 2025 documents chimpanzees at a sanctuary in Zambia inserting blades of grass and small sticks into their ears and rectums.
Which chimps are doing this, and where?
One group of eight chimpanzees at the Chimfunshi Wildlife Orphanage Trust in Zambia. The investigation did not find this behavior across captive chimps generally.
Who started it and how did it spread?
A male chimp named Juma was observed starting the behavior in August 2023, and it spread to most of his groupmates within about a week.
Why are the chimps doing this?
Researchers say the behavior serves no obvious physical or medical purpose and appears to be socially learned, similar to a human fashion trend or fad.
Do researchers know for certain how the behavior spread from one chimp to another?
No. The case file notes that the precise mechanism of social transmission is inferred rather than proven.