Experts puzzled as chimps reportedly getting extra cheeky with grass fad

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Chimpanzees are cheeky trendsetters and a new study of their behaviour proves they’re more human than we realize.

The apes at a Zambian wildlife sanctuary have been going viral, but it’s not for the typical shenanigans like escaping or throwing feces. Rather, it’s their bizarre behaviour that has left experts puzzled.

One group of captive chimps at the Chimfunshi Wildlife Orphanage has taken to dangling grass out of their ears, part of a trend that researchers first spotted in 2010, as originally reported on by Live Science.

Now a second chimp crew is sticking blades of grass in another place: Where the sun doesn’t shine.

A new study published July 4 in the journal Behavior reveals the last primate pastime, which involves wedging grass into their rectums and letting it hang out like a tail. Nobody is sure why the animals have started doing this.

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More than a decade ago, a female chimp named Julie started the grassy ear craze. She died in 2013 and her son and a few others kept the tradition alive. However, it wasn’t until 2023 that the butt-branch group started up.

Juma – a male chimp – debuted the rear-end version of the fad and within a week his entire group of following him with the grass manoeuvre.

Researchers, who watched the apes closely for more than a year, said the trend isn’t about hygiene or comfort. It’s about clout.

“In captivity, they have more free time than in the wild,” said study lead author Ed van Leeuwen, an assistant professor of behavioural biology at Utrecht University in Netherlands. “They don’t have to stay as alert or spend as much time searching for food.”

Less work and more play, perhaps?

“It could also serve a social purpose,” van Leeuwen added. “By copying someone else’s behaviour, you show that you notice and maybe even like that individual. So, it might help strengthen social bonds and create a sense of belonging within the group, just like it does in humans.”