It all started with a Zambian chimpanzee named Julie in 2010. Julie stuck a piece of grass into her ear, and left it there. And she would do it over and over again. But why? To save it for later, for some unknown purpose? For fun? To show that she understood she would become dust and one day fertilize the grass, in an ironic nod to The Lion King?

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Actually, this "grass-in-ear-behavior" appears to serve no discernible function. But after Julie did it, other chimps in her group began to follow suit.

It's no surprise that chimpanzees have "culture," in that different groups develop different traditions, including unique behaviors and tools. But usually these things have a concrete function, whereas this one doesn't, according to the study, published in the journal Animal Cognition.

“Our observation is quite unique in the sense that nothing seems to be communicated by it,” study author Edwin van Leeuwen, a primate expert at the Max Planck Institute in The Netherlands, told The Dodo.

To make sure that the ear-grass thing wasn't just a random occurrence, researchers watched four different groups in Zambia's Chimfunshi Wildlife Orphanage Trust for a year. Only group put grass in their ears, and the behavior spread from one to another after one saw another doing it.

The finding has prompted scientists to speculate that it might be akin to some kind of chimp fashion statement. “Any kind of subculture fad in human culture, I'd say, could be the parallel to this grass-in-ear behavior,” van Leeuwen said.