The chimpanzee who invented a strange fashion trend – and swept up the whole gang

A new study reveals that chimpanzees at a sanctuary in Zambia have adopted a habit of inserting grass stems into their ears and rear ends, with no practical benefit. The behavior spread through imitation, similar to human trends, and may have been learned from human caretakers.

A new study published in the journal Behaviour reveals that chimpanzees at a wildlife sanctuary in Zambia have adopted an unusual habit: inserting grass stems into their ears and rear ends, with no clear practical reason. The behavior was first observed in the 2010s, when a female chimpanzee named Julie began putting grass in her ears, and soon other chimpanzees in the group imitated her. After her death, the habit continued as a kind of social tradition. More than a decade later, another group at the same sanctuary adopted a similar habit, influenced by a male chimpanzee named Juma, who inserted grass into his ears and behind him. Researchers from Utrecht University and Durham University examined whether the behavior was meant to relieve itching or serve another physical need, but found no clear explanation. An intriguing detail: both groups were cared for by the same staff, who sometimes clean their ears with a grass stem in the presence of the animals. The researchers speculate that the chimpanzees first imitated the caretakers, then spread the habit among themselves. According to the researchers, the findings demonstrate how chimpanzees can learn pointless actions from each other, and may help in understanding the development of culture in animals.