Chimpanzees Adopt Bizarre Grass-in-Ear Trends Like Humans
A scientific study reveals that sanctuary chimpanzees in Zambia have adopted bizarre trends of placing grass in their ears and hindquarters. Researchers suggest this social imitation mirrors human fashion and sheds light on animal cultural evolution.
Bizarre trends are no longer an exclusively human phenomenon. A study published in the scientific journal Behaviour reveals that chimpanzees at a wildlife sanctuary in Zambia have adopted an unusual custom of placing grass blades in their ears and hindquarters without any clear practical purpose. Researchers from Utrecht University in the Netherlands and Durham University in the United Kingdom found that the behavior spread among group members through imitation, much like fashions and trends propagate in human society.
The phenomenon was first identified in the 2010s at the Chimfunshi Wildlife Sanctuary in Zambia. A female chimpanzee named Julie began inserting grass blades into her ears and leaving them there. Before long, other chimpanzees in the group began to imitate her, even though researchers found no practical utility in the behavior. The custom even persisted after Julie's death, evolving into a kind of social tradition.
A New Twist in a Second Group
More than a decade later, it was discovered that a different group of chimpanzees at the same sanctuary had adopted a similar habit, despite never having direct contact with the original group. However, this time the trend took an even stranger turn. Influenced by a male chimpanzee named Juma, members of the second group began placing grass blades in their ears and subsequently letting them hang from their hindquarters as well.
Out of the eight chimpanzees in the group, five adopted the custom of putting grass in their ears, and six began doing so in their hindquarters as well. Researchers tested whether the behavior was intended to relieve itching or serve another bodily need, but found no clear explanation.
Did Chimpanzees Imitate Humans?
During the course of the study, an intriguing detail emerged: both groups of chimpanzees were cared for by the same staff members. The caretakers reported that they occasionally clean their own ears using a grass blade or matchstick, sometimes doing so in the presence of the animals. Researchers raised the possibility that the chimpanzees initially imitated human handlers and subsequently spread the custom among themselves, although no definitive proof was found.
According to researcher Edwin van Leeuwen from Utrecht University, the compelling question is not necessarily why the chimpanzees chose to put grass in their ears, but why others decided to copy them. Researchers believe that imitation may play a social role even when a behavior lacks practical advantage. Much like humans who adopt fashions to fit into a group, chimpanzees may also mimic one another to strengthen social bonds.
Scientists note that such behaviors might be more common among sanctuary-dwelling chimpanzees because they have significantly more leisure time compared to wild counterparts, who must spend their days foraging for food and avoiding predators. Researcher Jake Brooker from Durham University explained that the findings demonstrate how chimpanzees are capable of learning even seemingly pointless actions from one another, shedding light on the evolution of animal culture and the true uniqueness of human trend-following.
