Chimps develop fashion trend by shoving grass in their ears — and in their butts
Captive chimpanzees started to hang the grass of their ears and butts in an unusual “trend” of the fashion type, according to a new study.
Chimpanzees (Pan troglodytes) Insert a grass blade or stick into their ear or rectum, then let it hang it for a while, researchers reported. The behavior does not seem to have a physical or medical objective, but is socially spread from chimpanzee to chimpanzee.
Researchers first pointed out the Ear grass behavior In 2014. At the time, a single group of chimpanzees living in the fauna orphanage in Chimfunshi in Zambia presented the behavior. Now another group of the sanctuary has adopted behavior independently and has introduced a new daring style – carrying the grass in their rectums. The researchers described the new behavior in a study published on July 4 in the journal Behavior.
The two groups have no contact between them, but they share the same human guards. The researchers suspect that the part of the ear of behavior originated from chimpanzees as a copy of their human guards, before spreading through the groups and changing slightly.
“These guards indicated that they sometimes put a grass blade or a match in their own ears to clean them”, the main author of the study Edwin Van Leeuwenassistant professor of animal behavior and cognition at the University of Utrecht in the Netherlands, said in a statement. “The guards in the other groups said they had not done so. The chimpanzees of the group alone understood to stick the grass blade in another place as well.”
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Social animals often copy behaviors from each other. These behaviors are generally focused on finding food or other critical survival competence. However, researchers have also sometimes documented temporary modes spreading through populations without obvious advantage. Some orcas (Orcinus Orca) in the northwest of the Pacific are famous for this, having developed a bizarre habit of swimming with died salmon on the head.
The authors of the new study first noticed the behavior of the grass in a chimpanzee named Julie in 2010. Julie put on several occasions grass blades and let them hang there. Researchers then recorded seven other members of his group who picked up the trend. Julie died in 2013, but part of the group continued with behavior, which suggests that this had become a cultural tradition, according to the study. The second group then began to do the behavior in 2023.
To reassess this trend, the researchers observed all the chimpanzees of the sanctuary over 12 months between 2023 and 2024. Only two chimpanzees of the group of Julie still wore grass to their ears – one of which was Julie’s son. Meanwhile, in the other group, a man by the name of Juma was identified as the possible innovator of the new daring variation of the grass in the Butt, who has spread to most of his group comrades in a week, according to the study.
Researchers suspect that captivity has played a role in trends. Wild chimpanzees, which have not been observed adopting such apparently frivolous behaviors, fill their days of food for food and have to face many challenges that captive chimpanzees, which generally have their meals.
“In captivity, they have more free time than in the wild.” Van Leeuwen said. They don’t have to stay as alert or spend so much time looking for food. “”
The jury is always on what chimpanzees withdraw from their grassy hole accessories. However, researchers have hypothesized that this type of social learning can help strengthen social identity and social cohesion.
“It could also serve a social goal,” said Van Leeuwen. “In copying the behavior of someone else, you show that you notice and perhaps even as this individual. So this could help strengthen social ties and create a feeling of belonging within the group, just like in humans.”
