January 20, 2025
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Peeing among chimps is contagious
While people often yawn or scratch when they see someone else do it, for chimpanzees peeing is contagious.
Chimpanzee (Pan troglodytes) urinating on a tree, Nyungwe National Park, Rwanda, Africa.
Eric Baccega/Nature Picture Library/Alamy Stock Photo
Some primates pee together. Ena Onishi knew this, the Japanese also have a word for when humans go to the bathroom together: in tsuresh. However, Onishi it became strange when he noticed behavior among chimpanzees He was observing as a doctoral student at Kyoto University’s Wildlife Research Center. He was aware of well-studied “contagious” behaviors such as yawning in humans, and he wondered if Chimps may exhibit “contagious urine.”
In a new article published on Monday Today’s biology Onishi and his co-authors found that “see monkeys, do monkeys” holds true for these chimpanzees (although they are not technically monkeys). Even more interestingly, the condition of each animal seems to affect the social hierarchy of who pee and when. The findings are the first known scientific study of contaminated urine, according to the authors.
“It’s not something I would have ever thought to study, for sure,” says Matthew Campbell, a psychologist at California State University in the Channel Islands, who was not involved in the new study but has studied contagious behavior in chimpanzees. “I thought it was clever and novel, and it raises a lot of interesting questions.”
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Onishi and his colleagues studied 20 chimpanzees, most of them male, living in four groups at Kyoto University’s Kumamoto Sanctuary between 2019 and 2021. they were at that time. “It was a little overwhelming because I didn’t know if I was going to get meaningful results or if all that effort was going to be for nothing,” says Onishi. “It was definitely nerve wracking at times!”
“On the surface, it seems like a silly topic, but it really touches on something fundamental.” —Matthew Campbell, psychologist
By comparing the observations with computer simulations of random urination, Onishi and his colleagues determined that the chimpanzees were indeed more likely to urinate within 60 seconds of each other than if they played randomly. Distance also played an important role: animals within a few meters of the first chimpanzee were much more likely to follow the path than chimpanzees that were 10 meters or more away.
But perhaps the most interesting study came when Onishi and his colleagues considered it social relations between chimpanzees chimpanzees. They were surprised that it was a rattlesnake Friends with the first animal that peed it was no longer possible to continue. But there was a chimp that was less dominant than the first one was more vulnerable to infectious urine.
“I initially expected that if there were social influences, they would resemble those seen in yawning, such as greater contamination between socially close pairs,” says Onishi. “Then we saw a clear effect of social rank, with people of lower rank being more likely to follow other people’s pee.”
The new paper is just a first report, so a lot of additional research is needed to understand the phenomenon, and what insight it provides into the lives of chimpanzees. For example, scientists could conduct a similar analysis in wild animals, although Onishi expects the results to be inconsistent. Campbell also wonders if the apparent synchronized urination led by the dominant chimps simply reflects the group’s daily routines, in which relocations may be timed by the dominant animal and include a pre-road trip bathroom stop.
The study’s author Shinya Yamamoto, a professor at Kyoto University, says the discovery has made him think differently about chimpanzees. “This reinforces my impression of chimpanzees as ‘social animals,'” he says. “This study shows that their physiological aspects are also influenced by their social context.”
Depending on how accurately the behavior is transmitted between animals, the findings could also help reveal how a chimpanzee understands its own body and the concept of urination, Campbell said. “How that works and what it means for the mental life of a chimpanzee, that’s really intriguing to me,” he says. “On the surface, it seems like a silly topic, but it really touches on something fundamental.”
