Ena Onishi, a doctoral student at Kyoto University, spent more than 600 hours observing chimpanzees urinating. But there's a good reason why she's such a peep. She is part of a team of researchers who recently discovered that primates tend to tinkle when they see nearby chimpanzees doing the same thing.
In a study published Monday in the journal Current Biology, Onishi and colleagues described the phenomenon, called infectious urination. Their findings raise questions about the role pee plays in the social lives of chimpanzees and other primates.
Onishi first discovered contagious urination in 2019 while observing chimpanzees at the Kumamoto Sanctuary in Kyoto, Japan. “While observing a group of captive chimpanzees for another research project, I noticed that they tended to urinate at the same time,” Onishi said. “It got me thinking: Maybe this is one of those contagious behaviors, like contagious yawning?” I then explained that we have a natural tendency to yawn.
To find out, Onishi studied 20 chimpanzees at a sanctuary and observed them urinating together more than 1,300 times. After crunching the numbers, Onishi and his colleagues realized that the chimpanzees were indeed urinating in quick succession. They found that the closer a chimpanzee was to the first person to urinate, the more likely it was to join the group. They also found that chimpanzees with lower social status were more likely to go when other chimpanzees went.
“This result was a surprise to us as well,” Onishi said. “This raises interesting questions about the social function of this long-overlooked behavior.”
Why chimpanzees behave this way remains a mystery, but Onishi and his colleagues have several hypotheses. “Contagious urination may help strengthen group bonds and increase overall social cohesion,” she says. “It could foster common readiness for collective action. There are so many possibilities.”
Although this study was limited to captive chimpanzees, many of whom were rescued from the biomedical research industry, this behavior is unlikely to be unique to this group.
“When you walk with great apes in the wild, you see that group members are really working together,'' said Martin Surbeck, an evolutionary biologist at Harvard University who studies the behavioral ecology of chimpanzees and bonobos. I understand that very well,” he says. the study.
Dr Surbeck said he was not surprised to learn that Kumamoto chimpanzees practice contagious urination, and that the behavior is not unexpected in the wild. “You might see it in other social species,” he says.
Although more research is needed into contagious urination and its evolutionary function, Onishi and her colleagues were pleased to learn so much from a simple observation.
“There are many discoveries to be made from the daily activities of animals,'' says Onishi.
