In a surprising discovery, researchers have found that chimpanzees urinate together when they see others doing so, a behavior dubbed “contagious urination.” Doctoral student Ena Onishi and her team observed this phenomenon among 20 captive chimps at the Kumamoto Sanctuary in Japan over 1,300 times. The study reveals that chimps tend to urinate in rapid succession, with those closer to the initial urinator more likely to join in. Even those lower on the social ladder are more likely to go when others are going.
While the reasons behind this behavior remain a mystery, Onishi and her colleagues have several hypotheses. They suggest that contagious urination might help reinforce group connections, boost overall social cohesion, or promote shared readiness for collective behaviors. The study’s findings raise intriguing questions about the role of peeing in primate social life.
The research team believes that contagious urination may be more widespread than initially thought, with some even speculating that it could occur in other social species. According to evolutionary biologist Martin Surbeck, who studies chimpanzee and bonobo behavior, this behavior is not unexpected in the wild and might even be seen in other primates.
The study’s lead author notes that observing daily activities of animals can reveal a wealth of information about their behavior and social lives. Onishi’s research highlights the importance of simple observation in uncovering fascinating insights into animal behavior.
Source: https://www.nytimes.com/2025/01/20/science/contagious-peeing-chimps.html