A new paper on the social influences on joint urination in chimpanzees led by Ena Onishi (a doctoral student at Kyoto University’s Wildlife Research Center) and Professor Shinya Yamamoto (Kyoto University Institute for the Future of Human Society) has been published in Current Biology.

The act of urinating alongside others is a social phenomenon observed among humans across different eras and cultures. However, while it is believed that both physiological and social factors are intricately involved in the decision to urinate, the social aspects of urination have received little academic attention. Moreover, whether non-human animals show similar behavior has remained entirely unexplored.

In this study, an IFOHS-affiliated research group led by Prof. Yamamoto has now found that urination behavior can be contagious among chimpanzees. The team conducted over 600 hours of observation of 20 chimpanzees housed at Kyoto University Kumamoto Sanctuary, recording a total of 1,328 urinations. Detailed analysis of these events showed that chimpanzee urination tends to synchronize within the group, that urination is more easily transmitted among individuals in close proximity, and that lower-ranking individuals are more prone to urinate following another’s urination.

These findings provide the first evidence that chimpanzee urination behavior is influenced by social factors and highlight the previously underappreciated social aspects of a basic physiological phenomenon. Urinating at the same time with others may play an important role in maintaining group cohesion and facilitating smooth collective behavior. Further investigations into the urination behaviors of various animals could contribute to our understanding of group behavior and societal evolution.

For a more detailed explanation, please refer to the EurekAlert! or the article itself.

Reference:

Onishi, E., Brooks, J., Inoue, S., & Yamamoto, S. (2025). Socially contagious urination in chimpanzees. Current Biology, 35(2), R58-R59.