Peeing Is Socially Contagious In Chimps

After observing 20 chimpanzees for over 600 hours, researchers in Japan found that chimps are more likely to urinate after witnessing others do so. “[T]he team meticulously recorded the number and timing of ‘urination events’ along with the relative distances between ‘the urinator and potential followers, the results revealed that urination is, in fact, socially contagious for chimps and that low-dominant individuals were especially likely to pee after watching others pee. Call it: pee-r pressure.” The findings have been published in the journal Cell Biology. From the study: The decision to urinate involves a complex combination of both physiological and social considerations. However, the social dimensions of urination remain largely unexplored. More specifically, aligning urination in time (i.e. synchrony) and the triggering of urination by observing similar behavior in others (i.e. social contagion) are thought to occur in humans across different cultures (Figure S1A), and possibly also in non-human animals. However, neither has been scientifically quantified in any species.

Contagious urination, like other forms of behavioral and emotional state matching, may have important implications in establishing and maintaining social cohesion, in addition to potential roles in preparation for collective departure (i.e. voiding before long-distance travel) and territorial scent-marking (i.e. coordination of chemosensory signals). Here, we report socially contagious urination in chimpanzees, one of our closest relatives, as measured through all-occurrence recording of 20 captive chimpanzees across >600 hours. Our results suggest that socially contagious urination may be an overlooked, and potentially widespread, facet of social behavior.

In conclusion, we find that in captive chimpanzees the act of urination is socially contagious. Further, low-dominance individuals had higher rates of contagion. We found no evidence that this phenomenon is moderated by dyadic affiliation. It remains possible that latent individual factors associated with low dominance status (e.g. vigilance and attentional bias, stress levels, personality traits) might shape the contagion of urination, or alternatively that there are true dominance-driven effects. In any case, our results raise several new and important questions around contagious urination across species, from ethology to psychology to endocrinology. […]