Is peeing contagious in chimpanzees?

A new study has for the first time described a phenomenon researchers refer to as ‘contagious urinations’. The study of 20 captive chimpanzees living at the Kumamoto Sanctuary in Japan shows that, when one chimpanzee pees, others are more likely to follow. The researchers documented peeing behaviours in the Kumamoto chimpanzees over more than 600 hours, including 1,328 urination events. They analysed the observational data to see whether peeing among the chimpanzees was significantly synchronized in time. The evidence showed that urination events were significantly more synchronised during observations than would be expected if the chimpanzees were simply peeing at random times with respect to one another. The likelihood of contagious urination also increased with physical proximity to the initial urinator, they report. Interestingly, individuals with lower dominance ranks were more likely to pee when others were peeing. The finding suggests that urination patterns are influenced by social hierarchy, with a tendency for the behaviour to ‘flow down’ the dominance structure.