While watching a group of captive chimpanzees for her graduate research, wildlife researcher Ena Onishi noticed something odd about the primates: They seemed to have a tendency to urinate around the same time. Oshi was reminded of human behaviors of going to the bathroom together—and when seeing someone else yawn, getting the urge to yawn yourself. So she spent over 600 hours watching twenty chimps in an animal sanctuary, observing each time a chimp peed relative to other chimps. One hypothesis: Peeing together could facilitate group behaviors, like watching for predators…or, simply being a form of social bonding.
