For Chimpanzees, Peeing Might Be Contagious — A Fascinating Look at Social Behavior

When someone yawns, it’s hard not to join in—a strange yet familiar quirk of human behavior. But what if I told you chimps might experience something similar… with peeing? This well-known phenomenon, called “contagious yawning,” has a surprising parallel in our evolutionary relatives: peeing might also be contagious.

Kumamoto Sanctuary

A recent study published in Current Biology observed that captive chimpanzees were more likely to urinate after seeing others do the same. This "socially contagious urination" sheds light on the shared behaviors between humans and our closest evolutionary relatives.

How Did Researchers Uncover This?

Ena Onishi, a primatologist at Kyoto University, first noticed this behavior in 2019 while observing chimpanzees at the Kumamoto Sanctuary in Kyoto, Japan. Onishi recalls how the chimps often peed simultaneously, much like humans might opt to visit the restroom in groups. Interestingly, this social habit even has cultural parallels: in Japan, the term “Tsureshon” describes the act of urinating together.

Inspired by these observations, Onishi and her team set up an experiment, recording over 600 hours of footage involving 20 chimpanzees. In their analysis of 1,328 urination events, the researchers found clear evidence that one chimp’s urination often triggered others to follow suit. Lower-ranking chimps were particularly likely to join in, while proximity to the original urinator also played a role. Surprisingly, social bonds between chimps, which strongly influence contagious yawning, didn’t seem to impact urination.

Why Does This Happen?

While the study doesn’t offer a definitive answer, the researchers suggest several theories. Contagious urination could help reinforce group cohesion or serve as a defensive strategy. Coordinating bathroom breaks might reduce the chances of predators tracking individuals based on isolated scents or trails. Shinya Yamamoto, a co-author of the study, highlights that such behaviors may have deep evolutionary roots, noting similar tendencies in humans.

Are Humans Really That Different?

Humans also exhibit behaviors influenced by social contexts. From synchronized yawning to walking in step with others, we’re wired to mirror those around us. Even decisions to visit the restroom can be influenced by social dynamics—think of how restroom breaks are often coordinated during events. This study on chimpanzees suggests that these behaviors may have originated from a common ancestor shared by humans and great apes.

What’s Next for Research?

Though this study focused on captive chimps, scientists believe contagious urination could also occur in the wild. Wild apes are known for their coordinated activities, which could include bathroom breaks. Future research might explore whether this behavior exists among other social species or uncover more about its evolutionary significance.

How Social Behaviors Shape Our Lives

Contagious behaviors, whether it’s yawning, tapping along to a rhythm, or even urinating, highlight how group living shapes both human and animal lives. As Ena Onishi points out, “Humans and non-human animals share many social phenomena linked to group living—we’re all influenced by the presence of others, even in everyday activities.”

This study’s findings offer a fascinating glimpse into the ways social interactions permeate even the most basic activities. It’s a reminder that sometimes, our instincts to “go with the flow” might be more literal than we think.

Products Related to This Topic

For those curious about the behaviors of chimpanzees or interested in evolutionary biology, check out these products on Amazon:

• "The Chimpanzee Whisperer" by Stany Nyandwi
• "Our Inner Ape: A Leading Primatologist Explains Why We Are Who We Are" by Frans de Waal
• "Evolutionary Analysis" by Jon Herron and Scott Freeman

Note: These are affiliate links, meaning I may earn a small commission if you make a purchase through them. This comes at no extra cost to you.

Have you ever noticed a seemingly small behavior that connects us with the animal kingdom? Let me know your thoughts in the comments below!