Sanctuary

Male chimpanzees can be pretty cruel to the females in their group. Why are some of them such jerks sometimes?

From an evolutionary perspective, this aggression is thought to serve two functions. First, it may serve the purpose of establishing dominance. This is particularly true for adolescent males, who rise through the ranks in their communities by establishing dominance over each of the females before working their way into the adult male hierarchy. But it may be true for adults as well, as these displays of dominance can signal their fighting ability to other males in the group without the increased risks associated with directing aggression towards those other males.

Second, research suggests that, in adults, female-directed aggression by males also serves as a form of coercion. In some communities, males that exhibit more aggression towards females have been shown to sire more offspring by either increasing the probability that a female will mate with them or decreasing the probability that she will mate with someone else.

Most captive male chimpanzees, Willy B included, don’t even exhibit copulatory behavior, since they were raised in such atypical physical and social environments. It’s interesting then, and unfortunate, that this predisposition towards female-directed aggression nevertheless persists.

These same adult males and females can at other times be quite playful with one another. In wild environments, this appears to be more evident when resources are abundant, which suggests that play—known to have significant social and developmental benefits in adolescents—also benefits adults when time and energy are available. This may be why we see so much play in adult captive chimpanzees—after all, in better environments, most of the nutritional resources they need are all provided to them. Of course, some forms of play can be a mechanism to ease an underlying tension, which may be why play is so common before feeding times. But in most cases, it’s hard to see it as anything other than two chimps having fun.

When we study other animals, we don’t think in terms of “good” and “bad” behavior. Instead, we try to describe what is and develop explanations for how it came to be that way. Living with chimpanzees on a daily basis, though, can challenge this kind of impartiality. You cheer when you see them playing together and film it so others can share in their fun. And you become frustrated and upset with them when they fight. And before long you find yourself—biology be damned!—rooting for Honey B, who would sooner die than give an inch to any of those dumb, bullying boys.