Chimpanzee Sanctuary Northwest

Hope. Love. Home. Sanctuary for primates.

aggression

Slo Mo Dominance Display

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What’s more terrifying than a chimpanzee dominance display? A dominance display in slow motion.

The chimps have been crazy all day. Burrito can become very sexually aroused when the girls have their swellings, particularly when all three girls who cycle are in estrus at the same time. But because he was raised by humans (like most entertainment and research chimpanzees), he doesn’t exhibit normal sexual behavior. The result is a lot of tension, a lot of frustration, and a whole lot of chaos.

Jamie stepped out of the playroom during the afternoon to release some of that tension in the form of a dominance display. Displays are partly under conscious control and partly not. In this case, it seemed clear to me that Jamie climbed to the top of the platform with the intention of displaying. But at the same time she wasn’t fully in control of the display. We often liken displays in this way to sneezes. You know when you have to sneeze but you just can’t? And you can’t do anything else until the sensation either dissipates or culminates in a sneeze? That’s what displays can seem like for chimpanzees. Jamie stood on that platform for three minutes, rocking back and forth, softly pant hooting, and then repositioning and hooting some more, until she finally got everything out in a two-second display. When she was finished, she went about her business as if nothing had happened.

I think we’ll all be a lot happier in a few days when Burrito can start to focus on other things…

Balance

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Chimpanzees have a well-deserved reputation for being aggressive. They fight over food, over sex, and over territory. They fight for dominance and out of jealousy.

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Sometimes I don’t think they even know why they are fighting – some fights among the seven end with all of them standing in a circle, screaming and looking around at each other as if to see if anyone else remembers what they are fighting about.

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But as violent as chimps may be, fights are relatively infrequent. They are much more likely to be hugging,

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and kissing,

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and grooming,

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and holding hands (and feet).

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I used to think it was strange that animals capable of such extreme violence could be so tender and gentle. But I’m beginning to think it’s precisely because they are so violent that they are also so tender and gentle. A society with that level of aggression would not last long without an equally powerful force holding it together.

Violence

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Recently, an infant chimpanzee at the L.A. Zoo was killed by an adult member of the troop in full view of zoo visitors. A few days later, a student volunteering at the Chimp Eden sanctuary in South Africa was pulled into an enclosure and attacked by two adult male chimpanzees. Both incidents served as startling reminders of the capacity for violence in our closest relatives and have left many people wondering what makes chimpanzees commit such severe acts of aggression.

Unfortunately, while incidents like these are rare, they are not abnormal. Put simply, violence is a fact of life in chimpanzee society. While males typically grab all the attention with their aggressive dominance struggles and their lethal intergroup raids, females also kill on occasion, with infants and other adult females being their most likely victims. In chimpanzee communities, severe aggression can be a means to reduce or prevent resource competition. This can result in the killing of members of other communities, as well as immigrant females and even infants within the troop. In some cases, the killing of an infant can increase mating opportunities for males. For instance, if a female gives birth, she will not enter estrus for another four to five years while she nurses and raises her new child. If that child dies, however, she will quickly become receptive again. Thus, there can be an incentive for a male who is not the parent to kill the infant so that he can mate with the mother (this is one reason primatologists believe that females may try to confuse paternity).

Violent behavior can serve many functions in chimpanzee society. What functions did these incidents at the L.A. Zoo and Chimp Eden serve? Honestly, we don’t know. It’s much easier to offer an evolutionary explanation for why violence exists in general than it is to explain specific acts.

As caregivers for captive chimpanzees, we witness aggressive behavior on a daily basis. Sometimes the motivation behind it is clear; other times we are left scratching our heads. The way I think about it is this: evolution has endowed chimpanzees with certain tendencies for aggressive behavior, but it does not control how those tendencies are applied. Aggression towards non-group members in the wild can help chimpanzees defend territory and the resources located therein. But that same aggressive tendency can also result in an attack on the very people trying to care for them in captivity.

All we really know is that violence in chimpanzees is not an aberration, nor is it all they are capable of. In fact, one of the reasons why we might be uncomfortable with chimpanzee violence is that it hits a little too close to home. To be sure, aggression in chimpanzees is shocking in its sheer physicality – teeth and fists instead of knives and guns. But even though chimpanzees exhibit higher rates of aggression overall, rates of lethal violence in chimpanzees are similar to those in some human societies. In some ways, we are more alike than we’d like to believe.