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.
Julie H says
Well put, J.B. Thank you for your insight and education.
Margaret. And Karen says
Thank you for this clear information, J.B.
Katelyn says
J.B., thank you for commenting on these incidents and always striving to educate others through a balanced perspective. This is so important and I really appreciate that CSNW is always willing to speak realistically about all aspects of chimpanzee nature in a professional and respectful manner. While we may not be able to fully comprehend the motivations behind their behaviors, it gives all of us the opportunity to hold much deserved appreciation and respect, simply for who they are.
Meg says
These unfortunate incidents are good reminders and hopefully will keep people from wanting a chimpanzee for a “pet” or a movie studio from using chimpanzees in ads or a movie.
dr mel richardson says
It is interesting that we as humans, the most violent primate, insist on believing a Disneyesque view of the natural world. Violence & compassion are two faces of the same coin. As has already been stated, this illustrates why great apes should never be kept as pets!!
Carissa says
Thank you for this post. I thought it interesting that both of these incidents happened so close together. I love chimpanzees and understand that aggression is part of their nature, but I think it’s interesting that they are more violent than gorillas (aren’t gorillas quite a bit bigger than chimps?) and orangutans. Why do you think that is? I think it’s a good thing, of course, otherwise I can imagine humans everywhere having them as pets / raising them as children.
J.B. says
There are a number of theories that attempt to explain the different levels of aggression seen in the great apes. I am not familiar enough with them to explain them adequately, but if you are interested in learning more I would recommend a book called Demonic Males by Wrangham and Peterson.
Maria Blake says
Chimps may have a certain amount of violence inherent in their makeup, but it’s also true that in the zoo the male chimp had no way to get away from an annoying youngster, and the mother had no way to get the little one away from the adults. There was no where for the little one to go and play with other little ones and not annoy the grown ups. Plus there is a certain amount of stress in captive animals that cannot be relived in a zoo setting. I think you will agree these are all factors that should be considered.
J.B. says
Certainly. Captivity affects chimpanzee behavior in countless ways, to the extent that I don’t believe it can ever meet their physical and mental needs. It leads to chronic stress, frustration, and boredom, and the unnatural physical and social environment results in chimpanzees that don’t know how to be chimpanzees. But as much as I would like to see an end to keeping and breeding chimps in captivity, I do believe that we should at least be cautious in assigning blame or ascribing motivation behind specific incidents. We know that infanticide is a rare but normal occurrence in the wild, so we shouldn’t be surprised if it happens with a similar relative frequency in captivity. I have very little experience with young chimpanzees, but I know that three-month-old chimpanzees spend almost all of their time clinging to their mothers (they are about as independent as a three-month-old humans), so I would doubt that the youngster did much to aggravate the situation.
Sara L., Fairfax, VA says
You said in the last paragraph exactly what I was thinking throughout the whole piece – not only are we so genetically close, but so societally as well. Whereas it is my hope that these comparisons can shed perspective (and motivation?) on cognizant human evolution away from violent tendencies, we also are reminded of the biological connections that bind our two species.
Thank you for sharing your knowledge and providing us this first hand education about chimpanzee behavior.
Seewolfman says
Although we are genetically very close to chimpanzees, incidents like in Stamford or at Chimp Eden remind me of the fact ,that there is still one big difference: We have a moral codex and an understanding of right and wrong, whereas chimpanzees like all animals are guided by instinct.
We humans would think: It makes no sense to attack a caregiver: He is no enemy, he does not compete to get mating chances or climb the hierarchy, he does not mean food: Just the opposite, he provides it, but this is how a reflective human would ponder in the process of making a decision.
Even the often as “hippie-apes” labelled bonobos have obviously that side: I read that an incident happened at lola ya bonobo, where caregivers were attacked and partly mutilated by bonobos, who formerly lived in the sanctuary.
Although I wish that chimps would not have that violent side, I guess there is nothing that can be done about it except being careful…This is one reason I have chihuahuas as pets, by the way!
J.B. says
Yes, better to stick with chihuahuas, although I have known a few that could give chimps a run for their money 🙂
I agree that a reflective human might think that way, but I think we give ourselves too much credit if we believe we are always so reflective. Human cultures have developed ways to inhibit violence in day to day interactions. We have cultural norms against overly aggressive behavior, we have laws to enforce those norms, and we ritualize our struggles for dominance. But this does not end violence altogether. Open a newspaper on any day in any city and you can find countless examples of human violence, despite our best efforts to contain it.
Chimpanzees also have norms and ritualized behavior in their societies. Young chimpanzees learn the norms of their society from their mothers, other adults, and their peers. I would argue that chimpanzees do have a sense of right and wrong, however their rights and wrongs are sometimes different than ours. Furthermore, not all members of a society will follow the laws and norms of that society. Our prisons are filled with people we consider to be rule breakers; chimpanzee societies have rule breakers as well.
Violence against caregivers is always difficult to accept, but in my mind it is understandable. If I were held captive for decades, I would get pretty frustrated with the people that held the keys to my cage. And even if resentment is not a factor, captivity creates an “us and them” dynamic, just by virtue of chimpanzees and humans living on different sides of steel bars and electric wire. In chimpanzee society, members of the outgroup are more likely to be victims of severe aggression. This is another unfortunate trait that we both share.
I hope I didn’t imply in my blog post that chimpanzees are mindlessly aggressive, but I think it’s important that we accept chimpanzees for who they are, and resist the temptation to explain away all behaviors that we find unpleasant. If we allow ourselves to believe that we can explain all acts of violence, then we develop the illusion that we can control it, and that is very dangerous. Humans aren’t strong enough to deal with chimps on their own terms, nor are we smart enough to predict with perfect accuracy when they will become aggressive. So the best we can do is to let chimps be chimps, and as you say, make it our responsibility to stay as safe as possible.
Seewolfman says
Thx for the detailed answer. I am aware that a lot of humans don`t play by the rules and show antisocial behavior. Perhaps I should have mentioned it in my previous post.
I appreciate that you pointed out that animals (chimps) have their rules , too, what is right in their society and what wrong. But I wonder how far does the insight really go. For example my Chihuahuas: Do they understand that it is wrong not to mess on the carpet, because it gets dirty, or do they not mess on it, because they know I don`t like it…This is just a small example, that came to my mind. But I guess we will never know what is really going on in their minds. This is – for example- why a human that is criminal should be punished ( in case he knows right from wrong) but not an animal- they just have different rules and different perception of reality than we.