As an undergraduate at MIT, I wrote a term paper for 9.20 (Animal Behavior) about carnivorous chimpanzee behavior. Many years earlier, I had watched a documentary on apes, and a single brief scene described the basics of male chimpanzee hunting parties. The majority of that scene was filled with ominous music and wild screams, with little or no footage of chimps engaging in true raids. When the topic of ape feeding behavior arose in 9.20, I was mystified by the absence of any mention of meat-eating chimps in the texts. Why so little discussion? My curiosity was further aroused, and it turned out to be a fine topic for a term paper.
Over the course of my research, I couldn't ignore the many papers on inter-species chimpanzee fighting, often because there were common authors such as John Mitani. One of the most interesting cases I came across in my research was an instance where a group of males encountered a female with a young baby at the edge of the group's territory. The female had not been seen in the area for at least a few months. Researchers believed she might have been with an adjacent group, among their males.
The males she encountered seemed to think so, or at very least knew that none of them had copulated with her anytime recently. Her baby was not of their group, so, they forcibly took it from her and tore it apart. This fit into my carnivorous behavior research because the males then ate some of the baby after it was assuredly dead.
Chimps take their borders quite seriously. Now, from more recent research by Mitani with the chimps of Ngogo in Uganda, it has been revealed that their wars are even more sophisticated.
Chimpanzee gangs kill for land, new study shows
ScienceDaily (2010-06-22) -- Bands of chimpanzees violently kill individuals from neighboring groups in order to expand their own territory, according to a 10-year study of a chimp community in Uganda that provides the first definitive evidence for this long-suspected function of this behavior. ... > read full article
Good read. Mitani concedes that they can't be sure if the territorial acquisition is aimed at increasing resources or mates. I like their take on cooperation: while these findings are incredibly violent, it is still worth noting the incredible level of group unity necessary for the success of such efforts. So much cooperation research emphasizes friendly or altruistic interactions, probably because the competitive and violent sorts are not pleasing for most audiences to hear about.
I like chimps a lot. Some people complain that they're too aggressive and unfriendly, unlike bonobos or gorillas. First of all, chimps aren't that aggressive; I think they have a bad rap. Secondly, yes, they are more aggressive than many other apes, but so are humans.