Nice article by Nick Wade about the longitudinal research of John Mitani, from the University of Michigan, and colleagues, on a large chimp colony in the Kibale National Park in Uganda. Mitani et al have watched this colony grow, and watched the periodic patrolling of male chimps into adjoining territory - often attacking and killing the neighbouring males. This is a much better researched surveillance of chimp territorial aggression than has ever been previously reported. Eventually the Ngogo chimp colony annexed the neighbouring territory altogether - adding a valuable new resource of fruiting trees to their territory - important because good food supply correlates with more babies for chimp females.
The article goes on to debate the old saw about the origins of such aggression, whether or not it was shared by a common ancestor of chimps and humans, and, therefore, about whether or not chimp aggression and territoriality can tell us anything interesting about human aggression and territoriality. Richard Wrangham is cited opining that it is very unlikely that chimps could marshal enough future strategising to link current aggression with the future ceding of territory and suggests that such aggression is simply hard-wired into chimps. He believes the ability to wage war against one's own species goes back to the common ancestor of chimps and gorillas some 7 million years ago, as well as the human-chimp common ancestor some 5 million years ago. Mitani stresses the high level of cooperation between chimps of one colony - that allows cohesive war-like behaviour. He raises the controversial idea that group selection of such behaviour, involving a degree of altruism, might be part of the explanation. That sets him at odds with the vast majority of the evolution community.