Chimpanzees are well known for their territorial behavior. They are among the few animals that engage in cooperative group aggression that sometimes results in fatalities.
Encounters between communities typically take place during boundary patrols. Communities defend a specific territory within the surrounding forest. Males form border patrols and walk the perimeter of their community’s territory looking for invading neighbors. Several factors influence territory size, including the number of individuals in the community, habitat quality (food availability and variety), pressure from neighboring communities, and population density. The main difference between chimpanzee communities and other multi-male primate groups is that male chimpanzees remain in their natal communities and females may disperse to neighboring communities once they have reached sexual maturity. This allows male chimpanzees to form strong bonds within their groups and results in close genetic ties. As a male dominant, hierarchical species, chimpanzee alliances are critical to achieving a high rank within the community.