ABSTRACT
Aggression is found throughout the animal kingdom and occurs between members of the same and different species. Depending on the species and the setting, intraspecies aggression can serve several functions, including obtaining food and other resources, gaining access to mates, defending territories, and establishing and maintaining position in a dominance hierarchy. Interspecies aggression can function to subdue prey and fend off their counterattacks, defend against predators, and defend others-especially the young. Selection pressure for the development and refinement of fighting skills has likely been significant, given the importance of the previously mentioned activities for survival and reproductive success.
