Agonistic interactions of captive female orang-utans with infants.

Female orang-utans with infants were pair-tested for dominance (displacement behavior) and for competitive food-getting. Dominance was quickly established in the first test for each pair, displacements were unidirectional in all tests and dominant animals obtained essentially all food incentives in 3 of the 4 series of tests. Agonistic interactions were similar in most respects to those of monkey, but were not influenced by location of testing, i.e. home cage. Aggressive behavior and food-getting were related to body weight but displacement was not. This development of dominance relationships is similar to those reported for many territorial vertebrates confined to restricted spatial conditions.