III.

Social Behavior

Chimpanzees form loosely organized bands of 2 to 80 individuals on fairly large home ranges, where the animals remain for years. Within a community, smaller groups may form, break up, and reform; sometimes a female migrates to another community. Males never migrate. Except between mother and young, little permanency exists in individual relationships. Members of a community cooperate in hunting and sharing food. On finding a food source, they hoot, scream, and slap logs to attract others. A constant interplay occurs between adults, and all members of the group groom one another.

Major differences exist between the social structure of groups of common chimpanzees and bonobos. A dominant male typically heads a group of chimpanzees, using size and strength, or even aggression to assert authority. Bonobo groups are dominated by females and males rarely show aggression. Male common chimpanzees form gangs to hunt prey or patrol their territories. In a behavior that has been likened to warfare, the gangs of males will sometimes attack and kill chimpanzees from neighboring troops that are found near their territories. Bonobos are much less aggressive toward neighboring troops and have been seen intermingling peacefully with other groups of bonobos for short periods.