Nonhuman Primate Behavior Chapter Nine Nonhuman Primate Behavior

Why Primates Form Groups There are two main hypotheses: the resource-defense model the predation model The resource-defense model is based on the idea that a group of animals can defend access to resources, such as fruit trees. The predation model emphasizes the risk that primates face from predators. Primates in larger groups will have a better chance to detect predators and potentially defend themselves against predation.

Kinds of Primate Social Organization Several factors determine the size of a particular primate group. These include whether the primate is: nocturnal or diurnal arboreal or terrestrial the type of diet Primate groups are usually based on relationships between females (female bonded kin groups). The types of groups that primates form include monogamous pairs polyandrous groups one-male groups multi-male groups fission-fusion societies

Case Study: The Gibbon Gibbons live in monogamous groups. Grooming is a behavioral pattern common to primates. Play behavior among juveniles is also important. Gibbons are highly territorial. Territorial conflict is expressed mainly through vocalization and display.

Case Study: The Gelada Geladas are large, primarily terrestrial monkeys. The basic social units are the harem and the all-male group. The smaller units may gather into larger social units that share a home range. Agonistic behavior is frequently seen.

Case Study: The Savanna Baboon Baboons live in a social unit called a troop. Troops remain within a home range, but the boundaries are not defended. The adult males are arranged into a dominance hierarchy. Behaviors associated with this include threat gestures, displacement, presenting, and mounting. Adult females also form dominance hierarchies, but dominance interactions are not observed as often among females as among males. Females display a sexual swelling that indicates estrus. Grooming clusters of females are commonly seen.

Photos of Baboon Behavior

Case Study: The Chimpanzee The chimpanzee spends much time in the trees feeding, resting, and sleeping. Movement between the trees is done on the ground. Chimpanzee groups are based on bonds between males. A chimpanzee community is made by of a continuously changing series of smaller groups, an example of a fission-fusion social organization. The hunting of meat and use of tools, such as termite sticks, also characterize the chimpanzee.