1. Nonhuman Primate Behavior
Chapter Nine
Nonhuman Primate Behavior

2. 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.

3. 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

4. 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.

5. 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.

6. 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.

7. Photos of Baboon Behavior

8. 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.