1. Nonhuman Primate Behavior
Chapter 9

2. Anthropocentrism
Anthropocentric - Viewing nonhuman animals in terms of human motives, and experience and capabilities
Emphasizing the importance of humans over everything else

3. What is Behavior?
Anything organisms do that involves action and response to internal or external stimuli
The response of an individual or group to its environment
May or may not be deliberate
Not necessarily the result of conscious decision making
The underlying principles of behavioral evolution lie in the interactions between a number of environmental and physiological variables

4. Behavioral Ecology
Focus on the relationship between behaviors, natural environment, and biological traits of the species
Based on the assumption that animals, plants, and microorganisms evolved together
Behaviors have evolved through the operation of natural selection:
Some behaviors are influenced by genes and are subject to natural selection the same way physical characteristics are

5. The Evolution of Behavior
Behavior as phenotype
Behavioral phenotypes that increase fitness pass on genes at a faster rate
Genes do not code for specific behaviors (aggression, cooperation, etc.)
Genetics
Species vary in their limits and potentials for learning and behavioral flexibility
Natural selection acts on genetic factors shaped by the ecological setting of past and present

6. Why Be Social?
Group living exposes animals to competition with other group members, so why not live alone?
Costs of competition are offset by the benefits of predator defense provided by associating with others
Group living evolved as an adaptive response to a number of ecological variables

7. Social Bonding
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 groups

8. Why Primates Form Groups
There are two main hypotheses:
Resource-defense model
Focus on the notion that a group of animals can better defend resources
Species that rely on foods distributed in clumps tend to be more protective of resources
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

9. Resources Leaves Insects Fruits and nuts
Abundant, dense, and support large groups of animals
Insects
Widely scattered, causing animals to feed on them alone or in small groups of two or three
Fruits and nuts
Occur in clumps and are most efficiently exploited by smaller groups of animals
Large groups break up into smaller subunits to feed

10. Predation Primates are vulnerable to many predators
Snakes, birds of prey, leopards, wild dogs, lions, other primates, etc.
Where predation pressure is high, large communities are advantageous
These may be multi-male, multi-female groups or congregations of one-male groups

11. Group Size
Several factors determine the size of a particular primate group. These include whether the primate is:
Nocturnal or diurnal
Arboreal or terrestrial
Type of diet
Benefits in terms of energy (calories) obtained from food versus costs (energy expended) of obtaining and digesting

12. Other Factors that Influence Social Structure
Body Size
Larger animals require fewer calories and therefore consume larger amounts of lower quality foods
Larger animals are better able to retain heat and their overall energy requirements are less
Relationships with Non-predatory Species
Many primate species associate with other primate and non-primate species for various reasons, including predator avoidance

13. Other Factors that Influence Social Structure (cont’d)
Dispersal
Members of one sex leave the group in which they were born when they become sexually mature
Individuals who leave find mates outside their natal group
Life Histories
Developmental stages that typify members of a species and influence reproductive rates
Examples: length of gestation, time between pregnancies, period of infant dependency, age of sexual maturity, and life expectancy

14. Dominance
Dominance hierarchies – Primate organization that imposes order and establishes parameters of individual behavior
Higher-ranking animals have greater access to preferred food items and mating partners than lower ranking individuals.
Dominance hierarchies are sometimes called “pecking orders”
Learned
May change over the animal’s life
Factors that influence dominance:
Sex
Age
Aggression
Time in the group
Motivation
Mother’s position

15. Aggression Intragroup Aggression Intergroup Aggression
Lead to group disruption
Frequently develops out of competition for resources
Often resolved through submission
Dominant individuals may keep subordinates from food
Intergroup Aggression
Home range – permanent association with a territory
Core area – are within the home range which contains the highest concentration of predictable resources
Where the group is most frequently found
Territory - portion of the home range defended against intrusion

16. Primate Cultural Behavior
Cultural behavior is learned
Passed from generation to generation through observation and instruction
Nonhuman primate infants
Observe their mothers and others
Learn about food items, appropriate behaviors, and how to use and modify objects

17. Examples of Cultural Behavior
Japanese macaques and sweet potato washing
Orangutan nest building
Gorilla depth testing
Chimpanzee termite fishing, leaf sponges, hunting “spears,” nut cracking