Nonhuman Primate Behavior Chapter 9 Anthropocentrism Anthropocentric Viewing

Nonhuman Primate Behavior Chapter 9

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

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

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

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

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

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

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

Resources • Leaves • 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

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

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

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

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

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

Aggression • Intragroup 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

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

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