Chapter 7 Primate Behavior

Observing Primates (a) Rhesus macaques spend much of their time on the ground and are easier to observe than (b) black- and-white colobus.

Terms Behavior – Anything organisms do that involves action in response to internal or external stimuli. Free-ranging – Pertaining to non-captive animals living in their natural habitat. Social Structure – The composition, size, and sex ratio of a group of animals. Behavioral Ecology - An approach that focuses on the relationship between behaviors, the natural environment, and biological traits of the species.

Factors That Influence Social Structure: Body Size Larger animals are better able to retain heat and their overall energy requirements are less than for smaller animals.

Factors That Influence Social Structure Basal Metabolic Rate (BMR) and Diet –Smaller animals generally have a higher BMR than larger ones. –Consequently, smaller primates require an energy-rich diet high in protein, fats, and carbohydrates. Metabolism – The chemical processes within cells that break down nutrients and release energy for the body to use.

Factors That Influence Social Structure Distribution of Resources –Leaves can be abundant and will support large groups of animals. –Fruits and nuts occur in clumps. These can be efficiently exploited by smaller groups of animals.

Distribution of Resources This male mountain gorilla has only to reach out to find something to eat.

Factors That Influence Social Structure Predation –Primates are vulnerable to many types of predators –Where predation pressure is high, large communities are advantageous.

Factors That Influence Social Structure Relationships with Other, Nonpredatory Species

Factors That Influence Social Structure Dispersal –Members of one sex leave the group in which they were born when they become sexually mature.

Factors That Influence Social Structure Life Histories –Life history traits are characteristics or developmental stages that typify members of a species and influence reproductive rates.

Factors That Influence Social Structure

Activity Patterns –Nocturnal species tend to forage for food alone or in groups of two or three and many use concealment to avoid predators.

Factors That Influence Social Structure – Human Activity

Matrilines Groupings of females who are all descendants of one female Matrilines also include dependent male offspring.

Types of Nonhuman Primate Social Groups One male-multifemale. Multimale-multifemale Monogamous pair Polyandry Solitary Philopatric

Sympatric Living in the same area. Kibale Forest, Uganda

Primate Social Strategies

Primate Social Behavior: Dominance Many primate societies are organized into dominance hierarchies. These impose order by establishing parameters of individual behavior.

Breeding and Suppressed Males Fully mature, breeding male orangutan with well- developed cheek pads (a) compared to a suppressed adult male without cheek pads (b).

Factors that Influence Dominance Status –Sex –Age –Aggression –Time in the group –Intelligence –Motivation –Mother’s social position One young male savanna baboon mounts another as an expression of dominance.

Primate Social Behavior: Communication An adolescent male savanna baboon threatens with a characteristic “yawn” that shows the canine teeth. Note that the eyes are closed briefly to expose light, cream colored eyelids. This has been termed the “eyelid flash.”

Displays Sequences of repetitious behaviors that serve to communicate emotional states. Nonhuman primate displays are most frequently associated with reproductive or agonistic behavior.

Chimpanzee Facial Expressions

Primate Social Behavior: Aggression Conflict within a group frequently develops out of competition for resources, including mating partners and food items.

Primate Social Behavior Affiliative Behaviors Common affiliative behaviors include reconciliation, consolation, and simple amicable interactions between friends and relatives.

Patterns of Reproduction In most primate societies, sexual behavior is tied to the female’s reproductive cycle.

Reproductive Strategies Behavioral patterns that contribute to individual reproductive success. K –selected Sexual Selection

Infanticide As A Reproductive Strategy? Hanuman langurs live in groups of one adult male, several females, and offspring. Males without mates form groups and occasionally attack a reproductive male and drive him from his group. Sometimes the new male kills some or all of the group’s infants.

Chacma Baboons When chacma baboon males migrate into a new group, they “deliberately single out females with young infants and hunt them down”.

Mothers, Fathers and Infants The basic social unit among primates is the female and her infants. (a) Sykes monkey. (b) Patas monkey.

Primate mothers with young. (c) Mongoose lemur. (d) Orangutan. (e) Chimpanzee.

Infant Macaque Clinging to Cloth Mother

Misunderstanding Primates This unfortunate advertising display is a good example of how humans misunderstand and misrepresent our closest relatives.