Why Study Non-Human Primates?

Why Study Non-Human Primates?

1. Behaviors universal among modern primates give us clues to our ancestors’ behavior

2. Allows reconstruction of social structure, ecology, and intelligence of early humans

3. Compare and contrast primate social organizations, communication, intelligence

4. Better understand the environmental factors that led to the divergence of the human lineage

5. Learn how we can preserve the endangered primates

The Evolution of Behavior Behavior has evolved through

natural selection

Individuals act to maximize its own reproductive success

Natural selection acts on behaviors in the same way it acts on physical characteristics

Behavior is the product of complex interactions between genetic and environmental factors

Factors That Influence Behavior Quantity and quality of foods

Spatial distribution of food resources

Distribution and reliability of water supplies

Body size

Distribution and types of predators

More Factors That Influence Behavior

Distribution and types of sleeping sites

Activity patterns

Relationships with other nonpredator species

Impact of human activities

Comparing Behavior HOMOLOGIES = Traits shared by 2 or

more species through inheritance from a common ancestor

Ex. = chimps more homologous to humans (diverged 5 mya) v. baboons & humans (diverged 20 mya)

ANALOGIES = Traits shared by 2 or more species that are similar in function but not evolutionarily related

Ex. = bat and insect wings The more evolutionarily distant, the

less useful the comparison!

Dominance Relative hierarchical position of an

individual in a social group

Most primate societies are organized into dominance hierarchies

Reduces the amount of actual physical violence: determines who gets what & when

Dominant animals can often exert control with only a gesture

Dominance (cont.)

Measured by: looking at access to limited resources, interactions between individuals

Influenced by: age, sex, personality, amount of time in the group, intelligence, mother’s status, number of relatives in the group

Status is learned

Communication• Transmission of information through the

senses

• Scents, facial expressions, gestures, postures, vocalizations

• Displays = repetitious behaviors that communicate emotional states

• May be unintentional or intentional

• Submissive gestures reduce aggression

• Functions: threaten, invite play or grooming, express dominance, reassure, greet, warn about predators, etc.

Aggression

Conflict develops out of competition for resources

Most situations are resolved through submissive and appeasement behaviors

Competition for mates frequently results in injury, and occasionally death

Affiliative Behaviors

Physical contact promotes peace in social groups

Grooming reinforces social bonds

Relationships are crucial and bonds between individuals can last a lifetime

Altruism is common among many primate species

Affiliative Behaviors (cont.) Reconciliation, consolation, and

friendly interactions

Based on physical contact (hugging, hand holding, touching, kissing)

Nonhuman primates form alliances: two or more animals join together for a common purpose

Play Difficult to define, but you know it when

you see it Occurs most commonly in infants and

juveniles Requires curiosity (intelligence?) and

can be dangerous…requires parental vigilance

Functions to build the individual’s mental, social, and physical skills

Time spent in play declines when the individual is stressed (e.g. malnutrition)

Adults also play, but usually is oriented toward parenting responsibilities

Patterns of Reproduction Females are receptive to males

only when they are in estrus Permanent bonding is not common

Sometimes, mating relationships are formed, temporary relationships that last while the female is in estrus

Reproductive Strategies Estrus = behavioral and physical

changes that indicate that a female is ovulating and receptive to copulation

Some primates (including humans, gibbons, and bonobos) mate throughout the female’s cycle and give no obvious signals of ovulation

Influences how the two sexes interact and the species’ mating system

Reproductive Strategies (cont.)

• Females spend almost all of their adult lives pregnant, lactating and/or caring for offspring

• Males try to secure as many mates as possible to increase genetic contribution to the next generation

Mothers and Infants Basic social unit among primates

Monkeys and apes raised in captivity without contact with their own mothers did not know how to care for infants

Males do not participate greatly in the rearing of offspring

Culture Culture is learned and passed on from

one generation to the next

May be learned through instruction (common only for humans) and through observation (common in all primates)

Cultural traditions are behaviors that become common in the entire group

Examples: washing potatoes, tool use, dietary preferences, greeting styles

AnthropocentricViewing nonhuman primates in terms of human experience; emphasizing the importance of humans over everything else

Dominance hierarchiesIndividuals within a group are ranked relative to one another

GroomingPicking through fur to remove dirt, parasites, and other materials, reinforces social relationships

Primate Behavior: Some Key Terms

Reproductive strategiesBehavior patterns that contribute to individual reproductive success

Sexual selectionType of natural selection that operates on only one sex within a species

AltruismAny behavior or act that benefits another individual but poses some potential risk or cost to oneself (adoption, protecting young, helping another in a fight)

Primate Behavior: Some Key Terms

Langur: Old World Monkey (Vietnam, India, Cambodia)

Langur: “Takeover” Behavior Social

Organization: 1 adult male, several adult females, offspring; other males live in “bachelor” groups

Takeovers involve running out the resident male and killing all unweaned infants

Why do Langurs “Takeover”?

Males kill infants to cause mothers to begin reproductive cycles

Takeover male can father offspring faster than if he waited 1-2 years for weaning to occur

Male tenure in the group is short--3 years or less

Takeover male is attempting to maximize his reproductive success