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 their 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

Primate Behavior: Some Key Terms Anthropocentric Viewing nonhuman primates in terms of human experience; emphasizing the importance of humans over everything else Dominance hierarchies Individuals within a group are ranked relative to one another Grooming Picking through fur to remove dirt, parasites, and other materials, reinforces social relationships

Primate Behavior: Some Key Terms Reproductive strategies Behavior patterns that contribute to individual reproductive success Sexual selection Type of natural selection that operates on only one sex within a species Altruism Any behavior or act that benefits another individual but poses some potential risk or cost to oneself (adoption, protecting young, helping another in a fight)

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

Dettwyler questions Describe the goals and methods of the CARE health projects in the villages around Macina in northern Mali. What kinds of problems did the villagers face, and how did the CARE project help them deal wih their problems? Why does Katherine Dettwyler say that good nutrition may be more important than immunization against specific diseases or oral rehydration therapy, in the long run? How should development projects be designed? That is, who should decide what needs to be done and how to go about doing it? How much input should the villagers themselves have in designing and implementing projects? Give an example.