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Why Study Non-Human Primates?
1. Behaviors universal among modern primates give us clues to our ancestors’ behavior
2. Allows reconstruction of likely social structure, ecology, and intelligence
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
Individual acts 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
Comparing Behavior HOMOLOGIES = Traits shared by 2 or more
species through inheritance from a common ancestor
Examples= human arms & bat wings, chimp & bonobo behavior 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
Example= bat and insect wings The more evolutionarily distant, the less
useful the comparison!
Factors That Influence Behavior
Distribution and types of sleeping sites
Activity patterns
Relationships with other nonpredator species
Impact of human activities
Nonhuman Primate Behavior: Dominance
Most primate societies are organized into dominance hierarchies
Reduces the amount of actual physical violence
Dominant animals can often exert control with only a gesture
Dominance
The relative hierarchical position of an individual in a social group
Maintains group order by determining who gets what, when
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
Nonhuman Primate Behavior Communication
• Transmission of information by sensory means Scents, facial expressions and displays,
gestures, postures, vocalizations Displays--sequences of repetitious behaviors
that communicate emotional states• May be unintentional or intentional• Submissive gestures reduce
aggression• Physical contact and grooming reinforce
friendly intentions• Used to threaten, invite play or
grooming, express dominance, reassure, greet, warn about predators, food
Nonhuman Primate Behavior 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
Nonhuman Primate Behavior 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 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
Nonhuman Primate Behavior 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• 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
Nonhuman Primate Cultural Behaviors
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
social structureComposition, size and sex distribution of a group of animals
dominance hierarchiesSystems of social organization wherein individuals within a group are ranked relative to one another
communicationActs that convey information, in the form of a message, to another individual
displays Sequences of repetitive behaviors that serve to communicate emotional states
affiliativePertaining to amicable relationships between individuals
territoriesAreas aggressively protected by an animal or group of animals
groomingPicking through fur to remove dirt, parasites, and other materials that may be present; common among primates; reinforces social relationships
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)
Langur: “Takeover” Behavior One 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 does this behavior occur?