Why Study Non-Human Primates?

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Why Study Non-Human Primates?
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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 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

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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

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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

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More Factors That Influence Behavior

• Distribution and types of sleeping sites
• Activity patterns
• Relationships with other nonpredator species
• Impact of human activities

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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!

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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

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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, mothers status,
  number of relatives in the group
• Status is learned

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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.

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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

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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

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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

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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
  dangerousrequires parental vigilance
• Functions to build the individuals 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

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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

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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 females cycle and
  give no obvious signals of ovulation
• Influences how the two sexes interact and the
  species mating system

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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

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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

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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

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Primate Behavior Some Key Terms

• 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

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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)

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Langur Old World Monkey (Vietnam, India,
Cambodia)
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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

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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