Primate Social Behavior


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Basics of primate research and characteristics of primate behavior, including grooming, dominance hierarchies, and agonistic interaction

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Primate Social Behavior

  1. 1. Primate Social Behavior Are Chimps Like Us?
  2. 2. Why Study Primate Behavior? <ul><li>In terms of taxonomy and genetics, chimps and bonobos are our closest relatives. </li></ul><ul><li>Anatomically, they are very similar to us </li></ul><ul><li>Chimps have 98.5% of our genes </li></ul><ul><li>Human and chimp ancestors diverged about six million years ago; chimps and bonobos separated about 4 million years ago </li></ul><ul><li>So understanding chimpanzee behavior may give us a clue to our own and raise the question of which behavior may be genetically determined. </li></ul>
  3. 3. Other Dimensions of Primate Behavior <ul><li>To What Extent do genes govern our behavior? </li></ul><ul><li>Ant society are genetically determined </li></ul><ul><li>“ Instinctual” behavior is found among nonprimate mammals </li></ul><ul><li>Humans are guided by culture </li></ul><ul><li>Culture is the product of learning </li></ul><ul><li>Culture involves language, lacking in all other species so far as we know. Whether chimps, bonobos, or even gorillas have language is a matter of debate </li></ul><ul><li>Are their parallels between nonhuman primate behavior and our own? </li></ul>
  4. 4. Primatology: Basic Concepts <ul><li>Ethology : Study of any animal’s behavior </li></ul><ul><li>Primatology: Study of nonhuman primate behavior, a subfield of ethology </li></ul><ul><li>Field Research: To avoid influencing primate behavior, some researchers wait until the primates come to them, or at least get used to their presence </li></ul><ul><li>Provisioning: Providing food to primates to shorten time in field; Japanese primatologists have relied on this technique for decades. The drawback is that provisioning does influence primate behavior </li></ul>
  5. 5. Social Groups <ul><li>Primates form social groups known as troops </li></ul><ul><li>Primate interactive behavior is the most complex among nonhuman animals </li></ul><ul><li>Why do primates form groups? </li></ul><ul><li>Defense of resources against rival troops </li></ul><ul><li>Defense against predators—ensuring safety in numbers </li></ul><ul><li>Social control through dominance hierarchies </li></ul><ul><li>Group cohesion achieved primarily through grooming, or picking through each other’s hair to remove stems, seeds, and dried skin. </li></ul><ul><li>Protection and raising of young: mother-infant bonds become secure </li></ul>
  6. 6. Types of Social Groups <ul><li>Fusion-fission society: Groups come and go; chimpanzees ( Pan troglodytes) shown in the top photo </li></ul><ul><li>Harems (gorillas): one male, several females as found in this group of gorillas; one male (an older silverback) and several females. There may be other, related males in the group </li></ul><ul><li>Multimale (baboons): several males and females. Male dominance hierarchies are rigid </li></ul>
  7. 7. Mother-Infant Bonds <ul><li>Mother-infant bonds are strong among all primates </li></ul><ul><li>(Top) mother baboon drags a reluctant infant along </li></ul><ul><li>(Bottom) quality time between a mother chimp and her offspring </li></ul><ul><li>Most apes and some monkeys give birth to one and sometime two offspring </li></ul>
  8. 8. Social Behavior: Grooming <ul><li>All primates groom: one individual combs fur of another to pick out dried skin, parasites, grass leaves or seeds (top photo) </li></ul><ul><li>Main function of grooming is interaction to maintain social bonds </li></ul><ul><li>All primates but prosimians use fingers; some prosimians use tooth combs </li></ul><ul><li>We haven’t lost the grooming habit, as this hairdresser shows (lower photo) </li></ul>
  9. 9. Social Behavior: Territoriality <ul><li>Home range : area of cyclical migration </li></ul><ul><li>Core area: smaller unit which is the primary area of activity </li></ul><ul><li>Chimps defend their core area against other troops </li></ul><ul><li>These chimps are on patrol for that purpose; any “intruder” is in deep trouble if caught </li></ul><ul><li>Baboons are more tolerant of baboons from other troops </li></ul>
  10. 10. Social Behavior: Communication <ul><li>Gibbon calls (like this one) are closed communication systems </li></ul><ul><li>Danger are indicated by high-pitched shouts; clatters and clicks indicate assembly. </li></ul><ul><li>Shouts and clatters and clicks cannot be combined to form a third meaning. </li></ul><ul><li>Chimps have some aspects of language </li></ul><ul><li>Kanzi—bonobo capable of making requests by pressing computer keys with symbols </li></ul><ul><li>Some chimpanzees, such as Washoe, were able to use American Sign Language </li></ul><ul><li>Whether chimps have language remains a matter of debate </li></ul>
  11. 11. Social Behavior: Dominance Hierarchies <ul><li>Dominance hierarchies: systems of rank among nonhuman primates </li></ul><ul><li>Here, the alpha chimp touches the back of the lower ranked one (top) </li></ul><ul><li>Bonobo dominance behavior centers on females (bottom) </li></ul><ul><li>Sons’ hierarchy depends on that of their mothers </li></ul><ul><li>Curiously, females leave their natal troop and form the core of another troop. </li></ul>
  12. 12. Communication: Threats <ul><li>Chimps make calls of greeting or threats when two troops meet </li></ul><ul><li>Threat gestures vary across species </li></ul><ul><li>Baboons: baring canines (top) </li></ul><ul><li>Chimpanzees: A s lack jaw is a sign of anger or extreme irritation </li></ul><ul><li>Chimpanzee : Displays, screams (bottom), tearing vegetation are all common threats </li></ul><ul><li>Reactions of target individuals who surrender mark their message by grimacing, crouching, or presenting their rear end to the dominant male </li></ul>
  13. 13. Communication: Reconciliation <ul><li>Embracing is one common response similar to humans </li></ul><ul><li>One individual may extending its hand for reassurance (top) </li></ul><ul><li>Grooming is often used to curry favor from a dominant male </li></ul><ul><li>Even kissing is common; where have we seen this before? </li></ul>
  14. 14. Sexual Behavior: Individual <ul><li>Estrus: cyclical female receptivity </li></ul><ul><li>Swelling of sexual skin is found among monkeys, such as this hamadryas baboon, and among apes </li></ul><ul><li>Receptivity is longer among bonobos and humans </li></ul><ul><li>Sexual positioning in copulation </li></ul><ul><li>Among most primates: male copulates with female from the rear </li></ul><ul><li>Bonobos and human engage in frontal (ventro-ventral) copulation, as between this bonobo couple </li></ul>
  15. 15. Sexual Behavior: Partners <ul><li>Gibbons form lifetime monogamous pairs (top) </li></ul><ul><li>Other species: </li></ul><ul><li>Harems are found among baboons and gorillas (such as these two females, bottom) </li></ul><ul><li>Multiple male-female sexuality among chimpanzees and especially bonobos </li></ul><ul><li>Homosexual and heterosexual behavior are found among bonobos, </li></ul>
  16. 16. Phases of Growth <ul><li>Newborns: cling to mother’s stomach </li></ul><ul><li>Up to a year, they start riding mother’s back </li></ul><ul><li>Juveniles form play groups, a good to learn basic skills </li></ul><ul><li>Juveniles may also show empathy, as with this distressed adult </li></ul><ul><li>Imitative behavior gradually integrates subadults into troop </li></ul>
  17. 17. Foraging and Sharing <ul><li>Prosimians forage on insects and plant foods </li></ul><ul><li>Most anthropoids eat roots, fruits, seeds—some species eat meat of small animals </li></ul><ul><li>Gorillas (top) are strict vegetarians </li></ul><ul><li>Chimpanzees often cooperate in stalking, killing prey, and sharing the meat </li></ul><ul><li>Here, chimps are feasting on a red colobus monkey (bottom). About 10% of these monkeys are killed and eaten every year. </li></ul>
  18. 18. Tool Making and Tool Use <ul><li>Chimpanzees at Gombe are famous for termite fishing with twigs </li></ul><ul><li>They also use leaves as sponge </li></ul><ul><li>Tool making and use may be culturally derived: </li></ul><ul><li>Chimps in West Africa crack nuts but don’t fish for termites </li></ul><ul><li>Other species: </li></ul><ul><li>Bonobos make rain hats from leaves </li></ul><ul><li>Orangutans also use tools </li></ul><ul><li>Gorillas and gibbons do not make or use tools </li></ul>
  19. 19. Agonistic Behavior and Warfare <ul><li>Agonistic behavior characteristic of all species </li></ul><ul><li>Conflict is mostly competition for females </li></ul><ul><li>Competing for dominance is another source of conflict </li></ul><ul><li>Primates were once thought incapable of killing their own kind. </li></ul><ul><li>Chimpanzees </li></ul><ul><li>Warfare actually was observed between one troop and a breakaway group. </li></ul><ul><li>Cannibalism has been observed and reported </li></ul><ul><li>Bonobos </li></ul><ul><li>Philosophy: “Make love, not war” </li></ul><ul><li>Frequent sexual contact between sexes and within one sex defers tension . </li></ul>
  20. 20. Primate Behavior and Fossil Hominid Behavior: Inferring the Past <ul><li>Similarities between nonhuman primate and human behavior </li></ul><ul><li>Behavior suggests non-stone tool making might have been practiced before the Paleolithic. </li></ul><ul><li>Interaction without language involves gestures and vocalization </li></ul><ul><li>When did language become necessary? The answer is unknown </li></ul><ul><li>Interpreting the evidence </li></ul><ul><li>Nature of prehominid and early hominid society </li></ul><ul><li>Child rearing techniques resemble our own </li></ul><ul><li>Was hierarchy inevitable? So far, dominance hierarchies indicate yes. </li></ul><ul><li>Was warfare inevitable? Bonobos are a make love, not war society; chimps are inclined toward conflict </li></ul>