Primate social organization


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Primate social organization

  1. 1. TO KNOW FOR EXAM: <ul><li>Taxonomy down to and including family (subfamily for OW monkeys and apes) level for extant primates (fill in the blanks) </li></ul><ul><li>Evolutionary trends </li></ul><ul><li>Characteristics of each of the extant groups of primates, e.g. apes do not have tails </li></ul><ul><li>Overview of the evolutionary history of the primates, e.g. what was happening during the Eocene, what were names of important groups, where are their fossils found, and what group(s) is derived from them </li></ul><ul><li>Locomotor categories and species examples </li></ul><ul><li>Social organizations and species examples </li></ul><ul><li>Terms, e.g. rite mirabile, tapetum lucidum, sympatric/allopatric… </li></ul>
  3. 3. ‘ Most primates spend their life in a social group. Primate social groups are often complex and permanent and group members perform most of their activities within the confines of their group. They depend on the group for survival in terms of protection from predators, conspecifics, and/or other group members, as well as for finding resources and mates. Group life does not come without its share of constraints, primarily competition for resources. Group size and structure vary from species to species but within a species, are somewhat stable, i.e. one type of social structure is seen in each species and group size remains stable over time under natural conditions via emigration, predation, and group fission.’ (Berman)
  4. 4. <ul><li>How a group is organized…and classified </li></ul><ul><ul><li>Numbers of particular aged-sexed individuals </li></ul></ul><ul><ul><ul><li>Immigration and emigration </li></ul></ul></ul><ul><ul><li>Mating system </li></ul></ul><ul><ul><li>Patterns of interactions between members </li></ul></ul><ul><ul><li>Dominance hierarchy </li></ul></ul>
  5. 5. Strier: Primate social organization “reflects the compromises between female and male strategies to gain access to mates, food, and other resources that they and their offspring need to survive. These compromises are constrained by life history and physiology, and vary with ecological and demographic conditions”
  7. 7. I. Where the nature of the diet warrants females foraging solitarily: <ul><li>Dispersed polygyny </li></ul><ul><ul><li>Male monopolizes a couple of females or acts as satellite </li></ul></ul><ul><li>Territorial pair </li></ul><ul><ul><li>Cooperate in home range defense and be (almost) assured of paternity </li></ul></ul><ul><li>Community: “resource defense polygyny” </li></ul><ul><ul><li>Males cooperate and defend home range containing females </li></ul></ul>
  8. 8. Solitary foragers / dispersed polygyny orang, galago, potto, loris, nocturnal lemurs
  9. 9. <ul><li>Group composition </li></ul><ul><li>Male-biased dispersal </li></ul><ul><ul><li>Female relatives may associate, sleep together </li></ul></ul><ul><li>Dispersed polygyny </li></ul><ul><li>Evolutionary/ecological significance </li></ul><ul><li>More social than thought : </li></ul><ul><ul><li>Orangs: adolescents, fruit trees </li></ul></ul><ul><ul><li>Galago sisters </li></ul></ul><ul><ul><li>Mouse lemur sleep groups </li></ul></ul><ul><li>Communication – scent, vocal </li></ul>
  10. 10. Monogamous or territoreal pairs indri, night monkey, gibbon, siamang
  11. 11. <ul><li>Group composition </li></ul><ul><li>Territorial </li></ul><ul><ul><li>Spacing mechanism: duet </li></ul></ul><ul><li>Emigration </li></ul><ul><li>Couples are stable but EPC’s </li></ul><ul><li>Monomorphic </li></ul><ul><li>Evolutionary / ecological significance </li></ul><ul><li>Male caretaking </li></ul>
  12. 12. Community / Fission-fusion chimps, bonobos, spiders, muriquis
  13. 13. <ul><li>Group composition </li></ul><ul><li>Emigration </li></ul><ul><li>Evolutionary / ecological significance </li></ul><ul><ul><li>Resource-defense polygyny </li></ul></ul><ul><li>Female chimps & muriquis mate promiscuously – confuse paternity </li></ul><ul><li>Sperm competition </li></ul><ul><ul><li>Avoids conflict with kin </li></ul></ul>
  14. 14. II. Where the nature of the diet allows females to forage together: <ul><li>Where resources are defensible -> females cooperate (female-bonded) in resource defense and groups are larger and multi-male </li></ul><ul><li>Where resources are not defensible or worth defending -> females do not cooperate and groups tend to be smaller </li></ul><ul><ul><li>Monopolizable -> 1-male </li></ul></ul><ul><ul><li>Hamadryas and gelada </li></ul></ul><ul><ul><ul><li>Multi-tiered SO </li></ul></ul></ul>
  15. 15. One-male groups / harem all non-savanna baboons, patas, some colobines, lowland gorillas Hamadryas Langurs and leaf monkeys Patas Mandrill Gelada
  16. 16. <ul><li>Group composition </li></ul><ul><li>Misleading </li></ul><ul><li>Emigration </li></ul><ul><li>Evolutionary / ecological significance </li></ul><ul><ul><li>Nature of resources -> small groups -> monopolizable </li></ul></ul><ul><li>Infanticide </li></ul><ul><li>Complex social organization in open living baboons </li></ul><ul><ul><ul><li>Resource-poor dangerous environments </li></ul></ul></ul><ul><li>Hamadryas: 1-male units -> clans (2-4 units + bachelors) -> band (several clans ~60) -> troop (multiple bands) -> several troops come together on sleeping cliffs </li></ul><ul><li>Geladas: 1-male units + bachelors-> bands ->herd (↑600) </li></ul>
  17. 17. Age-graded multi-male Mountain gorilla (red howler, hanuman langur)
  18. 18. Mountain gorillas <ul><li>Group composition </li></ul><ul><li>Emigration </li></ul><ul><li>Female mountain gorillas attracted to >1 male </li></ul>
  19. 19. Multi-male/multi-female macaques, savanna baboons, capuchins, squirrel monkey, vervets… Mine!
  20. 20. <ul><li>Group composition </li></ul><ul><ul><li>Usually – ♀- philopatric </li></ul></ul><ul><li>Emigration </li></ul><ul><ul><li>Solitary, all-male bands, other group </li></ul></ul><ul><ul><li>Exceptions </li></ul></ul><ul><ul><ul><li>Squirrel monkeys </li></ul></ul></ul><ul><ul><ul><ul><li>CR ♀’s </li></ul></ul></ul></ul><ul><ul><ul><ul><li>SA ♂’s </li></ul></ul></ul></ul><ul><ul><ul><li>Howlers </li></ul></ul></ul><ul><li>Ecological significance </li></ul><ul><li>Fission </li></ul>
  21. 21. Polyandry Tamarins and Marmosets
  22. 22. <ul><li>Where polyandry reported: </li></ul><ul><li>Group composition </li></ul><ul><ul><li>Two adult males </li></ul></ul><ul><ul><ul><li>Both may be reproductively mature </li></ul></ul></ul><ul><ul><ul><li>Usually only one sires offspring </li></ul></ul></ul><ul><ul><li>1 breeding female </li></ul></ul><ul><ul><ul><li>Chemical suppression </li></ul></ul></ul><ul><ul><li>Possibly mature offspring </li></ul></ul><ul><ul><li>Immature offspring </li></ul></ul>
  23. 23. <ul><li>Mean number offspring: twins </li></ul><ul><li>Helpers </li></ul><ul><ul><li>Males </li></ul></ul><ul><ul><li>Siblings </li></ul></ul><ul><ul><ul><li>Inclusive fitness </li></ul></ul></ul><ul><li>Emigration </li></ul><ul><li>Evolutionary / ecological significance </li></ul>