11/1/201711Primate Mating Systems & Life History211/1/20172Topics• Examples of mating systems among particular primates: Tamarin, Savannah Baboon, Hamadryas Baboon, Gibbon, Orangutan, Gorilla, Chimpanzee, Bonobo• Primate life histories: precocial vs. altricialbabies• Explanations for the relatively large brains of the primates.• Why study this? No time machines.3Marmosets & Tamarins: One-Female, Multi-Male (Polyandry)1. Gum eaters: patchy food distribution2. Obligate twins require more parental care: No RS without paternal investment.1. Small body size. Party size of only 4-6 restricts group size. Territorial defense of gum trees.2. Polyandry. No male-male competition selecting for dimorphism, kin-selection. Sibling nannies, fathers related (usually brothers)4Ecological ForcesEcological Consequences11/1/201735Olive Baboons (& most OW Monkeys): Polygynandry: Multi-male, Multi-female1. Even food distribution2. Easy terrestrial and top-of-limb arboreal locomotion.1. Male resource defense impossible. Party size is large, female-bonded. Males disperse from natal group.2. Moderate sexual dimorphism with male hierarchy (w/ alpha male). Male-female “friendships”Ecological ForcesEcological Consequences6Hamadryas Baboons: Polygyny: Single-male, Multi-female1. Patchy, terrestrial food distribution2. Easy terrestrial and top-of-limb arboreal locomotion.1. Female defense possible. Party size is limited by patch size.2. High sexual dimorphism due to male-male competition for the harem. Ecological ForcesEcological Consequences11/1/201747Gibbons & Siamangs: Monogamy1. Patchy, seasonal, canopy food distribution.2. High cost of locomotion by brachiation. 1. Party size of only 2-4 restricts group to breeding pair plus offspring.2. Low male-male competition results in no dimorphism = monomorphic.7Ecological ForcesEcological ConsequencesRemember: there’s monogamy and then there’s monogamy.Anatomical adaptations for…vs.Seeking extra parental investment or worthier genes…Monogamous pairs defending their territory with verbal calls, while the male frequently grooms the female.811/1/201759Orangutan: Solitary Polygyny, One-male, multi-female1. Patchy, seasonal, food distribution.2. Slow, but expensive, quadrumanousclimbing. 3. No serious predators1. Party size of only 2-4 restricts group size to mother & offspring.2. Extreme male-male competition selecting for high sexual dimorphism9Ecological ForcesEcological Consequences10Quad vs Suspense Brain ComparisonBody Weight Index of Dimorphism (male/female = 175 lbs/86 lbs= 2.02)1011/1/2017611Orangutans: Solitary, One-male, Multi-femaleTwo male strategies:1.Very dimorphic male 2. Small but mature male using forced copulations1112Gorillas: Polygyny: One-male, Multi-female1. Even food distribution: mostly Terrestrial Herbaceous Vegetation (pith & shoots).2. Easy terrestrial knuckle-walking & some quadrumanousarboreal locomotion.3. No serious predators1. Resource defense impossible. 2. Extreme male-male competition selecting for high sexual dimorphism.Ecological ForcesEcological ConsequencesBut given the food, why does gorilla society look like a harem?11/1/20177Can Males Change Female Reproductive Strategies?YES, IF:1. Food distribution is patchy.2. Physical ability to defend females given locomotory needs & limits on sexual dimorphism.MODIFIED BY:Requirements of Parental Investment (infanticide?)&Predictability of Female CyclingDegree of Actual Monopolization = Mating System13Gorillas: Polygyny: One-male, Multi-female1. Even food distribution of fruit but mostly Terrestrial Herbaceous Vegetation (pith & shoots) 2. Easy terrestrial knuckle-walking & some quadrumanousarboreal locomotion.3. No serious predators1. Resource defense impossible. 2. Extreme male-male competition selecting for high sexual dimorphism.3. Female defense possible due to “Logic of the Hired Gun.” Females & sometimes males disperse from natal group.14Ecological ForcesEcological Consequences11/1/20178Chimpanzee: Polygynandry: Multi-male, Multi-female1. Patchy, seasonal food distribution of leaves & fruit (& insects) in patchy forests.2. Easy terrestrial knuckle-walking & some quadrumanousarboreal locomotion.1. Foraging in small parties of 4-6 but congregation at other times (Fission/Fusion).2. Moderate male-male competition = moderate sexual dimorphism. Male coalitions (kin selection) rule the group. Females disperse.15Ecological ForcesEcological ConsequencesChimpanzee: Polygynandry: Multi-male, Multi-female1. Patchy, seasonal food distribution of leaves & fruit (& insects) in patchy forests.2. Easy terrestrial knuckle-walking & some quadrumanuous arboreal locomotion.1. Foraging in small parties of 4-6 but congregation at other times (Fission/Fusion).2. Moderate male-male competition = moderate sexual dimorphism. Male coalitions (kin selection) rule the group. Females disperse.16Ecological ForcesEcological ConsequencesInter-group warfare by male coalitions11/1/2017917Chimpanzee BiogeographyLimited distribution of Pan paniscusBonobo: Polygynandry: Multi-male, Multi-female1. Patchy, seasonal food distribution of leaves & fruit (& insects) in more continuous forests.2. Easy terrestrial knuckle-walking & some quadrumanousarboreal locomotion.1. Foraging in larger, more stable parties but still Fission & Fusion.2. Moderate sexual dimorphism. Male-bonded. Females disperse.3. BUT: female coalitions are equally important as the male coalitions!!!!!4. Only one killing suspected.18Ecological ForcesEcological Consequences11/1/201710Can Males Change Female Reproductive Strategies?YES, IF:1. Food distribution is patchy.2. Physical ability to defend females given locomotory needs & limits on sexual dimorphism.MODIFIED BY:Requirements of Parental Investment (infanticide?)&Predictability of Female CyclingDegree of Actual Monopolization = Mating System1920Estrus: reproductive cyclingSexual swellingwhile in estrusNo swelling in chimp out of estrusChimps: 10 of 37 days (25% of cycle)Wild Bonobos 13 of 33 days (39% of cycle)Captive Bonobos 23 of 49 days (49% of cycle)!11/1/20171121A life to make a porn-star blush…Sex as: •communication•alliance formation •tension reduction •aggression reduction •reconciliation 22Bonobos: Polygynandry: Multi-male, Multi-female• Slightly concealed ovulation via longer signaling of estrus.• Females who are actually fertile (not just looking so) cannot be guarded as well by alpha male.• Greater
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