Primatology Notes #13
Greater and Lesser APES

  • Gibbons ("Lesser Apes", Hylobatidae).
    • Differences from great apes (with details below):
      • Smaller
      • Skillful brachiation
      • No sexual dimorphism
      • Social groups: usually 1 male + 1 female + offspring
      • Chromosome numbers different than great apes
    • Now listed in 4 genera:
      • Hylobates (6 species, 2N=38)
      • Hoolock (1 species, 2N=44)
      • Nomascus (1 species, 2N=52)
      • Symphalangus (1 species, 2N=50) "siamang", larger, wider neck
    • Skilled brachiators (acrobatic); clumsy if forced to walk on ground
    • Competetive exclusion! (ecologically similar)
    • Diet: Fruit ~60%, leaves ~30%, flowers+insects ~10%
    • Figs and other seeds disseminated widely
    • Travels in family groups (male, female, offspring); frequent grooming
    • High paternal investment; shared care of offspring; no dimorphism
    • Serial monogamy over time:
      • Newcomer is often usurper
      • Usu. at least one partner has previously mated; seldom 2 novices
      • Occasional extra-pair copulation

  • Remainder are "Great Apes" (Pongidae, with 2N=48):
     
  • Orang-Utans (Pongo):
    • Habitat on Borneo and Sumatra (several nations) (2 species)
    • Habitat is threatened
    • Field work-- B. Galdikas
    • Quadrumanual clambering-- energetically clostly
    • Diet mostly fruit, esp. figs; seeds dispersed widely-- perpetuates forest
    • Figs seasonal; memory map of canopy
    • Wide home range when food is abundant (but sleeps more and roams less when food is scarce, conserving energy)
    • Sexually dimorphic (males much larger)
    • Coerced sex
    • Flanged vs unflanged males (Flanged males thought to give louder calls, audible for greater distance.)

  • Gorillas (Gorilla):
    • Western gorilla (Gorilla gorilla):
      • Western lowland gorilla (G. gorilla gorilla)- Cameroon, Gabon, Rep. of Congo, etc., ~200,000 pop.
      • Cross River gorilla (G. gorilla diehli)- Nigeria/Cameroon border, ~250 pop.
    • Eastern gorilla (Gorilla beringei):
      • Grauer's gorilla (G. beringei graueri)- eastern Dem.Rep.Congo, ~5000 - 28,000 pop.
      • Mountain gorilla (G. beringei beringei)- Rwanda/Uganda/D.R.Congo borderlands, ~700 pop.
    • Mostly leaf-eaters (folivores); hindgut fermentation; only animal foods are ants and termites
    • Long-lived, slow maturation; play very important
    • Dominant "silverback" males; Male threat display (bravado)
    • Early studies, "King Kong" reputation vs. "Gentle Giants" (Schaller)
    • Both sexes may disperse, but variations occur
    • Weak female bonds
    • Females often mate with more than one male
    • Social relations vary with habitat, density, etc.; may be atypical at low densities
    • Human poaching is a problem

  • Chimpanzees and Bonobos (Pan):
    • Chimpanzee (Pan troglodytes)- widespread across Equatorial belt, Guinea to Tanzania
    • Bonobo (Pan paniscus)- only in Dem.Rep.Congo
          Bonobos are smaller and do not have prominent brow ridges
    • Canines dimorphic in P. troglodytes, less so in bonobos
    • Widespread dietary variation-- over 100 plant species eaten
    • Hunting is uncommon, but has been observed in nearly all populations; usually successful
      — prey include red colobus monkeys, other primates, small birds and eggs, small or young antelopes (e.g., duikers)
    • Home ranges vary, generally large, 10-50 km2   (The city limits of Worcester include about 100 km2)
    • Multi-male, multi-female social groups; fission and fusion; females may disperse but not always
    • Male dominance interactions frequent, some alliances; dominant individuals have more mating opportunities
      dominance often age-related, so it changes over time
    • Female-female bonds weak among P. troglodytes, stronger among bonobos (female homosexuality common)
    • Chimpanzee (Pan troglodytes) communities may be territorial, occasionally genocidal; bonobos are more peaceful
    • Infanticide by both males and females has been observed
    • Tool use in wild includes: termite twig, leaf sponge, drinking brush (all fashioned by modifying local materials)


  • Primate habitat and the Threat of Extinction:
    Threats include:
    • Habitat destruction (incl. mining, agriculture)
    • Poaching-- hard to control in some places
    • Epidemic diseases (e.g., Ebola)
    Extinction risk (AAAS article)
    Extinction risk (NY Times article)
  • Proposed solutions:
    • Stronger law enforcement against poaching, habitat encroachment, mining
    • Forect reserves, national parks
    • Rainforest agriculture   }   Encourages local economy to be
    • Ecotourism                  }     in harmony with conservation goals
    • Captive breeding and reintroduction


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