Orangutan

Species: Pongo pygmaeus

PHYSICAL DESCRIPTION: Largest arboreal primates. Male Ht. 4-5 ft., Wt. 150-200 lbs. Female Ht. 3 ft., Wt. 75-100 lbs. Coat: long, coarse reddish brown. Males have large cheek pads and throat pouches used in territorial calls. Large canines, esp. males. Quadramanual climbers, although males occasionally travel bipedally while on the ground. Longevity: about 35 years in wild.

GEOGRAPHIC LOCATION: Sumatra, Borneo.

ECOLOGY: Arboreal frugivore/folivores. Primary rainforest, middle canopy. Knowledge of 500 plant spp. Solitary foragers. Active from 6:30AM - 6:PM. 45% feeding, 40% resting, 10% travelling. Home range: Adult males 5 km2, adult females 1 km2 Day range: 50-1000 m. Population density: variable, approx. 2 / km2. Slow locomotion, about .35 km/hr.

DIET: Fruit, young leaves, bark, insects.

SOCIAL ORGANIZATION: Least gregarious of all diurnal primates. Adult males are solitary, adult females travel with dependent offspring. Large adult males occupy large territories, from whcih they exclude other large adult males, but tolerate younger, smaller males. Encounters between adult males are rare, but evidently involve fighting. Most males have scars suggestive of male-male combat. Adult males give "long calls" which apparently serve to communicate their presence to other adult males and perhaps females.

REPRODUCTION: Males sexually mature at 7 yrs, but unlikely to be successful reproducers until 15+. Males continue growth until they are in their late teens. Females sexually mature at 7 yrs, but continue growth until they are 10. Gestation length: 9 months. No estrus swellings. Forcible copulations by smaller males. Litter size: 1. Interbirth interval: 7 yrs (!). Infant birth wt.: 5 lbs.

PARENTAL CARE: Infants carried by females for 2 yr. Weaning at 3 yrs. Offspring stay with mother for 5 yrs.+ No male parental care.

TOPIC OF SPECIAL INTEREST: Extreme sexual dimorphism, solitary, forcible copulations by subordinate males.

BIBLIOGRAPHIC SOURCES:

MacKinnon, J. 1978. A comparative ecology of Asian apes. Primates 18:747-772.

Mitani, J. 1985. Sexual selection and adult male orangutan long calls. Animal Behavior 33:272-283.

Wrangham, R. Demonic males. Cambridge MA: Harvard University Press.

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