Lincoln Park Zoo

Common name: Western lowland gorilla
Latin Name: Gorilla gorilla gorilla

Class: Mammals
Order:    Primates

Description
Largest of the living primates; males up to 6 feet tall and 400 pounds, females up to 5 feet and 200 pounds. Greater weights occur in captivity. Coat black to brown-gray, turning gray with age. Adult males with broad, silvery-white "saddle" on back, extending to rump and thighs. Small ears, nostrils bordered by broad ridges, which extend to the upper lip. Young have a white tuft of hair on the rump.

Range
Cameroon, Central African Republic, Gabon, Congo and Equatorial Guinea

Status
The gorilla is listed as critically endangered, and commercial trade of this species is prohibited by international law. Principal causes of population decline are habitat destruction and hunting. Poachers prize adult males and disrupt troops by killing leaders. Lincoln Park Zoo participates in the Gorilla Species Survival Plan® and is world-famous famous for its success in breeding captive western lowland gorillas.

Habitat
Tropical secondary forest: the herbs, shrubs and vines that make up its diet grow best where the open canopy allows plenty of light to reach the forest floor.

Niche
Herbivorous: feeds mainly on leaves and stems but never strips one site completely. Western subspecies takes a higher proportion of fruit, a more limited resource, which appears to limit troop size to 5-10. Primary predator in historical times is man. Troop ranges overlap; troop consists of dominant silverback plus a harem of females with their young, including subadult males. Lone males occur. Diurnal; mainly terrestrial, walking on the soles of rear feet and knuckles of forelimbs. Will build nests on the ground or in trees (especially young gorillas), using brachiatation to travel.

Life History
Mating non-seasonal. Single young born after about 9-month gestation, weighs 4-5 pounds. Young cling to dam within a few days of birth, crawl at about 9 weeks, walk at about 5 months and are weaned at 2-3 years. Females mature at 7-8 years, males later. Females leave natal troop to join other troops or lone males; adult males leave without conflict. Life span about 35 years, up to 50 years in captivity.

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Special Adaptations

  • Opposable thumb enables manipulation of objects; big toe also opposable for grasping.
  • Exceptionally large and powerful arms used to break stalks or uproot vegetation while foraging.
  • Large teeth and powerful jaw muscles help to chew tough vegetation.
  • High intelligence probably an adaption for finding scarce or isolated fruit plants in the rain forest. A good memory for time and place and the ability to make deductions are essential in predicting food locations.
  • Chest-beating display, accompanied by hoots, barks and roars to impress females. Silverbacks will defend their troops from intruding lone males in this way, as intruders may kill troop young. Chest-beating alone may simply indicate excitement; youngsters will mimic adults and beat their chests during play.