Gorillas

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Gorillas

Gorillas inhabit forests of Central Africa, and are the largest and most powerful of all primates. Adult males stand 6 ft (1.8 m) upright (although this is an unnatural position for a gorilla) and weigh up to 450 lb (200 kg), while females are much smaller. Gorillas live up to about 44 years. Mature males (older than 13 years), or silverbacks, are marked by a band of silver-gray hair on their back; the body is otherwise dark-colored.

Gorillas live in small family groups of several females and their young, led by a dominant silverback male. The females comprise a harem for the silver-back, who holds the sole mating rights in the group. Female gorillas produce one infant after a gestation period of nine months. The large size and great strength of the silverback are advantages in competing with other males for dominance of the group, and in defending against outside threats.

Gorillas are herbivores. During the day these ground-living apes move slowly through the forest, selecting species of leaves, fruit, and stems to eat from the surrounding vegetation. Their home range is about 9-14 square miles (25-40 sq km). At night the family group sleeps in trees, resting on platform nests that they make from branches; silverbacks usually sleep at the foot of the tree.

Gorillas belong to the family Hominidae, which also includes chimpanzees, orangutans, and humans. Chimpanzees and gorillas are the animal species most closely related to humans. Gorilla numbers are declining, and only about 100,000 survive in the wild. There are two species of gorilla. The western gorilla (Gorilla gorilla ) has two recognized subspecies: the western lowland gorilla (G. g. gorilla ) and the Cross River gorilla (G. g. diehli ). There are also two recognized subspecies of the eastern or mountain gorilla (G. berin-gei ): G. b. beringei and G. b. graueri. Both species are endangered.

The western gorilla is found in West Africa, including Nigeria, Cameroon, Gabon and extending into Congo and the Central Africa Republic. The hair of this species is primarily black, but is red to brown on the crest of the head. The black-haired eastern gorilla is found in East Africa, from the Demoncratic Republic of Congo into Rwanda and Uganda. Deforestation and hunting are serious and intensifying threats to gorillas throughout their range.

The eastern or mountain gorilla has been well-studied in the field, notably by George Schaller and Dian Fossey (the film Gorillas in the Mist is based on the work of Fossey). This species inhabits forest in the mountains of eastern Rwanda, Republic of Congo, and Uganda at altitudes up to 9,000 ft (3,000 m). Field research has shown these powerful primates to be intelligent, peaceful, shy, and of little danger to humans (unless provoked).

Other than humans, adult gorillas have no important predators, although leopards occasionally take young individuals. Illegal hunting, capture for the live-animal trade (a mountain gorilla is reputedly worth $150,000), and habitat loss are causing populations of all gorillas to decline rapidly. The shrinking forest refuge of these great apes is being progressively deforested to accommodate the ever-expanding human population of all countries of Central Africa. Mountain gorillas are somewhat safeguarded in the Virunga Volcanoes National Park in Rwanda, although the recent civil war there has threatened their population and status. The protection of gorillas in that park has been funded by closely controlled, small-group, gorilla-viewing ecotourism, existing alongside long-term field research programs, although these enterprises were seriously disrupted by the civil war.

Both species of gorilla are in seriously threatened in the wild. These evolutionarily close relatives of humans could easily become extinct if people do not treat them and their habitat in a more compassionate manner.

Resources

BOOKS

Dixson, A.F. The Natural History of the Gorilla. New York: Columbia University Press, 1981.

Fossey, D. Gorillas in the Mist. Boston: Houghton Mifflin, 1983.

_____ The Year of the Gorilla. Chicago: University of Chicago Press, 1988.

Robbins, M.M., P. Sicotte, and K.J. Stewart, eds. Mountain Gorillas: Three Decades of Research at Karisoke. Cambridge: Cambridge University Press, 2001.

Schaller, G.B. The Mountain Gorilla: Ecology and Behavior. Chicago: University of Chicago Press, 1988.