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Gorillas

lowland mountain eastern republic

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 silverback, A nine-year-old male lowland gorilla playing with a two-year-old juvenile. Photograph by Tom McHugh/Photo Researchers, Inc. Reproduced by permission.
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 Pongidae, which also includes chimpanzees, orangutans, and gibbons. Chimpanzees and gorillas are the animal species most closely related to humans. Gorilla numbers are declining rapidly, and only about 50,000 survive in the wild. There are three subspecies: the western lowland gorilla (Gorilla gorilla gorilla), the eastern lowland gorilla (G. g. graueri), and the mountain gorilla (G. g. beringei). Recent population estimates are 44,000 western lowland gorillas, 3,000-5,000 eastern lowland gorillas, and fewer than 400 mountain gorillas. All species are endangered, and the mountain gorilla critically so.

The rusty-gray, western lowland gorilla is found in Angola, Cameroon, Central African Republic, Congo, Equatorial Guinea, Gabon, Nigeria, and the Republic of Congo (formerly Zaire). The black-haired eastern lowland gorilla is found in eastern Republic of Congo. Deforestation and hunting are serious and intensifying threats to lowland gorillas throughout their range.

The 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 critically endangered subspecies 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.

All three subspecies of gorillas are in serious trouble. 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.

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

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

Periodicals

Gouzoules, Harold. "Primate Communication By Nature Honest, Or By Experience Wise." International Journal of Primatology 23, no. 4 (2002): 821-848.

Maestripieri, Dario. "Evolutionary Theory And Primate Behavior." International Journal of Primatology 23, no. 4 (2002): 703-705.

"Profile: Ian Redmond: An 11th-Hour Rescue for Great Apes?" Science 297 no. 5590 (2002): 2203.

Sheeran, L. K. " Tree Of Origin: What Primate Behavior Can Tell Us About Human Society." American Journal off Human Biology 14, no. 1 (2002): 82-83.


Neil Cumberlidge

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