Gorilla

The gorilla, genus Gorilla, is a member of the family Pongidae, or great Apes, which also includes the chimpanzee and orangutan. Together with the lesser apes - a group that includes the gibbon and the Siamang (in Kalimantan)- the great apes are close relatives of monkeys and human, all belong to the order Primates.

The gorilla is the largest living primate: males some times reach 180 cm (6 ft) in height and in nature weigh between 135 and 180 kg (1300 and 400 lb). Females are shorter and weigh about half as much as the males. A silverback gorilla is an adult male whose hair on its back has turned from black to silver gray. A silverback is the dominant male of its troop and defends females and infants from intruders.

Gorillas become sexually mature at 6-9 years of age and live about half as long as a human. Single infant are born following a pregnancy of 8 1/2 months, are partially weaned by 1 year, but remain with the mother for at least 3 years. The hair or the male's back turns silver gray with maturity giving rise to the term "silverback" for adult males.

Gorillas are the most terrestrial of the great apes, their bulky size making them ill-suited to tree dwelling. Locomotion on the ground is quadrupedal, and the knuckles of the hands are used to support the upper body. Youngster and females with infants demonstrate their arboreal heritage, however, by building sleeping nest in trees each night.

Gorilla live in family groups that consist of a single male leader, or silverback: some younger, black-backed males, possibly sons of the silverback; several adult females; and varied numbers of juvenile and infant offsoring. Group size varies with geographic location and food availability.

Gorillas are rather amiable vegetarians. They spend most of their day foraging for food. When gorilla groups meet, fighting is rare. When tension does develop between silverbacks of two groups, it is generally relieved in nonaggression ways such as impressive displays of chest beating.

There are three geographic variants, or races of gorilla, all of which are found in the African rain forest; the western lowland gorilla (Gorilla gorilla gorilla), the mountain gorilla (G. gorilla beringen), and the eastern lowland gorilla (G. gorilla groueri). The gorilla is threatened with extinction in its natural habitat by various human activities, and its last chances for survival may be a few gorilla sanctuaries in Africa and zoos and other captive environments that maintain gorillas in other parts of the world.