Gorillas, the largest of the great apes, were long inaccurately portrayed as ferocious and aggressive. The well-known movie image of King Kong was fed by and has fueled such misconceptions. As humans have become more familiar with gorillas both in captivity and in the wild, their true nature as shy, gentle vegetarians has become apparent.
In the wild, gorillas inhabit rain forests in equatorial Africa. The single species of Gorilla gorilla has three identified subspecies: the western lowland gorilla (G.g. gorilla ), the eastern lowland gorilla (G.g. graueri ), and the mountain gorilla (G.g. beringei ). Lowland gorillas are familiar to us as the star attractions of the zoo scene and are the only gorillas to have been studied in captivity. However, their life in the wild has had less documentation; their habits and habitat have made observation difficult. Mountain gorillas, on the other hand, have been the subjects of ongoing research in their small habitat near the Rwanda-Uganda-Zaire border. Mountain gorillas are endangered due to habitat reduction, poaching, and war; Dian Fosseys single-handed battle for their protection may have saved them from extinction.
A full-grown male gorilla can measure six feet in length and weigh as much as 400 pounds (181 kilograms). Females are smaller and weigh only about half as much. Like the other apes, gorillas have no tails. They usually travel along on all fours with their weight on their feet and on the knuckles of their hands. Their bodies are adapted to this gait with an armspan which greatly exceeds their standing height.
The massive body of a gorilla is covered with a thick coat of coarse black hair; there are color variations between subspecies. Mountain gorillas have longer, silkier hair than the lowland varieties. Mature males are called silverbacks because the hair across their backs becomes silver with age. High crowns or skull crests, which are more pronounced in mountain gorillas, also identify older males.
Gorillas live in close-knit groups often consisting of a dominant silverback, one or two other males, several females and young. Silverbacks are known to show off by hooting, standing erect, throwing plants around, beating their chests, and making loud barking vocalizations. Such displays have certainly fueled the gorillas reputation for ferocity but generally serve to frighten away intruders and reinforce the dominant males position as leader without further need for aggression. When the leader of a group dies, the younger males contest for dominance.
Though they sometimes climb trees, adult mountain gorillas spend most of the time on the ground. Lowland gorillas spend more time in trees, one of the reasons they have been more difficult to study in the wild. Each evening, gorillas make night nests of twigs and leaves. Young gorillas under three years old sleep with their mothers, but all others have their own nests.
Almost exclusively vegetarian, though they may eat insects and other invertebrates, gorillas consume huge quantities to sustain their bulk, stripping vines for leaves, chewing bark, fruits, flowers, berries, and sometimes roots of a wide variety of plants. They do not seem to need to drink due to the high moisture content of their diet. The silverback determines where and when his group will forage, meandering perhaps a third of a mile a day before bedding down for the night.
There does not appear to be a breeding season, and females give birth every 3.5 to 4.5 years. The births are single, with the rare exception of twins. Newborn gorillas are tiny (less than four pounds [1.8 kilograms]) and are helpless. At first the baby gorilla clings to its mothers chest. Later it learns to ride on her back. By two years a gorilla has begun to move around on its own.
National Geographic Society-supported researchers such as Dian Fossey, Francine Penny Patterson, and J. Michael Fay have contributed a great deal to our knowledge of the gorilla.