Gorillas are stocky animals with broad chests and shoulders, large hands, and forearms that are much shorter than the upper arms. The face is black and hairless, with small eyes that are close together and large, prominent nostrils. Adult male gorillas are known as silverbacks due to the characteristic silver hair on their backs reaching to the hips, and have a sagittal crest along the midline of the skull. The eastern gorilla is more darkly colored than the Western gorilla, and has a longer face and broader chest. The Western Lowland gorilla can be brown or grayish with a reddish forehead.
The largest living primates, wild male gorillas weigh 135 to 180 kg (298 to 397 lb) while adult females usually weigh half as much at 68-113 kg (150–249 lb). Adult males are 170 to 180 cm (5.6 to 5.9 ft) tall, with an arm span that stretches from 230 to 260 cm (7.5 to 8.5 ft). Female gorillas are shorter with smaller arm spans.
Western Lowland gorillas
are found throughout the forests of Gabon
, the forested southwestern part of the Central African Republic
, southern Cameroon
, mainland Equatorial Guinea
and the Cabinda province of Angola
The range of the Cross River gorilla
is restricted to the hilly rainforest region along the Nigeria-Cameroon border, scattered across a surface area of approximately 12,000 km².
The Mountain gorilla
is found in two isolated subpopulations: Bwindi Impenetrable National Park (Uganda
) and the Virunga volcanoes region (Rwanda
, and DR Congo
The Eastern Lowland gorilla
is found in the forests east of the Lualaba River and the Burundi-Rwanda-Uganda border.
Female gorillas are sexually mature at around 7-8 years of age. However, they do not usually reproduce until they are 10-12 years old. Males mature later than the females (11-13 years of age) and are rarely strong and dominant enough to reproduce before 15 to 20 years of age. Gorillas mate year round. The gestation period lasts 8.5 months. Birth intervals for wild Mountain gorillas are 4 years.
Male gorillas are not active in caring for the young, but they do play a role in socializing them to other youngsters. Infants begin to break contact with their mothers after 5 months, slowly increasing the time and distance between them and their mothers until being weaned at around 3 years of age. After their offspring are weaned, females begin to ovulate and soon become pregnant again. A gorilla’s lifespan in the wild is normally between 35 and 40 years.