status: Endangered, IUCN Endangered, ESA
Description and biology
The gorilla is considered the most intelligent land animal other than humans. It is the largest of the living primates, an order of mammals that includes lemurs, monkeys, chimpanzees, orangutans, and human beings. When standing on its hind legs, an average male gorilla measures 5 to 5.75 feet (1.5 to 1.75 meters) high. It can weigh between 300 and 500 pounds (136 and 227 kilograms). Females are smaller, measuring about 5 feet (1.5 meters) in height and weighing between 200 and 250 pounds (91 and 114 kilograms). The color of a gorilla's coat varies from brown-gray to black. In males, the hair on the back begins to turn silver after 10 years of age. Males also have a large bone on top of their skull (called the sagittal crest) that supports their massive jaw muscles and gives them their distinctive high
forehead. Both sexes have small ears, broad nostrils, and a black, hairless face.
Gorillas are active during the day, foraging for a variety of vines, herbs, leaves, fruit, roots, and bark. During the wet season (April to June), the animals may move as little as 1,500 feet (457 meters) a day in search of food. During the dry season (July to August), they may travel almost 1 mile (1.6 kilometers). At night, gorillas build individual nests from branches and leaves in trees or on the ground.
Highly social animals, gorillas form groups of 5 to 10 members, although larger groups have been documented. An average group is composed of a dominant mature male (called a silverback) and several females and their young. When young males in the group become mature (at about age 11), they leave to form their own groups. Young females also leave upon reaching maturity (at about age 8), joining lone males or other groups.
Breeding between males and females can take place any time during the year. After a gestation (pregnancy) period of 250 to 270 days, a female gorilla gives birth to a single infant. She will carry her infant for the first few months of its life, after which time it will begin to crawl and then walk. The young gorilla will remain dependent on its mother for up to three years. Almost half of all infant gorillas die. Female gorillas successfully raise only two to three young during their lives.
Scientists have recognized three subspecies of gorilla: the western lowland gorilla (Gorilla gorilla gorilla), the eastern lowland gorilla (Gorilla gorilla graueri), and the mountain gorilla (Gorilla gorilla berengei).
Habitat and current distribution
All three gorilla subspecies prefer forest habitats. The western lowland gorilla is found in Nigeria, Cameroon, Central African Republic, Río Muni (the portion of Equatorial Guinea on the African mainland), Gabon, Congo Republic, and Angola. Its population is estimated to be about 35,000. The eastern lowland gorilla, having a population between 3,000 and 5,000, is found primarily in eastern Congo. The mountain gorilla is found in the Virunga Mountains, a range of volcanic mountains stretching across eastern Congo, southwestern Uganda, and northwestern Rwanda. With a population of about 600, the mountain gorilla is the most endangered of the three gorilla subspecies.
History and conservation measures
Hunting has been the leading threat to gorillas for years. The animals are killed for use as food or trapped for use as pets. Although current international agreements ban the selling or trading of gorillas as pets, illegal capture of the animals continues.
As human populations swell in Africa, increasing numbers of gorillas are hunted for their meat, known as bush meat. A hunter can receive $30 for the remains of a 400-pound (180-kilogram) male gorilla. Female gorillas are also slaughtered, and their infants are captured and sold to private collectors or zoos. Sometimes hunters make more money for live infant gorillas than for the remains of dead adults.
The destruction of African forests is another serious threat to gorillas. More and more of their habitat has been cleared to create farms and to supply European and Asian timber companies. Logging roads, built deep into the forests, also allow hunters easy access to remaining gorillas.
In 2003, a group of scientists and conservationists called for an upgrade in the status of gorillas from endangered to critically endangered. Data coming from Gabon and the Republic of Congo, where 80 percent of the world's gorillas live, reveal that the ape population there has decreased by half between 1983 and 2000. The reasons for the decline were continued hunting and outbreaks among gorillas and chimpanzees of the Ebola virus, a very deadly and contagious virus discovered in Africa in the 1970s that also afflicts human beings. The group of scientists warn that gorillas are in peril of becoming extinct in the wild. They called for greater enforcement of laws against hunting and capturing gorillas and an increased focus on research of the Ebola virus in primates.
African countries within the gorilla's range are trying to establish conservation programs for the animal. These efforts, though, are often thwarted by limited finances and social and political unrest. A successful program has been the Mountain Gorilla Veterinary Project, which provides health care for injured and sick mountain gorillas in Rwanda, Congo, and Uganda. It is one of the few programs in the world to provide treatment to an endangered species in its natural habitat.
gorilla, an ape, Gorilla gorilla, native to the lowland and mountain forests of western and central equatorial Africa. It is the largest of the apes, the males reaching a height of 5 to 6 ft (150–190 cm) with a 9-ft (144–cm) arm spread. Males weigh about 450 lb (200 kg) in the wild; in zoos they become obese and may reach 600 lb (270 kg) or more. The two species of gorilla are the western, comprising the western lowland (G. gorilla gorilla) and Cross River (G. gorilla diehli) gorillas, and the eastern, comprising the eastern lowland (G. beringei graueri) and mountain G. beringei beringei gorillas. The Cross River gorilla of the Nigeria-Cameroon border region and the mountain gorilla of Rwanda, Congo (Kinshasa), and Uganda each number in the hundreds and are closest to extinction. The western lowland gorilla is the most numerous, with 175,000 or more individuals. Male gorillas have prominent sagittal crests and brow ridges and large canine teeth; these features are less developed in females. Females are smaller than males, weigh about half as much, and do not develop the gray hair on the back characteristic of the sexually mature male. Dominant older males, called silverbacks, usually lead stable harem societies of 2 to 30 females and juvenile males in a daily search for food. The animals normally walk on all fours, resting their upper body on their knuckles. They are vegetarians, living on a variety of vines, leaves, fruit, roots, and bark. Mountain gorillas eat wild celery, bamboo shoots, nettles, thistles, and sometimes certain soils or a rare form of fungus. Adolescents and small females may climb trees in search of food and to build arboreal nests for sleeping. Adults of both sexes build ground nests daily. Quiet and retiring in temperament when compared to the excitable chimpanzee, gorillas have been known to attack humans in defense of their family group. Gorillas normally rely on bluffs, roaring and beating their chests to frighten intruders. Their main enemies are human poachers; in the lowlands, leopards may sometimes eat the young. Females bear one infant about every four years; the child is carried in the mother's arms and then on her back. Females mature in 8 or 9 years, males in 11 or 12; gorillas may live more than 40 years. Gorillas are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Primates, family Pongidae.
See D. Fossey, Gorillas in the Mist (1983); J. Shreeve, Nature: The Other Earthlings (1987).
go·ril·la / gəˈrilə/ • n. a powerfully built great ape (Gorilla gorilla) with a large head and short neck, found in the forests of central Africa. It is the largest living primate. ∎ inf. a heavily built, aggressive-looking man.