Western Gorilla (Gorilla gorilla): Facts and Habitat

What is a western gorilla?

Gorillas are the largest living primates and, after chimpanzees and bonobos, the closest living relatives of humans. Scientists recognize two species: the western gorilla of Cameroon, Gabon, the Congo Basin and neighboring countries, and the eastern gorilla of the eastern Democratic Republic of the Congo, Rwanda and Uganda. A gap of roughly 900 km (560 mi) of forest without gorillas separates the two.

The western gorilla has two subspecies:

• Western lowland gorilla (Gorilla gorilla gorilla): by far the more common, found across a large block of lowland forest from southern Cameroon to the Congo River. It is the gorilla seen in zoos.
• Cross River gorilla (Gorilla gorilla diehli): a tiny population of about 250–300 animals in hilly forest on the Nigeria–Cameroon border, about 250 km (160 mi) from the nearest lowland gorillas. It is the rarest great ape in Africa.

The species was first described scientifically in 1847. Like all great apes, gorillas have no tail, which separates them from monkeys (see Are chimpanzees monkeys?).

What does a western gorilla look like?

Western gorillas are massively built, with a broad chest, short legs, very long and muscular arms and large hands with nails on every finger. The face, ears, palms and soles are bare and black, and the rest of the body is covered in coarse hair. Compared with eastern gorillas, the coat is browner or grayer, and many western gorillas have a reddish-brown cap of hair on the crown.

Adult males develop a saddle of silver-gray hair on the back from about 12 years of age, which is why they are called silverbacks. In western lowland gorillas the silvering often spreads onto the rump and thighs. Males also grow a tall bony crest on top of the skull, which anchors huge jaw muscles and gives the head a domed shape, and they have much larger canine teeth than females. Each gorilla has a unique “nose print”, the shape of the nostrils and the wrinkles above them, which researchers use to recognize individuals.

Gorillas usually move on all fours by knuckle-walking, putting their weight on the knuckles of the curled fingers. They can stand and walk upright for short distances, for example while carrying food or during displays.

How big is a western gorilla?

Males are about twice as heavy as females, one of the largest size differences between the sexes among primates. Wild adult males usually weigh around 140–230 kg (310–500 lb) and stand about 1.5–1.8 m (4 ft 11 in–5 ft 11 in) tall when upright. Females weigh about 60–100 kg (130–220 lb) and stand about 1.25–1.5 m (4 ft 1 in–4 ft 11 in) tall. Zoo males are often heavier than wild ones.

The western gorilla is slightly smaller on average than the eastern gorilla, whose Grauer’s subspecies is the largest primate alive. For a full breakdown, see How much does a gorilla weigh?

Where do western gorillas live?

Western lowland gorillas live in the great forest block of western Central Africa: southern Cameroon, Gabon, the Republic of the Congo, the southwestern Central African Republic, mainland Equatorial Guinea and the Cabinda enclave of Angola. They once also lived in a small part of the Democratic Republic of the Congo west of the Congo River, but may now be gone from there. Important strongholds include Nouabalé-Ndoki and Odzala-Kokoua National Parks in the Republic of the Congo, Loango and Lopé National Parks in Gabon, and Dzanga-Sangha in the Central African Republic.

They live mostly below 1,000 m (3,300 ft) in tropical rainforest, swamp forest and the edges of rivers. They are especially fond of bais, natural marshy clearings in the forest where they wade to eat water plants and which are among the best places to watch them. The Cross River gorilla lives higher, in rugged hill and submontane forest up to about 1,600 m (5,250 ft).

Groups do not defend territories. They wander a home range of roughly 8–30 km² (3–12 sq mi) or more, and neighboring ranges overlap widely.

What do western gorillas eat?

Western gorillas are mainly plant-eaters, but they eat far more fruit than mountain gorillas. When trees are fruiting, ripe fruit can make up most of the diet, and groups travel farther each day to find it, often around 1–2 km (0.6–1.2 mi). In the dry season, when fruit is scarce, they fall back on leaves, stems, pith, bark and fibrous herbs such as wild ginger relatives.

They also eat termites and ants, which provide extra protein, and sometimes soil, which may supply minerals. They rarely need to drink, because juicy plants supply most of their water. By swallowing fruit and passing the seeds, gorillas act as important seed dispersers for many rainforest trees. Read more in What do gorillas eat?

Social life and behavior

Western gorillas live in groups, also called troops, that usually number from 2 to about 20 animals and are often smaller than mountain gorilla groups. A typical group has one adult male, the silverback, several adult females and their young. Most western groups have only one adult male; young males leave home as they mature and may live alone or in all-male groups for several years before attracting females of their own. Females also leave the group they were born in and join another before they breed. To learn more about the leader’s role, see What is a silverback gorilla?

Gorillas are active by day. They spend the morning and late afternoon feeding, rest at midday while the young play, and before dusk each animal builds a new nest of bent branches and leaves to sleep in, on the ground or in a tree. Infants share their mother’s nest.

They communicate with grunts, barks, hoots, screams and soft rumbling “belch” sounds that signal contentment. A silverback warding off a rival or a threat may stand up, hoot, tear at vegetation, beat his chest with cupped hands and charge. Despite this dramatic display, gorillas are generally calm and peaceful, and serious fights are rare.

Reproduction and life cycle

Gorillas breed at any time of year. After a pregnancy of about eight and a half months, a female gives birth to a single infant weighing about 2 kg (4.4 lb). The baby clings to its mother’s belly and later rides on her back. Young gorillas nurse for about three to four years and stay close to their mothers even longer.

Females usually give birth for the first time at around 10 years old, and then only about once every four years. Because many infants die young, a female may raise a surviving offspring only every six to eight years. Males seldom breed before about 15 years of age, when they are big enough to win and protect a group. This slow breeding is one reason gorilla populations recover so slowly from losses.

Wild western gorillas usually live about 35–40 years, and zoo gorillas often reach their 50s. The oldest gorilla on record, a female named Fatou at Berlin Zoo, was born around 1957 and was still living in her late 60s. See How long do gorillas live?

Predators and threats

Adult gorillas have few natural enemies. Leopards may occasionally kill gorillas, especially young ones, and infants can be killed by unfamiliar males that take over a group. The serious threats all come from people.

• Poaching: gorillas are killed for bushmeat, sometimes in snares set for other animals, and infants are taken for the illegal pet trade. Logging roads open up remote forest to hunters.
• Disease: the Ebola virus has killed huge numbers of gorillas. Outbreaks in the early 2000s killed an estimated 5,000 gorillas in one area of the northwestern Republic of the Congo alone. Gorillas can also catch human respiratory diseases.
• Habitat loss: logging, mining, farming and new roads are cutting into the forest, and climate change is expected to add pressure.

Conservation status

The IUCN Red List classifies the western gorilla as Critically Endangered, with a decreasing population; both subspecies are Critically Endangered. The assessment estimates that numbers may fall by more than 80 percent over three generations, a period of about 66 years from 1980.

Population figures have changed as surveys improved. A large study published in 2018 estimated about 360,000 western lowland gorillas, more than earlier counts suggested, because large numbers live in remote swamp forests. The same work found the population falling by roughly 2.7 percent a year. Most gorillas live outside national parks, so forest management and anti-poaching patrols across the wider landscape matter as much as protected areas.

The Cross River gorilla is in a much worse position, with about 250–300 animals split among roughly a dozen forest patches. Protected areas such as Cross River National Park in Nigeria and Takamanda National Park in Cameroon now cover part of its range. The western gorilla is listed on Appendix I of CITES, which bans international commercial trade.

Myths and facts

Myth: gorillas are aggressive monsters. Films such as King Kong gave gorillas a fearsome image, but field studies show they are shy, gentle and mostly peaceful. Displays and charges are usually bluffs meant to avoid a fight.

Myth: gorillas beat their chests with their fists. They usually strike the chest with cupped, open hands, which makes a hollow popping sound that carries through the forest.

Myth: gorillas are monkeys. Gorillas are great apes, in the same family as chimpanzees, orangutans and humans. Compare the chimpanzee, a smaller and more fruit- and meat-eating relative that shares parts of the same forests.

Relationship with people

Western gorillas have long fascinated people. Western lowland gorillas are kept in many zoos in Europe and North America, where breeding programs maintain a backup population. A western lowland gorilla named Koko became famous for learning a large number of hand signs, although scientists still debate how much her signing resembled language.

In the wild, a few groups in places such as Dzanga-Sangha in the Central African Republic and Loango in Gabon have been habituated, or slowly made used to people over several years, for research and small-scale tourism. Visits are strictly limited in group size and time, visitors keep their distance and often wear masks, and the income helps pay for protection. Respecting these rules protects both people and gorillas, which can easily catch human illnesses.