Mountain gorillas

There are just over a thousand mountain gorillas left in the wild, and roughly half of them live in Uganda's Bwindi Impenetrable Forest. Their numbers are rising, which makes them one of the few great apes with a hopeful trend. This guide covers who they are, how families work, what they eat, how they communicate, the threats they face and how gorilla tourism helps keep them alive.

What a mountain gorilla is

Mountain gorillas are a subspecies of the eastern gorilla. They live in cool, misty forest at altitudes between about 1,200 and 4,000 metres, which is why they have longer, thicker fur than their lowland cousins. The fur keeps them warm on cold nights when temperatures can drop close to freezing on the volcano slopes.

They are the largest living primates by weight. An adult male can weigh around 160 kilograms or more, and stands about 1.6 metres tall when upright, though gorillas usually walk on all fours, resting their weight on their knuckles. Females are about half the weight of males. Their arms are longer than their legs, their hands are remarkably similar to ours, and their faces are expressive in ways that many visitors describe as almost human.

Where they live

Only two populations exist. One lives in the Virunga Massif, a chain of volcanoes shared by Uganda, Rwanda and the Democratic Republic of Congo. The other lives in Bwindi Impenetrable National Park and the neighbouring Sarambwe reserve in Congo. The two populations are separated by farmland and cannot mix. Ugandans can point to Bwindi, which holds roughly half of the world's mountain gorillas, and to Mgahinga, which shares the Virunga population.

The species was once thought to be doomed. Mountain gorillas were classified as Critically Endangered for years, and in 2018 they were reclassified as Endangered after numbers rose. That is a real conservation success, but the population is still small and every family matters. Learn about the forest itself in our guide to Bwindi Impenetrable Forest, or see how the parks compare on our destinations page.

Family life

Gorillas live in stable families led by a dominant male called a silverback. He is named for the band of silver-grey hair that develops across his back when he matures at about twelve years old. A typical family contains one silverback, several adult females, their young, and often one or two younger males called blackbacks. Families in Bwindi tend to be somewhat smaller than those in the Virungas, and some have more than one silverback.

The silverback's role is to protect the family, settle disputes and decide when and where the group moves. Females choose to stay with a male who protects them and their infants well, and they can transfer between groups. Young males usually leave when they mature and either wait to attract females or challenge an older silverback.

Raising young

A female gorilla is pregnant for about eight and a half months and usually gives birth to a single infant every four years or so. Newborns weigh only around two kilograms, and for the first months they cling to their mother's chest, then ride on her back. Infants are weaned at around three to four years old. Slow reproduction is one reason the population recovers so slowly: a female may raise only three or four surviving young in her lifetime.

Juveniles play constantly, wrestling, chasing and swinging from saplings, and this play is one of the joys of watching a family. The silverback tolerates it with a calm patience that surprises many visitors.

What they eat

Mountain gorillas are herbivores. They eat leaves, stems, shoots, bark and roots, and in Bwindi they eat more fruit than the Virunga gorillas do because more fruiting trees grow there. An adult male can eat around eighteen kilograms of vegetation a day, and gorillas spend much of the day feeding, resting and moving slowly through the forest.

Some favourite foods include wild celery, thistles, bamboo shoots, nettles and vines. They handle stinging plants with practised technique, folding leaves and stripping stems to avoid the hairs. Because their food is spread through the forest, families move each day, building fresh nests each evening. Following that pattern, trackers can find where the group slept and where it is heading. See how this shapes a trek in our gorilla trekking guide.

How they communicate

Gorillas communicate with a range of sounds, gestures and postures. Researchers have identified more than twenty distinct vocalisations. Among the most common are:

• Belch vocalisations. Low rumbling sounds made while feeding or resting. They usually signal contentment and help the family keep in touch.
• Grunts and barks. Short calls used to reprimand a young gorilla, warn of a threat, or express irritation.
• Roars. Loud calls from a silverback to challenge another male or alert the group.
• Chest beating. A drumming display, usually by a silverback, that can signal excitement, strength or warning. It is often more theatrical than dangerous.

Every gorilla also has a unique nose print, a pattern of wrinkles above the nostrils. Researchers and trackers use these to identify individuals, just as fingerprints identify people. Facial expressions, eye contact and touch are all part of how family members read each other, and visitors quickly learn that a lowered gaze is respectful while a stare is a challenge.

Threats to their survival

• Habitat loss. Farmland presses right up against the edge of both Bwindi and Mgahinga. Forest that is cleared for agriculture is forest gorillas cannot use.
• Snares and poaching. Gorillas are not usually targeted, but snares set for antelope and bush pigs can maim them. Rangers patrol daily to remove snares.
• Disease. Gorillas are vulnerable to human illnesses, especially respiratory infections and diseases that spread through close contact. That is why visitors with colds cannot trek and why the seven-metre distance rule exists.
• Climate change. Shifting rainfall and temperature could change the plants gorillas depend on and push them to higher, smaller areas.
• Instability. In neighbouring Congo, conflict and insecurity have made conservation work difficult and dangerous for rangers.

How tourism helps

Mountain gorillas are one of the best examples of tourism paying for conservation. Permit fees fund rangers, trackers and veterinary teams who monitor every habituated family daily. A share of park revenue goes to communities around the parks, turning neighbours into stakeholders who benefit from a healthy forest. Because habituated families are seen every day, illness and injuries are spotted quickly and vets can intervene. Learn how the money flows in our permit guide, and how long-term habituation works on the Habituation Experience page.

Tourism is not risk-free, which is why the rules are strict: no more than eight visitors per family per day, one hour per visit, seven metres of distance, no flash, and no visitors with infectious illnesses. Treat those rules as part of the price of admission.

A short history of mountain gorilla conservation

Western science barely knew mountain gorillas until 1902, when a German officer shot two on the slopes of Mount Sabyinyo. For decades afterwards, hunting, land clearance and the sale of infants and body parts pushed the species toward extinction. By the early 1980s, the Virunga population had fallen to only a few hundred animals, and many experts expected it to vanish.

The turning point came from a mix of research, anti-poaching work and a new idea: that living gorillas could be worth more than dead ones. Long-term field studies in the Virungas, beginning in 1967, showed how gorillas live and gave conservationists the evidence they needed. In Uganda, Bwindi and Mgahinga were gazetted as national parks in 1991, and the first gorilla group opened to tourists in Bwindi in 1993. Since then the model has been copied across the region: protect the family, monitor it every day, earn income from limited and carefully managed visits, and share a part of that income with neighbouring communities.

How researchers count and monitor them

Because gorillas are so closely watched, we know an unusual amount about them. Habituated families are visited every day by trackers, who record who is present, who is pregnant, who is sick and who has been born or died. Vets can be called if an animal is injured in a snare or shows signs of illness.

Counting the wild, unhabituated groups is harder. Researchers use several methods together: counting the nests that gorillas build each night, collecting dung samples for DNA analysis so that individuals can be identified without seeing them, and walking systematic surveys through the forest. Bwindi and the Virungas have each been surveyed several times, and the most recent counts recorded a continued rise. Those surveys are the reason we can say confidently that the population is growing rather than hoping it is.

What you can expect to see on a trek

Visitors often expect drama, but most of an hour with gorillas is quietly absorbing. You may find the silverback lying back to doze while infants tumble over him. Females might be grooming each other or picking through vegetation for the best shoots. A young gorilla could approach with curiosity, then run back to its mother. Very occasionally the silverback will give a short display to remind everyone who is in charge.

Try not to spend the whole hour behind a lens. Take a few photographs, then put the camera down and watch. What stays with most people is not a picture but the moment a gorilla looks at them and holds the gaze.

Frequently asked questions