There are two species of gorillas recorded: the Eastern and Western Gorillas. The three subspecies of gorillas recognized are:
The most common race, the western lowland gorilla (G. g. gorilla), is not found in Uganda, but an estimated 40,000 live in the rainforests of west and central Africa.
The endangered eastern lowland gorilla (Gorilla beringei graueri) is restricted to forest patches in the east of DRC, estimated to be 4,000 animals. Compared to the other eastern gorilla subspecies, the mountain gorilla has longer fur, teeth, and arms.
The most threatened race of gorillas is the mountain gorilla, the only one found in Uganda.
Mountain Gorilla (Gorilla beringei beringei) Uganda’s mountain gorilla is a subspecies of the Eastern gorilla, found only in the east-central African rainforests. As their name hints, they live in the mountains at elevations between 8,000 and 13,000 feet.
Uganda conserves two populations, those found in Bwindi Impenetrable National Park and those found in the Virunga Volcanoes. Initial surveys of this species estimated about 450 individuals in the Virunga Volcanoes and 130 in Bwindi in 1960. Habitat loss and hunting caused numbers in the Virunga Volcanoes to plummet to 230 in the mid-1970s, but with conservation support, the mountain gorilla population has gradually increased to 480. Similarly, numbers are now estimated at 320 in Bwindi Impenetrable National Park. This makes a total of some 800 individuals in the world today.
“The mountain gorilla faces grave danger of extinction – primarily because of the encroachments of native man upon its habitat – and neglect by civilized man, who does not conscientiously protect even the limited areas now allotted for the gorilla’s survival. -By Dian Fossy”
How do Mountain Gorillas relate to humans? Mountain gorillas share 98% with humans, which means that exposure to human illnesses – even a cold – can have potentially detrimental impacts on gorillas. They are so genetically similar to us and haven’t developed the necessary immunity to common human diseases.
Size and diet of Mountain Gorillas Mountain gorillas are the bulkiest and most powerful living primates. An average male mountain gorilla can weigh 136 to 230 kilograms (300 to 485 pounds) and reach a standing height of 4 to 6 feet (1.2 – 1.8 meters).
Mountain gorillas are vegetarian, with their diet primarily including roots, shoots, fruit, wild celery, and tree bark and pulp. In the thick forests of central and east Africa, troops find plentiful food for their vegetarian diet.
They spend about a quarter of their day eating mainly leaves and shoots, but observers have also noticed them eat snails, ants, and bark, a good source of sodium.
Social Life of a Mountain Gorilla
Baby gorillas are classed as infants until they reach around three-and-a-half years old and adults from about eight years. Males between 8-12 years are called ‘blackbacks.’ Then, from 12 years old, they develop a silver section of hair over their back and hips, earning them the name ‘silverback.’ In the wild, mountain gorillas can live up to 35 years old.
Most mountain gorillas live in stable family groups (called troops or bands) of around 10 – 40 individuals, with one dominant male (a silverback) and several females. The Silverbacks are responsible for defending the family from invaders and organizing troop activities like eating, nesting in leaves, and moving about in a home range of 0.75-to 16 square miles.
Those who challenge this alpha male are apt to be cowed by impressive shows of physical power. He may stand upright, throw things, make aggressive charges, and pound his massive chest while barking out powerful hoots or unleashing a frightening roar. Despite these displays and the animals’ evident physical power, mountain gorillas are generally calm and nonaggressive unless someone/something threatens them.
In the gorilla group, both males and females care for their infants, hugging, carrying, and playing with them. When they get older, most males and around 60% of females leave their birth group to join another troop, which helps prevent inbreeding.
At night, mountain gorilla groups sleep together in nests on the ground or in trees they make from foliage. Infants will share their mother’s nests, staying safe and warm.
Communication In captivity, gorillas display significant intelligence and have even learned simple human sign language. Primatologists have observed mountain gorillas use 16 different types of communication calls. Mountain gorillas use short barks when they’re mildly alarmed or curious. To intimidate rivals, male gorillas strut with stiff legs, beat their chests, and use vocalizations like roars or hoots.
Reproduction Female gorillas give birth to one infant after a pregnancy of nearly nine months. Unlike their giant parents, newborns are tiny—weighing four pounds—and can only cling to their mothers’ fur. These infants ride on their mothers’ backs from four months through the first two or three years of their lives. From three to six years old, young gorillas are adorable to watch on a gorilla trekking excursion because they remind us of children with their charming antics. Much of their day is spent in play, climbing trees, chasing one another, and proudly swing from branches.