There are about a thousand mountain gorillas remaining on Earth, and about half live in the forests of the Virunga mountains in central Africa. Mountain gorillas are a subspecies of eastern gorilla (Gorilla beringei). As their name hints, they live in the mountains at elevations between 8,000 and 13,000 feet.
These gorillas live on the green, volcanic slopes of Rwanda, Uganda, and the Democratic Republic of Congo—areas that have seen much human violence from which the gorillas have not escaped unscathed. Habitat loss is a major threat: agriculture, illegal mining, and forest destruction for charcoal production have degraded their forests. They often get caught in snares laid out to trap other animals for bushmeat. Climate change also poses a threat: While gorillas are adaptive, moving to higher elevations to adapt to warmer temperatures, those areas are densely populated with little forest remaining. Catching illnesses from humans is also a threat. The majority of mountain gorillas are habituated to human presence because of the tourism industry, and while there are strict sanitation protocols in place and touching the gorillas is prohibited, disease could spread quickly.
The International Union for the Conservation of Nature, which sets the conservation status of species, changed their status from "crticially endangered" to "endangered" in 2008 as their numbers improved. Scientists, however, warn that they could quickly slip back into being critically endangered.
Alpha males and social behavior
To stay warm in the mountains, mountain gorillas have longer hair than their eastern lowland cousins, the Grauer's gorillas (Gorilla beringei graueri). They also tend to be a bit larger than other gorillas and have shorter arms.
Gorillas can climb trees, but are usually found on the ground in communities of up to 30 individuals. These troops are organized according to fascinating social structures. Troops are led by one dominant, older adult male, often called a silverback because of the swath of silver hair that adorns his otherwise dark fur. Troops also include several other young males, some females, and their offspring.
The leader organizes 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 huge chest while barking out powerful hoots or unleashing a frightening roar. Despite these displays and the animals' obvious physical power, gorillas are generally calm and nonaggressive unless they are disturbed.
In the thick forests of central and west Africa, troops find plentiful food for their vegetarian diet. They eat roots, shoots, fruit, wild celery, and tree bark and pulp.
Female gorillas give birth to one infant after a pregnancy of nearly nine months. Unlike their powerful parents, newborns are tiny—weighing four pounds—and able only to cling to their mothers' fur. These infants ride on their mothers' backs from the age of four months through the first two or three years of their lives.
Young gorillas, from three to six years old, remind human observers of children. Much of their day is spent in play, climbing trees, chasing one another, and swinging from branches.
In captivity, gorillas have displayed significant intelligence and have even learned simple human sign language.