The Mountain Gorilla (Gorilla beringei beringei) is one of the two subspecies of the Eastern Gorilla. There are two populations. One is found in the Virunga volcanic mountains of Central Africa, within three national parks: Mgahinga, in south-west Uganda; Volcanoes, in north-west Rwanda; and Virunga in the eastern Democratic Republic of Congo (DRC). The other is found in Uganda's Bwindi Impenetrable National Park. Some primatologists say that the Bwindi population in Uganda may be a separate subspecies, though no description has been finished.
The fur of the Mountain Gorilla, often thicker and longer than that of other Gorilla species, enables them to live in colder temperatures. Gorillas can be identified by nose prints unique to each individual. Males usually weigh twice as much as the females, and this subspecies is on average the largest of all gorillas. Adult males have more pronounced bony crests on the top and back of their skulls, giving their heads a more conical shape. These crests anchor the powerful masseter muscles, which attach to the lower jaw, or mandible. Adult females also have these crests, but they are less pronounced.
The Mountain Gorilla inhabits the Albertine Rift montane cloud forests and of the Virunga Volcanoes, ranging in altitude from 2,200–4,300 metres (7,200–14,100 ft). Most are found on the slopes of three of the dormant volcanoes: Karisimbi, Mikeno, and Visoke. The vegetation is very dense at the bottom of the mountains, becoming more sparse at higher elevations, and the forests where the Mountain Gorilla lives are often cloudy, misty and cold.
The Mountain Gorilla is primarily an herbivore; the majority of its diet is composed of the leaves, shoots and stems (85.8%) of 142 plant species. It also feeds on bark (6.9%), roots (3.3%), flowers (2.3%), and fruit (1.7%), as well as small invertebrates. (0.1%). Adult males can eat up to 34 kilograms (75 lb) of vegetation a day, while a female can eat as much as 18 kilograms (40 lb).
The home range size (the area used by one group of gorillas during one year) is influenced by availability of food sources and usually includes several vegetation zones. George Schaller identified ten distinct zones, including: the bamboo forests at 2,200–2,800 metres (7,200–9,200 ft); the Hagenia forests at 2,800–3,400 metres (9,200–11,200 ft); and the giant senecio zone at 3,400–4,300 metres (11,200–14,100 ft). The Mountain Gorilla spends most of its time in the Hagenia forests, where gallium vines are found year-round. All parts of this vine are consumed: leaves, stems, flowers, and berries. It travels to the bamboo forests during the few months of the year fresh shoots are available, and it climbs into subalpine regions to eat the soft centers of giant senecio trees.