The mountain gorilla inhabits the Albertine Rift Montane cloud forests and of the Virunga Volcanoes, ranging in altitude from 2,200–4,300 meters (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 sparser 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), Adult male feeding on insects in a rotting tree trunk.
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 meters (7,200–9,200 ft); the Hagenia forests at 2,800–3,400 meters (9,200–11,200 ft); and the giant Senecio zone at 3,400–4,300 meters (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.