Habitat and General Information about the Mountain Gorilla

Note: photo taken by Timothy Geer and posted here with permission of manager, Mr. Fulke Wolf

Mountain gorillas have extreme sexual dimorphism, with females weighing an average of 95 kg and males averaging 160 kg. They have robust bodies, long muscular arms, short legs, massive heads, and males are equipped with large sharp canines. Mountain gorilla coats range in color from blue-black to brownish-gray. Mature males develop a large patch of silver or gray hair on their backs, giving them the name silverbacks (Schaller, 1963).

Habitat

Gorillas are found from sea level in West Africa to thousands of meters high in the Virunga Volcanoes of east central Africa. Most studies observing moutain gorillas have been conducted in the Virunga rangethat separate eastern Zaire from northwest Rwanda and eastern Uganda.

Gorillas inhabit three major vegetation types: lowland rain forest, mountain rain forest, and, in some seasons, bamboo stands (Schaller, 1963). About three-quarters of all mountain gorillas occur in the lowland rain forest, and most of the remaining ones inhabit the mountain rain forests. Gorillas tend to avoid the dense canopy and bare floor of primary tropical forests (Schaller, 1963). The preferred forestry habitats have an open canopy and dense ground and shrub strata, where gorillas find most of their food. During most of the day, mountain gorillas spread out in the thick vegetation, moving slowly and feeding as they go (Stewart and Harcourt, 1987). Bamboo is a vegetation type of minor importance to gorillas, not only because of its limited distribution but also because it contains relatively little forage during the drier seasons of the year (Schaller, 1963).

Daily Travel

The mountain gorilla is constantly moving around for food. A gorilla group’s day typically has early morning and late afternoon peaks of travel and feeding. Day journey length is from 0.5 to 1 km, which is small in relation to range size (Stewart and Harcourt 1987). Feeding periods, which take up about 45% of an adult’s day (Stewart and Harcourt, 1987), are interspersed with intervals of relatively rapid, concerted travel. During most of the day, however, travel is slow and gorillas move lazily about as they eat.

The Gorilla and Its Neighbor

The gorilla is vulnerable in most parts of its range, especially in East Africa, where populations are often split into tiny isolated pockets surrounded by human habitation (Schaller, 1963). The least endangered of the subspecies is the western lowland gorilla, where the human population is low and vast tracks of forest still exist. Stewart and Harcourt (1987) provide hard numbers in terms of gorilla populations. First, in terms of the western lowland gorilla, estimates are rough guesses everywhere except in Gabon, where a recent census indicated a population of about 35,000 gorillas, plus or minus 7,000. They estimate that between 3,000 and 5,000 eastern lowland gorillas remain in eastern Zaire. The mountain gorilla, which they more accurately censured, numbers only around 400, of which about 250 live in the Virunga Volcanoes (Stewart and Harcourt, 1987).

The mountain gorilla’s endangerment is due both to habitat destruction and severe poaching pressures. According to Stewart and Harcourt (1987), “forest clearance for commercial purposes or agriculture is the main threat to gorillas,” but hunting also takes its toll. Gorillas are killed for food, as crop pests, or souvenirs. The heads, hands and feet of these animals are prized by collectors and have generated a huge poaching industry (Lindsley et al., 1995). Infants may be captured and sold for sale to foreign zoos or for research.