Gorillas are ground-dwelling, predominantly herbivorous apes that inhabit the forests of central Sub-Saharan Africa. The genus Gorilla is divided into two species: the eastern gorillas and the western gorillas (both critically endangered), and either four or five subspecies. They are the largest living primates. Gorillas’ natural habitats cover tropical or subtropical forests in Africa. Although their range covers a small percentage of Africa, gorillas cover a wide range of elevations. The mountain gorilla inhabits the Albertine Rift montane cloud forests of the Virunga Volcanoes, ranging in altitude from 2,200–4,300 metres (7,217–14,107 ft). Lowland gorillas live in dense primary and secondary forests and lowland swamps and marshes as low as sea level; by contrast, cross River gorillas inhabit savannah woodlands and grasslands near rivers in Cameroonian equatorial rainforests.
Gorilla diets consist almost entirely of plant matter such as leaves, stems, pithy fruits like figs, as well as flowers and invertebrates if available seasonally. They eat large quantities of fruit—up to 34 kg (75 lb) per day—and spend most hours each day feeding on foliage within their home ranges which average between 5 and 15 km2 (1.9–5.8 sq mi). Adult male gorillas weigh 140–205 kg (309–452 lb), while adult females usually weigh 90–140 kg (198–309 lb). Males tend to be about twice the size of females—hence known as “silverbacks”—although sexual dimorphism can be much less pronounced depending on subspecies; for example males only slightly larger than females have been recorded for Grauer’s gorilla at 1 m (3 ft 3 in) versus .95 m (3 ft 1 in) for adult females. Silverbacks also have longer hair on their backs than do other members of their troop; this “silver” saddle extends from shoulders to base of tail but does not completely encircle their bodies nor extend down onto legs or arms like human hair would when allowed to grow long without trimming it regularly.[citation needed]
Females form groups with one silverback plus several other related females including daughters and sisters with offspring usually staying close to this silverback until he dies whereupon one his sons will take over his position leading them until he too dies some years later after fathering many infants.[citation needed] Male offspring emigrate upon reaching maturity whereas female offspring stay with their birth group which continues to expand its membership by attracting immigrant males.[citation needed] Groups may occasionally split apart due either to infanticide perpetrated by an incoming silverback or voluntary departure by an adolescent male seeking to join another group.[citation needed] Allogrooming among gorillas serves multiple functions such as maintaining bonds between individuals, increasing social cohesion, removing ectoparasites, cooling off, sun protection, soothing injuries, etc., although it has been suggested that dominant individuals gain more from allogrooming sessions than lower ranking ones.. Grooming parties often last for over an hour just between two animals but commonly involve many individuals simultaneously grooming each other.”” In addition,” play fighting” among juveniles allows them not only hone skills useful during adulthood such as wrestling rivals for mates but possibly understand how much force they can apply against others without causing serious injury.”