Gorilla gorilla Savage and Wyman 1847
INTRODUCTION
Gorillas occur in two main areas: equatorial West Africa (Western Lowland Gorilla Gorilla gorilla gorilla) and eastern Central Africa (Eastern Lowland Gorilla G. g. graueri and Mountain Gorilla G. g. beringei). The species is globally threatened, most recently categorised as Endangered.
The Western Lowland Gorilla has a brownish-grey coat with red or auburn crest. In mature males, a silvery white saddle extends from the back to the rump and thighs. The Eastern Lowland Gorilla is mainly black and the saddle of males is restricted to the back. The most threatened of the three subspecies, the Mountain Gorilla Gorilla gorilla beringei is similar to the Eastern Lowland Gorilla in appearance but has longer hair, jaws and teeth and shorter arms.16,17 Gorillas have a well developed social structure, living and travelling in family groups which vary in size from 2-35 individuals, but are more frequently in the range of 5-10. Group composition varies between groups and subspecies but in Mountain Gorillas usually consists of a single dominant silver back male, three adult females and four or five offspring.17 Standing upright, the gorilla reaches a height of 1.25 to 1.75 m.25, Occupying a home range which varies in size from 5-30 km2, gorillas are mainly herbivorous, feeding on stems, shoots and a variety of fruit species; this is supplemented with bark and invertebrates.9
Nearly all female gorillas emigrate from their natal group at maturity, to join other groups or single males.25 Females become sexually mature at 7-8 years but do not start to breed until several years later. Males mature later than females with few breeding before the age of 15 years. High infant mortality, a long gestation period (251-295 days), a tendency for single births and a prolonged period of high maternal care means that on average, one infant is reared in a 6-8 year period.17,25
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