Distribution
Restricted to six extinct volcanoes of the Virunga Range straddling the Zaire-
Rwanda-Uganda border and probably a small separate population in south-western Uganda.
Habitat
Tropical secondary forest at altitudes of
about 1,650-3,790m.
Current population
Estimate total population as 370-440 (Vedder 1987).
Status
Gorillas in general are classified as endangered by the USDI and is on appendix 1 of
the CITES. The mountain gorilla is consi
dered endangered by the IUCN.
Size
When standing, height of 1.25-1.75m. Span of outstretched arms is about 2.00-2.75m.
Chest is as much as 50.8cm with a circumference of 1.25-1.75m in males.
Weight
70-140kg in females and 13
5-275kg in males (Grzimek 1975).
Average life-expectancy
35 years in wild, 50 years in captivity.
Normal diet
Predominately folivorous feeding mainly on leaves and stems rather then fruits.
85.8% diet consists of leaves, sho
ots and stems. Small amounts of wood, roots, flowers, fruits
and grubs are also eaten (Fossey & Harcourt 1977). Many small insects eaten inadvertently
whilst feeding on plants (Harcourt & Harcourt 1984). Spends 45% of the day feeding (Harcourt
& Stewart
1984).
Normal lifestyle
Live in relatively permanent groupings, with the same adult individuals
travelling together for months and usually years at a time. Group size ranges from 2 to 35, but
averages 5 to 10 individuals. The male silverba
ck is the most important individual for the
cohesiveness of the group. Since females leave their natal group at puberty to join other troops
the degree of relatedness of females in any one silverbacks harem is low. For this reason social
ties between fem
ales in a group are weak and there is little difference in social status. Bonds
between females and the male silverback hold the group together. Males leave a group and
wander alone for a few years before eventually beginning a new group. Sons of the dom
inant
male may stay in the natal group and take over leadership once the dominant male dies.
Mutual grooming is not as common as in the other social primates. It usually occurs between
mother and offspring, adult female and silverback and sometimes immat
ure and silverback.
Social grooming among females is rare.
There is no evidence of a particular breeding season (Schaller 1963). Females give birth every
3.5-4.5 years, unless the infant dies. Normally a single young is born. Sexual maturity is
reach
ed at 8 years for females and 10 years in males, but breeding does not normally begin
until females are 10 and males are 15 years old.
Previous geographical spread
Nigeria ?
Reasons for decline
The main reasons are deforesta
tion, hunting, increased human
population encroaching on the forests and capture for zoos. Gorilla meat is eaten not just by
rural people but in Gabon is served in restaurants in the main town. Although legislation to
control hunting and capture of goril
las exists, it is only in Zaire that the gorilla is totally protected
by law and even so the laws are not adequately enforced. During the 1970s poaching
intensified in the Virunga region, especially to obtain gorilla heads for commercial sale (Harcourt
&
Curry-Lindahl 1978). The number of gorillas in this area fell from 450 in 1960 to about 225
twenty years later (Harcourt & Fossey 1981). Villages and logging yards are present within
Gabon's Okanda National Park.
Current threats
Same thre
ats as above still exist today.
Conservation projects
A conservation program implemented in Rwanda in 1978 and funded
in part by tourism have helped stabilise the population and reduce threats to the habitat in this
area (A. Harcourt et a
l. 1986).
In all of these countries it is difficult for governments to fund major conservation programs and
long-term ecological stability is usually sacrificed for short-term economic gain. Ultimately the
local people must come to value the mountain
(and other) gorillas and the forests in which they
live. The only way to do this is through conservation and education programs and through the
development of tourism.
File last modified Thursday, October 3, 1996