beringei (aka Mountain Gorilla)
gorilla is the largest primate in the world, with
males reaching a length of 6 feet and weight of
353 pounds; females are significantly smaller,
with an average length of 5 feet and weight of
198 pounds. They have robust bodies, long
muscular arms, short legs, massive heads, and
males have large, sharp canine teeth. Mountain
gorilla coats are silky and long, ranging in
color from blue-black to brownish-grey. Mature
males develop a large patch of silver or grey
hair on their backs, giving them the name
silverbacks. Males also have apocrine (sweat)
glands in their armpits that emit a strong odor
when the animal is under stress.
gorillas differ from other gorillas in having
longer hair, larger jaws and teeth, smaller nose,
and shorter arms.
There are two subspecies of eastern gorillas,
the mountain gorilla (G.b. beringei) and
the eastern lowland gorilla (G.b. grauen).
The first is found in the Virunga Volcanoes
region, situated on the borders of Rwanda, Uganda
and the Democratic Republic of Congo, the other
in Bwindi Impenetrable National Park in
southwestern Uganda. There remain only about
5,000 eastern lowland gorillas and about 700
mountain gorillas in the wild.
social unit is a male with a harem of females and
their offspring. These groups are nonterritorial,
but severe intergroup conflicts can occur when
groups encounter each other and especially if a
lone male contacts the group. The dominant male
of a group is massive compared to the other
members and they all defer to him. Eastern
gorillas tend to have larger group sizes than
their western relatives, exceptionally numbering
more than 50 individuals.
transfer from their natal group to a new group
before breeding. This generally occurs at around
8 years of age. Often they join a lone male and
start a new group, rather than join an
established group and be a lower ranking female.
Males often leave the natal group at around 11
years of age. Males, however, can't join an
establish group, and they spend much time in
solitary existence until they can gain females
and begin a group of their own at age 15 or
known to use vocalizations to communicate with
one another. Tactile communication, in the form
of grooming, play, and sexual contact, also
occurs. Males emit a strong odor when stressed,
which appears to function as a type of chemical
communication. In addition to these, gorillas use
body postures and facial expressions, as well as
other visual signals, to communicate with one
another. Grooming often occurs between females
and males, and sometimes among females.
The dominant male in each group has exclusive
access to all the females in the group, but all
mating behavior is initiated by the female. A
female is receptive only during estrus, and she
will cease to ovulate for several years after
giving birth. The length of the estrous cycle of
a female mountain gorilla is 28 days.
A single, dependent young is born after a
eight and a half month gestation period. Weaning
often doesn't occur until three years of age, and
juveniles may remain with mothers for years after
that. Females provide most of the parental care
in this species, nursing and carrying their young
for about 4 years. They also play with the young,
teach them, and groom them. The role of males in
parental care is less direct, although no less
important.consisting primarily of protecting the
females and the young within their social group
from potentially infanticidal rival males who may
take control of the group.
sexually mature by 10 years of age, but males are
unlikely to start breeding before 15 years.
Reproductive rates are slow, and a female may
leave only 2 to 6 offspring over a 40+ year
life-span. Males that have a harems of 3 to 4
females increase their reproductive output by
fathering 10 to 20 offspring over 50 years.
Although they will occasionally eat
invertebrates, eastern gorillas are primarily
folivorous. They eat the roots, leaves, stems,
and pith of herbs, vines, shrubs, and bamboo,
supplemented by small amounts of bark, wood,
roots, flowers, fruit, fungi, epithelium stripped
from roots, galls, invertebrates, and even their
Other Habits and
quadrupedal, walking on the knuckles of their
forelimbs and the soles of their feet.
spend about 30% of the day feeding, 30%
traveling, and 40% resting. They make nests to
sleep and rest in that can be in trees, on steep
slopes, or even on the ground.
afraid of water and will cross streams only if
they can do so without getting wet (i.e. crossing
over fallen logs).
genus & species Gorilla beringei
Animal Diversity Web http://animaldiversity.org/accounts/Gorilla_beringei/
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