Critically endangered (G. gorilla), Endangered (G. beringei)
Life span: 30 to 40 years (wild), 50 years (captive)
Total population: approx. 130,000 (wild), 350 (captive)
Regions: Western and eastern central Africa
Gestation: 8.5 months (256 days)
Height: 1700 mm (M), 1500 mm (F)
Weight: 181 kg (M), 72 to 98 kg (F)
Species: G. beringei, G. gorilla
Subspecies: G. b. beringei, G. b. graueri, G. g. diehli, G. g. gorilla
Other names: gorilla (Finnish); gorille (French); gorilla (German); gorila
(Spanish); bergsgorilla, gorilla, or låglandsgorilla (Swedish); G.
gorilla: western gorilla; G.g. diehli: Cross River gorilla; G.g.
gorilla: western lowland gorilla; G. beringei: eastern gorilla; G.b.
beringei: Bwindi, mountain, or Virunga; G.b. graueri: eastern
lowland gorilla or Grauer's gorilla
Western and eastern gorillas are more genetically distant from one
another than are chimpanzees
(Pan troglodytes) and bonobos
(Pan paniscus) (Butynski 2001). There are few striking physical
differences between subspecies of gorilla, though differences in
dentition and craniometric
reveal distinguishing morphological
characteristics of each subspecies (Rowe 1996; Leigh et al. 2003). To
some extent, even the inexperienced observer can distinguish the
subspecies from one another. Mountain gorillas have significantly
longer hair than their conspecifics,
while western gorillas have brown, not black, hair on their heads, and eastern
gorillas have longer faces and broader chests than western gorillas (Rowe 1996;
Nowak 1999). Gorillas have dark brown to black fur and black skin. Dominant adult
males, called silverbacks, have a prominent sagittal
crest and striking silver
coloration from their shoulders to rump. Males and females are sexually
with males weighing up to 181 kg (400 lb) in the wild and 227 kg (500 lb) in captivity
and measuring, on average, 1700
mm, while females weigh between 72 and 98 kg (159 and 216 lb) and measure, on
average, 1500 mm (4.92 ft) (Rowe 1996).
Gorilla gorilla gorilla
Photo: Rick Murphy
Spending the majority of their lives on the ground, the main locomotion pattern
of gorillas is quadrupedal knuckle-walking although
they do climb and spend limited amounts of time standing bipedally.
Because of their sheer size, adult gorillas must climb near the main trunk
of a tree or on large branches while juveniles and adolescents are more agile
(Tutin et al. 1995; Rowe 1996).
Gorillas live between 30 and 40 years in the wild and up to 50 years in captivity (Stoinski pers.
CURRENT RANGE MAPS (IUCN REDLIST):Gorilla beringei
| Gorilla gorilla
Gorillas are patchily distributed in east central and equatorial west
Africa, separated by the Congo River and its tributaries. Western
gorillas (including western lowland and Cross River gorillas) are found
in a geographic area of about 709,000 km² (273,746 mi²)
covering parts of Nigeria, Cameroon, Central African Republic (CAR), Equatorial
Guinea, Gabon, Republic of Congo, Angola, and far-western Democratic Republic
of Congo (DRC). Cross River gorillas are found in only a 750
km² (290 mi²) area in Nigeria and Cameroon, a pocket of
land that is isolated from the majority of this region. Eastern gorillas (including
mountain and eastern lowland gorillas) are found in portions of eastern
DRC, Uganda, and Rwanda, in an area approximately 112,000
km² (43,243 mi²), though mountain gorillas are restricted
to two locations, Virunga Volcanoes where the borders of Uganda, Rwanda, and
DRC meet, and Bwindi-Impenetrable National Park, Uganda (Nowak 1999;
Butynski 2001; Sarmiento 2003).
Population estimates based on nest counts, known areas of available
habitat, and population density reveal startlingly low numbers for some
subspecies: as high as 110,000 (G.g. gorilla), 250 to 300 (G.g.
diehli), 17,000 (G.b. graueri), and 700 (G.b.
beringei) (Butynski 2001; Plumptre et al. 2003; Stoinski pers. comm.). There are about
350 gorillas in zoos in the United States, all of them are western
lowland gorillas (Goodall et al. 2003).
For more than 30 years, ongoing field research on the mountain gorillas
has made them the most studied subspecies of gorilla. George Schaller
conducted the first long-term research study on mountain gorillas
starting in 1959. In 1967, notable researcher Dian Fossey spearheaded
the Karisoke Research Center in the Virunga Volcanoes and since the
inception of this field site, researchers have been unraveling the
complexities of gorilla society, behavior, and ecology by studying habituated groups (it is one of the
only study sites where gorillas are fully habituated). Another
long-term study site is at the Lopé Reserve of Gabon, where
Caroline Tutin and Michael Fernandez have been studying western lowland
gorillas since 1984 (Doran & McNeilage 1997). Most of the information
available about wild eastern lowland gorillas comes from studies in
Kahuzi-Biega National Park in DRC (Tutin & Vedder 2001).
Because of their great geographical separation, about 750 km (466 mi), western
and eastern gorillas live in dramatically different habitats (Tutin &
Vedder 2001). Even within-species habitat variation is quite great,
from swamp to montane forest. Eastern gorillas live in submontane and
montane forests from 650 to 4000 m (2132 to 13,123 ft) (Butynski 2001; Sarmiento 2003).
Mountain gorillas live at the highest elevations, from 2200 to 4000 m (7218 to 13,123 ft),
in the Virunga Volcanoes while eastern lowland gorillas occupy
submontane forests from 700 to 2900 m (2297 to 9514 ft) (Butynski 2001). Where mountain
gorillas exist, there are two rainy and two dry seasons per year, with
average rainfall of 2000 mm (6.56 ft) per year (McNeilage 2001). The rainy
seasons are from March until May and September to November while the dry
seasons are June through August and December through February (McNeilage
2001; Robbins & McNeilage 2003). Temperatures range between 3.9° C
(39° F) and 14.5° C (58° F), though they may reach 25.8°
C (78.44° F) (Sarmiento 2003). Eastern lowland gorillas live in primary and secondary forests in both highland
and lowland forests across their
range. They occupy montane, bamboo, and lowland forests at elevations
of 600 to 3308 m (1969 to 10,853 ft) (Ilambu 2001). There are two rainy seasons, the first
lasting from March to June and the shorter lasting from September to
December. There are also two dry seasons, the longer from June to
September and the shorter from December until March (Yamagiwa et al.
Gorilla gorilla gorilla
Photo: Rick Murphy
Western gorillas live in lowland, swamp, and montane forests from sea
level to 1600 m (5249 ft) (Butynski 2001; Sarmiento 2003). As their common name
implies, western lowland gorillas live in lowland and swamp forests at
elevations up to 1600 m (5249 ft) while Cross River gorillas inhabit low-lying and
submontane forests at elevations from 150 to 1600 m (492 to 5249 ft) (Sarmiento 2003).
Western lowland gorillas that live in mixed swamp forests experience one
rainy and one dry season per year. Average rainfall is 1526 mm (5.01 ft) with the
greatest amount of rain falling between August and November and
diminishing during December through March (Poulsen & Clark 2004).
The considerable dietary differences between mountain, western, and
eastern lowland gorillas impact home range size and social behavior.
Despite these differences, though, all gorilla groups exhibit
synchronized activities and, throughout the day, alternate between rest
periods and travel or feeding periods (Stewart 2001). Mountain gorillas
are folivores, feeding on leaves,
stems, pith, and shoots of terrestrial herbaceous vegetation. They
preferentially choose high quality, high protein, low fiber, and low
tannin foods from a small number of species and incorporate little fruit
into their diets (McNeilage 2001). Where bamboo is available, it is
usually favored and they spend much time digging to unearth tender
shoots. Because they depend on a readily available, easily accessed
food source, there is little competition for resources between groups,
their home ranges are small, typically between three and 15
km² (1.16 and 5.79 mi²), and they move only 500 m (.311 mi) or less within a typical day
(McNeilage 2001; Robbins & McNeilage 2003). Though they only utilize a
few species in each habitat, mountain gorillas show wide dietary
flexibility which enables them to occupy a wide variety of habitats
within their range (McNeilage 2001).
Gorilla beringei beringei
Photo: A. W. Weber and A. Vedder
The diet of eastern lowland gorillas is more diverse than the mountain
gorillas' and changes seasonally. While leaves and pith are staple
parts of their diets, eastern lowland gorillas depend heavily on fruit
(25 percent of their total diet), especially during the times of year
when fruits are abundant. When they include insects in their diet,
eastern lowland gorillas prefer ants (Yamagiwa et al. 1994). Eastern
lowland gorillas generally use a small area for a few days and then
travel long distances to another area. Eastern lowland gorillas that
depend more heavily on fruit must travel farther in a day to find
fruiting trees and have larger home ranges because of a relative
scarcity of fruit. Their home ranges vary from 2.7 to 6.5
km² (1.04 to 2.51 mi²) while their day range is between 154 and 2280 m (.096 and 1.42 mi) (Yamagiwa
et al. 1996).
Western lowland gorillas have little dependable access to high quality
terrestrial herbs across their range, but some areas are rich in aquatic
herbs and they do eat herbaceous vegetation. Fruit is widely available,
though dispersed, across their range, and is a central component of
their diet, especially during times of fruit abundance (Tutin 1996;
Doran & McNeilage 2001; Doran et al. 2002). Termites and ants are also
important dietary staples. Western lowland gorillas have the largest
home ranges and travel the farthest of all gorilla subspecies because of
their reliance on fruit. The average distance traveled per day is 1105
m (.687 mi) and western lowland gorillas range over seven to 14 km² (2.70 to 5.41 mi²)
In some parts of their ranges, gorillas are sympatric with chimpanzees
(Pan troglodytes) and
dietary overlap in plant food and fruit is great. Where they occur
together, gorillas and chimpanzees also have similar habitat use
patterns and ecological competition is likely to occur (Kuroda et al.
1996). Though they share a similar niche, competition has not been
recorded at any of the sites where the two apes overlap (McNeilage
Gorillas are vulnerable to predation by leopards (Panthera
pardus), though direct documentation of attacks is difficult to
obtain and rare. Evidence from leopard scat in areas where gorillas
range is often the only means of confirming leopard predation, though
even this is questionable as the large cats could simply be scavenging
carcasses (Fay et al. 1995).
Content last modified: October 4, 2005
Written by Kristina Cawthon Lang. Reviewed by Tara Stoinski.
Cite this page as:
Cawthon Lang KA. 2005 October 4. Primate Factsheets: Gorilla (Gorilla) Taxonomy, Morphology, & Ecology . <http://pin.primate.wisc.edu/factsheets/entry/gorilla/taxon>. Accessed 2014 October 1.