Eastern Gorilla
Encyclopedia
The eastern gorilla is a species of the genus Gorilla
and the largest living primate
. At present, the species is subdivided into two subspecies. The eastern lowland gorilla
(G. b. graueri) is the most populous, at about 5,000 individuals. The mountain gorilla
(G. b. beringei) has only about 700 individuals. In addition, scientists are considering elevating the Bwindi gorilla population (which numbers about half of the mountain gorilla population) to the rank of subspecies.
of the eastern gorilla: the mountain gorilla
(Gorilla beringei beringei) of the volcanic
slopes of Rwanda, Uganda and eastern Democratic Republic of Congo; and the eastern lowland gorilla
(Gorilla beringei graueri) of the lowlands of eastern Democratic Republic of Congo and Uganda. A small population from the Bwindi Impenetrable Forest
in southern Uganda and adjacent areas in Congo differs genetically from the other subspecies, and is therefore often considered as a separate, yet undescribed, subspecies.
The eastern lowland gorilla and mountain gorilla were previously thought to be two of the three subspecies of one single species, the gorilla (Gorilla gorilla). However, genetic research
has shown that the two eastern subspecies are far more closely related than the western subspecies: the western lowland gorilla
(G. gorilla gorilla), which justified the separate classification. The two eastern subspecies are now classified as G. beringei.
with a large head, broad chest, and long arms. It has a flat nose with large nostrils. The face, hands, feet and breast are bald. The fur is mainly black, but adult males have a silvery "saddle" on their back. When the gorilla gets older, the entire fur becomes grayish, much like the gray hair
of elderly people. This is why the older males are sometimes called Silverbacks. The eastern lowland gorilla has a shorter, thicker, deep black fur, while the mountain gorilla has a more bluish color. The mountain gorilla is slightly smaller and lighter than the eastern lowland gorilla, but still slightly larger than the western lowland gorilla. Males are much larger than females. A full-grown adult male Eastern gorilla weighs an average of 195 kg (429.9 lb) and stands 1.7 m (5.6 ft) upright and a female typically weighs 100 kg (220.5 lb) and stands 1.4 m (4.6 ft). The tallest silverback recorded was a 1.94 metres (6.4 ft) individual shot in Alimbongo, northern Kivu
in May 1938. The heaviest gorilla recorded was a 1.83 metres (6 ft) silverback shot in Ambam
, Cameroon
which weighed about 266 kilograms (586.4 lb), although the latter area is within the range of the western gorilla, far outside that of the eastern gorilla.
s and subalpine forests of eastern Democratic Republic of the Congo
, southwestern Uganda
and Rwanda
, within the triangle between the Lualaba River
, Lake Edward
and Lake Tanganyika
. The eastern gorilla prefers forests with a substrate of dense plant material.
Eastern gorillas are herbivorous, with a heavily foliage based diet . They have smaller home ranges than western gorillas as foliage is more abundant than fruit. They are diurnal but the majority of foraging occurs in the morning and late afternoon. At night they build nests by folding over vegetation, usually on the ground.
and the decline in suitable habitat as a result of intensifying forestry
and the development of agriculture
form the most important threats for the species. In some national park
s, expeditions in search for mountain gorillas are a popular tourist attraction
. This has both advantages (environmental awareness, financial benefit) and disadvantages (disturbance of natural behavior) for the conservation of the gorillas.
As opposed to the western lowland gorilla, the eastern gorilla is seldom found in zoos. The Antwerp Zoo
is probably the only Western
zoo that has eastern lowland gorillas (two older females). The mountain gorilla is not held in captivity at all.
Gorilla
Gorillas are the largest extant species of primates. They are ground-dwelling, predominantly herbivorous apes that inhabit the forests of central Africa. Gorillas are divided into two species and either four or five subspecies...
and the largest living primate
Primate
A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...
. At present, the species is subdivided into two subspecies. The eastern lowland gorilla
Eastern Lowland Gorilla
The Eastern Lowland Gorilla is a subspecies of Eastern Gorilla that is now only found in the forests of eastern Democratic Republic of the Congo...
(G. b. graueri) is the most populous, at about 5,000 individuals. The mountain gorilla
Mountain Gorilla
The Mountain Gorilla is one of the two subspecies of the Eastern Gorilla. There are two populations. One is found in the Virunga volcanic mountains of Central Africa, within three National Parks: Mgahinga, in south-west Uganda; Volcanoes, in north-west Rwanda; and Virunga in the eastern Democratic...
(G. b. beringei) has only about 700 individuals. In addition, scientists are considering elevating the Bwindi gorilla population (which numbers about half of the mountain gorilla population) to the rank of subspecies.
Classification
There are at least two subspeciesSubspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of the eastern gorilla: the mountain gorilla
Mountain Gorilla
The Mountain Gorilla is one of the two subspecies of the Eastern Gorilla. There are two populations. One is found in the Virunga volcanic mountains of Central Africa, within three National Parks: Mgahinga, in south-west Uganda; Volcanoes, in north-west Rwanda; and Virunga in the eastern Democratic...
(Gorilla beringei beringei) of the volcanic
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
slopes of Rwanda, Uganda and eastern Democratic Republic of Congo; and the eastern lowland gorilla
Eastern Lowland Gorilla
The Eastern Lowland Gorilla is a subspecies of Eastern Gorilla that is now only found in the forests of eastern Democratic Republic of the Congo...
(Gorilla beringei graueri) of the lowlands of eastern Democratic Republic of Congo and Uganda. A small population from the Bwindi Impenetrable Forest
Bwindi Impenetrable Forest
Bwindi Impenetrable Forest is a large primeval forest in the Virunga Volcanoes mountain range, and is located in south-western Uganda on the edge of the western Great Rift Valley. It is one of the most biologically diverse areas in the world, where half the world's population of highly endangered...
in southern Uganda and adjacent areas in Congo differs genetically from the other subspecies, and is therefore often considered as a separate, yet undescribed, subspecies.
The eastern lowland gorilla and mountain gorilla were previously thought to be two of the three subspecies of one single species, the gorilla (Gorilla gorilla). However, genetic research
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
has shown that the two eastern subspecies are far more closely related than the western subspecies: the western lowland gorilla
Western Lowland Gorilla
The western lowland gorilla is a subspecies of the western gorilla that lives in montane, primary, and secondary forests and lowland swamps in Angola, Cameroon, Central African Republic, Congo, Democratic Republic of the Congo, Equatorial Guinea and Gabon. It is the gorilla usually found in zoos...
(G. gorilla gorilla), which justified the separate classification. The two eastern subspecies are now classified as G. beringei.
Physical characteristics
The eastern gorilla is a large hominidHominidae
The Hominidae or include them .), as the term is used here, form a taxonomic family, including four extant genera: chimpanzees , gorillas , humans , and orangutans ....
with a large head, broad chest, and long arms. It has a flat nose with large nostrils. The face, hands, feet and breast are bald. The fur is mainly black, but adult males have a silvery "saddle" on their back. When the gorilla gets older, the entire fur becomes grayish, much like the gray hair
Hair color
Hair color is the pigmentation of hair follicles due to two types of melanin: eumelanin and pheomelanin. Generally, if more melanin is present, the color of the hair is darker; if less melanin is present, the hair is lighter...
of elderly people. This is why the older males are sometimes called Silverbacks. The eastern lowland gorilla has a shorter, thicker, deep black fur, while the mountain gorilla has a more bluish color. The mountain gorilla is slightly smaller and lighter than the eastern lowland gorilla, but still slightly larger than the western lowland gorilla. Males are much larger than females. A full-grown adult male Eastern gorilla weighs an average of 195 kg (429.9 lb) and stands 1.7 m (5.6 ft) upright and a female typically weighs 100 kg (220.5 lb) and stands 1.4 m (4.6 ft). The tallest silverback recorded was a 1.94 metres (6.4 ft) individual shot in Alimbongo, northern Kivu
Kivu
Kivu was the name for a large "Region" in the Democratic Republic of Congo under the rule of Mobutu Sese Seko that bordered Lake Kivu. It included three "Sub-Regions" : Nord-Kivu, Sud-Kivu and Maniema, corresponding to the three current provinces created in 1986...
in May 1938. The heaviest gorilla recorded was a 1.83 metres (6 ft) silverback shot in Ambam
Ambam
Ambam is a town and commune in South Province of Cameroon on the border with Equatorial Guinea and Gabon. This frontier town is located approximately 220 km from Yaounde and as of 2005 had a population of 1,596. Traditionally, it has traded with its neighbouring countries across the border...
, Cameroon
Cameroon
Cameroon, officially the Republic of Cameroon , is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the...
which weighed about 266 kilograms (586.4 lb), although the latter area is within the range of the western gorilla, far outside that of the eastern gorilla.
Distribution and ecology
The eastern gorilla occurs in the lowland and mountain rainforestRainforest
Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...
s and subalpine forests of eastern Democratic Republic of the Congo
Democratic Republic of the Congo
The Democratic Republic of the Congo is a state located in Central Africa. It is the second largest country in Africa by area and the eleventh largest in the world...
, southwestern Uganda
Uganda
Uganda , officially the Republic of Uganda, is a landlocked country in East Africa. Uganda is also known as the "Pearl of Africa". It is bordered on the east by Kenya, on the north by South Sudan, on the west by the Democratic Republic of the Congo, on the southwest by Rwanda, and on the south by...
and Rwanda
Rwanda
Rwanda or , officially the Republic of Rwanda , is a country in central and eastern Africa with a population of approximately 11.4 million . Rwanda is located a few degrees south of the Equator, and is bordered by Uganda, Tanzania, Burundi and the Democratic Republic of the Congo...
, within the triangle between the Lualaba River
Lualaba River
The Lualaba River is the greatest headstream of the Congo River by volume of water. However, by length the Chambeshi River is the farthest headstream. The Lualaba is 1800 km long, running from near Musofi in the vicinity of Lubumbashi in Katanga Province. The whole of its length lies within the...
, Lake Edward
Lake Edward
Lake Edward or Edward Nyanza is the smallest of the African Great Lakes. It is located in the western Great Rift Valley, on the border between the Democratic Republic of the Congo and Uganda, with its northern shore a few kilometres south of the Equator...
and Lake Tanganyika
Lake Tanganyika
Lake Tanganyika is an African Great Lake. It is estimated to be the second largest freshwater lake in the world by volume, and the second deepest, after Lake Baikal in Siberia; it is also the world's longest freshwater lake...
. The eastern gorilla prefers forests with a substrate of dense plant material.
Eastern gorillas are herbivorous, with a heavily foliage based diet . They have smaller home ranges than western gorillas as foliage is more abundant than fruit. They are diurnal but the majority of foraging occurs in the morning and late afternoon. At night they build nests by folding over vegetation, usually on the ground.
Behavior
Eastern gorillas live in stable, cohesive family groups, led by a dominant silverback male. Eastern gorillas tend to have larger group sizes than their western relatives, numbering up to 35 individuals. There is no distinct breeding season and females give birth only once every 3-4 years due to the long period of parental care and a gestation period of 8.5 months. Newborn gorillas have greyish-pink skin and can crawl after 9 weeks; they are not fully weaned until 3.5 years. Males defend their females and offspring using their large size in intimidating displays involving charging and chest-beating.Status
The eastern gorilla is the more critically endangered of the two gorilla species. The hunt for bushmeatBushmeat
Bushmeat initially referred to the hunting of wild animals in West and Central Africa and is a calque from the French viande de brousse. Today the term is commonly used for meat of terrestrial wild animals, killed for subsistence or commercial purposes throughout the humid tropics of the Americas,...
and the decline in suitable habitat as a result of intensifying forestry
Forestry
Forestry is the interdisciplinary profession embracing the science, art, and craft of creating, managing, using, and conserving forests and associated resources in a sustainable manner to meet desired goals, needs, and values for human benefit. Forestry is practiced in plantations and natural stands...
and the development of agriculture
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
form the most important threats for the species. In some national park
National park
A national park is a reserve of natural, semi-natural, or developed land that a sovereign state declares or owns. Although individual nations designate their own national parks differently A national park is a reserve of natural, semi-natural, or developed land that a sovereign state declares or...
s, expeditions in search for mountain gorillas are a popular tourist attraction
Tourist attraction
A tourist attraction is a place of interest where tourists visit, typically for its inherent or exhibited cultural value, historical significance, natural or built beauty, or amusement opportunities....
. This has both advantages (environmental awareness, financial benefit) and disadvantages (disturbance of natural behavior) for the conservation of the gorillas.
As opposed to the western lowland gorilla, the eastern gorilla is seldom found in zoos. The Antwerp Zoo
Antwerp Zoo
Antwerp Zoo is a zoo in the centre of Antwerp, Belgium, located right next to the Antwerpen-Centraal railway station. It is the oldest animal park in the country, and one of the oldest in the world, established on 21 July 1843.- History :...
is probably the only Western
Western world
The Western world, also known as the West and the Occident , is a term referring to the countries of Western Europe , the countries of the Americas, as well all countries of Northern and Central Europe, Australia and New Zealand...
zoo that has eastern lowland gorillas (two older females). The mountain gorilla is not held in captivity at all.