Habitat and Ecology
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2000Endangered (EN)
- 1996Endangered (EN)
- 1996Endangered (EN)
- 1990Endangered (E)
- 1988Endangered (E)
- 1988Endangered (E)
Eastern lowland gorilla
The eastern lowland gorilla (Gorilla beringei graueri) also known as the Grauer's gorilla is a subspecies of eastern gorilla endemic to the mountainous forests of eastern Democratic Republic of the Congo. Important populations of this gorilla live within the Kahuzi-Biega and Maiko National Parks and their adjacent forests, the Tayna Gorilla Reserve, the Usala forest and on the Itombwe Massif.
It is the largest of the four gorilla subspecies. It has jet black coats like the mountain gorilla (Gorilla beringei beringei), although the hair is shorter on the head and body. The male's coat, like that of other gorillas, turns silver at the back as the animal matures. There are many more western lowland gorillas than the eastern variety; compared to a possible total of over 100,000 western lowland gorillas, there are only about 5,000 eastern lowland gorillas in the wild. Outside the native range, only a single female is in captivity at the Antwerp Zoo in Belgium.
Eastern lowland gorillas are the largest subspecies of gorilla and the largest living primates. Males weigh 163 kg (359 lb) on average while females usually weigh half as much. Males have a standing height of 1.76 metres (5 ft 9 in) on average and females stand at 1.60 metres (5 ft 3 in) or less.
Gorillas living in zoos are usually heavier than those in the wild, since they get less exercise and can weigh as much as 270 kilograms (600 lb). One of the largest captive gorillas was a male named Phil that lived between 1941 and 1958 at the St. Louis Zoo, estimated to weigh 250 kilograms (550 lb). Phil's recorded measurements were: height 1.7 m (5.6 ft), bust 182 cm (72 in), neck 91.5 cm (36.0 in), and wrist 25.4 cm (10.0 in).
Habitat and ecology
Gorillas must eat frequently due to their large size and therefore must spend long hours feeding every day. Gorillas are stable apes as they travel together for months and years at a time, much like the structure of a family. Gorillas travel in permanent groups because of their foliage diet, which allows them to travel. In comparison to the Western Gorillas, the groupings of eastern gorillas are usually much larger and split into temporary groups much less frequently.
The eastern lowland gorilla has the widest altitudinal range of any of the gorilla subspecies as they can be found in mountainous, transitional and lowland tropical forests. One of the most studied eastern lowland gorilla population lives in the highlands of Kahuzi-Biega where habitats vary between dense primary forests to moderately moist woodland, to Cyperus swamp and peat bog.
The eastern lowland gorilla has a varied diet including plants, fruits, seeds, leaves, stems and bark as well as small insects such as ants and termites. Although they occasionally feed on ants, it is only a minor part of their diet. In comparison to western lowland gorillas, found in low altitude forests, eastern lowland gorillas travel much less and increase their consumption of herbaceous vegetation.
Eastern lowland gorillas tend to be sociable and very peaceful, living in groups of five to 30. A group usually consists of one silverback and a few subdominant males. Silverbacks are the strong, dominant troop leaders (see alpha male). They are in charge of leading the group to food and protecting the group from danger. Males will slowly begin to leave their original group when they reach maturity, usually traveling with a group of other males for a few years before being able to attract females to form a new group.
Very little is known about the social behaviour, history and ecology of the eastern lowland gorillas primarily because of the civil war taking place in the Democratic Republic of the Congo making it impossible for researchers to get the data necessary. However, some aspects of social behaviour have been studied. For example, gorillas form harems with usually includes two full-grown males, as opposed to one, which was previously believed to be the group structure for this gorilla subspecies. Evidence shows that one third of gorilla groups in East Africa have two grown males in their group.
Most primates are bonded together by the relationship between females, a pattern also seen in many human families. In the eastern lowland gorilla population, the group is held together between each individual female and the silverback, much like the historically traditional view of a heterosexual Homo sapiens family structure. Once the gorillas reach maturity, both females and males usually leave the group. Females usually join another group or a single lone young adult male, whereas males typically remain together until they find females and establish their own groups. It is commonly believed that the structure of the gorilla group is to prevent predation.
A female will give birth to twins or a single infant after a gestation period of about 8½ months. They breastfeed for about 12 months. The baby can crawl at around nine weeks old and can walk at about 35 weeks old. Infant gorillas normally stay with their mother for three to four years and mature at around 11 to 12 years old.
Conservation and threats
The primary causes of habitat loss directly cause the decline in eastern lowland populations. These primary causes are: the killing of gorillas for bushmeat, instances of killing gorillas as revenge for confiscation of illegal charcoal or other law enforcement, or the destruction of gorilla habitat as a result of logging, charcoal, agricultural expansion or mining. Widespread artisanal mining activities (often controlled by rebel militias) are the major source of hunting pressure for gorillas and other wildlife. The eastern lowland gorilla is also suffering a range reduction in some areas due to an expanding human population.
Threats to the eastern lowland gorilla's survival include: logging, mining, civil unrest and hunting.
Civil unrest in the Democratic Republic of Congo has resulted in a decline in eastern lowland gorillas as well as mountain gorillas in this region. The region inhabited by eastern lowland gorilla has decreased from 8,100 square miles to 4,600 square miles in the past 50 years. This primate species now occupies only 13% of its historical area. Violence in the region has made research difficult, however, scientists have estimated that the population has decreased by more than 50% since the mid-1990s. In the mid-1990s, the population was recorded to nearly 17,000 gorillas.
The civil war taking place in the Democratic of the Congo means military groups remain within the forest for long periods of time. Thus, poaching has increased as militia and refugees become hungry. Military leaders have also disarmed the park security guards in national parks meaning they have virtually no control over the activities that occur within the park, and those that enter it, when faced with armed soldiers. The militia groups present in the region restrict protection of the eastern lowland gorilla. It has been estimated that more than half of the 240 gorillas known in one study have been killed as a result of poaching. Researchers have also stated that it is more difficult to patrol areas outside of the park and expect to find even higher levels of poaching.
Conservation groups negotiated with rebels who control the eastern Democratic Republic of the Congo to re-arm the park guards  After the war began, government funding of the park was stopped. Conservation groups, International Gorilla Conservation Program and Deutsche Gesellschaft für Technische Zasammenarbeit (German development agency) have funded the guards for the past several years 
Many multinational corporations are indirectly, and some directly, funding the civil war in the Democratic Republic of the Congo by buying illegal resources from the area or by trading resources for military weaponry. Reports from 2007 state that 14,694 tons of cassiterite ($45 million USD), 1,193 tons of wolframite (worth $4.27 million USD) and 393 tons of coltan ($5.42 million USD) were exported in 2007. Coltan in particular is one of the main export resources bought by multinational corporations illegally and is growing in demand due to its use for cellphones. Traxy’s alone bought $226 tonnes of coltan in 2007 which is 57% of the Democratic Republic of the Congo’s entire coltan. The United Nations Environmental Programme reported that resources from multinational corporations and pension funds in industrialized countries are "directed through subsidiary companies to help finance corruption and arms sales, processes that may involve 'conflict' natural resources" Private companies have been found to trade weapons for resources or provide access to weapons through subsidiary companies.
Approximately two million people, directly and indirectly related to the Rwandan genocide in 1994, fled to Tanzania and the Democratic Republic of the Congo, mainly in Virunga National Park. It has been estimated that there were 720,000 refugees living in five camps in the DRC bordering the park (Katale, Kahindo, Kibumba, Mugunga and Lac Vert), 24. Deforestation occurred as 80,000 refugees travelled into the park daily to find wood. Deforestation occurred at a rate of 0.1 km2 per day. Once the Congo war began in 1996, 500,000 refugees remained, putting pressure on the natural resources, including the eastern lowland gorilla.
Bushmeat is useful for displaced peoples residing in the region affected by the civil war, militias groups and loggers and miners. Surveys have shown that great apes, chimpanzees and bonobos comprise 0.5-2% of the meat found in bushmeats markets. Some researchers have found that up to 5 million metric tons of bushmeat are traded annually. This has a detrimental affect on the eastern lowland gorilla populations because of their slow rate of reproduction and their already struggling population. Although gorilla bushmeat only constitutes a small proportion of the bushmeat sold, it continues to encourage a decline in the gorilla populations being subjected to hunting. Endangered Species International stated that 300 gorillas are killed each year to supply the bushmeat markets in the Congo.
Banana plantations have been affected by gorillas. Gorillas rarely eat the banana fruits, but they do eat the nutritious pith. Farmers who have come in contact with gorillas in their plantations have killed the gorilla and obtained a double benefit, protecting their crop and using the meat of the gorilla to sell at the market.
Most parks in the Democratic Republic of the Congo are insecure areas restricting the access of park rangers. Although park rangers are trained to stop illegal hunting, the small number of park rangers do not have access to further training or equipment to handle the militia groups. In the Virunga National Park, for example, 190 park rangers have been killed in just the past 15 years from civil war. Laws in place enforce trans-boundary collaboration and have been proven successful in reducing the decline of the eastern lowland gorilla  Illegal extraction of resources from the Virunga National Park has been reduced by policing transportation across borders. This has reduced the financial input available to the militias in the region. Although park rangers have been successful in restricting the amount of illegal resources being transported out of the region, militias groups have retaliated by purposely killing a group of gorillas to threaten the park rangers. On July 22, 2007, 10 gorillas were killed in retaliation to the park rangers for interfering with the exportation of illegal resources such as wood.
The militia have remained in control in the region as a result of the neighbouring countries. These militia groups trade minerals and timber illegally in exchange for arms from neighbouring countries, corrupt officials and subsidiaries of many multinational companies. Gorillas are also threatened directly by militia groups because of the prevalence of booby traps placed randomly throughout the forest. Although the eastern lowland gorilla population is affected directly from violence caused by militia groups, their population is endangered mainly from the extraction of natural resources disrupting their habitat.
Conservation groups negotiated with rebels who control the eastern Democratic Republic of the Congo to re-arm the park guards. After the war began, government funding of the park was stopped. Conservation groups WWF, International Gorilla Conservation Program and Deutsche Gesellschaft für Technische Zasammenarbeit (German development agency) have funded the guards for the past several years.
Illegal logging may occur from companies with no rights to the land or by legal landholders. Over-harvesting is an illegal practice often conducted by legal concession holder and encourages deforestation and illegal resources exportation. The areas logged are prime gorilla habitat and is considered an international concern. Companies involved in illegal exploitation therefore encourage environmental destruction in the area and fuel the illegal export industry controlled by militia groups.
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