Mountain Gorilla is among the largest and biggest animals and it belongs to the Eastern Gorilla species.
Where to Find Mountain Gorillas?
Mountain gorillas are found in Mgahinga Gorilla National Park and Bwindi Impenetrable National Park in Uganda, Volcanoes National Park in North West Rwanda and the Virunga National Park in Eastern Congo.
The Mountain Gorilla (Gorilla beringei beringei) belongs to the eastern gorilla species, which also includes the Eastern Lowland Gorilla (Gorilla beringei graueri). There are two populations of G. b. beringei. one among the volcanoes of the Virunga Massif at the border of the Democratic Republic of the Congo (DRC), Rwanda and Uganda, the other in Bwindi Impenetrable National Park in southwest Uganda on the border with DRC.The Bwindi Mountain Gorilla could be a third subspecies, Gorilla beringei bwindi (Sarmiento et al., 1996), but the taxonomic status of the populations is as yet unclear (McNeilage et al., 2001).
Nomenclature
The American physician and missionary Thomas Staughton Savage first described the Western Gorilla (he called it Troglodytes gorilla) in 1847. The name was derived from a Greek translation of the word Gorillai (“tribe of hairy women”), described by Hanno the Navigator, a Carthaginian explorer who led a voyage (circa 480 BC) around the coast of West Africa. There is much academic debate over whether the ‘hairy women’ he saw are what we know as gorillas today.
Scientific name
Gorilla beringei beringei (Matschie, 1903)
The name beringei was first given by Paul Matschie, a mammalian taxonomist working at the Humboldt University Zoological Museum in Berlin, in 1903. He described a new species of gorilla inhabiting the Kirunga (= Virunga) Volcano. Matschie named the species Gorilla beringei in honour of Captain von Beringe.
Common names
English – Mountain Gorilla
French – Gorille de montagne
German – Berggorilla
Spanish – Gorila Montañés
Description
The Mountain Gorilla is very black and densely furred, with a broad face and massive jaws. It has a long blue-black coat and the small of the back, or ‘saddle’, of mature males becomes grey or white with age, hence the name of ‘silverback’ for mature males.
General Biology
Gorillas are mainly terrestrial. The gorilla’s large size and folivorous habits mean that the animals must spend long hours
feeding every day to maintain their body weight. Of all the great apes, the gorilla shows the most stable grouping patterns. The same adult individuals travel together for months and usually years at a time. It is because gorillas mainly eat foliage that they can afford to live in these relatively permanent groups. Foliage, unlike patchy fruit sources generally and ripe fruit in particular, is widespread and abundant and supports large groups of animals. Gorilla groups can include up to 30-40 animals, but more usually number 5-10 individuals.
Habitat
The characteristic habitat of the Mountain Gorillas (Gorilla beringei beringei) is high-altitude montane forests with a dense herb layer and low abundance of fruit (reviewed in Doran & McNeilage, 1998, 2001). A number of vegetation zones have been identified in the Mountain Gorilla habitat of the central Virunga Volcanoes region, which mostly consist of woodland with a relatively open canopy and extremely dense herbaceous understorey (Watts, 1997). Mountain Gorillas range up to 3,400 m in altitude with occasional forays even higher (IUCN, 1982).
Bwindi gorillas tend to live in lower elevations, warmer temperatures and are more arboreal than Virunga gorillas (Sarmiento et al., 1996). The area of habitat occupied by the Mountain Gorilla in the Virungas is approximately 450 km2 and the Bwindi
gorillas occupy an area of approximately 215 km2.
Adaptation
Gorillas are herbivorous (plant-eating). Plant material contains cellulose, which is indigestible to many non-herbivorous animals. With regard to digestion, herbivorous animals that do not ruminate (re-chew their food as part of the digestive process) rely solely on the microbes (microscopic bacteria) living in their colon. The bacteria function to breakdown the indigestible plant cellulose and turn it into valuable digestible carbohydrates through the fermentation process.
Social behaviour
As far as group structure is concerned, gorillas form harems. It was once thought that gorilla groups contained only one adult male, but around one third of groups in Albertine Rift have been found to host two full-grown males. Adult females in any one silverback’s (dominant adult male) harem are mostly unrelated, and the social ties that exist between them are weak. In contrast to many other primates, it is the bond between each individual female and the silverback, rather than bonds between the females that hold the group together. Upon reaching maturity, both the males and females leave the natal group. The females usually join another group or a lone young adult male, whereas the males remain solitary until they can attract females and establish their own groups (Robbins, 1995).
Distribution (current and historical)
There are two known populations of Mountain Gorilla, both of which occur in protected areas (national parks and reserve). One population occurs on the extinct volcanoes of the Virunga Massif along the borders of the Democratic Republic of the Congo (DRC), Rwanda, and Uganda within the Virunga National Park of DRC, the Volcanoes National Park in Rwanda and to a lesser extent the Mgahinga Gorilla National Park, Uganda. A separate population of Mountain Gorillas is found in the Bwindi-Impenetrable National Park in southwest Uganda, on the border of DRC (UNEP -WCMC & WWF, 2001). In this report these populations will be referred to as either the Virungas or Bwindi population of Mountain Gorillas.
Gorillas are found in two widely separated areas of Africa. The western and eastern populations were probably originally separated first by the massive inland Congo basin lake of the Miocene, and then, from about 5 million years ago, by the gradual drying of the region and the retreat of forest to higher areas. Subsequently, gorillas have not spread back into the central Congo basin, either because they have not had time, or because the heavily shaded primary forest there does not allow the growth of sufficient ground vegetation to support such a large, predominantly terrestrial animal (MacDonald ed., 2001).
Evaluation and evolution of populations
Based on recent census, the total number of Mountain Gorillas is between 1060, living in two isolated populations. Both populations are entirely located within protected areas. The number of
Mountain Gorillas declined throughout the 1970s and early 1980s, and some declines were seen into the 1990s (e.g Binyeri et al., 2002). IUCN (1982) described a decline in the Mountain Gorilla numbers in the Virungas, from 400-500 in the late 1950s, to 275 in 1973 to 250 by 1981, with most of the decline occurring in the Democratic Republic of Congo. However, since the mid 1980s, the Mountain Gorilla appears to be gradually increasing in numbers. A census of the Virunga Volcanoes Mountain Gorilla population carried out in 2003 shows a 17% increase in population size since 1989. Their number is now estimated at a total of 380. 71% of these animals are habituated (used to the presence of humans). A census conducted in Bwindi in 2018 resulted in an estimate of 480 gorillas from 28 groups, along with 7 lone silverback males.
The Mountain Gorilla (G.g.beringei) is listed as Critically Endangered on the IUCN Red List of Endangered Species (IUCN 2008, CR C1). It faces an extremely high risk of extinction in the wild due to its very small population level, habitat loss,
poaching, human disease and war.
Migrations
The Mountain Gorillas of the Virunga Volcanoes inhabit an area that is shared between three countries, the DRC, Rwanda and Uganda. Daily foraging movements may involve crossing international borders. The area of habitat occupied by the Virungas Mountain Gorillas is approximately 450 km2 and that occupied by the gorillas of Bwindi-Impenetrable National Park is approximately 215 km2 (Butynski, 2001). A study by Vedder (1984) in Volcanoes National Park of Rwanda indicated that,
within each of the dietary seasons (October-November and December-September), gorillas responded to decreases in food abundance by expanding their range and travelling further as well as by altering their diet. Solitary male Mountain Gorillas travel further and expand their home range, and Mountain Gorilla home ranges typically overlap extensively (Watts, 1994). Watts (1998) found that they used areas less than or equal to 25 km2 and that annual home range size and core area size varied considerably both between groups and across years. Food and male mating competition influence home-range use and core area selection and size.
Conservation status, by range state
Democratic Republic of the Congo (Critically Endangered): The Mountain Gorilla occurs in the Mikeno sector of Virunga National Park. The Virunga National Park is 7,900 km2 in size and is contiguous with the Ruwenzori Mountains and Mgahinga Gorilla National Parks, Uganda and Volcanoes National Park, Rwanda.
Rwanda (Critically Endangered): The Mountain Gorilla occurs in the Volcanoes National Park, which is 160 km2 in size and is contiguous to Virunga National Park in DRC and Mgahinga Gorilla National Park in Uganda. It ranges in altitude from 2,400m to 4,507m (UNEP-WCMC, 2003c).
Uganda (Critically Endangered): The Mountain Gorilla occurs in the Mgahinga Gorilla National Park and in Bwindi- Impenetrable National Park. The Mgahinga Gorilla National Park is 33.7 km2 in size and is found in the extreme south-west of Uganda on the borders with DRC and Rwanda. It ranges in altitude from 2,700m to 4,127m. The Bwindi-Impenetrable National Park is 331 km2 and ranges in altitude from 1,190m to 2,607m.
Actual and potential threat
The major threats affecting or having affected Mountain Gorilla populations are (1) habitat loss or modification and forest encroachment (Muruthi et al., 2000), (2) disease and disease transmission from humans and (3) war or political unrest (Plumptre et al., 2003; Muruthi et al., 2000; IUCN, 2002).
Degradation and decline of habitats
The Mountain Gorilla lives in a region where there is a very high human population. In eastern DRC, Rwanda and Uganda fragments of forest form part of a landscape that supports one of the highest densities of rural human populations in Africa (Taylor et al., 1999). The main threat to gorillas in DRC is forest clearance by refugees and, although no land has been appropriated from the habitat of the Virunga gorillas, declines may be due to the presence of livestock in the Virungas (IUCN, 1982). Deforestation to supply refugees’ demand for fuelwood affected 105 km² of the park in 2003, of which 35 km² has been completely stripped, though not in the Mikeno sector, where the gorillas are found (UNEP -WCMC, 2003b).
Relatively intensive illegal woodcutting and the extraction of gold and production of charcoal do occur in certain areas. In the long or medium term, agricultural encroachment is the major threat to forest integrity (UNEP-WCMC, 2003a). The Bwindi-Impenetrable National Park population is relatively well protected. Historically, only about 10% of BINP remained free from human disturbance (UNEP-WCMC, 2003a).
Direct exploitation – The bushmeat trade
Mountain Gorillas are not usually hunted for bushmeat, but they are frequently maimed or killed by traps and snares intended for other animals (Plumptre & Williamson, 2001). Very recent information suggests that a few mountain gorillas have been killed for their meat (Wildlife Direct, 2007).
Other forms of direct exploitation
In the past Mountain Gorillas were killed for their heads, hands, and feet, which were sold to collectors, and a few infants have been captured for potential illegal sale to zoos. Binyeri et al. (2002) reported a number of incidents in the Virunga National Park of DRC in which infant gorillas were abducted for sale, and several adults killed to gain access to the infants, Williamson and Fawcett (2008) reported similar incidents in Rwanda.
Diseases
Another potential threat to gorillas is exposure to human dis eases (e.g Graczyk et al., 2001; Graczyk et al., 2003) particularly for habituated gorillas that come into contact with humans, in areas of gorilla tourism (Homsy 1999). Gorilla tourism exposes gorillas to humans and hence to any diseases that humans may be carrying, some of which the gorillas may never have been exposed to before. An outbreak of a respiratory disease, with the possibility of measles as the primary infection, in the Volcanoes NP in Rwanda claimed six gorilla lives, and 27 other gorillas were successfully treated (Wallis & Lee, 1999). Strict rules are in place to regulate tourist visits (Homsy 1999).
Beside severe impacts on human populations, several outbreaks of the Ebola virus since 2000 might have claimed thousands of great apes in Africa. Ebola hemorrhagic fever is a severe, often fatal disease that affects humans, gorillas and chimpanzees. Many scientists believe the disease is spread through the butchering and handling of primate bushmeat. Mountain Gorillas have not yet been affected.
Impact of Conflicts
The impact of wars and political conflicts is particularly well documented for the Mountain Gorilla. The early 1990s saw the
outbreak of fighting in Rwanda, which by April 1994 resulted in a stream of refugees pouring into gorilla habitat in DRC. Shortly afterwards came the 1996 war between the armed forces of DRC and a rebel movement. Subsequently fighting again broke out in 1998 between Rwandan and Ugandan troops on the one side and the DRC army on the other.
The displacement of refugees during these conflicts led to uncontrolled firewood harvesting, increased poaching in the Virunga National Park and disruption of natural animal migration patterns (UNEP-WCMC, 2003b). Three of the four refugee camps in North Kivu were located in or near to the park, and it is estimated that at least 500,000 ha of the park were affected by wood harvesting or poaching (UNEP-WCMC, 2003b). Kalpers et al. (2003) report that between 12 and 17 gorillas are known to have died between 1992 and 2000 in the Virungas Volcanoes Region as a direct result of military activity. Concern for the protection and management of the site, especially with regards to recurring encroachments, deforestation, poaching, population growth, and the refugee-related problems that have arisen due to civil unrest in Rwanda, led to Virunga National Park being placed on the World Heritage in Danger List in 1994 (UNESCO, 1994).
The situation around the Virungas remains unstable and militia groups are still active in the region. Much of the Virungas has been severely affected by this civil war, the continuous political unrest and economic instability. The ongoing conflict has caused the death of several guards in the last two years and has made wardening of the area extremely difficult and dangerous. The conflict remains a threat to the Virungas gorillas and to the protected areas.
Other threats
Accidental entrapment in wire snares used to trap other wild animals is also a threat to the mountains gorillas. Plumptre et al. (1997) stated that the setting of snares for ungulates in the Volcanoes National Park, Rwanda is one of the greatest threats to Gorilla beringei beringei. The isolation and low numbers of Mountain Gorillas have given rise to concerns about inbreeding (Garner & Ryder, 1996). The two populations of Mountain Gorilla are too small to meet theoretical survival criteria, and are vulnerable to catastrophic events such as outbreaks of disease, sudden wide loss of habitats, and would quickly be decimated by poaching if the vigilance of conservationists were to be relaxed. International trade in live gorillas and gorilla parts, which used to be a threat, has declined since the gorilla was listed in Appendix I of CITES.
Anti-poaching and law enforcement
The taxon is legally protected in all three of its range states. Great efforts must be made by the range states to enforce their laws concerning gorillas, including not only effective anti-poaching, but also follow-up of the legal process through arrest and prosecution of all cases judged guilty.
Maintenance of habitat and corridors
The level of legal protection given to Mountain Gorillas and their habitat is appropriate. The four national parks are managed and supported by the governments of DRC, Rwanda and Uganda, by international conservation NGOs, and partially financed through gorilla watching tourism. The gorillas are highly vulnerable to disease and poaching but, in comparison with the other gorilla subspecies, they are for the moment relatively secure. However, given the current insecurity and instability in eastern DRC, this could change quickly.
Regulatory provisions
International
CMS: Gorilla gorilla sl has been listed on the Appendix I of the CMS since 2005.
CITES: Gorilla on Appendix I of the Convention on International Trade in Endengered Species of Wild Fauna and Flora (CITES) since 1975.
ACCNNR: Gorilla listed in A class of The African Convention on the Conservation of Nature and Natural Resources since 1969.
National
Management of National Parks, faunal reserves, and game reserves in DRC is delegated to the Institut Congolais pour la
Conservation de la Nature (ICCN), which also manages scientific research. Effective control of many protected areas in the east of the country has been in the hands of rebel authorities in recent years. The Mountain Gorilla is totally protected in DRC, owning, transport and/or trade is forbidden or regulated. A person who captures or kills gorillas in a strict nature preserve faces imprisonment from 1 to 10 years.
The Rwandan Office of Tourism and National Parks (ORTPN) has direct responsibility for management of national parks and
matters relating to ecotourism. The Volcanoes NP therefore falls under its responsibility. The Department of Environment has overall responsibility for biodiversity conservation. The Mountain Gorilla is totally protected in Rwanda. Owning, transportation and/or national trade is forbidden or regulated (ECOLEX). Volcanoes National Park in Rwanda is a biosphere reserve.
In Uganda, the Uganda Wildlife Statute provides tools for the establishment of wildlife conservation areas, which fall under two categories: wildlife protected areas (national parks or wildlife reserves) and wildlife management areas (wildlife sanctuaries and community wildlife areas). It is forbidden by the national legislation to capture Mountain Gorillas (Uganda Wildlife Division, 2002a). As all Mountain Gorilla populations occur within protected areas (national parks and reserve), they and their habitat have some degree of protection.
However, political and institutional instability as well as illegal hunting and poaching may undermine such protection. National laws in all range states exist for the control of hunting and capture of gorillas, although wide enforcement of the legislation is difficult due to lack of funds and inaccessibility (Nellemann & Newton, 2002). When Bwindi Impenetrable and Mgahinga Gorilla National Parks were created, access to the park was forbidden for everyone except authorized researchers, which resulted in a significant reduction in illegal activities (Nowak, 1995). Extractive use of non-timber forest products is allowed in certain zones (multiple-use zones) of the park.