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Western Lowland Gorilla

The Western Lowland Gorilla (Gorilla gorilla gorilla) has suffered exceptionally high levels of hunting- and disease-induced mortality (over 90% in some areas), which combined are estimated to have caused an overall decline of more than 60% over the last 20 to 25 years. Most protected areas have serious poaching problems and Ebola has hit almost half of the habitat under protected status. Both these threats are not readily mitigated.

 

Because gorillas are long-lived and their reproductive rates are extremely low (maximum intrinsic rate of increase about 3%, Steklis and Gerald-Steklis 2001), they are particularly susceptible to even low levels of
hunting. Moreover, perhaps 20 to 30 years into the future, in addition to on-going habitat loss and degradation, climate change may well become another major threat. (2008 IUCN Red List, Walsh, P.D., Tutin, C.E.G., Baillie, J.E.M., Maisels, F., Stokes & E.J., Gatti, S).

Bangha, a Western Lowland Gorilla. Picture by Ian Redmond, GRASP.



Estimates from the 1980s placed the entire population, which occurs in seven Central African nations, at fewer than 100,000. Since then, scientists believed this number had dwindled by at least half, due to commercial hunting and disease, particularly outbreaks of the Ebola virus, which have extirpated gorillas from a great deal of otherwise intact forest. In early 2008, the estimate of the world’s population of critically endangered Western Lowland Gorillas received a boost with the discovery by WCS teams of large numbers of gorillas in remote and not easily accessible swamp forests in the northern part of the Republic of Congo, bringing the population estimates for north eastern Congo to 125,000. Current estimates of the total population are in the order of 150,000 -200,000 individuals.



The Eastern and Western Gorilla are separated by approximately 1,000 km (Garner & Ryder, 1996). Western and Eastern Gorillas can be distinguished by external features (Groves, 2002), together with clear geographic and morphological distinctions (Garner & Ryder, 1996). Western Lowland Gorillas live in the western Congolese forest, west of the Congo/Oubangi Rivers and south of the Sanaga River.



Scientific name
Gorilla gorilla gorilla (Savage & Wyman, 1847)



Common names
English – Western Lowland Gorilla, Coast Gorilla
French – Gorille de plaine de l’ouest
German – Westlicher Flachlandgorilla
Spanish - Gorila de llanura del oeste ou Gorila de planicie occidental



Description
The shape of the nose provides a point of difference between the eastern and western forms; the western species has an overhanging tip to its nose that is absent in the eastern forms. Western Lowland Gorillas have chestnut-brown, not black, hair on their heads though the extent is variable. Western Gorillas have more rounded faces and slender chests than Eastern Gorillas (Rowe 1996; Nowak 1999). Although predominantly terrestrial, they climb well, if cautiously. The Western Lowland Gorilla is the smallest and lightest of the four subspecies, and also the one in which sexual dimorphism is most pronounced (Gautier & al, 1999).



General Biology
Gorillas are mainly terrestrial. The gorilla's large size and folivorous diet mean that the animals must spend long hours feeding everyday. 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 are mainly foliage eating that they can afford to live in these relatively permanent groups. Foliage, unlike fruit (especially the ripe fruits that the ape gut requires), comes in large patches than can in turn support large groups of animals. In West Africa, where fruits form a far higher proportion of the gorilla's diet than in the East, gorilla groups tend much more often to split into temporary feeding subgroups than they do in east Africa, as animals range far apart searching for the relatively scarce ripe fruit. Sleeping subgroups have also been reported but are anecdotal and seem to occur in the process of permanent splitting of a multi-male group into two single male groups. Groups usually number 5 to 10 individuals, but some groups can count as many as 20 to 32 animals (Bermejo, 2004).

 

Gorillas are closely related to humans and are considered highly intelligent. It is possible that western gorillas have a food culture, with learned preferences passed on between individuals and generations (Nishihara, 1995). Use of tools has also recently been observed in the wild (Breuer, 2006).



Habitat
Western Lowland Gorillas inhabit dense primary rainforest, swamp forest, thicket, secondary vegetation, forest edges and clearings, riverine forests and abandoned cultivated fields within or adjacent to forest. They have occasionally been observed nesting along savannah-forest edges or in the savannah itself, but do not live permanently in these savannah habitats. They have also been observed feeding in seasonally fruiting trees in coastal forests.

 

Two orphaned Western Lowland Gorillas keep each other company. Picture by Ian Redmond, GRASP.

Western Lowland Gorillas inhabit primary and secondary lowland tropical forests at elevations from sea-level to 1,300 m. Gorilla occurrence and density seems to be positively correlated with terrestrial herbaceous vegetation, particularly monocotyledonous plants (e.g. gingers and palms). The average rainfall in their area of distribution is around 1,500 mm with the greatest amount of rain falling between August and November and diminishing during December through March (Poulsen & Clark 2004). Western Gorillas appear to be absent from areas close to human settlement and disturbed secondary forests, avoiding utilized roads and plantations (Tutin & Fernandez, 1984). Gorillas favour areas where edible herbs are more abundant, which is often the case in moderately disturbed or secondary forest.

 

In the Odzala-Koukoua NP in Congo, Western Lowland Gorillas occupy a large variety of habitats. Here they primarily live in open-canopy forest with a rich understorey of vegetation of Marantaceae. This forest type is dominant in the northeastern part of the park. The ground vegetation is dominated by an almost impenetrable thicket of Marantaceae species, including Haumania liebrechtsiana, Megaphrynium macrostachyum, and Sarcophrynium spp.

 

Western Lowland Gorillas are also found in more closed-canopy primary forests. In and around the northern part of the Odzala-Koukoua NP there are more than 100 forest clearings. They have a particularly sodium-rich herbaceous vegetation and are known as saline or bais. Gorillas are known to visit these clearings on a regular basis to feed on plants from families such as Cyperaceae and Asteraceae. Swamp forests are now considered important habitats and feeding areas for western gorillas, supporting them in high densities both in the wet and the dry season (Fay et al., 1989). High densities of gorillas in swamp habitat in northern Congo were recently reported at the International Primatological Society Congress (Stokes et al. 2008). In Northern Congo western gorillas favour swamp forests where Raphia, a palm used both for food and nest construction (Blake et al, 1995), is common. In southwestern Central African Republic the distribution of gorillas seems to be influenced by the availability of Afromomum spp. (Carroll, 1988).



Food
Gorillas are largely 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 digestible carbohydrates through the fermentation process.



Food availability affects both diet and foraging behaviour of gorillas. High quality herbs that are easily digestible and rich in proteins and minerals are scarce and patchily distributed in outside swamp forest areas. Fruit is relatively widely available in their habitats and forms an important part of the diet of Western Lowland Gorillas. The availability of seasonal fruit appears to shape foraging and ranging patterns of gorillas (Remis, 1997). When fruit is abundant, it may constitute most of the diet.



High-quality herbs (rich in minerals and proteins contents) are eaten all year round, while low-quality herbs are eaten only when fruit is scarce. More leaves and woody vegetation are consumed during the dry season (January-March) when few fleshy fruits are available. In habitat where the leguminous tree Gilbertiodendron dewevrei is present, gorillas feed heavily on its seeds and can travel some distance during mass fruiting events (occurring at five year intervals) to congregate in stands of G. dewevrei (Blake & Fay, 1997). Insects are also part of their diet (termites and ants), although their relative importance is still undetermined (Tutin & Fernandez 1992; Remis, 1997; Deblauwe, 2003; 2006). Western gorillas travel farther when more fruit (and termites) are available in the forest and have shorter day ranges when they must rely on leaves and woody vegetation (Goldsmith, 1999).



Social Behaviour
Gorillas form harems. Reproductive groups of Western Gorillas almost always contain only one dominant silverback male plus three or four females and four or five offspring (Fay, 1989). Adult females in any group 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 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 (Parnell, 2002).



Western Lowland Gorillas generally form stable cohesive groups. The takeover of a group during which another male from outside ousts the group’s silverback has never been reported, and a group splitting has been reported on only one occasion (Remis, 1997). However, western gorillas do not appear to be as cohesive on a daily basis as their eastern counterparts. In some groups, members spread out with distances of over 500m between them, other groups split up during the day and then reunite at the nest site. Recent studies at bais also suggest that around those particularly attractive locations, population dynamics might be more active than previously thought (Gatti et al, 2004), with frequent exchange of individuals between groups.



The very large groups sometimes observed among eastern gorillas have not been reported to occur in western gorillas. Group size appears to be influenced by the size of the foraging patches and fruit abundance. Western gorillas eat considerably more fruit than eastern gorillas, and this preference for clumped food resources may constrain their group size. Total group size ranges from two to 32 individuals with an average of four to six adults.



Distribution (current and historical)
The historical distribution was probably very close to the current distribution: the Western Lowland Gorilla inhabits the tropical forests of Cameroon, Central African Republic, Gabon, Congo, and Equatorial Guinea. It is also reported to be present in the Mayombe forests in extreme southwest DRC, with at least some groups said to migrate seasonally across the Angola (Cabinda) border, north of the Congo River (Redmond, 2006). The Congo/Oubangi River seems to be the eastern limit of the distribution; the Sanaga River represents the northern limits of the closed forest and concomitantly of the Western Lowland Gorillas. However, a small population exists North of the river in Ebo Forest (Morgan et al., 2003). The Atlantic Ocean represents the western boundary of the distribution and the southern edge of the Western Lowland Gorilla’s distribution is defined by forest-savannah.



The Western Lowland Gorilla is still a relatively widespread species, but if the recent decline continues, a notable reduction in their distribution is to be expected. Surveys conducted in the 1980s indicated that healthy populations existed in many areas remote from human settlements. However, despite the fact that western equatorial Africa has one of the lowest human population densities of any tropical forest area in the world, gorilla (and chimpanzee) populations in this region are, today, in dramatic decline. This is due to increased commercial hunting, the spread of logging, which alters forest structure and facilitates poaching, and outbreaks of Ebola. Figures in areas where studies have take place are frightening: the average annual rate of decline in Gabon between 1983–2000 (Walsh et al., 2003) was 4.7% and the high mortality (>80%) recorded in two known populations affected by Ebola (Bermejo et al., 2006; Caillaud et al., 2006) underline a critical state for conservation and the urgent need for protection.



Evaluation and evolution of populations
Accurate population estimates for gorillas are often difficult to establish, because their vast range has not yet been thoroughly surveyed. However the recent paper of Walsh et al (2003) used two countrywide surveys twenty years apart to show that roughly half of Gabon’s gorillas vanished between 1983-2000. A recent set of surveys encompassing much of Northern Congo showed that there are very high densities in Raphia swamps and that well protected logging concessions can also have medium densities (Stokes et al., 2008).



Previous estimates of Western Lowland Gorillas were based on habitat suitability (Harcourt 1996) but unfortunately in this region, even good habitat type does not necessarily mean that there are gorillas present. Hunting and Ebola have taken their toll and continue to do so. Numbers have been boosted by additional populations discovered in previously unsurveyed swamps in northern Congo, but it should be remembered that of the oft-quoted 125,000 gorillas in that area, at least 46,000 were already known about, in the Nouabale-Likouala landscape (Stokes et al 2008). Many of them live outside of existing protected areas, and their survival is essentially due to remoteness (from villages) of the areas recently surveyed.



The vast majority of Western Lowland Gorillas occur in Congo and Gabon, followed by southwest Cameroon. Equatorial Guinea still harbours some, but there is no country estimate. There is a population in the Dzanga-Sangha area of southwest Central African Republic, shared with the contiguous Nouabale-Ndoki area of Congo. Finally, gorilla numbers in the contiguous Cabinda province (Angola) and Mayombe (Bas-Fleuve region) are unknown but probably very low - perhaps a few dozen- as a result of the combined effects of habitat loss, fragmentation and poaching (Redmond 2006).



The Western Lowland Gorilla (Gorilla gorilla gorilla) is listed as Critically Endangered on the IUCN Red List (IUCN 2008, CR A4cde) even though the taxon occurs over a wide area with relatively low human population densities. The subpopulations generally occur at low densities and their distribution is patchy. It has been estimated that 80% of the population live outside protected area (Harcourt 1996).



Ranging behaviour
Western Lowland Gorilla groups travel within a home range averaging 5 to 30 km². Gorillas do not display territorial behaviour, and neighbouring groups often overlap ranges (Bermejo, 2004, Doran et al., 2004). The group usually favours a certain area within the home range but seems to follow a seasonal pattern depending upon the availability of ripening fruits and, at some sites, localised large open clearings (swamps and "bais"). Gorillas normally travel 0.5-3.0 km per day (Remis, 1997b, Doran et al., 2004). Populations feeding on high-energy foods that vary spatially and seasonally tend to have greater day ranges than those feeding on lower-quality but more consistently available foods. Larger groups travel greater distances in order to obtain sufficient food (Remis, 1997b). Human hunters and leopards (Panthera pardus) can also influence the movement patterns.



The annual home ranges (the areas used by a group over a year) of western gorillas are larger than those of mountain and eastern lowland gorillas and the home ranges of different groups overlap quite extensively. Wherever these home ranges are divided by international boundaries, the movement of gorillas back and forth across the border in search of seasonally available food plants is considered migratory under the terms of the Convention on Migratory Species. Transboundary populations of Western Lowland Gorillas occur between Gabon and Equatorial Guinea, Gabon and Cameroon, Gabon and Congo, Cameroon and Equatorial Guinea, Congo and the Central African Republic, Congo and Angola and DRC.



Conservation status
Habitat loss is one of the greatest threats to gorilla survival. Picture by Ian Redmond, GRASP.Angola (status unknown)
The Western Lowland Gorilla is found in the northern part of the Cabinda exclave of Angola in the Mayombe forests. Only a few dozen individuals remain.

Cameroon (Critically Endangered)
The nominate form (Gorilla gorilla gorilla) is distributed in Cameroon southeast of the Sanaga River. The vast majority of Cameroon’s gorillas (several thousand) are found in the humid tropical forests of the southeast, with strongholds in the Lobeke, Boumba-Bek and Nki National Parks. There is a small population of gorillas in the Ebo forest, north of the Sanaga, but from genetic information it is suspected that these, and any others north of the Sanaga, may be members of a separate subspecies already known from the Cameroon-Nigeria border, the Cross River Gorilla (G. g. diehli).

Central African Republic (Critically Endangered)
The gorilla is found in the southwestern corner of Central African Republic. It is present in Dzanga-Ndoki National Park and in the Dzanga-Sangha Reserve (ca 5,000 km²). This area is contiguous with good habitats in the Congo (Nouabale-Ndoki National Park and its buffer zone (Sangha Region).

Republic of the Congo (Critically Endangered)
The Western Lowland Gorilla still occurs in the Republic of Congo north of the Equator, particularly in the well-protected areas of the Nouabale-Ndoki National Park and its buffer zone, the Lac Tele Community Reserve (especially in the patches dominated by Raphia swamp forests), and the area east of the Odzala National Park known as the Ngombe-Pikounda area. The Odzala National Park itself, once the stronghold of many thousands of apes, has suffered from the Ebola outbreaks of the early 2000’s in which large numbers of apes have died. Recent surveys by WCS (2007-2008) indicate that perhaps half of the world population of Western Lowland Gorillas lives in the forests of northern Congo.

Democratic Republic of Congo (formerly considered Probably Extinct)
The Western Lowland Gorilla was until very recently considered as probably extinct in the Mayombe forests (Bas-Congo, extreme western DRC). Recent reports (Redmond, 2006) suggest that a small (transboundary) migrating population of a few tens of animals might survive.

Gabon (Critically Endangered)
Western Lowland Gorillas used to occur throughout Gabon’s forests, but in the last two decades their distribution has shrunk alarmingly and about half of the population has disappeared. The northeast of the country was hit by Ebola haemorrhagic fever between 1996-2003 and almost all apes in that area died. In addition they are absent from all areas around larger towns and are quasi-absent in most of the northwest of the country due to hunting pressure.

Equatorial Guinea (Critically Endangered)
The Western Lowland Gorilla still occurs in Rio Muni, the continental part of the country but no recent surveys have taken place. In the 1990s, gorillas occurred in Monte Alen National Park just across the border from the Monts de Cristal in Gabon (Garcia & Mba 1997). In 1999 gorillas were still present in Parque Nacional de Los Altos de Nsork. During a survey by Larison et al (1999), no sign of gorillas was recorded at Rio Campo or Montes Mitra, although, local people claimed they were present.



Actual and potential threats
In evaluating threats to gorillas in western equatorial Africa it is useful to think on two time scales. In the short term, by far the most serious threats are poaching and disease epidemics. In the longer term, habitat loss and disturbance will increase as a threat and are likely to become as serious a threat as hunting and disease. All these traditional threats may be exacerbated by climate change and possible changes in rainfall patterns and temperatures, which may result in significant changes in forest cover.



Although still widely distributed across a large forested region, and occurring in numerous Protected Areas, the Western Lowland Gorilla is listed as Critically Endangered because of a series of cumulative threats of increasing scale: poaching and commercial hunting is identified as a major real or potential threat for every site of the Gorilla’s range. Diseases, and Ebola hemorrhagic fever epidemics in particular, are identified as a potent actual threat and a potential future threat to gorillas (particularly where they are found at high densities, which facilitates transmission). Logging has emerged as one of the greatest future threats, especially in concessions surrounding protected areas, the roads and transport opportunities created by industrial logging leading to a massive increase in commercial bushmeat hunting. Commercial and artisanal mineral exploitation affect some areas and require specific responses.



Direct exploitation
A gorilla skull. Picture by Ian Redmond, GRASP.Western Lowland Gorillas are hunted for their meat, for sale to private collections, for trophies and for traditional ritual or medical purposes. Although this is illegal everywhere, the regulations in most range states are poorly enforced. The intensity of hunting of Western Lowland Gorillas varies throughout their range. Factors affecting bushmeat hunting are local taboos, poor enforcement of legislation and the wide availability of ammunition and guns. Logging roads allow greater access to remote areas, making the entire fauna more vulnerable to hunting in areas under exploitation or previously exploited.



The bushmeat trade
In the forested region of western Africa, bushmeat hunting for subsistence is a major threat to western gorillas. Although bushmeat in general has always been culturally and nutritionally important in many regions, the impact of bushmeat hunting is now more widespread and serious. Hunting is increasing rapidly with improved access to remote areas, and new markets are developing to serve a rising demand among urban human populations, where bushmeat is considered a delicacy. Gorilla meat forms only a small proportion of the commercial bushmeat trade, but the impact on ape populations is disproportionately great because of their slow reproductive rate and the social consequences of silverbacks being killed (infanticide may ensue when nursing mothers join a new male).



There are no estimates of either the overall Western Lowland Gorilla population losses due to hunting, nor of its impact on population trends, although the negative impact of hunting on other gorilla populations is well known. In the northeast of Congo (Motaba River region) it has been estimated that 5 percent of the Western Lowland Gorilla population is killed each year by hunters, despite the low density of local human populations. This level of offtake is unsustainable (Kano & Asato, 1994). In contrast, effective controls of hunting are in place in Nouabaé-Ndoki NP (Congo) and its buffer zone, in Odzala - Koukoua NP (Congo) and in the Dzanga Sector of Dzanga-Ndoki NP (Cameroon) where gorillas are rarely hunted (Blom et al., 2001). The controls are the result of successful collaboration between national administration and international agencies or NGOs.



Other forms of direct exploitation
In the past, gorillas have been killed for their heads, hands and feet, which were sold to collectors. This probably grew out of expatriates showing interest in gorilla body parts on sale in traditional medicine stalls (Redmond, 1989). Infants were sold to zoos, researchers and people who wanted them as pets. Both these trades – live infants and body parts for traditional medicine or amulets - continue to this day, either as a by-product of bushmeat hunting or sometimes, when a trader commissions hunters to kill a gorilla and/or capture an infant, in the erroneous belief that there is a market for great apes.

 

The abduction of infants generally involves the death of at least two adults, as members of a group will fight to protect their young. Gorilla infants are susceptible to post-traumatic stress and poor nutrition; as a result, mortality rates of 80 per cent have been reported among confiscated infants (Redmond, 1989). These losses create a startling multiplier effect, because if four out of five infants die, and each infant is captured by killing two adults, this means that every infant that survives probably represents a loss of 15 gorillas to the population (5x2 dead adults, four dead infants and one live one).



Diseases
Disease is a potentially devastating threat to gorillas and other great apes. Gorillas are susceptible to many of the same diseases as humans, such as Ebola, common colds, pneumonia, smallpox, chicken pox, tuberculosis, measles, rubella, yellow fever and yaws. Outbreaks of the Ebola virus since 2000 have claimed thousands of great apes in Africa. Ebola haemorrhagic fever is a highly infectious, usually fatal disease that affects humans and non-human primates, such as monkeys, gorillas and chimpanzees. Many scientists believe Ebola is transmitted to humans through the butchering and handling of primate bushmeat. This disease has been confirmed in six African nations: the Democratic Republic of Congo, the Republic of Congo, Gabon, Sudan, Ivory Coast, and Uganda.



Ebola haemorrhagic fever is an incurable human disease that kills about 80 percent of its human victims. This virus has an even higher mortality rate of 95-99 percent among western gorillas (and chimpanzees). Recent Ebola epidemics in western equatorial Africa have affected the gorilla in Gabon and Congo. Ebola outbreaks are thought to have strongly contributed to the decline of great ape populations in Gabon, where four outbreaks are known to have occurred. Farther East, declines in Western Gorilla populations attributed to Ebola have also been reported in the Lossi Gorilla Sanctuary of Congo (Walsh et al., 2003; Bermejo et al., 2006), and has lately decimated a gorilla population in the Odzala-Koukoua NP (Caillaud et al., 2006; Devos et al., 2008).



Another potential general threat to gorillas is exposure to human diseases (e.g Graczyk et al., 2001; Graczyk et al., 2003; Mudakikwa, 2001) particularly for habituated gorillas that come into contact with humans, in areas of gorilla tourism (Butynski, 2001). Gorilla tourism exposes gorillas to humans, sometimes close enough for droplet infection by sneezing or coughing, and hence to any diseases that humans may be carrying, some of which the gorillas may never have been exposed to before (Homsy, 1999).



At present, this threat is not significant for the Western Lowland Gorilla. The Western Lowland Gorilla has proved to be difficult to habituate, particularly as the dense vegetation of its habitat does not allow it to be tracked easily (Williamson & Feistner, 2003). Gorilla tourism is therefore not as well established as it is with eastern gorillas. However the discovery that Western Lowland Gorilla could easily be seen at bais has increased the likelihood of successful gorilla tourism and could, if unregulated, lead to increased contacts with humans as happens in Rwanda or Uganda. Strict regulations concerning tourist group size, health, visiting hours and behaviour must be adopted as soon as possible in areas where Western Lowland Gorilla tourism is being, or planned to be established.



Degradation and decline of habitats
Rainforest timber for export, Tala-tala, Republic of the Congo. Picture by Ian Redmond, GRASP.Throughout the Western Lowland Gorilla's range, the forests on which it depends for survival are being cut down for timber and to make way for agriculture. As the global demand for palm-oil continues to rise, both for food and bio-fuels, land to be converted into oil palm plantations is now being sought in Africa. Until recently, there has been relatively little habitat degradation over much of the Congo Basin, with low conversion to agricultural land. As late as the 1980s West and Central African timber was considered to be of low commercial value, which limited the pressure, posed by selective logging. This situation changed dramatically during the 1990s.



By 2000, more than half of Gabon’s forests had been allocated as logging concessions (Anon, 1999). In Cameroon, over 170,000 km² of the country’s forests have either been logged or allocated for logging. Satellite images have revealed that networks of new logging roads have now spread into what had previously been considered the least accessible forests in the country (Minnemeyer et al., 2002). Logging roads and access routes fragment forest and improve access for hunters. Forest fragmentation poses a potential threat to Western Lowland Gorillas in that it can block transfers between groups and access to seasonal food resources.



Impact of Conflict
The impacts of wars and political conflicts, particularly well documented for the Mountain and Eastern Lowland Gorilla, could have affected the Western Lowland Gorilla in a similar way. Civil wars and unrest increase hunting levels by exacerbating poverty and dependence on natural resources, particularly among displaced peoples and refugees. Angola, the Republic of Congo, Central African Republic and the DRC have all suffered periods of instability in recent decades. In addition to influxes of refugees, the forests have served as hiding places and retreats for rebel forces, leading to disturbance and hunting. This is a common phenomenon in times of war, particularly in forests close to international borders.



Other threats
There is a lack of fundamental knowledge regarding numbers and distribution, and insufficiency in biological information crucial to assessing population viability and mechanisms of population decline. Accidental entrapment in wire snares used to trap other wild animals is also an ever-present threat. International trade in live gorillas and gorilla parts, which used to be a major threat, has declined since the gorilla was listed in Appendix I of CITES, but cases are still reported.

 

Anti-poaching and law enforcement
The taxon is legally protected in all the seven countries of its distribution. The killing or sale of live or dead gorillas or of their body parts, and the disturbance of them in the wild is illegal throughout their range. Nevertheless, poaching and the illegal capture of live individuals are an important problem in all of these countries. Great efforts must be made by the range states to enforce their laws concerning gorillas, including not only effective anti-poaching and seizure of gorilla parts or live individuals on the ground, but follow-up of the legal process through arrest, the passage of each case through the tribunal, and eventually to prosecution of all cases judged guilty.



Maintaining transboundary links for gorillas
Although current habitats are not as fragmented in Central Africa as in West Africa or the Albertine Rift, they will become so in the next few decades. Particular attention to protecting existing transboundary protected areas, the creation of new ones, and the protection of intact forest corridors between range states will allow the long-term maintenance of genetic flow between gorillas living in neighbouring countries.



Additional remarks
Western Lowland Gorillas are a keystone species in their forest habitat, and so their protection is essential to the long-term management of the Congo basin, now recognized as a globally important factor in inter-continental weather patterns and for maintaining climate stability. The COMIFAC Convergence Plan and the efforts of the Congo Basin Forest Partnership, which aim for the coordinated management of the whole Congo Basin Ecosystem, must recognize that gorilla conservation is integral to their programme of work. Now that payment for the eco-system services provided by the Congo Basin to the rest of the planet – including carbon sequestration and storage, rainfall generation and bio-diversity – is being seriously considered, it is essential that the ecological role of gorillas is taken into account.



Regulatory Provisions
International
CMS: Gorillas listed on Appendix I of the CMS since 2005.

CITES: The Gorilla has been on the Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) since 1975.

ACCNNR : Gorilla is also listed in A class in the African Convention on the Conservation of Nature and Natural Resources in 1969.

The Gorilla Agreement: a treaty under the CMS, negotiated in October 2007, came into force 1st June 2008.

National
National laws for control of hunting and capture exist in all countries with gorilla populations, but a lack of funds and inaccessibility make widespread enforcement of this legislation rare.

In Angola, biodiversity protection and management are under the responsibility of the Ministry of Urban Affairs and Environment, but in practice the Forestry Development Institute (IFD) remains in overall charge of the forest sector, sharing with the National Directorate of Agriculture and Forest (DNAF) responsibilities of policy formulation and guidance. Poor enforcement of laws, poaching, harvesting and settlements inside Protected Areas are other problems.

In Cameroon, the country’s forestry, wildlife and fishery regulations list gorillas as a Category A species, which are fully protected by law against hunting, capture or sale. Protected areas such as national parks and wildlife reserves are established under the auspices of the “Direction de la Faune et des Aires Protégées” (DFAP) of the Ministry of Environment and Forestry (MINEF), which is also responsible for the protection of the country’s biodiversity in general.

In the Central African Republic, the Ministry of the Environment, Waters, Forests, Hunting and Fishing is responsible for wildlife conservation and the use of natural resources in CAR. These are governed by Ordinance n°84.045 (1984) and Law n°90.003 (1990). Great Apes are listed in Category A as ‘completely protected’ under Ordinance N° 84.045.

In the Republic of the Congo, the Ministry of Forest Economy and the Environment (MFEE) is responsible for wildlife conservation and regulated use, including the management of protected areas.

In Gabon the Ministry of Water and Forests is responsible for the management of natural resources. Gabon set up a wildlife management service and an anti-poaching service. Gorillas (and chimpanzees) are now fully protected species under Gabonese law.

In Equatorial Guinea, conservation issues are administered by the Instituto Nacional de Desarrollo Forestal y Gestion del Sistema de Areas Protegidas (INDEFOR), within the Ministry of Infrastructure and Forests. Many of the priority populations identified by GRASP for Western Lowland Gorillas are at least partly protected and occur within (proposed) National Parks, Biosphere Reserves or Community Managed Nature Reserves, but many are also, at least partly, in logging concessions.



References
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Anon (2003) Massive great ape die-off in Africa – Ebola suspected. National Geographic February 6 2003.
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Bermejo, M. (1999) Status and conservation of primates in Odzala National Park, Republic of the Congo. Oryx 33 (4): 323–331

Bermejo, M. (2004) Home-range use and intergroup encounters in western gorillas (Gorilla g. gorilla) at Lossi Forest, North Congo. American Journal of Primatology 64, 223-232

Blake, S., Fay, J.M. (1997) Seed production by Gilbertiodendron dewevrei in the Nouabale-Ndoki National Park, Congo, and its implications for large mammals. Journal of Tropical Ecology 13: 885–891

Blake S., M. Rogers, J. Fay, M. Ngangoue & G. Ebeke. 1995. Swamp gorillas in the northern Congo. Afr J Ecol 33:285290

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