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Endangered Silverback Gorillas Research Paper

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The mountain gorillas are considered one of the rarest mammals in the world, with an estimated population of 380 for those in Virunga and 340 for those in Bwindi. (Fung 1) A German explorer Oscar von Beringia first described mountain gorillas in 1902, but it soon became necessary for a handful of individuals, both local and foreign, to become seriously concerned for the survival of these now-rare Central African mammals. (“Mountain gorillas”) The efforts of American primatologist Dian Fossey to document the plight of the fragile population of mountain gorillas were immortalized in the film “Gorillas in the Mist” and it is believed that she herself was murdered by poachers in 1985. (Flanagan)

This paper will provide an overview of the mountain gorillas found in the protected forests in the tri-country area of Rwanda, Uganda, and the Democratic Republic of Congo (DRC), including the conservation efforts aimed at ensuring their survival as a species.

Some basic information

The mountain gorilla was first identified in 1902, and by 1989 the population had been severely decimated by human activities such as poaching and conversion of forest areas to agricultural use. (“Recent findings on mountain gorillas show hope for species’ survival”)

Central Africa is the only place where mountain gorillas can be found, and the area of concern is confined to about 780 square kilometers of medium altitude (2,500 to 4,000 meters) forests northwest of Rwanda, southwest of Uganda, and east of the DRC. “The two groups of particular focuse are the Bwindi mountain gorillas, so named because they live only in the Bwindi Impenetrable National Park found in Uganda, and the Virunga gorillas, found in the Mgahinga Gorilla National Park, also in Uganda, Volcano National Park in Rwanda and Virunga National Park in the Southern Sector of the DRC”. (“Mountain Gorillas: some social and biological data”) As of 2007, the total combined population is placed at 720 animals, with about 20% in habituated groups, or attenuated to tourism, for the benefit of gorilla watchers.

The term “silverback” refers to adult males between 12 to 15 years of age, on account of the silver streak of hair that traverses his back and hips. The average lifespan of a mountain gorilla is 45 years, and females normally start reproducing as early as 10 years old, every three to five years. They carry the developing baby for nine months and care for them for about 3.5 years.

A juvenile is between 3.5 to 6 years, a subadult from 6 to 8 years in which they are non-reproductive. Males reach “blackback” status at age 8 and evolve into a silverback by age 12. (“Mountain Gorillas: some social and biological data”).

In appearance, adult male mountain gorillas are typically about 350 to 400 lbs while the females reach an adult weight of 215 lbs. They have longer hair than other gorilla species. The standing height of a typical gorilla is between 1.25 and 1.75 meters, with an arm span of 2 to 2.75 meters. (“Gorilla”).

The diet consists mostly of leaves, stems, and the shoots of herbaceous plants, with the occasional fruit and flowers as well larvae, ants, and snails. Gorillas are considered folivores. On occasion, gorillas have been observed to eat their fecal matter, speculated to be an attempt at recycling minerals from the undigested foliage. However, this has not been determined to be the true motive for such behavior. (“Mountain Gorillas: some social and biological data”).

Silverbacks are not generally territorial, meaning they are not behaviorally programmed to keep the parameters of their territory free from outsiders. Some territories may thus overlap, but they will defend the members of their group, especially juveniles and infants from contact or harm from outsiders, whether gorillas from other groups or humans. The chest-beating, dragging of foliage, and slapping of the ground are actions designed to ward off unwanted attention. It is also used to prevent a female from leaving the group or wandering into neighboring groups. In general, however, silverbacks are not aggressive, leading peaceful lives. They are active during the day and prefer to stay on land, spending a quarter of their time eating, resting at midday, and sleeping in nests prepared from plants that they do not habitually consume.

About twelve distinct vocalizations have been identified. “Hooting” is used to warn off intruders who may be perceived as encroaching onto the group circle. “Belching” may alternately be a contact call as well as a sign of foraging satisfaction. (“Mountain Gorillas: some social and biological data”).

Virunga gorillas inhabit the contiguous forests, about 375 square kilometers in the area of the national parks of Rwanda, Uganda, and the Democratic Republic of the Congo (DRC). While considered genetically of the same subspecies, the Virunga and Bwindi mountain gorillas exhibit morphological and behavioral differences. In terms of geography, the two gorilla populations are separated by 40 square kilometers and have not been observed to interbreed. Some experts consider the possibility that the Bwindi gorillas may warrant a separate classification (Fung 2-3)

Bwindi mountain gorillas are now number 340 as reported by the global conservation organization World Wide Fund (WWF). The 2007 survey, using genetic analysis of feces, means that the population growth is at 12% over the last 10 years, indicating a slow but steady improvement in the population. The Eastern Africa Regional Programme representative is cautiously optimistic, stressing the need for even more conservation efforts to ensure the survival of the species, in light of the perils facing the habituated animals from human activities such as hunting, civil unrest, and conversion of forestry for agricultural purposes.

The gorillas are often unwary, inured by years of being observed by tourists, and are easy targets for harm, as evidenced by the killing of two fully mature male gorillas in Virunga National Park, or silverbacks in the DRC in early 2007. (“Recent findings on mountain gorillas show hope for species’ survival”)

The Bwindi census was conducted between April and June of 2006 using trails, nests, and genetic analyses of feces to identify individual animals. The results show a 6% growth over figures garnered in the 2002 census. The census also revealed that the Bwindi population is expanding to the northern part of the park. (Delaney)

Satellites are also keeping an eye on land cover and other changes in the gorilla habitats that would otherwise be unavailable for study by conservationists and other scientists. NASA’s remote sensing capabilities produce Landsat images for free that shows how humans are inexorably using up the land in the southern sector of Virunga National Park, an unwelcome development in light of the increase in the Virunga gorilla population by 56. The use of satellites eliminates political complications as well as financial constraints associated with aerial surveys. (“Gorillas in the midst of extinction”).

Virunga mountain gorillas typically live in groups ranging from 2 to 20 members and more often than not includes just one fully mature male, referred to as a “silverback” in reference to the silvering of the hairs of the back of a male when full maturity is reached. Males in the wild normally start breeding at the age of 15, although full maturity can occur at eight years of age in males in captivity. This may be due to competition from older, dominant males in the group. Females reach sexual maturity at age seven and a half.

At this stage, most sexually mature male and female gorillas leave the natal group although they remain within the home range, to form new groups, usually a lone male attracting several females. Mountain gorillas prefer specific types of plants, favoring in particular certain bamboo shoots (Arundinaria Alpina). Other plants include leaves of the Galium ruwenzoriense and Peucedanum lingerie stems. In general, Virunga gorillas eat less fruit than Bwindi gorillas. (“Report on the status and conservation of the Mountain Gorilla” 1-2).

Forty percent of the family groups, however, have more than one silverback, a result of some of the juvenile males staying with the natal group when they mature. In the multimale group, the role of the alpha silverback is somewhat modified in terms of reproduction, as will be explained further on. About 3% of mountain gorillas are silverbacks that have yet to form a group or are part of an all-male group. In terms of female dominance in a mixed group, there has been no observed hierarchy. (“Mountain Gorillas: some social and biological data”).

In eastern mountain gorillas, although the dominant male tends to monopolize reproduction, noninvasive DNA research of wild gorilla groups in Rwanda shows that second-ranking males also contribute to reproduction, approximately 15% in the study groups between 1985 and 1999. It is concluded that rank is the basis for reproductive success rather than age and possibly due in some part to the choice of a female mate. The fertility cycle of female gorillas is approximately 28 days, able to successfully mate for a maximum of three days within the cycle. (“Mountain Gorillas: some social and biological data”) Genetic data also suggest that not all subordinate contributing males are paternally related to the dominant male. This paternity pattern is not reflected in western gorillas, were members of the same age had so far come from the same male. (Bradley et al. 9418-9423).

The ecological value of the mountain gorillas is their role in seed transport, as is true for most great apes. The various subspecies are confined within their specific areas and play a key role in ensuring biodiversity and forest regeneration. As to genetic importance, gorillas are only 3% different in terms of genetic makeup from humans, which impacts the study of human origin. (Fung 8) Gorilla watching tourism is also a major source of income, accounting for approximately US$5 million annually to the DRC, Uganda, and Rwanda. In Bwindi, five out of the 30 gorilla groups are habituated, and plans are underway to increase this to seven to increase income even more. (“Recent findings on mountain gorillas show hope for species’ survival”).

Many jobs have been created from gorilla tourism, including guides, hotel workers, and handicraft makers. Each gorilla watcher pays a US$500 fee to spend an hour gazing at the gorillas. Some part of this income goes back to the village inhabitants in the area, paying for water tanks, health clinics, schools, and new trees. (Anderson and Morgan).

The biggest threat to Virunga mountain gorillas is loss and degradation of their habitat, due mostly to the encroachment of growing human populations in search of subsistence at unsustainable rates. (Fung 7) Moreover, civil unrest in Rwanda has resulted in the arrival of 2 million war refugees in the DRC, settling in the buffer areas and boundaries of the Virunga National Park and increasing the need for wood for fuel to a dangerously high degree. (12) The threat to mountain gorillas is exacerbated by war and political unrest in the area. (Fung 1).

Aside from poaching and habitat degradation and loss, respiratory diseases such as influenza are also a significant contributing factor to the death toll of mountain gorillas. The study carried out by the Mountain Gorilla Veterinary Project estimates that about 25% of the deaths occurring within the population are attributed to respiratory distress. In efforts to minimize human contribution, tourists are allowed to observe the animals no nearer than seven yards away and for no more than an hour. (“Respiratory Diseases Kill Mountain Gorillas”) Only 30 tourists a day are allowed to visit the gorillas in Rwanda. (Flanagan).

Conservation efforts

The Karisoke Research Centre in Rwanda was established in 1967 for the preservation of the gorillas in the Parc National des Volcans. Similar programs established later were the Mountain Gorilla Project (1978), and the Virunga Veterinary Centre (1987). (“Gorilla”).

The International Union for the Conservation of Nature and Natural Resources (IUCN), better known as the World Conservation Union, includes mountain gorillas in the “critically endangered” category in its Red List of Threatened Species as of 2000. (Fung 1) As of 2007, however, mountain gorillas have been upgraded to the “endangered” (EN) category, which means it is no longer Critically Endangered but faces a very high probability of extinction in the wild. (2007 Red List of Threatened Species) While this is still a matter of concern, the improvement of status has heartened conservationists and has provided the impetus to strive for even better results in the future, somewhat tempered by the various factors that are currently working against them in the area, including civil unrest and the poaching of juveniles as well as the killing of mature gorillas.

The mountain gorilla is also covered under the Convention on Migratory Species (CMS) as well as the Convention on International Trade in Endangered Species (CITES), international treaties designed to protect the species; however, problems of enforcement continue to effectively prevent the loss of habitat for these animals (Fung 1)

The World Heritage Convention (WHC) and the CMS each seek to protect mountain gorillas for different reasons. The WHC designated the Virunga mountain habitat as a World Heritage site while the CMS enables the transboundary cooperation of the three countries connected by the Virunga Mountains in conserving and managing the area, including the native gorillas. (Fung 9-11)

“The International Gorilla Conservation Programme (IGCP), on the other hand, is designed for the conservation of the mountain gorilla habitat in Uganda, Rwanda and the DRC and is supported by international organizations, specifically the Fauna & Flora International, African Wildlife Foundation and the WWF”. (“Recent findings on mountain gorillas show hope for species’ survival”)

International conservation groups have attempted unsuccessfully to reintegrate a young female, rescued from animal traffickers in October 2002, into the wild. She was reintroduced into a gorilla group two months after her rescue but was rejected as an “outsider” which resulted in biting injuries. It is believed the female gorilla’s original group was one of the unhabituated groups in the Rwandan area. (“First attempt made at mountain gorilla reintroduction”)

Recent developments

The taxonomy of the gorilla species has undergone some recent modifications, with the growing inclination of primatologists to classify the western and eastern mountain gorillas, referred to as Gorilla gorilla and Gorilla beringei respectively, as distinct species. Cross River gorillas in Nigeria-Cameroon or Gorilla gorilla diehli and the Western Lowland gorilla or Gorilla gorilla gorilla are considered subspecies of the western mountain gorilla while Eastern lowland gorillas or Gorilla beringei graueri and gorillas in the Virunga Volcanoes and the Bwindi Impenetrable Forest or the Gorilla beringei beringei are considered subspecies of the eastern gorillas. (Fung 1-2) It is with the Virunga and Bwindi gorillas, the most populous of the gorillas that most scientific interest and research has focused upon.

The Bwindi gorillas may well be classified as Gorilla beringei Bwindi although further taxonomic research is still needed. (“Report on the status and conservation of the Mountain Gorilla” 1)

There is evidence of a gradual increase in the Virunga gorilla population, rising from a 1989 census of 324 to 380 in October 2003, an average increase of about 1.2% a year. (Fung 2)

With the total mountain gorilla population at about 720, the killing of ten (3 silverbacks, 5 females, and 2 infants) in Virunga National Park in the DRC from January to September 2007 is of serious concern for gorilla conservationists. There are about 72 habituated and about 120 non-habituated gorillas in the DRC. In some cases, the killings are suspected to be the work of traffickers. Two are still missing, both females, one of reproductive age. (“Rare mountain gorillas under threat since 3rd sep due to Congo war”)

Head of non-profit organization WildlifeDirect Dr. Emmanuel de Merode was one of the people present when the slaughtered bodies of four members of the Rugendo gorilla family, three females and one silverback was discovered by rangers in July 2007. Two of the silverbacks found dead in Virunga National Park, one of whom was 18-year-old Karema, were eaten, based on the report of a local farmer ordered by rebels to collect the meat.

The killings are thought to have been carried out by rebel group Rally for Congolese Democracy-Goma led by war criminal Laurent Nkunda. (Owen) The slain gorillas also included a female named “Safari” who had just given birth. The infant remains missing and is presumed dead. The gorillas had all been shot, and Safari had been set on fire postmortem.

The motive for the killings is thought to be as a form of intimidation conservation enforcers who had been trying to prevent the encroachment of the protected prime gorilla habitat to make charcoal. Typically, burning wood found in the protected area makes the charcoal, which is in great demand. The practice is encouraged by protection from businessmen who stand to reap considerable profits, referred to as the “charcoal mafia.” (Anderson and Morgan) United Nations agency Educational, Scientific and Cultural Organization (UNESCO) was prompted by the discovery of the four gorilla killings in Virunga National Park to send a mission to investigate the slayings and take steps to prevent it from occurring again. (“Killings of mountain gorillas in Congo prompt U.N. probe”)

The presence of armed rebel groups has frustrated attempts by rangers to provide continuous protection and surveillance for the 200 mountain gorillas in the DRC. Since the beginning of the civil war in 1996, about 97 rangers have been killed from heavy artillery and bombing by rebels who are after the rifles and ammunition. The rangers were outgunned by the rebel groups and had no choice but to abandon their posts. (Anderson and Morgan)

The killing of the Rugendo silverback could have serious repercussions for the family because the dominant male provides leadership and protection for the group, of which six survive from the original 12. (“Killings of mountain gorillas in Congo prompt U.N. probe”) The loss of the alpha male and the halving of the group’s number may well lead to the breaking up of the habituated group, which could lead to some of the members having no group, especially the juvenile males. Other groups will probably reject the outsider, as happened in the attempted reintegration of a stolen juvenile female discussed earlier. Because gorillas have established social behavior, the loss of group membership is a significant problem for the survivors.

There has been speculation that attacks on the mountain gorillas may be to satisfy the whims of collectors. In 2002, two Virunga adult females were killed and one male gorilla wounded by poachers, the first such incident of its kind since 1985, in the course of stealing a juvenile. Some people have been arrested on suspicion of being gorilla dealers. (Flanagan)


Habituated gorilla groups have become vulnerable to poachers because they have become so used to human contact that they become easy targets, a concern for conservationists fighting to keep the species from extinction. However, tourist income is of considerable importance in funding the costs of keeping the national parks open, which is a dilemma that has plagued conservationists since the 1992 killings. (Flanagan)

Many factors contribute to the risks of extinction for mountain gorillas. Their habitat is restricted to a small area, which is even then being gradually taken over by human populations for agricultural purposes. Even if the population growth rate improves in the future, there may not be enough resources available to sustain their growing numbers in their present area.

Their diet is as specialized as their habitat, preferring varieties that may not be readily available in other areas. Their rate of reproduction is comparatively slow. A female gorilla becomes sexually mature at the age of eight, producing offspring at a rate of one every three years, and with a lifespan of about 50 years. This means that a female will realistically produce at most 12 offspring in 50 years.

In the meantime, a reign of terror has started to decimate the sparse gorilla population with malicious acts of violence by humans either against the gorillas themselves for intimidation or profit, or against the rangers who are tasked to ensure their protection. The civil unrest has led to the increase of the human population in the area as refugees escaping persecution settle in the protected areas of the gorilla habitats, using up resources that are needed for the gorillas to survive. Aside from this, rebels have started killing off gorillas for their meat and poachers to ensure that the charcoal-making business continues to thrive or to satisfy the whims of unscrupulous animal collectors.

With 720 gorillas surviving in the Bwindi and Virunga forests, and a population increase of approximately 1% a year, the mountain gorillas continue to be at considerable risk for extinction given the instability of the political climate in Central Africa, and the continuing failure of international conservation organizations to effectively enforce the treaties designed to protect the species. While it is in the interest of the respective tourist agencies of Rwanda, Uganda, and the DRC to ensure that gorilla tourism continues to bring in foreign income, coordinating efforts for protecting the gorillas remain problematic.

Even if taxonomists succeed in proving that the Bwindi mountain gorillas deserve their own subclassification apart from their Virunga counterparts, there may not be enough of them left to make the distinction an issue apart from an academic point of view, much like the dinosaurs.

Works Cited

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“Gorilla.” United Nations Environment Programme. 2007. World Conservation Monitoring Centre. 2008. Web.

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” Planet in Peril. 2007. CNN International. Web.

“Mountain gorillas.” International Gorilla Conservation Programme. 2007. Web.

“Mountain Gorillas: some social and biological data.” International Gorilla Conservation Programme. 2007. Web.

“Rare mountain gorillas under threat since 3rd sep due to Congo war.” Happy Hollow Park and Zoo. 2007. Web.

“Recent findings on mountain gorillas show hope for species’ survival.” Success Stories. 2007. WWF. Web.

“Report on the status and conservation of the Mountain Gorilla.” World Conservation Monitoring Centre. 2003. Convention of Migratory Species. Web.

“Respiratory diseases kill mountain gorilla.” Reuters News Service. 2005. Planet Ark. Web.

Anderson, Robert & Morgan, Casey. “Gorillas: Kings of Congo.” CBS News. 2007. CBS Interactive Inc. Web.

Bradley, Brenda J., et al. “” Ed. Frans B. M. de Waal. Proceedings of the National Academy of Sciences of the United States of America 102 (26). 2005. Web.

Delaney, John. “” Science News. 2007. Eureka Alert. Web.

Flanagan, Jane. “Poachers kill rare mountain gorillas in raid for rich collector.” 2002. The WELL. Web.

Fung, Melissa. “A World Heritage Species Case Study: The Virunga Mountain Gorillas.” International Environmental Law Project. 2005. Lewis & Clark College. Web.

McNeilage, Alastair, Robbins, Martha M., Gushanski, Katerina and Kagoda, Edwin. “Mountain Gorilla Census – 2006.” International Gorilla Conservation Programme. Web.

Owen, James. “Mountain gorillas eaten by Congolese rebels.” National Geographic News. 2007. Web.

Walker, Robert. “Mountain gorillas escape poachers.” BBC News. 2004. Web.

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