These are only found in the Virunga Conservation Area which comprises of three National Parks that is Mgahinga National Park in Uganda, Volcanoes National Park in Rwanda and Virunga National Park in Democratic Republic of Congo. The only other location where mountain gorillas exist is Bwindi Impenetrable National Park in Uganda.
Mountain gorillas Population trends (Gorilla Census)
George Schaller the gorilla researcher carried out the first census of the gorilla population in the Virungas in 1959-1960. He estimated that the total number could be between 400 to 500 individuals within the Virunga Conservation area. The following census was done by the Dian Fossey Karisoke team between 1971 and 1973 which showed a dramatic decline in numbers, down to 250 gorillas. One of the reasons behind this fall is that Volcanoes National Park lost 40 percent of its size to agricultural cultivation and at the same time poaching of gorillas was on the increase. In 1978 another census done by the Karisoke Centre counted about 260 gorillas, with forty two infants below three years as a good sign.
After the death of Dian Fossey on 27th December 1985, the Census of the Population of mountain gorillas in 1989 continued and it was found out that there were approximately 324 Gorillas in the Virunga Conservation Area and 320 in Bwindi Impenetrable Forest.
In 2003, another gorilla census was carried out in the Virunga massif and estimated the gorilla population to be 380 individuals. Measures of conservation have since been carried throughout the major three gorilla countries and a positive result has been yielded according to the last census in 2010.
In March and April 2010, a recent census of mountain gorillas in the Virunga Massif was carried out and showed that the area had 480 individual Gorillas which showed that there had been a 26.3% increase in the population over the past seven years (2003-2010) and an encouraging sign that conservation efforts are succeeding within the area.
These 480 individual gorillas were in 24 habituated groups with 352 (73%) gorillas (349 in groups and 3 solitary males), 12 unhabituated groups with 128 individuals (117 in groups and 11 solitary males).
This population made a remarkable recovery from the approximately 250 individuals that existed only three decades ago. This recovery is due to the conservation efforts of many organizations and institutions in the three major countries of Democratic Republic of Congo, Rwanda and Uganda. Organizations under these efforts are: International Gorilla Conservation Programme (IGCP), African Wildlife Foundation (AWF), Fauna & Flora International, and the World Wide Fund for Nature.
The main objective of the gorilla census was to establish an update on total population size in the Virunga massif and to compare with the previous censuses. There was also need to determine the level of the human disturbance, survey for diseases and take fecal samples for genetic analysis on the gorillas.
In Bwindi, the census has been carried differently with the first census in 1997 which revealed 300 gorillas, in 2002 with 320 individuals which showed an increase in the numbers. However, due to increase in poaching and death of mountain gorillas, the number decreased to 302 according to the 2006 census and as of now, the world is looking forward to the 2011 census of the Bwindi - Sarambwe population of mountain gorillas which was carried out in September to October 2011.
In 2006 the total number of mountain gorillas was 682 between Virunga and Bwindi national park. In 2012 we estimate a total population of 820 gorillas between Virunga and Bwindi.
Scientific research about mountain gorillas
Mountain gorillas were first discovered by a German explorer named Capt Robert Von Beringe on 17th October 1902 on the ridges of the Virunga Mountains. In the 1920’s when Carl Akeley of the American Museum of Natural History traveled to Africa, the first study about gorillas was conducted and in 1959 after the Second World War, George Schaller turned out to be the first researcher to conduct a field study about the primates and a systematic study specifically about the mountain gorillas. Later Louis Leakey, National Geographic and Dian Fossey conducted a much longer and comprehensive study of the mountain gorillas and Dian Fossey in particular published her work which disproved many misconceptions and myths about gorillas which included a myth of gorillas being violent.
For several years, it was believed that gorillas had one species with three subspecies like the western and eastern lowland gorillas and the mountain gorillas until of recent when it was finally agreed on that there are only two species with two subspecies from each species and that the third subspecies exists in one of the species. During the ice age, there existed one gorilla specie but it was separated when their forest habitats shrunk.
Recent DNA tests show that the Bwindi and Virunga gorillas show sufficient genetic differences to suggest that they have formed mutually isolated breeding populations for many millennia. In which case the mountain gorilla should be split into two discrete races where by one named the Bwindi gorilla-only endemic to Uganda and the Virunga gorilla which is unique to the Virunga Mountains.
The mountain gorilla is distinguished from its lowland counterparts by several adaptations to its high altitude home of 1,650-3,790 m/5,413-12,435 ft. They are the biggest apes of this species where an adult male weighs as twice as the female and can weigh up to 220kg while a female can weigh up to 90kg. These apes are massive with a short thick trunk, broad chest with dwarfed shoulders, eyes and ears by the large and hairless head. Males develop crowns of muscle and hair that makes their heads longer. Their arms are also longer than the legs.
Mountain gorilla consumes parts of at least 142 plant species and only 3 types of fruit (there is hardly any fruit available due to the high altitude. About 86% of their diet is leaves, shoots, and stems, 7% is roots, 3% is flowers, 2% is fruit, and 2% ants, snails, and grubs. They are able to survive on vegetation or foliage such as leaves, stems, roots, vines, herbs, trees, and grasses but such vegetation has relatively low nutritional quality. However, now some gorillas are seen eating fruits on a small scale. An adult male gorilla may consume more than 18 kg (40 lb) of vegetation per day. They also eat insects with ants being a particular protein supplement.
Behavior and Characteristics
Mountain gorillas live in groups called troops and they tend to be made of an adult male called a Silverback and multiple adult females with their offspring. Silverbacks are typically more than 12 years of age and named for the distinctive patch of silver hair on their back which comes with maturity. It’s the silverback which makes all decisions in the group and also responsible for the protection of the group from different fights. They seek no trouble unless harassed or in defense of their families. Since they are nomadic, the Silverbacks lead the families to where they eat and nest each day. He is responsible for the mating of the female gorillas. These animals are rather shy and retiring than ferocious and treacherous which is expected of them due to their huge body and huge muscles. These apes are usually calm and seek no trouble unless when attacked. For protection, they normally move in groups and there has to be a main protector which is the silverback.
Gorillas construct nests for daytime and night use. These nests tend to be simple aggregations of branches and leaves which are about 2 to 5 feet in diameter and are constructed by individuals. The young Gorillas nest with their mothers but later on construct their own nests after three years of age. A gorilla's lifespan is between 35–40 years, although some Gorillas may live longer like Ruhondeza who passed away on 27th June 2012.
Mountain gorillas only have sex for reproduction purposes and not anything else. The younger males subordinate to the silverback, known as blackbacks, serve as backup protection and are aged between 8 and 12 years of age. Female gorillas are sexually mature at the age of seven to eight years and they do not reproduce until they are ten years old. Males mature later than the females and are rarely strong and dominant enough to reproduce before 15 to 20 years of age. At this age, they are ready to become independent and take care of their own families.
Mountain gorillas mostly live on the rich volcanic soils of the Virunga though it is highly valued as agricultural land by the neighboring communities. Habitat loss is the biggest threat to them and it destroys their habitat and brings hungry people who hunt them for bushmeat, expansion of farming lands, settlement thereby shrinking the gorilla’s space. However a regional conservation program sensitizing about the importance of maintaining the forest watershed, the need to habituate gorillas for tourist activities in Rwanda, Uganda and Congo. This has helped in the reduction of encroachment.