GENTLE GIANTS OF THE FORESTS
“The thrill of trekking for mountain gorillas in the astonishingly beautiful misty highlands of East Africa is not difficult to explain. Quietly observing these gentle giants as they go about their day is a once-in-a-lifetime opportunity for a privileged few, and to be treasured beyond compare. If you are lucky enough to exchange glances with one of the troop, you will become aware of that narrow genetic gap between our two great ape species. The exchange of recognition, of awareness, is apparent.
“This is not the heart-thumping primordial fear one experiences when a twitchy lion gives you the stare, or that adrenaline rush when that cantankerous old buffalo bull rises from the bluebush thicket and fixes you with his myopic glare. No, this is different. This is gentle to-and-fro communication at a spiritual level.”
~ Simon Espley, CEO of Africa Geographic
Conservation status and distribution
A recent survey produced the excellent news that the mountain gorilla population is now estimated at 1,063 individuals, up from fewer than 900 individuals in 2010. This increase is primarily due to the co-operation from communities that live near mountain gorillas, NGOs that operate on the ground, and tourists, who pay in hard currency for the privilege of trekking to see mountain gorillas.
Mountain gorillas are found in two populations in Africa:
1. An estimated 604 individuals in the Virunga Massif – which includes Volcanoes National Park (Rwanda), Virunga National Park (DR Congo) and Mgahinga National Park (Uganda);
2. An estimated 459 individuals in Bwindi Impenetrable National Park (Uganda).
As a result of the above conservation successes, the mountain gorilla was recently reclassified in the IUCN Red List as ‘Endangered’ (facing a very high risk of extinction), improved from its previous category of ‘Critically Endangered’ (facing an extremely high risk of extinction).
Factors contributing negatively to mountain gorilla conservation status include poaching for bushmeat, the continuing political instability of the DR Congo region of the Virunga National Park, habitat loss/degradation, and the risk of disease transmission by humans, domestic animals and livestock. There is a distinct possibility that the subspecies could experience a 25% reduction in the next generation of 20 years. At the time of writing, Virunga National Park is closed to tourists while security in the area is stabilised after two tourists were kidnapped before being safely returned.
The primary threat to mountain gorillas comes from forest clearance and degradation, as the region’s growing human population struggles to eke out a living. Conversion of land for agriculture and competition for limited natural resources such as firewood lead to varying degrees of deforestation. Also, the harvesting of charcoal – as a fuel source in cooking and heating – has also destroyed gorilla habitat.
Gorillas are vulnerable to human diseases, and when coming into contact with humans can pick up a variety of illnesses, from the common cold to Ebola, all of which can prove fatal. As gorillas have not developed the necessary immunities, first time exposure to an illness or virus that is relatively innocuous to humans may devastate an entire population. However, studies have found that mountain gorillas that are regularly habituated with researchers and tourists have survived better than unvisited gorillas; they benefit from the greater protection available in those areas and from regular monitoring. Increased survival is also largely due to better veterinary care of sick and injured gorillas.
There is little to no direct targeting of mountain gorillas for bushmeat or the pet trade, but they can be caught and harmed by snares set for other animals.
Read our story about Gorilla Doctors, a non-profit organisation made up of a dozen or so local veterinarians in DR Congo, Rwanda, and Uganda, as well as several international experts and the occasional volunteer. Their mandate is to monitor the populations of mountain and Grauer’s gorillas – the two subspecies that live in the Congo Basin – and, when the life or well-being of an individual gorilla or family group is at stake, intervene.
There are two gorilla species – the eastern gorilla (Gorilla beringei) and the western gorilla (Gorilla gorilla).
There are two subspecies of the eastern gorilla, namely the mountain gorilla (Gorilla beringei beringei); and the eastern lowland/Grauer’s gorilla (Gorilla beringei graueri). There are two subspecies of the western gorilla, namely the western lowland gorilla (Gorilla gorilla gorilla); and the Cross River gorilla (Gorilla gorilla diehli).
For further detail about these four subspecies, read Get to Know the Gorillas.
More about mountain gorillas
Mountain gorillas live for 35 – 40 years in the wild, in troops with home ranges that vary from three to 15 km². They typically move only about 500 metres per day, due to the mountainous terrain and readily available food. Male mountain gorillas usually weight 195 kg with an upright standing height of 168 cm. This compares to females, at 100 kg and 140 cm. They live primarily on the ground but will climb sturdy trees in pursuit of food.
Mountain gorillas live in troops of up to 20 individuals, made up of one adult male who is usually older than 12 years (often called a ‘silverback’ because of the silver fur on his back), a few adult females and their offspring of various ages. Some troops will have more than one mature male, but only one leader/alpha male. The subordinate male (often called a ‘blackback’, and typically 8 – 12 years old) plays a backup role and will assume the leadership role if the silverback dies. Both males and females tend to emigrate from their natal groups, with females leaving at an earlier age than males.
The silverback is the troop leader – making all the decisions, mediating conflicts, determining the movements of the group between feeding and resting/sleeping sites and taking responsibility for the safety and well-being of the troop. The bond that a silverback has with his females forms the core of gorilla social life. Females seek relationships with males, for mating rights and for protection against predators (primarily leopards) and outside males (which may kill young gorillas). If a mother dies or leaves the group, the silverback will often look after her abandoned offspring. Experienced silverbacks are known to remove poachers’ snares from the hands or feet of their group members.
Read an article here about how, according to research, gorilla males who babysit have greater reproduction success
Aggressive encounters between males and females in a troop are rare, but females can act aggressively towards each other (particularly if not related). Conflicts are most often resolved by threat displays intended to intimidate, including hooting, rising onto the legs, throwing of sticks and leaves, chest-beating, kicking with one leg, sideways running on all fours and thumping the ground with the palms.
Rival silverbacks from different troops have been known to kill each other during territorial battles, where they use their huge canines as effective weapons. When a silverback dies, his position in the group may be taken over by one of the younger group males, failing which a new silverback may join the group, often killing all of the infants of the dead silverback.
Mountain gorillas make nests on the ground, for daytime resting and for sleeping at night. The nests are made of a loose pile of branches and leaves. Babies sleep with their mothers and start building their own nests when they are about three years old.
Mountain gorillas are vegetarian, eating leaves, stems, pith, and shoots, with fruit making up a small part of their diet. Protein in the form of insects and grubs makes up about 3% of the diet.
Mountain gorillas mate year-round, once they reach sexual maturity, which is at the age of 10 to 12 years for females and 11 to 13 years for males. The gestation period lasts 8.5 months, and females can give birth every four years.
Baby mountain gorillas are, like humans, vulnerable and dependent on their mothers for survival. Male gorillas are not active in caring for the young (unless the mother dies), but they do play a role in socialising them to other youngsters and protecting them from aggression within the group. Infants remain in contact with their mothers for the first five months, sleeping in the same nest and suckling at least once per hour during that time. After five months, infants start moving away from their mothers, gradually gaining independence. By the third year, juveniles are weaned and sleeping in separate nests to their mothers.
Mountain gorillas use a variety of distinct vocalisations to communicate within their densely-forested home. These include grunts and barks while travelling, to screams and roars to signal alarm or warning and rumbling belches of contentment during feeding and resting periods.
There is an uncomfortable paradox playing itself out in the mountain gorilla conservation space, which is the role that humans play on both sides of the equation. On the one hand, humans pose the greatest threat to gorillas, and, at the same time, humans represent the most viable conservation solution.
Mountain gorilla populations are now slowly trickling upwards, thanks to the dedicated work of so many passionate people on the ground – from locals who live amongst these gentle giants to government conservation agencies, researchers, non-profit entities and paying tourists. Let’s savour this rare victory in the ongoing war to keep Earth’s charismatic species, in fact, all species, safe from extinction.
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