The Mountain Gorilla Population of the Virunga Massif and Bwindi Impenetrable Forest

The mountain gorilla is one of the rarest great apes on Earth, surviving today in only two isolated forest ecosystems in East-Central Africa: the Virunga Massif, a chain of volcanic mountains straddling Rwanda, Uganda and the Democratic Republic of Congo (DRC), and the Bwindi-Sarambwe ecosystem, centred on Bwindi Impenetrable Forest in south-western Uganda and the adjoining Sarambwe Nature Reserve in the DRC. These two populations are geographically separated by about 25–30 kilometres of farmland and settlement, and although genetic studies once suggested the Bwindi gorillas might belong to a distinct subspecies, subsequent analysis confirmed both populations are indeed mountain gorillas. Together, they represent one of conservation’s most celebrated recovery stories: a species pulled back from the edge of extinction through decades of sustained protection, scientific monitoring, transboundary cooperation and community engagement.

Population Status and Trends

In the early 1980s, the mountain gorilla was on the brink of disappearing altogether. Poaching, civil conflict, habitat loss and disease had reduced the Virunga population to roughly 240–254 individuals, and the species was feared to be heading toward extinction within a generation. The work of primatologist Dian Fossey, who established the Karisoke Research Centre in Rwanda in 1967 and campaigned fiercely against poaching until her murder in 1985, is widely credited with galvanising the international conservation response that followed.

Since then, the population has grown steadily, making the mountain gorilla the only wild great ape whose numbers are confirmed to be increasing. The most recent full census of the Virunga Massif, conducted in 2016, recorded a minimum of 604 individuals living in roughly 41 social groups, up from 480 five years earlier. In the Bwindi-Sarambwe ecosystem, the 2018 census recorded 459 gorillas, comprising 36 social groups and 16 solitary silverbacks — an increase from 400 gorillas in the previous survey. Combined, the global mountain gorilla population now stands at approximately 1,063 individuals, up from around 1,004 in 2018. This sustained growth led the International Union for Conservation of Nature (IUCN) to reclassify the species in 2018 from “Critically Endangered” to “Endangered” — still a precarious status, but a genuine milestone.

A new, sixth transboundary census of the Bwindi-Sarambwe population was launched in May 2025 under the coordination of the Greater Virunga Transboundary Collaboration (GVTC) and the International Gorilla Conservation Programme (IGCP), in partnership with the Uganda Wildlife Authority and DRC’s Institut Congolais pour la Conservation de la Nature. For the first time, this survey also included a parallel count of the Bwindi-Sarambwe chimpanzee population. Field sweeps were completed by late 2025, with full results expected in 2026 and likely to refine the current global population estimate. Despite this progress, conservationists caution that the overall population remains small and vulnerable to disease outbreaks, climate change, habitat encroachment and, in parts of the DRC, ongoing armed conflict.

The Virunga Massif

The Virunga Massif is a range of eight volcanoes — five extinct and three still active — that spans the borders of Rwanda, Uganda and the DRC. Politically, it is divided into three separate protected areas: Volcanoes National Park (Parc National des Volcans) in north-western Rwanda, Mgahinga Gorilla National Park in south-western Uganda, and Virunga National Park in eastern DRC. Ecologically, however, it functions as a single contiguous forest block; the gorillas themselves recognise no borders and regularly cross between all three countries. This shared ecosystem has made transboundary cooperation not just desirable but essential to gorilla survival, and it underpins much of the conservation architecture described below.

Volcanoes National Park, Africa’s oldest national park (gazetted in 1925 as Albert National Park), covers about 160 square kilometres across five of the Virunga volcanoes — Karisimbi, Bisoke, Sabyinyo, Gahinga and Muhabura. It is Rwanda’s flagship tourism destination and hosts the historic Karisoke Research Centre founded by Dian Fossey.

Mgahinga Gorilla National Park, Uganda’s smallest national park at just 34 square kilometres, sits at the meeting point of Uganda, Rwanda and the DRC, dominated by the volcanic peaks of Muhabura, Gahinga and Sabyinyo. It shares its ecosystem directly with Volcanoes National Park, and its resident gorilla group is known to migrate seasonally into both Rwanda and Congo.

Virunga National Park in the DRC is by far the largest of the three, and Africa’s oldest UNESCO World Heritage-listed park, but decades of armed conflict, militia activity and instability in eastern DRC have made large parts of it extremely difficult and often unsafe to visit, severely limiting organised gorilla tourism there compared with its Rwandan and Ugandan neighbours.

Bwindi Impenetrable Forest

Bwindi Impenetrable National Park, a UNESCO World Heritage Site in south-western Uganda, is one of the oldest and most biologically diverse rainforests on the continent, believed to have survived largely unchanged for over 25,000 years. Covering roughly 331 square kilometres, it shelters more than half of the world’s mountain gorillas alongside extraordinary biodiversity: around 120 mammal species, over 340 bird species, 11 primate species and more than 1,000 flowering plant types. Bwindi is contiguous with the small Sarambwe Nature Reserve just across the border in the DRC, together forming the Bwindi-Sarambwe ecosystem. Unlike the Virunga Massif, whose gorillas roam volcanic slopes and bamboo zones, Bwindi’s gorillas inhabit dense, steep, mid-altitude tropical rainforest — terrain that gives the park its name, meaning “a place of darkness” in the local dialect, and makes trekking here notably more physically demanding.

Gorilla Families Available for Tracking

Gorilla tracking (or trekking) is only possible with gorilla groups that have been deliberately “habituated” — a process, typically taking about two years, in which researchers and trackers gradually accustom a wild family group to the presence of humans without altering its natural behaviour. Only habituated families are opened to tourism; others remain reserved for scientific research or are left entirely undisturbed. Across the three parks most commonly visited by tourists, the current numbers of habituated families available for tracking are approximately as follows:

Volcanoes National Park (Rwanda): around 12 habituated gorilla families are open to tourists each day, out of roughly 18–20 total groups in the park (the remainder are reserved for ongoing scientific research by the Karisoke Research Centre). Well-known tourist groups include Susa, Sabyinyo, Amahoro, Umubano, Kwitonda, Agashya, Hirwa, Bwenge, Karisimbi, Ugenda, Kwisanga and Muhoza. A maximum of eight visitors per family per day is enforced, giving a total daily permit capacity of around 96. Permits cost US$1,500 per person.

Mgahinga Gorilla National Park (Uganda): only one habituated family, the Nyakagezi group, is currently available for tracking. This makes Mgahinga the most exclusive of the three parks, though also the least predictable for visitors, since Nyakagezi periodically ranges across the border into Rwanda or the DRC, occasionally leaving the park temporarily without a trackable group. When present, the group offers roughly eight permits per day at US$800 per person.

Bwindi Impenetrable National Park (Uganda): the largest number by far, with approximately 19–22 habituated families spread across the park’s four trekking sectors — Buhoma, Ruhija, Rushaga and Nkuringo. Buhoma and Ruhija, in the north and east, each host several groups (including families such as Mubare, Habinyanja, Rushegura, Bitukura, Oruzogo and Kyaguliro), while Rushaga in the south is the largest sector, with numerous families including Nshongi, Mishaya, Busingye, Kahungye and Bweza, and Nkuringo hosts its own smaller cluster. Bwindi’s scale makes it Africa’s premier gorilla-tracking destination and the only park offering the option of a second trek in a different sector on consecutive days.

(Virunga National Park in the DRC also maintains several habituated families, historically around eight, but access has fluctuated considerably in recent years due to insecurity, and it is not typically counted among the three most consistently accessible tracking parks.)

Conservation Measures

Volcanoes National Park, Rwanda. Rwanda has built one of the most tightly managed gorilla conservation and tourism systems in the world. The Rwanda Development Board deploys armed ranger patrols and trackers who monitor every habituated family daily, deterring poaching and snaring and providing early warning of injury or illness. High-value, low-volume tourism — permits capped at eight visitors per family and priced deliberately high — limits stress on the animals while generating substantial revenue, a share of which is legally required to flow back to neighbouring communities through the park’s revenue-sharing scheme, funding schools, health centres and infrastructure and giving local people a direct economic stake in the gorillas’ survival. Former poachers have been formally integrated into tourism and conservation work, such as through the Iby’Iwacu Cultural Village. Veterinary care is provided by the NGO Gorilla Doctors, which conducts regular health checks and emergency interventions on habituated groups. Rwanda also hosts the annual Kwita Izina gorilla-naming ceremony, a high-profile event that reinforces political commitment and international visibility for conservation, and continues to support the Karisoke Research Centre’s long-term behavioural and demographic monitoring, first established by Dian Fossey.

Mgahinga Gorilla National Park, Uganda. Conservation in Mgahinga is managed by the Uganda Wildlife Authority (UWA) and centres on ranger-based anti-poaching patrols, boundary monitoring and close coordination with Rwandan and Congolese authorities, since its single resident gorilla family ranges freely across all three countries. Because Mgahinga’s population is so small and mobile, its protection depends heavily on the broader transboundary framework: the Greater Virunga Transboundary Collaboration (GVTC), a treaty-based partnership signed by Rwanda, Uganda and the DRC in 2015, coordinates joint patrols, shared law enforcement, disease surveillance and information exchange across the whole Virunga ecosystem. Golden monkey tracking and volcano-hiking tourism supplement gorilla permit revenue, funding community projects around the park and reducing local dependence on forest resources that might otherwise drive encroachment.

Bwindi Impenetrable National Park, Uganda. Bwindi’s conservation strategy similarly rests on UWA ranger patrols and law enforcement against poaching, snaring and illegal logging, supported by a network of community conservation rangers and local scouts. The Institute of Tropical Forest Conservation conducts long-term ecological and gorilla-health research, while Gorilla Doctors and Conservation Through Public Health work to monitor and reduce disease transmission risk between humans and gorillas, an especially serious concern given the close genetic relatedness between the two species and the density of human settlement around the forest. The Bwindi Mgahinga Conservation Trust channels tourism revenue and donor funding into community development, education and alternative livelihoods for the roughly half a million people living around the park’s boundary, aiming to reduce pressure on the forest. Strict visitor rules — including a minimum distance from gorillas, mask requirements during outbreaks of respiratory illness, group size limits and a one-hour viewing cap — are enforced to minimise disturbance and disease risk. Bwindi also participates fully in the GVTC/IGCP-led transboundary census programme and collaborates with Sarambwe Nature Reserve authorities in the DRC to manage the shared Bwindi-Sarambwe ecosystem as a single conservation unit.

Conclusion

The recovery of the mountain gorilla from fewer than 300 individuals in the 1980s to over 1,000 today stands as one of the great success stories in wildlife conservation, achieved through a combination of intensive ranger protection, veterinary care, scientific monitoring, regulated high-value tourism and, critically, transboundary cooperation between Rwanda, Uganda and the DRC. Yet the species remains classified as Endangered, confined to two small forest islands surrounded by some of the densest human populations in Africa. Continued vigilance — against poaching, disease, habitat loss, climate change and, particularly in the DRC, armed conflict — will determine whether this fragile recovery can be sustained into the coming decades.