The eastern lowland gorilla: Africa’s largest primate and its forest home

Most visitors to Uganda come specifically to see mountain gorillas — the approximately 1,100 Gorilla beringei beringei living in Bwindi and the Virungas — but there is another gorilla subspecies living in the broader region whose story is equally compelling and whose conservation situation is considerably more desperate: the eastern lowland gorilla, or Grauer’s gorilla (Gorilla beringei graueri), the world’s largest primate by body size, found only in the lowland forests of eastern DRC, and assessed by the IUCN as Critically Endangered after losing an estimated 77% of its population between 1995 and 2016 — a collapse driven by armed conflict, charcoal production, and bushmeat hunting in an area where ranger protection has been repeatedly disrupted by war. See Uganda gorilla trekking and Uganda safari packages.

Most visitors to Uganda come specifically to see mountain gorillas — the critically endangered population of Gorilla beringei beringei that lives in Bwindi and Mgahinga. But there is another gorilla subspecies living in the broader region whose story is equally compelling and whose conservation challenges are in many ways more severe: the eastern lowland gorilla, or Grauer’s gorilla, Gorilla beringei graueri, found exclusively in the Democratic Republic of Congo. Understanding the relationship between these two subspecies — and the contrasting trajectories of their populations — illuminates the complex, geopolitically shaped reality of gorilla conservation in Central Africa.

Who is Grauer’s gorilla?

The eastern lowland gorilla is the largest of all four gorilla subspecies and arguably the largest living primate. Adult males — silverbacks — can weigh up to 220 kilograms and stand nearly two metres tall, with broader chests and more massive builds than their mountain gorilla relatives. Despite their size, Grauer’s gorillas are generally described by researchers as quieter and more placid than mountain gorillas, with a diet that spans a wider range of plant material and a habitat that extends from lowland tropical forest through montane forest zones.

Grauer’s gorilla is endemic to the eastern DRC — it exists nowhere else on earth. Its range centres on the Albertine Rift, overlapping geographically with the mountain gorilla but at lower elevations and across a much larger area. Key populations are found in Kahuzi-Biega National Park (the most accessible site for tourism), Maiko National Park, the Itombwe Massif, and the Virunga National Park’s lowland sectors.

A population in crisis

While mountain gorilla numbers have increased from approximately 250 in the 1980s to over 1,100 today — a conservation success story that has become a model for the field — the eastern lowland gorilla has followed the opposite trajectory. Estimated at around 17,000 individuals in the 1990s, the Grauer’s gorilla population had declined to approximately 3,800 by 2016, according to the most recent systematic survey. This represents a loss of approximately 77 percent of the population in less than 30 years.

The causes are directly connected to the ongoing armed conflict that has destabilised eastern DRC since the mid-1990s. Armed groups operating in the forests mine minerals, bushmeat is hunted to feed mining camps and militias, and the breakdown of law enforcement makes the kind of consistent ranger presence that protects mountain gorillas in Uganda and Rwanda impossible to maintain. Kahuzi-Biega National Park — the only place where Grauer’s gorilla tourism operates reliably — has seen its ranger force attacked multiple times and large areas of its territory controlled by armed groups rather than the park authority.

The Grauer’s gorilla’s situation illustrates a fundamental truth about wildlife conservation: it is inseparable from political stability, governance, and the rule of law. The mountain gorilla’s recovery has been possible in part because Uganda and Rwanda are relatively stable, well-governed states with functioning national park authorities and political will to enforce conservation law. In the DRC’s volatile east, those conditions do not reliably exist, and no amount of conservation science or international funding can fully substitute for them.

Taxonomy and the four gorilla subspecies

Gorillas are divided into two species: western gorilla (Gorilla gorilla) and eastern gorilla (Gorilla beringei). Each species has two recognised subspecies. The western gorilla includes the western lowland gorilla (Gorilla gorilla gorilla) — the most numerous and the subspecies most commonly seen in zoos — and the Cross River gorilla (Gorilla gorilla diehli), one of the rarest primates on earth with fewer than 300 individuals surviving in a small area of the Nigeria-Cameroon border zone.

The eastern gorilla includes the mountain gorilla (Gorilla beringei beringei) and the eastern lowland gorilla (Gorilla beringei graueri). All four subspecies are listed as Critically Endangered on the IUCN Red List. The mountain gorilla, uniquely among the four, is the only subspecies whose population is currently increasing.

The taxonomic distinction between mountain and eastern lowland gorillas has been the subject of ongoing scientific discussion. Morphologically, they differ meaningfully: mountain gorillas have longer, denser fur adapted to the cold of high-altitude environments; shorter arms relative to body size; and slightly different facial features. Their ranges overlap ecologically but not geographically — mountain gorillas live at 1,400–3,800 metres elevation, while Grauer’s gorillas occupy a broader altitudinal range including lowland zones below 1,000 metres.

Conservation efforts for Grauer’s gorilla

Despite the formidable obstacles posed by the DRC’s instability, conservation organisations continue to work for Grauer’s gorilla. The Wildlife Conservation Society, WWF, and the Dian Fossey Gorilla Fund have maintained programmes in eastern DRC throughout the decades of conflict, at significant personal risk to local staff. The Gorilla Doctors programme provides veterinary support for habituated Grauer’s groups, similar to their work with mountain gorillas.

Kahuzi-Biega National Park, despite its challenges, has maintained a small tourism programme with habituated Grauer’s gorilla groups accessible to visitors when security conditions permit. In periods of relative stability, visiting Grauer’s gorillas at Kahuzi-Biega is possible in combination with a Uganda gorilla trekking trip — the drive from Kisoro (near Mgahinga, Uganda) to the park’s highland sector in eastern DRC takes several hours. However, the security situation must be assessed carefully and recently before making this journey.

What the two subspecies share

Despite their geographic separation and population trajectories, mountain gorillas and Grauer’s gorillas share the fundamental characteristics that make all gorillas remarkable: complex social structures built around the silverback’s leadership; strong, long-lasting mother-infant bonds; sophisticated plant knowledge; apparent capacity for play, grief, and social attachment; and a genetic closeness to humans that makes their emotional lives impossible to dismiss.

Visitors who trek mountain gorillas in Uganda are often asked whether they would like to see Grauer’s gorillas as well — whether knowing of the eastern lowland gorilla’s crisis changes their experience of observing the mountain gorilla’s relative success. Many say yes: the awareness that the same animals, in a different country with different political circumstances, are in catastrophic decline gives the Bwindi encounter an additional weight. The mountain gorillas’ recovery is real, hard-won, and worth celebrating. It is also, as the Grauer’s gorilla’s situation illustrates, deeply fragile — dependent on conditions of governance and stability that cannot be taken for granted, even in Uganda.