The Status of Grauer's Gorilla

In 1959, John Emlen and George Schaller assessed the distribution of eastern gorillas for the first time. Since then, few attempts were made to characterize these populations. In 1991, WCS (in collaboration with ICCN, Berggorilla & Regenwald Direkthilfe and other organizations) began a systematic effort to identify all populations of Grauer's gorilla and evaluate their status.
We identified 11 populations of Grauer's gorilla (Gorilla gorilla graueri) across its 90,000 km² range and estimate the total population to be approximately 16,900 individuals. The gorillas found in the Kahuzi-Biega National Park lowland area and the Kasese region represent 86% of the subspecies's total population. The mountain and lowland populations of Kahuzi-Biega are not in reproductive contact but effectively severed.
In the mountain sector at least one individual in each of the tourist groups has lost a hand to snares; this underscores the precarious status of the subspecies. Gorillas were no longer present in some of the regions noted by Emlen and Schaller. There have been reports that many gorillas were killed in the chaos after the civil war. In the lowland sector Grauer's gorillas are also no longer as widely distributed as they were during the time of Emlen and Schaller. Reports indicate heavy hunting of gorillas within the Kasese region.
In the Maiko National Park, the westernmost population is extinct. The northern population has been relatively stable in recent years, and the southern population suffers from poaching and habitat pressure. North of the Lowa river an additional population has recently been confirmed. It is at risk because of its small size and isolation.
The 9 subpopulations in the Itombwe Forest can be pooled into 4 populations that are reproductively isolated from one another by large rivers. There are several small and isolated populations in the North Kivu region. Reports indicate that the Masisi population has recently been eliminated. Until a more complete investigation can be undertaken, the number and location of different populations will remain unknown.
The Kivu region has one of the highest human population densities in central Africa. A series of reports has documented the threats to Grauer's gorilla posed by hunting and forest conversion; today the most significant threat is the burgeoning human population's increasing need for land. Outside protected areas, people clear forest and eliminate gorilla populations with little regard for their protected status. In areas of low human population density, gorillas are often considered pests and are killed in retaliation for crop raiding and for meat.
The successful conservation of Grauer's gorilla populations will necessitate a multi-disciplinary approach. The combined results from recent surveys indicate that 67% of known Grauer's gorillas are found within the national parks Kahuzi-Biega, Maiko and Virunga. The apparent success in maintaining these populations suggests that they serve as a core for conservation of the subspecies. Creative alternatives to protect other forested lands must be explored.
The negative effects of habitat clearance and fragmentation, as well as hunting pressures, will increase for all Grauer's gorilla populations. Thus, the optimism offered by our population size estimates should not be accompanied by complacency. Without significant and sustained conservation efforts, the opportunity to ensure the conservation of the subspecies will be lost.

Jefferson S. Hall, Kristin Saltonstall, Bila-Isia Inogwabini and Ilambu Omari
Summary of an article published in Oryx 32(2), April 1998

Jefferson S. Hall led the Grauer's gorilla survey for WCS (Wildlife Conservation Society) and is presently a doctoral student at Yale in the School of Forestry and Environmental Studies.
Kristin Saltonstall published an article on genetics of Grauer's gorilla and is a doctoral student at Yale University.
Bila-Isia Inogwabini recently created a GIS for the Kahuzi-Biega Park. He is presently director of a bonobo project of the ICCN and the Zoological Society of Milwaukee County.
Omari Ilambu is a conservation biologist with extensive experience in wildlife surveys and habitat assessment.He led the Itombwe Forest portion of the Grauer's gorilla survey and a biological monitoring program in Kahuzi-Biega in conjunction with WCS.

   Photo: Iris Weiche
The census team in Kahuzi-Biega

Estimated Sizes of the 11 Grauer's Gorilla Populations

Democratic Republic of the Congo overview

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