The current status of gorillas and threats to their existence at the beginning of a new millennium

Abstract

Gorilla numbers across Africa have declined dramatically over the last century. Some of the earliest conservation efforts on the continent were aimed at protecting mountain gorillas, but destruction of habitat, hunting, and human disturbance have all contributed to the reduction of gorilla populations. All gorilla subspecies are classified as “Endangered” according to the International Union for Conservation of Nature (IUCN) criteria (Oates, 1996; IUCN, 2000). However, in recent years, innovative new conservation ideas have been applied, which have shown some success in slowing the decline, and have even allowed some populations to start to recover. In this chapter, we review the current threats to gorilla populations, and outline some of the strategies that may hold the key to their survival in the twenty-first century. Gorillas are found in the forests of central Africa, from Nigeria in the west to Rwanda and Uganda in the east, with most animals occurring in the Congo Basin (Cameroon to eastern Democratic Republic of Congo) (DRC) (Fig. 17.1). Until recently there were thought to be three subspecies of gorilla, the mountain gorilla (Gorilla gorilla beringei), the Grauer’s gorilla (G. gorilla graueri) and the western lowland gorilla (G. gorilla gorilla). Recent taxonomic research is now suggesting that there are more subspecies (Sarmiento et al., 1996; Oates et al., this volume) and possibly that western and eastern populations should be given separate specific status, G. gorilla and G. beringei, on the basis of genetic and morphological differences (Groves, 2001, this volume) Where gorillas occur they are generally found at densities ranging between 0.1 and 2.5 individuals/km2, occasionally as high as 10.6 locally. They tend to occur at their highest densities in secondary forest (Carroll, 1988; Fay, 1989, 1997; Hall et al., 1998a). Extrapolating from where gorillas have been surveyed to their known range of occurrence allows us to estimate the sizes of the various populations (Table 17.1). If we use the taxonomic classification that