Gorilla distribution and taxonomy
Gorillas are found discontinuously in the tropical forests of equatorial Africa (Fig. 9.1) (for more detailed discussion of the distribution of gorilla populations see Groves, 1970b, 1971; Hall et al., 1998; Omari et al., 1999; Plumptre et al., this volume). The largest discontinuity in gorillas' distribution is between the gorillas from West Africa (Nigeria, Cameroon, Gabon, Equatorial Guinea, Republic of Congo, and Central African Republic) and those from East/central Africa (eastern Democratic Republic of Congo, Rwanda, and Uganda).
The taxonomy of gorillas (as well as the other great apes) is currently under debate. During the past two decades most authors have used a “one-species–three-subspecies” taxonomy (e.g., Groves, 1986; Fleagle, 1988; Uchida, 1996). Recently, however, not only are gorillas increasingly being considered as two separate species (i.e., Gorilla gorilla and Gorilla beringei: e.g., Groves, 1996, 2001, this volume Sarmiento and Butynski, 1996), but the exact number of recognized subspecies is also undergoing revision (Sarmiento and Butynski, 1996; Sarmiento et al., 1996; Oates et al., 1999, this volume; Groves, 2001, this volume; this volume; Stumpf et al.,). For the purposes of this discussion (and to avoid confusion), gorillas from West Africa (G. g. gorilla and G. g. diehli) and from East/central Africa (G. g. graueri and G. g. beringei, or G. b. graueri and G. b. beringei if two species of gorillas are recognized) will be referred to here simply as “western gorillas” and “eastern gorillas”, respectively.