Introduction

The diet, movement patterns, and habitat use of mountain gorillas (Gorilla gorilla beringei) have been extensively studied in the Karisoke study area (Fossey, 1974; Fossey & Harcourt, 1977; Vedder, 1984; Watts, 1984, 1991, 1998a, b), but little is known about the ecology of the gorillas in other parts of the Virungas. Variation in gorilla ecology could have important implications both for behavioral ecology theory and for conservation management practice. Mountain gorilla ecology has been examined in the context of foraging theory, but the Karisoke study area may only represent part of the picture. Gorillas occupying different habitats elsewhere in the Virungas, with potential differences in the abundance, distribution, and quality of resources, could further reveal howpatterns of habitat and food selection tend to maximize foraging efficiency. Comparisons have been made between gorillas in the Virungas and elsewhere with implications for both the evolution of social organization (Wrangham, 1986; Tutin, 1996; Wrangham et al., 1996; Doran & McNeilage, 1998) and gorilla taxonomy (Sarmiento et al., 1996). However, if such comparisons are to be realistic, they must be based on more than one small part of the Virunga population, and it is important to knowhowmuch particular traits vary within the Virungas. In considering the management of the park and the conservation of the gorilla population it is important to have an understanding of what constitutes “good” gorilla habitat and therefore what habitats are available, what resources they contain, and how these are used by gorillas. For these reasons it is important to examine mountain gorilla ecology across a wider range of altitudes and habitats within the Virungas than has been covered by previous studies.