Approaches in Density Estimates and Reconstruction of Social Groups in a Western Lowland Gorilla Population in the Ndoki Forest, Northern Congo.

Individual density and social group formation of a western lowland gorilla population were estimated by (1) the line transect method with direct detection and (2) reconstruction of social groups from direct observation and bed count in the Ndoki Forest, northern Congo. The line transect method gave an estimate of 4-5 gorillas per sq km along the transect course in the roughly 24 sq km study site. The small range of the strip width in dense vegetation, detectability of all members in a group, uncovered vegetation type by the census course, and the contagious distribution of the animals in space may affect the results. The reconstruction suggested the presence of 7 social groups as well as solitaries in the same gorilla popUlation, although individual identification will be necessary for more accurate results. In other study sites of lowland gorillas, the densities have been reported to be lower in primary forests than those in secondary regenerating forests. Aboundant fibrous foods, such as certain aquatic plants found in the marshy grassland, may increase the carrying capacity and allow for the high density of gorillas in this primary forest,