Fragmented living: Behavioural ecology of primates in a forest fragment inthe Lope Reserve, Gabon

A 17-month study was made of the primates using a 9-ha "island" of forest, surrounded by savanna, in the northern part of the Lope Reserve, Gabon. One group of Cercopithecus cephus (plus a young male Cercopithecus nictitans w ho was in permanent association with them) were resident in the fragment an d groups of five other species of primates made visits during 127 days of o bservation: Pan troglodytes, 15 visits; Cercocebus albigena, 10; Colobus sa tanas, 3; Cercopithecus nictitans, 2; C. pogonias, 1. Visits were also made by lone males of three species, C. nictitans, Cercocebus albigena, and Man drillus sphinx. The eighth species of diurnal primate present at Lope, Gori lla g. gorilla, did not visit the fragment during the study. Compared to co nspecific groups in neighbouring continuous forest, primates in the fragmen t ate less fruit, seeds, and flowers and more insects and leaves. The local population density of primates resident in the fragment was equivalent to that of the neighbouring continuous forest where all eight species occur, d espite the diversity and abundance of fruit being less in the fragment. The costs imposed on the resident group by the reduced diversity and availabil ity of preferred fruit foods appeared to be offset by a number of benefits that increased individual feeding efficiency for monkeys residing within a single fragment. These included lower travel costs, reduced feeding competi tion between individuals through group fission, and excellent knowledge of the location and quality of food resources in the small home range. It is a lso possible that the overall negative impact of inter-specific feeding com petition was lower in fragments than in continuous forest and that micro-ha bitat differences resulted in an increased availability of palatable insect and leaf fallback foods in the fragment.