Seasonal Variations of Diet Related to Species and Sex in a Community of Cercopithecus Monkeys

TLDR: Interspecific differences are related to search strategies which depend on body weight, forest levels used, social roles, etc, which suggests that interspecific competition is important in determining resource partitioning.

Abstract: (1) Fruit, leaves and animal matter form the main part of the diets of the three Cercopithecus monkeys studied. Cercopithecus nictitans eats less fruit and insects and more leaves; C. pogonias more fruit and insects and fewer leaves; C. cephus is intermediate. (2) Sex-related differences occur: males eat more fruit than females who eat more leaves and animal matter, especially when these foods are abundant. (3) Interspecific differences in food items taken are small for fruit (68% of the species are taken by the three monkeys), obvious for animal matter. Cercopithecus nictitans preys mainly on sedentary prey (caterpillars, ants), C. pogonias on mobile ones (orthoptera) while C. cephus captures both types. Sex-related differences occur in C. cephus and C. pogonias. (4) Interspecific overlap in diets is great during the main part of the year. Species diets change and overlap less when fruit, young leaves and animal matter production are short (main dry season). This suggests that interspecific competition is important in determining resource partitioning. A second decrease in diet overlap occurs at the end of the long rainy season while foods are abundant. Females are either pregnant or lactating and select protein-richer foods such as young leaves and/or insects while males eat more fruit. At this time, intraspecific competition could be the selective force in food sharing. However increasing protein-requirements could account for the reorientation in food choice of the females. (5) The intermediate trophic position of C. cephus rests upon sex-related differences. The cephus male behaves like nictitans while the cephus female behaves like pogonias. (6) Interspecific differences are related to search strategies which depend on body weight, forest levels used, social roles, etc. Differences in spatial and temporal feeding patterns are small.