How do differences in species and part consumption affect diet nutrient concentrations? A test with red colobus monkeys in Kibale National Park, Uganda

Within a primate species, diet can be highly variable in composition, even at small spatial scales within the same forest, or temporally, suggesting that primates use different plant species and parts to meet similar nutritional needs. To test whether such differences in the plant species and parts that primates eat affects the nutrient concentrations that they obtain, we observed feeding of seven groups of red colobus monkeys (Procolobus rufomitratus) residing in Kibale National Park, Uganda. The different groups consumed mostly young leaves from many of the same plant species, but spent different amounts of time feeding on them. As protein and fibre are suggested to be important determinants of colobine food choice and abundance, we analysed multiple samples of 47 food species for protein and fibre. Despite the differences in the plant species and parts eaten, the protein and fibre concentrations for the seven red colobus groups were similar. Our results suggest that colobus monkeys eating diets with differing amounts of species and parts may ultimately receive similar concentrations of nutrients.