Dietary response of chimpanzees and cercopithecines to seasonal variation in fruit abundance. II. Macronutrients

In a continuation of our study of dietary differentiation among frugivorous primates with simple stomachs we present the first comparison of differenc es in dietary macronutrient content between chimpanzees and cercopithecine monkeys. Previously we have shown that chimpanzee and monkey diets differ m arkedly in plant part and species content. We now examine whether this diet diversity is reflected in markedly different dietary macronutrient levels or the different feeding strategies yield the same macronutrient levels in their diets. For each primate group we calculated the total weighted mean d ietary content of 4 macronutrients: crude lipid (lipid), crude protein (CP) , water-soluble carbohydrates (WSC), and total nonstructural carbohydrates (TNC). We also calculated 4 fiber fractions: neutral-detergent fiber (NDF), which includes the subfractions hemicellulose (HC), cellulose (Cs), and su lfuric acid lignin (Ls). The HC and Cs are potentially fermentable fibers a nd would contribute to the energy provided by plans food depending on the h ind gut fermenting capacity of the individual primate species. The chimpanz ee diet contained higher levels of WSC and TNC because during times of frui t abundance the chimpanzees took special advantage of ripe fruit, while the monkeys did not. The monkey diets contained higher levels of CP because th e monkeys consumed a constant amount of leaf throughout the year. All four primate species consumed diets with similar NDF levels. However, the chimpa nzees also took advantage of periods of ripe fruit abundance to decrease th eir Ls levels and to increase their HC levels. Conversely, the monkey diets maintained constant levels of the different fiber fractions throughout the year. Nevertheless, despite these differences, the diets of the 4 frugivor es were surprisingly similar, considering the substantial differences in bo dy size. We conclude that the chimpanzee diet is of higher quality, particu larly of lower fiber content than expected on the basis of their body size.