Abstract:

Human population increases and an expanding agricultural frontier are driving tropical deforestation. As a result, some of the indigenous tree species which serve as primate foods are likely to become rare or even extinct from the wild. A better understanding of the nutritional composition of different primate foods and how primate species cope with the changes in diet quality due to fluctuating food resources is critical for conservation efforts. Previous studies indicated that Kibale chimpanzees prefer high-quality drupe fruits and the timing of reproductive events i.e. estrous, conceptions and births is often associated with availability of drupes. It has thus, been commonly assumed that consumption of drupe fruits leads to increased energy intake which favours reproduction in female chimpanzees. Against this background I focused on the female chimpanzees (Pan troglodytes schweinfurthii) of Kanyawara community in Kibale National Park, and: 1) examined whether dietary variation relates to macronutrient and energy intake variation; 2) applied the principles of nutritional geometry to examine the nutritional strategy of female chimpanzees; and 3) examined whether macronutrient intake variation relates to the timing of reproductive events in female chimpanzees. Fruit seasonality resulted into variations in macronutrient intake while energy intake was relatively stable. Female chimpanzees switched their diet and adjusted their behavior in order to maximize intake of high-quality nutrients, minimize foraging costs and acquire a nutritionally balanced diet. Similar to frugivorous spider monkeys (Ateles sp.) and humans, female chimpanzees tightly regulated protein intake while maximizing carbohydrate intake. The results also indicated that there was no predictable seasonality in the timing of reproductive events or in macronutrient or energy intake. While the patterns of timing of reproductive events were not consistent with the patterns in the intake of high-quality macronutrients, there was a positive relationship between energy intake and estrous and births. Additionally the findings suggest that minimum temperature has an effect on the estrous and conceptions. Since increase in minimum temperature negatively affects fruiting in tropical forests, there is a likelihood that female chimpanzees are using minimum temperature as a cue for predicting fruit availability. The increased consumption of carbohydrates and reduction of foraging costs during drupe months might allow female chimpanzees to reach a positive energy balance thereby resuming cycling when drupes are abundant. This study, supports the increasing recognition of nutrient balancing as a foraging strategy used by female chimpanzees and the relevancy of using feeding rates to estimate intake in wild primates. Furthermore, the study provides insights on the relevancy of the different food types in chimpanzee habitats and this information can be used to better manage chimpanzee ecosystems and captive chimpanzee populations.