Habitat use and nutrition of chimpanzees in an anthropogenic landscape: A case study in Bossou, Guinea, West Africa

Human population increases and an expanding agricultural frontier are driving tropical deforestation. As a result, many primates are increasingly found outside of protected areas in highly-disturbed environments in close proximity to humans. A better understanding of primate species adaptability to human pressures and the ability of anthropogenic landscapes to support viable populations in the long-term is critical for effective conservation efforts. By focusing on the chimpanzee (Pan troglodytes verus) community in the anthropogenic landscape of Bossou, Guinea, West Africa, I aimed to 1) empirically describe the composition and availability of chimpanzee resources across fine spatial scales, 2) examine chimpanzee use and activity budget across available habitat types and in relation to anthropogenic pressures and risks, 3) determine the macronutrient composition of wild and cultivated chimpanzee foods, and 4) investigate chimpanzee macronutrient intake and balancing from wild and cultivated foods.

To examine objective 1, I undertook quadrat vegetation surveys and phenology surveys to spatially and temporally quantify chimpanzee food resources in all available habitat types. Bossou is largely composed of regenerating forest and the scarcity of large fruit bearing trees is offset by a high diversity of wild and cultivated chimpanzee food species. Moraceae (mulberries and figs) is the dominant family, trees of which produce drupaceous fruits favoured by chimpanzees. The oil palm, which provides the chimpanzees with year-round food resources, occurs at high densities throughout Bossou. Mature and secondary forests are the most important habitat types for food species availability. Overall, these results emphasise the importance of examining ecological characteristics of an anthropogenic landscape as each available habitat type is unlikely to be equally important in terms of spatial and temporal availability of resources.

To examine objective 2, I conducted behavioural follows to record chimpanzee activities and habitat use across all forest and highly disturbed habitat types, and foraging locations in non-cultivated habitat in relation to anthropogenic pressures i.e. cultivated fields and roads and paths. Chimpanzees preferentially use forest habitat types for travelling and resting and highly disturbed habitat types for socialising. The availability of wild fruit and crops influences seasonal habitat use for foraging. The chimpanzees rely heavily on a small patch of mature forest, rich in food species and with low human presence, irrespective of season and activity. The chimpanzees avoid foraging in non-cultivated habitat within 200 m of cultivated fields, with no effect of habitat type or season, suggesting an influence of associated risk. Nevertheless, they did not actively avoid foraging close to roads and paths. These results reveal chimpanzee reliance on different habitat types and the influence of human-induced pressures on their activities.

To examine objective 3, I used standard wet chemistry procedures to estimate the macronutrient content of wild and cultivated chimpanzee foods. The composition of wild fruit, leaves and pith are consistent with previous reports for primate diets. Cultivars are generally higher in carbohydrates and lower in fibre than wild foods, while wild foods are higher in protein. Oil palm food parts are rich in energy, carbohydrates, protein, lipids and/or fermentable fibre fractions; adding nutritional support for the importance of oil palms for chimpanzees in anthropogenic landscapes. These results build on current understanding of chimpanzee feeding ecology and nutrition within forest-agricultural mosaics and provide further empirical evidence that cultivars offer primates energetic benefits over most wild plant foods.

To examine objective 4, I used the macronutrient composition of foods and recorded chimpanzee intakes of wild and cultivated foods during focal follows. Diet composition and macronutrient intakes vary little between the sexes; however females have higher total foods (i.e. wild and cultivated combined), digestible fibre (NDF), and protein intakes when controlling for metabolic body mass. There are no differences in wild or cultivated food intake between seasons; however lipid and protein intake from cultivars, and most likely oil palm food parts, is higher during the fruit scarce season. The chimpanzees maintain their proportional intake of protein while allowing carbohydrate and lipid intakes to vary. Furthermore, they were able to achieve a consistent balance of protein to non-protein (carbohydrates, lipids, and NDF) energy across the year. These results suggest the chimpanzees suffer little seasonal constrains in food quality or availability and are able to combine their consumption of available wild and cultivated foods to achieve a balanced diet.

Overall, this thesis provides new insights into the ecology of anthropogenic landscapes, the influence of human pressures on chimpanzee habitat use and behaviours, and the role of cultivars in chimpanzee foraging strategies and in allowing them to meet their nutritional requirements. Such information is important for informing conservation initiatives aimed at balancing the needs of people and chimpanzees that share space and resources within anthropogenic landscapes.