"This proposal aims at improving use of stable carbon and nitrogen isotope analysis for diet reconstruction, and applying these improvements to existing data for free-ranging African herbivores. Experiments with a mixed-feeding herbivore (goats Capra hirca) will be designed, to explore interactions of isotope recovery with diet, feeding behaviour and digestive physiology. These effects will be explored in experimental trials using different diets (grass or alfalfa) and diet mixtures (varying proportions of grass and alfalfa). Our objectives are to i) determine whether and how different types of diet influence isotope fractionation from diet to consumer; ii) determine and quantify interactions of carbon with nitrogen isotope abundances with respect to herbivore feeding niche; iii) determine how feeding behaviour is influenced by diet composition; and iv) model existing isotope data to determine effects of diet composition on feeding ecology in free-ranging herbivores. This study is one of few to attempt resolution of mechanistic models for isotope fractionation, and also, because the data gathered are directly relatable to existing field data (primarily from South Africa’s Kruger National Park), attempt to upscale these processes from experimental to free-range conditions. We will, in turn, develop and test mixing models explicitly accounting for variation in fractionation effects. Similarly, derived functional response parameters will be upscaled to landscape and population levels, allowing us to generate hypotheses about the role of diet composition on density-dependence in plant-herbivore interactions. This project merges researchers with expertise in stable isotope and population ecology, and nutritional evolutionary physiology, respectively. At the same time, it provides opportunity for integration of the fellow (an EU national) within an EU research institute, and to develop further collaborations with scientists in the EU community."