Abstract
Stable carbon isotope data (d13C) from feces of mixed-feeding impala Aepyceros melampus living in South Africa’s Kruger National Park are used to study dietary variations across a variety of spatio-temporal scales. We test hypotheses that ungulate dietary variations are related to relative proportions of woody plants:grass in surrounding landscapes, and that rainfall regulates ungulate ecology. Results show that impala diets traverse the browser/grazer spectrum, varying widely in proportions of browse: grass consumed at monthly, seasonal, annual, and regional scales. Impala living in open savanna and grassland landscapes generally eat more grass than their counterparts in savanna woodlands, but this differentiation is not consistent at all temporal scales. In one densely wooded region, Punda Maria in the far north of Kruger, impala consume more grass than elsewhere in the Park. Impala in riparian areas eat lower quantities of grass than in other habitat types, especially during the dry periods when spatial differences in diet are more pronounced. Hence assumptions that ungulate feeding ecology reflects the woody plant:grass composition of their habitats are not supported by our data, nor was a relationship between diet and rainfall detected. The results do support a model of increased grass consumption with increasing protein content of available grasses. Fecal %N data show minimal variations across space and time, suggesting that impala are selective feeders that choose foods, whether browse or grass, in order to maintain optimal levels of diet quality. Given these results, it is more likely that detailed models of food selection, available through optimal foraging theory, can better describe ecological variation
Codron, D