Cape mountain zebra (Equus zebra zebra) habitat use and diet in the Bontebok National Park, South Africa


Cape mountain zebra habitat utilization and diet in the dystrophic fynbos habitat of the Bontebok National Park was found to be highly selective. Mountain zebra concentrated in specific sectors and habitat types in the park on a seasonal basis, preferring recently burnt habitat with a veld age younger than one year in all seasons, except during the warm, dry summer. Proteoid Fynbos with a veld age between one and five years was preferred in the cool winter, while Drainage Lines and the fringes of Inland Pans were preferred during summer. Asteraceous Fynbos was avoided, irrespective of veld age, as well as all other habitats with a veld age greater than five years. Within habitat types with a veld age greater than one year, specific sites were selected and avoided on a seasonal basis, which were found to differ in terms of habitat suitability, based on the availability of dietary plant species. The annual diet consisted of 72.6% grass, 11.8% restio, 5.9% sedge, 8.8% geophyte and less than 1% forb and shrub species. Three grass species formed the bulk of the annual diet, Themeda triandra, Cymbopogon marginatus and Eragrostis curvula, for which leaf use was greater than stem use. Themeda trianda was preferred throughout the year, but contributed to the diet in greatest proportion in the warm, dry summer, when it was available at greatest leaf height and diameter. Cymbopogon marginatus was preferred during the cool winter, when diet composition and greenness was also greater than in other seasons. Preference of Cymbopogon marginatus decreased as leaf height and diameter increased. Eragrostis curvula was preferred in the warm autumn, when it composed the largest proportion of the diet, and selection of this species at feeding sites was based on both greenness and volume. In summer mountain zebra also preferred grass stems and inflorescences of Aristida diffusa, Stipagrostis zeyheri and Briza maxima. During the cool spring the diet included stems and inflorescences of sedges and restios, primarily Ischyrolepis capensis, and in autumn, dry bulbs of the geophyte Moraea collina were utilized. Habitat utilization, as well as grass height and greenness surveys in the Recently Burnt Area, and the nutritional status of mountain zebra was found to be in line with the Summer Nutritional Stress Hypothesis. The hypothesis
proposes that the harsh climatic conditions of the area during summer are linked to the low availability of C4 grass, on which grazers would depend in summer. This is supported by the avoidance of the Recently Burnt Area in summer, and the preference of species like Themeda triandra during summer despite low greenness levels. Faecal nitrogen and phosphorus for mountain zebra in Bontebok National Park and De Hoop Nature Reserve were at minimum levels during the warm seasons. Faecal nitrogen was below the threshold for dietary deficiency in all seasons except spring, and faecal phosphorus was above the threshold for deficiency during two seasons only. The findings of this study are in line with other recent work on mountain zebra in the Baviaanskloof suggesting that, due to a high required rate of forage intake, mountain zebra are limited by both poor resource quantity and quality in dystrophic fynbos ecosystems.