Habitat and seasonal effects on the nutrient status of selected roan (Hippotragus equinus) and sable antelope (Hippotragus niger) populations in South Africa

Abstract

Roan antelope numbers have declined drastically over the last 30 years in the Kruger National Park (KNP). Various hypotheses have been tested and suggested as reasons for their sharp decline. A change in habitat structure and nutrient deficiencies were among the factors considered for their population decline. The aim of this research was to study the influence of habitat structure on habitat selection in the absence of predators by two separate roan populations in predator-proof enclosures on the northern plains of the KNP. Seasonal variations in the nitrogen, macro-and micronutrient concentrations of the preferred grass species in every enclosure were determined. Faecal samples were collected and pooled seasonally in order to link nutrient concentrations in faeces with that in grass. Water and soil samples were also collected and analysed. The nutrient concentrations of grass and faeces in the wet-and dry season were compared with nutrient concentrations collected similarly from a roan antelope population at Vaalbos National Park, Northern Cape Province, South Africa. Where possible, serum samples were also collected and analysed for macro-and micronutrient concentrations. Results indicated that roan antelope disregard habitat structure in the selection of vegetation type or foraging areas in the absence of predators. This behaviour may jeopardise survival if captive bred roan are released to supplement free roaming roan populations in the KNP since previous studies indicated that free roaming roan antelope in the KNP prefer lightly wooded areas with a fairly high visibility. Results from grass, faecal and serum analyses indicated that some nutrient deficiencies might occur in each of the populations studied during specific times of the year and especially in animals in nutrient challenging production phases. Results suggested a possible induced copper deficiency in roan at N'washitsumbe in the KNP, mainly from a Cu-Mo-S interaction. Wet season faecal nitrogen levels of roan at N'washitsumbe was marginal to deficient and that of the Graspan population at Vaalbos National Park was marginal. Phosphorus levels of all the populations were sufficient in faeces despite low dietary intakes. Results were compared with faecal and serum nutrient levels of supplemented roan and sable antelope at Sable Ranch, Northwest Province, South Africa. In general, supplemented roan and sable antelope had a significantly higher nutrient status than un-supplemented populations. Significant species and gender differences in serum and faecal nutrient concentrations were identified in supplemented animals at Sable Ranch. Copyright