Feeding ecology of the kudu Tragelaphus strepsiceros (Pallas) in the Kruger National Park

Abstract

The study investigated aspects of the feeding ecology of kudus that could indicate their nutritional status, and which might affect their population performance; i.e. (i) potential food abundance, measured as the biomass of available forb and woody plant leaves (ii) the nutrient content of potential food (iii) an index of accepted food abundance, given by feeding time achieved per unit distance moved while foraging (iv) an index of food intake rate while foraging, given by the proportion of foraging time spent feeding (v) diet composition (vi) differences between food types in acceptance, as indicated by selectivity ratings. Potential food was most abundant in the late wet season at 60 g dry weight per m2 and least abundant in the late dry season at 12 g per m2 • Forbs were less abundant than woody plant foliage, but comprised about 65 per cent, as opposed to woody plants 35 per cent, of the kudus' diet during most of the year. The selectivity ratings of the various food types were positively correlated with their leaf protein, phosphorus and water contents in the wet season, suggesting that the kudus selected for plants with a high nutrient content. In the dry season, however, there was no relationship between acceptance and leaf nutrient content. This was because the kudus favoured woody plants armed with thorns during the wet season, but increased their acceptance of unarmed woody species in the dry season, despite the fact that the armed species averaged higher in nutrient content throughout the year. Thus plant structural defences may have outweighed leaf nutrient content as a factor influencing selection in the dry season. The index of accepted food abundance provided a satisfactory reflection of seasonal and between-habitat variations in food abundance as experienced by the kudus, but it5 reliability would be increased if it were accompanied by measurements of the rate of food intake per unit time spent feeding. This index offers a means of monitoring long-term changes in the quantity of food available to kudus, and of determining whether their population is limited by food availability.