Feeding ecology of the greater Kudu (Tragelaphus strepsiceros) in the central Free State
Butler, Vivian Page
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The objective on most wildlife ranches is to accommodate a diversity of wildlife species to satisfy the need for ecotourism, hunting and live sales. However, the small size of many wildlife ranches presents its own unique challenges. One of these is fencing that prevents animals from moving to more favourable areas during times of food shortages. Intensive management is thus required to prevent overstocking that can lead to the deterioration of natural resources or even total habitat destruction in the long term, or alternatively requires the provision of supplementary feed at a high cost over an extended period of time. The feeding habits of herbivores are largely determined by their food preferences and the availability of their preferred food plants, with food considered the most important resource that limits animal populations. It is thus important that an animal’s diet provides all the essential nutrients needed for survival, growth and reproduction. However, the quality and quantity of food available to herbivores can vary considerably from one season to the next or from year to year. A proper management plan is therefore essential for the sustainable utilisation and conservation of the ecosystem on these small fenced wildlife ranches. The main objectives of this study were to determine the diet and food preferences of kudu throughout the seasonal cycle of food availability and how this affected their habitat selection in a relatively small game fenced area in the central Free State. The potential food available to kudu was first determined in each of the identified plant communities and then in the study area as a whole. As kudu are predominantly browsers, only the woody browse (leaves + shoots < 0.5 cm) up to a feeding height of 2.0 m was considered to be available to kudu in the current study. Forbs were not included as they were rarely encountered in the study area, contributing an insignificant proportion of the herbaceous layer. Leaf phenology of woody species was also taken into account in these calculations due to the winter deciduous nature of several woody species in the study area. The diet composition and food preferences of kudu varied according to food quality and availability. Although the kudu population’s annual diet consisted of mostly woody browse, a considerable amount of grass was consumed from November to March. Kudu also changed their diet selection from mostly deciduous woody species during the growing season to mostly evergreen species during the dry season. In addition to this, kudus’ food preferences changed throughout the year due to the timing of leaf emergence and leaf fall in woody species. Although the habitat selection of kudu was affected by food availability, cover also played an important role in determining their habitat preferences. Kudu showed a definite preference for areas with high woody canopy cover throughout the year, often trading food for more cover. Kudu habitat selection also changed markedly between day and night time, with kudu selecting areas dominated by their preferred food items during the day and areas with more cover, but less of their preferred food items at night. The selection of areas predominantly for feeding or resting was further confirmed by the fact that kudu were less active at night, as they travelled shorter distances during the night compared to the day. Topography also became important in the habitat selection of kudu during the coldest part of the year, with kudu escaping the worst cold by moving to the hills, especially at night when temperatures dropped to well below freezing point. Proper habitat analysis thus plays a crucial role in determining the suitability of fenced areas for kudu, as the availability of sufficient cover is just as important as the food available to these animals.