Factors affecting the size and distribution of large herbivores in Kafue National Park, Zambia

Abstract

The distribution and abundance of African ungulates are limited by abiotic factors (soil nutrients and water), bottom-up processes (forage availability and density-dependent competition for food), top-down processes (direct predation and the costs of avoiding predation) and anthropogenic effects. The relative importance of biotic factors such as food limitation and predation have been well-studied for some species (e.g. wildebeest, Connochaetes taurinus), particularly in flagship ecosystems such as Serengeti and Kruger National Parks. Research on complete ungulate communities is needed to describe differences between ungulate species in the relative importance of these limiting factors, and how their importance varies across ecosystems. Moreover, ungulate populations are in decline across much of Africa, and research is needed to examine the importance of anthropogenic effects and the manner in which anthropogenic effects alter the strength of other limiting factors. Here, we used line transect data collected over three years to estimate population densities and determine what factors limit the distribution of large herbivores in Kafue National Park - North (KNP - N) of Zambia, in Southern Africa. With temporal replication within and among years, we sampled a set of systematically distributed transects, and used distance sampling models to correct for non-detection and test the effects on ungulate distributions of vegetation type, grass height and color, recent burning, distance to rivers and lagoons, soil type, pH and nutrients, lion use, and the distance to roads, tourist camps, and park boundaries. Our results show that the most abundant large herbivores in KNP are impala (Aepyceros melampus), puku (Kobus vardonii) and warthog (Phacochoerus africanus). Using AIC scores to test a set of distance sampling models, we found substantial variation among species in the relative importance of abiotic, bottom-up, top-down and anthropogenic effects. These results suggest that a range of species-specific strategies may be needed to conserve African large herbivores and ameliorate recent declines.