Intrinsic and extrinsic influences on African large herbivore assemblages and implications for their conservation.

Abstract

Understanding the intrinsic and extrinsic influences that affect large herbivore assemblages are important for protected area managers, especially if their current rate of population decline in Africa continues. I aimed to determine how large herbivore species in African grazing ecosystems, respond to intrinsic and extrinsic influences, and the implications of these influences for their conservation. Conservation planners struggle to reliably reconstruct grazer assemblages for ecological restoration into areas from which they were extirpated, because of the lack of historical distribution data for their regions. Large herbivore population trends in Mkambati Nature Reserve were investigated in order to determine how well grazing herbivores established since introduction, how the success of the introduction was influenced by facilitation and competition, and what the conservation implications are for the ecological restoration. Reconstructing species assemblages for ecological restoration, using biogeographic and biological information, could potentially provide the opportunity for a grazer assemblage which included beneficial facilitatory effects. A well-packed grazer assemblage in turn could potentially lead to an ecosystem which is able to maintain its grazer assemblage structure. I investigated the factors influencing forage patch use behaviour in Mkambati Nature Reserve. A limited set of traits yielded different patch use rules for different species. Patch use was influenced by anthropogenic impacts such as poaching and changed fire regimes. Environmental heterogeneity, species’ traits, water availability as well as anthropogenic influences, affected large herbivore behaviour. The dominant movement behaviour of large herbivores was Brownian motion, with one to four exponential distributions. When animals faced the trade-off between forage quality and quantity during the dry season, they moved further between forage areas and water sources in order to get to better forage. The number of movement scales, i.e. exponential

step length distributions, increased in more heterogeneous areas, and home range size and fences had a significant affect on the number of movement scales. Finding suitable forage patches in a heterogeneous landscape, where patches change both spatially and temporally, poses challenges to large herbivores for maintaining energy budgets. I tested whether large herbivores used visual cues to gain a priori knowledge about potential higher value foraging patches at a habitat-patch scale. Large grazing herbivores did not use visual cues but rather adapted their movement behaviour to the heterogeneity of the specific landscape. In conclusion, I demonstrated that intrinsic factors, including individual species’ traits can influence the way large herbivores interact with their environment. These factors, in turn, determine how large herbivores react to extrinsic factors such as poaching, fire, artificial water holes and fences which are important to consider in the conservation management of protected areas.