Demographic responses to changes in conservation management : a case study on elephants in the Kruger National Park

Abstract

Conservation management approaches for elephants in southern Africa, and particularly in the Kruger National Park, have changed. Recently, Kruger’s managers adapted their approach from artificially manipulating elephant numbers to reinstating and embracing densitydependent processes that could limit or regulate the elephant population. However, few studies have evaluated whether changes in Kruger’s elephant management approach were effective in achieving the desired outcomes. This is a common shortcoming in conservation endeavours and has the potential to undermine future initiatives. In my thesis, I address this shortcoming, and assess whether recent changes in conservation management in Kruger induced demographic responses from the elephant population that ecological theory predicted and managers desired. My assessment into how calf recruitment and population growth rates responded to ecological limitations (i.e. climate, primary productivity and density) during two contrasting management eras suggests that changes in management induced predicted and desired demographic responses. During the culling era (i.e. density suppression, water supplementation and fencing), population growth rates were primarily driven by the density-independent, climate-mediated, reproductive patterns of the population. In the post-culling era (i.e. natural variation in density, artificial waterhole and fence removals), density-dependence was reinstated and took over as the primary driver of population growth. Although not empirically tested, density-dependent weaned calf survival and dispersal likely contributed to densitydependent population growth during the latter era and should be the focus of future work. I then determined that the changes in management promoted density-dependent habitat selection, a fundamental driver of population regulation. I found that as densities increased following the cessation of culling, selection for woody cover, an important resource for elephants, generalized (i.e. decreased selection of areas with high woody cover and increased selection of areas with lower woody cover). Furthermore, selection for areas close to or far from rivers was mediated by rainfall. While not directly related to changes in density, varied selection for rivers may moderate density-dependent feedbacks to demographic parameters by alleviating foraging restrictions and clustering around key resources. The question remains however, whether density-dependent and rainfall-mediated changes to habitat selection have fitness consequences for elephants that could ultimately regulate the population. Elephants in Kruger responded, at least demographically and partly, to changes in conservation management as theory predicted and managers desired. Although the population has not yet entered the sought after state of long-term stability, my assessment suggests that some of the density-dependent processes necessary to regulate the population are present. I suggest avenues of further study and advocate that ecological principles provide an effective framework for the scientific evaluation and conservation management of elephants within and beyond the Kruger National Park.