Environmental determinants of the movement patterns of elephants in the Kruger National Park

Abstract

To improve the efficacy of protected areas in conserving ecological processes, initiatives such as the megaparks for metapopulations strive to increase connectivity between small and often isolated protected areas. Increasing connectivity between protected areas may mediate the apparent impact of elephants on vegetation and promote regional population stability through the spatial structuring of their populations. This relies on asynchronous population dynamics between interconnected subpopulations separated by distance. It is likely that the spatial responses of elephants to environmental variation drive this asynchrony. Therefore, developing a thorough knowledge of the spatial responses of elephants to their environment can inform management decisions to conserve suitable habitat, and promote population persistence through the maintenance of ecological processes. Most of what we know about the spatial responses of elephants is from studies that focused on explaining their spatial distribution or re-distribution in space, and studies that aimed to identify factors that determine resources use and selection. Recently, technological and analytical advances have marked a shift to studies that aim to assess the behavioural responses of animals to their environment by considering how individuals change their movement. Therefore, my approach in this thesis was to evaluate the environmental determinants of the movement patterns of elephants in the Kruger National Park. To do this, I used hourly location time series datasets acquired from 26-collared elephant cows distributed across Kruger. In chapter 3, I modelled the movement behaviour of the elephants using dynamic Brownian bridge movement modelling. I then evaluated how well different environmental factors explain changes in their movement behaviour using a mixed modelling approach at multiple temporal scales. Distance from water, primary productivity, vegetation structure, and temperature could explain changes in the movement behaviour of the elephants. The factors that could best explain changes in their movement behaviour varied between seasons and among temporal scales. Therefore, elephants adjusted their movement scale-dependently in response to their environment. Management interventions could induce artificial patterns of elephant movement, potentially uncoupling them from the processes that result in asynchrony in the dynamics of local populations. Therefore, the influence and consequences of management interventions such as the provisioning of water remain controversial. In chapter 4, I examined how the provisioning of water influences the movement patterns and the resulting spatial distribution of elephants. When elephants used artificial waterholes, they used areas more than double the distance away from natural water sources in comparison to when they used natural water sources. This increased the total area used by elephants by more than one third. The resulting change in the distribution of elephants may accentuate their impact on vegetation and have demographic consequences. Elephants respond to the distribution and availability of resources, and rather than returning to the artificial manipulation of numbers to relieve symptoms, I argue that management should continue to base their decisions on ecological principals. Many questions remain, and my hopes are that this research contributes to what we know about elephants and how best to manage them, or rather, how best to manage their responses to our interferences.