The impacts of climate change and veterinary fencing on savanna ungulate populations, communities, and behaviors

Abstract

As global change pushes ecosystems past climate tipping points, southern African savannas will experience more heat waves and droughts. These ecosystems are home to 90% of the world’s large herbivore diversity, millions of livestock, and a rapidly growing human population expected to reach 2 billion by 2040. As a unique vestige of large Pleistocene-era herbivores and a burgeoning powerhouse of global population, it is necessary to understand how African savanna ecological communities will respond to global change. Especially concerning for these communities are increased heat loads that may overwhelm ungulate thermoregulatory systems; more frequent droughts that may dry up key surface water resources; and the expansion of veterinary fencing across the landscape, which currently restricts historic great migrations of millions of ungulates. Large herbivores regulate nutrient cycling and vegetation structure on African savannas in a way that cannot be replaced by smaller herbivores or livestock; therefore, their responses to these threats are of utmost importance to preserving savanna functioning for the future.This dissertation addresses the effects of increasing heat, drought, and fencing on savanna ungulate communities from the individual to the metapopulation scale. In Kruger National Park, South Africa, we first address large-scale and long-term questions of drought impacts on rare antelope populations in the context of the full suite of large herbivores in the Kruger Park. We use forty years of harmonized aerial census data and a Bayesian Generalized Joint Attribute Model to understand how drought, and its interaction with other environmental covariates, drives herbivore community structure and rare antelope survival. In Khaudum National Park, Namibia, we then use a four-year dataset of 33 antelope fitted with GPS collars to answer questions on heat and fencing-induced behavioral changes on two species on opposite sides of a water-dependence spectrum. We investigate how these species differ in their reliance on surface water, cool microclimates, and shifting activity budgets when responding to higher temperatures. We then explore how they differ in their responses to veterinary fencing, and how these responses change seasonally. As climate change brings more drought and hotter temperatures to southern Africa, the findings of this dissertation indicate that the placement of artificial waterholes on the landscape will be key to rare antelope survival in the Kruger Park; that water dependence is a key factor in antelope responses to heat and fencing; and that the expression of thermoregulatory strategies for two savanna ungulates will intensify under higher temperatures. This dissertation adds these unique findings to the canon of savanna movement and fence ecology literature, and provides multiple points from which future research in this arena can improve on our expectations of savanna ungulate behavioral shifts under climate change.