Date of Award
Doctor of Philosophy (PhD)
Forestry and Environmental Conservation
David S Jachowski
Ecological processes can operate at different scales; individual characteristics can scale-up and affect individual performance, which in turn can influence population and community-level processes. Similarly, processes at the community or population level can affect individual characteristics. For mesopredators, the majority of prior research has focused on how top-down regulation by apex predators affects population dynamics. In contrast, less is known about how mesopredators can be affected by processes happening at the individual, population, and community-level simultaneously. I studied a population of cheetahs (Acinonyx jubatus) in the Mun-Ya-Wana Conservancy, South Africa to better understand how ecological processes across multiple scales can affect mesopredators. In Chapter 1, I investigated population-level drivers of survival, reproduction, and recruitment of cheetahs using a 25-year dataset. I found that demographic drivers were complex and context dependent. Specifically, cheetah monthly survival was best described by lion density and prey density, but opposite of predicted relationships; both adults and cubs had the highest survival when lion densities were highest and prey densities were lowest. I found that there were no strong drivers of litter size, but that cheetahs had the highest recruitment during times of low cheetah density and low prey density. Next, in Chapter 2 I considered how individual habitat use of cheetahs can scale-up and influence population survival. I assessed habitat use at short-term and long-term scales in relation to lion density, prey density, and habitat complexity and used these spatial covariates to predict survival. I found that over both the short-term and the long-term, cheetah survival was highest in areas with open vegetation, and that over the long-term cheetah survival was lowest in areas of high lion density. In Chapter 3, I examined how spatial and temporal variation in predation risk, as well as habitat complexity, can influence cheetah anti-predator behaviors. Using a playback experiment, I manipulated short-term risk in areas of varying long-term risk and assessed cheetah behavioral responses. I found that cheetah vigilance was not associated with long-term predation risk, but that cheetahs responded to short-term risk by being vigilant or fleeing. Additionally, habitat complexity affected cheetah anti-predator behaviors, with cheetah more vigilant in open areas and more likely to flee from lion sounds in closed vegetation and from leopard sounds in open vegetation. Finally, in Chapter 4 I investigated how habitat disturbance can affect carnivore coexistence and suppression. I used prescribed burning to experimentally increase prey densities and monitored how individual species, as well as large carnivores and small carnivores as a whole, respond to burning. I found that some large and small carnivores increased use of burned areas post-fire, but that most carnivores were unaffected by burning. Small carnivores may have experienced a suppression of opportunity, where they were not able to benefit from increased prey in burned areas because of high lion use in these areas. Collectively, my research highlights the need to consider multiple scales of ecological processes to understand mesopredator population dynamics. Specifically, I show that top-down effects on mesopredators are context-dependent and depend on the scale of investigation, so understanding how multiple factors simultaneously affect mesopredator populations is critical.
Gigliotti, Laura, "Individual, Population, and Community-Level Drivers of Cheetah (Acinonyx jubatus) Population Dynamics" (2020). All Dissertations. 2597.