Top predators can induce ecological state-shifts over large spatio-temporal scales in Australian forest ecosystems

Top predators are recognised as important ecological constituents because empirical studies demonstrate that they can supress populations of herbivores and smaller predators. Despite their important roles, top predators are subject to human-induced population declines globally. The main drivers of decline include habitat loss, habitat modification and human persecution resulting from conflict for resources such as livestock. One outcome of their declines has been a widespread interest in documenting the ensuing ecological effects owing to the fact that top predators are recognised as keystone species. In terrestrial ecosystems, research has shown that top predators can influence ecosystems and their species composition owing to direct effects on smaller predators and their prey species. These direct effects have been linked to far-reaching indirect effects at multiple trophic levels, that extend to vegetation and even the physical attributes of the landscape. The role of top predators is increasingly being viewed as an important component of healthy and functional ecosystems around the world. This thesis explores the hypothesis that Australia’s top terrestrial predator, the dingo (Canis dingo), induces shifts in mammal populations and vegetation in Australian forest ecosystems. The novelty of this thesis is that I test this hypothesis using longitudinal methodologies through time as opposed to snap-shot surveys. In my first chapter, I provide a detailed overview of the current state of knowledge regarding the role of top predators around the world. Specifically, I detail how top predators drive trophic cascades via direct and indirect effect pathways. My second chapter contains comprehensive meta-analyses which investigate the effects of dingo and fox control on mammal species. This provides a robust foundation for identifying knowledge gaps. My third chapter builds on the meta-analysis by conducting a multi-year occupancy analysis in forest ecosystems to determine how dingo control affects the occupancy of invasive mesopredators and native mammals. In chapter 4, I perform generalised linear modelling and quantile regression to improve our understanding of how dingoes supress foxes and to determine if environmental predictors have any bearing on this interaction. Finally, I test if reintroducing a marsupial predator back to mainland Australia can act as a surrogate for the dingo in some parts by restoring some lost ecological interactions to areas where dingoes have been extirpated