Mesopredator release among invasive predators: controlling red foxes can increase feral cat density and alter their behaviour

The mesopredator release theory predicts that the density of subordinate predators will increase as dominant predators decline. Persistent debate around mesopredator release in part reflects the lack of robust, replicated experiments to test this theory, and the use of population indices which confound changes in mesopredator density and detectability. This uncertainty has immediate impacts for conservationists who are faced with managing sympatric invasive predators.
We used replicated experimental designs and spatially-explicit models to examine whether mesopredator release of the feral cat Felis catus occurs in response to targeted control of the introduced red fox Vulpes vulpes. We surveyed three Control-Impact paired landscapes in a region with long-term fox control (1080 poison baiting), and conducted a Before-After Control-Impact Paired-Series experiment in another region. We used fox occurrence as a simple metric of fox populations and estimated feral cat density with spatial ma..., ,