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Feral cats (Felis catus) have devastated wildlife globally. In Australia, feral cats are implicated in most recent mammal extinctions and continue to threaten native species. Cat control is a high-profile priority for Australian policy, research and management. To develop the evidence-base to support this priority, we first review information on cat presence/absence on Australian islands and mainland cat-proof exclosures, finding that cats occur across >99.8% of Australia's land area. Next, we collate 91 site-based feral cat density estimates in Australia and examine the influence of environmental and geographic influences on density. We extrapolate from this analysis to estimate that the feral cat population in natural environments fluctuates between 1.4 million (95% confidence interval: 1.0–2.3 million) after continent-wide droughts, to 5.6 million (95% CI: 2.5–11 million) after extensive wet periods. We estimate another 0.7 million feral cats occur in Australia's highly modified environments (urban areas, rubbish dumps, intensive farms). Feral cat densities are higher on small islands than the mainland, but similar inside and outside conservation land. Mainland cats reach highest densities in arid/semi-arid areas after wet periods. Regional variation in cat densities corresponds closely with attrition rates for native mammal fauna. The overall population estimate for Australia's feral cats (in natural and highly modified environments), fluctuating between 2.1 and 6.3 million, is lower than previous estimates, and Australian feral cat densities are lower than reported for North America and Europe. Nevertheless, cats inflict severe impacts on Australian fauna, reflecting the sensitivity of Australia's native species to cats and reinforcing that policy, research and management to reduce their impacts is critical.

This paper examines the pattern of introduced herbivore and predator distribution in the Tanami Desert and tests a series of propositions put forward by Stafford Smith and Morton [1990. A framework for the ecology of arid Australia. Journal of Arid Environments 18, 255–278]. regarding the functioning of arid Australian environments. These authors proposed that introduced herbivore and predator species would be largely restricted to and reliant on productive refugia. We collected occurrence data on introduced and naturalized predators and herbivores at 227 plots stratified by substrate and fire age class across a study area of 700×400 km. We also collected data from 16 repetitively sampled transects stratified by substrate and latitude over a 4 year period. Each of the predator species was associated with different landscape parameters and the proposition that predator diversity and abundance would be greatest in the productive habitats was not supported. There was support for the proposition that introduced feral herbivores would be concentrated in the productive habitats. Overall, the parameters reflecting the climatic gradient were the most important determinants of introduced species distribution in the Tanami Desert. Substrate-related variables or episodic variables such as fire age were of secondary importance at the scale considered. Furthermore, the variables that reflected episodic rainfall or periods of rainfall deviance did not form a significant component of the minimum adequate models for any of the species.