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Average cat and fox densities at Roxby Downs, in northern South Australia, of 0.8 and 0.6 km–2 respectively, determined through spotlight counts over a 10-year period, probably considerably underestimate true densities. Peak rabbit populations coincided with high fox numbers, which probably suppressed cat densities. Cat abundance peaked when fox numbers were low but rabbit numbers were relatively high. When abundant, rabbits were the principal prey of both cats and foxes. Declines in rabbits numbers coincided with dramatic declines in fox numbers. By contrast, declines in cat populations were less marked, presumably because they could more effectively switch to hunting a wide range of native vertebrates. Sand-dwelling lizards, house mice and common small passerines were the most abundant non-rabbit, vertebrate prey taken by cats. We estimate that annual cat predation accounted for approximately 700 reptiles, 150 birds and 50 native mammals per square kilometre, whereas foxes consumed on average 290 reptiles per square kilometre and few native mammals and birds in the Roxby Downs region each year. Male cats and foxes were heavier than females. Feral cats typically weighed less than 4.0 kg, and cats weighing less than 2.5 kg typically preyed on more native vertebrates than did larger cats. Male and female cats were both typically tabby coloured, but a higher proportion of males were ginger in colour. Peak cat breeding coincided with rabbit and bird breeding and increased reptile activity during spring.

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Population control of socially complex species may have profound ecological implications that remain largely invisible if only their abundance is considered. Here we discuss the effects of control on a socially complex top-order predator, the dingo (Canis lupus dingo). Since European occupation of Australia, dingoes have been controlled over much of the continent. Our aim was to investigate the effects of control on their abundance and social stability. We hypothesized that dingo abundance and social stability are not linearly related, and proposed a theoretical model in which dingo populations may fluctuate between three main states: (A) below carrying capacity and socially fractured, (B) above carrying capacity and socially fractured, or (C) at carrying capacity and socially stable. We predicted that lethal control would drive dingoes into the unstable states A or B, and that relaxation of control would allow recovery towards C. We tested our predictions by surveying relative abundance (track density) and indicators of social stability (scent-marking and howling) at seven sites in the arid zone subject to differing degrees of control. We also monitored changes in dingo abundance and social stability following relaxation and intensification of control. Sites where dingoes had been controlled within the previous two years were characterized by low scent-marking activity, but abundance was similar at sites with and without control. Signs of social stability steadily increased the longer an area was allowed to recover from control, but change in abundance did not follow a consistent path. Comparison of abundance and stability among all sites and years demonstrated that control severely fractures social groups, but that the effect of control on abundance was neither consistent nor predictable. Management decisions involving large social predators must therefore consider social stability to ensure their conservation and ecological functioning.