For example, predation by feral cats on ship rats R. Predator-impacts may occasionally even be beneficial. Amarasekare ( 1994) showed further that three species of introduced mammalian predators had no obvious effects on endemic birds on Hawaii, while Diamond ( 1987) presented equivocal evidence for impacts of predators introduced to the Mascarene Islands. loss of ‘tameness’ has been interpreted as a loss of biological diversity although the lizards remain extant ( Stone et al. The introduction of feral cats to some Galápagos islands, for example, has apparently selected for increased wariness in lava lizards Tropidurus spp. The most obvious impact of exotic predators is that they cause extinctions or reductions of range and population size of native species. However, predatory birds, reptiles, amphibians and fish have also been implicated in the demise of native species ( Covacevich & Archer 1975, Wiley 1985, Savidge 1987) the impacts of some, such as the Nile perch Lates niloticus, have been severe ( Baerl et al. and feral domestic cats Felis catus have had particularly destructive effects on a broad range of native vertebrate species ( Atkinson 1985, Dickman 1996). However, impacts have occurred also on near-shore islands and even large continental areas ( Atkinson 1989, Dickman 1992a). 1988), in part because such species have evolved in the absence of predators and lack effective anti-predator adaptations ( Atkinson 1985). Impacts have been most conspicuous on species on small islands isolated from continents ( Brockie et al. Generalist predators have been introduced by humans to new environments in many parts of the world, often impacting negatively on native species. Further quantification of both the direct and indirect impacts of the three predators on native fauna is needed, and should be obtained from experimental field studies. Dingoes could have positive effects on smaller native species if they significantly suppress populations of foxes and cats. It is concluded that feral cats and especially foxes have major negative impacts on certain small and medium-sized native vertebrates in Australia, whereas dingoes have major negative impacts on large species. Alternative prey, especially rabbits Oryctolagus cuniculus, enhance negative impacts on native species by supporting large populations of the predators. ![]() Negative impacts appear to be increased in spatially fragmented forests where native species are restricted to remnant vegetation, and in arid landscapes when native species become restricted temporarily to scattered oases during drought. Impacts of all three predators are wrought primarily by direct predation. It effectively suppresses extant populations of large mammals, such as kangaroos, and emus, over large areas. ![]() The dingo Canis lupus dingo, introduced 3,500–4,000 years ago, probably caused the extinction of the thylacine Thylacinus cynocephalus and Tasmanian devil Sarcophilus harrisii on mainland Australia. Unequivocal demonstration of fox-impact has been obtained in removal experiments, especially on rock-wallabies Petrogale lateralis. The fox has also created recent failures of many management attempts to recover threatened native species. Its subsequent spread into all except parts of arid and tropical Australia coincided with local and regional declines of medium-sized (450 – 5,000 g) mammals, birds and chelid tortoises. The red fox Vulpes vulpes was released successfully in 1871. Evidence for cat-impact is largely historical and circumstantial, but supported by observations that afflicted native species are, or were, small (<200 g) occupants of open habitat and hence likely to be especially vulnerable to cat predation. The feral cat Felis catus, introduced over 200 years ago, is linked with early continental extinctions of up to seven species of mammals, regional and insular extinctions of many more species of mammals and birds, and the failure of management programs attempting to reintroduce threatened native species to parts of their former ranges. This paper reviews the impacts of three species of introduced mammalian predators on native fauna in Australia.
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