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Aim: Introduced predators negatively impact biodiversity globally, with insular fauna often most severely affected. Here, we assess spatial variation in the number of terrestrial vertebrates (excluding amphibians) killed by two mammalian mesopredators introduced to Australia, the red fox (Vulpes vulpes) and feral cat (Felis catus). We aim to identify prey groups that suffer especially high rates of predation, and regions where losses to foxes and/or cats are most substantial. Location: Australia. Methods: We draw information on the spatial variation in tallies of reptiles, birds and mammals killed by cats in Australia from published studies. We derive tallies for fox predation by (i) modelling continental‐scale spatial variation in fox density, (ii) modelling spatial variation in the frequency of occurrence of prey groups in fox diet, (iii) analysing the number of prey individuals within dietary samples and (iv) discounting animals taken as carrion. We derive point estimates of the numbers of individuals killed annually by foxes and by cats and map spatial variation in these tallies. Results: Foxes kill more reptiles, birds and mammals (peaking at 1071 km−2 year−1) than cats (55 km−2 year−1) across most of the unmodified temperate and forested areas of mainland Australia, reflecting the generally higher density of foxes than cats in these environments. However, across most of the continent – mainly the arid central and tropical northern regions (and on most Australian islands) – cats kill more animals than foxes. We estimate that foxes and cats together kill 697 million reptiles annually in Australia, 510 million birds and 1435 million mammals. Main conclusions: This continental‐scale analysis demonstrates that predation by two introduced species takes a substantial and ongoing toll on Australian reptiles, birds and mammals. Continuing population declines and potential extinctions of some of these species threatens to further compound Australia's poor contemporary conservation record. [ABSTRACT FROM AUTHOR]

The red fox Vulpes vulpes is one of the world's most widespread carnivores. A key to its success has been its broad, opportunistic diet. The fox was introduced to Australia about 150 years ago, and within 30 years of its introduction was already recognised as a threat to livestock and native wildlife.We reviewed 85 fox diet studies (totalling 31693 samples) from throughout the species' geographic range within Australia. Mammals were a major component of fox diet, being present in 70 ± 19% of samples across n = 160 locations. Invertebrates (38 ± 26% n = 130) and plant material (26 ± 25% n = 123) were also both staple foods and often the dominant food category recorded. Birds (13 ± 11% n = 137) and reptiles (10 ± 15% n = 132) were also commonly reported, while frogs were scarcely represented (1.6 ± 3.6% n = 111) in fox diet studies.Biogeographical differences reveal factors that likely determine prey availability. Diet composition varied with ecosystem, level of vegetation clearing and condition, and climate zone.Sample type (i.e. stomach versus scat samples) also significantly influenced reporting of diet composition. Livestock and frogs were underrepresented in records based on analysis of scats, whereas small mammals (native rodents, dasyurid marsupials, and bats) were more likely to be recorded in studies of scats than in studies of stomach contents.Diet varied seasonally, reflecting activity patterns of prey species and food availability. This synthesis also captures temporal shifts in fox diet over 70 years (1951–2020), as foxes have switched to consuming more native species in the wake of successful broadscale biological control of the invasive European rabbit Oryctolagus cuniculus.Diet analyses, such as those summarised in this review, capture the evidence required to motivate for greater control of foxes in Australia. This synthesis also highlights the importance of integrated pest species management to meet biodiversity conservation outcomes. [ABSTRACT FROM AUTHOR]

Context: Invasive species are a major cause of biodiversity loss across much of the world, and a key threat to Australia's diverse reptile fauna. There has been no previous comprehensive analysis of the potential impact of the introduced European red fox, Vulpes vulpes , on Australian reptiles. Aims: We seek to provide an inventory of all Australian reptile species known to be consumed by the fox, and identify characteristics of squamate species associated with such predation. We also compare these tallies and characteristics with reptile species known to be consumed by the domestic cat, Felis catus , to examine whether predation by these two introduced species is compounded (i.e. affecting much the same set of species) or complementary (affecting different groups of species). Methods: We collated records of Australian reptiles consumed by foxes in Australia, with most records deriving from fox dietary studies (tallying >35 000 samples). We modelled presence or absence of fox predation records against a set of biological and other traits, and population trends, for squamate species. Key results: In total, 108 reptile species (~11% of Australia's terrestrial reptile fauna) have been recorded as consumed by foxes, fewer than that reported for cats (263 species). Eighty-six species have been reported to be eaten by both predators. More Australian turtle species have been reported as consumed by foxes than by cats, including many that suffer high levels of predation on egg clutches. Twenty threatened reptile species have been reported as consumed by foxes, and 15 by cats. Squamate species consumed by foxes are more likely to be undergoing population decline than those not known to be consumed by foxes. The likelihood of predation by foxes increased with squamate species' adult body mass, in contrast to the relationship for predation by cats, which peaked at ~217 g. Foxes, but not cats, were also less likely to consume venomous snakes. Conclusions: The two introduced, and now widespread, predators have both compounding and complementary impacts on the Australian reptile fauna. Implications: Enhanced and integrated management of the two introduced predators is likely to provide substantial conservation benefits to much of the Australian reptile fauna. Australia's reptile fauna is rich and distinctive, but many species are declining. This study aimed to review one threat to that fauna, namely, predation by the introduced red fox; we provide an inventory and examine characteristics of reptile species known to be consumed by the introduced red fox, and compare this predation with that of the domestic cat. Enhanced and integrated management of these two introduced predators will benefit many Australian reptile species. Photograph by Stuart Dawson. [ABSTRACT FROM AUTHOR]

Two introduced carnivores, the European red fox Vulpes vulpes and domestic cat Felis catus , have had, and continue to have, major impacts on wildlife, particularly mammals, across Australia. Based mainly on the contents of almost 50,000 fox dietary samples, we provide the first comprehensive inventory of Australian mammal species known to be consumed by foxes, and compare this with a similar assessment for cats. We recorded consumption by foxes of 114 species of Australian land mammal (40% of extant species), fewer than consumed by cats (173 species). Foxes are known to consume 42 threatened mammal species (50% of Australia's threatened land mammals and 66% of those within the fox's Australian range). Reflecting the importance of mammals in their diet, foxes are known to consume a far higher proportion of Australian mammal species (40%) than of Australian birds (24%) and reptiles (16%). Both foxes and cats were most likely to consume medium-sized mammals, with the likelihood of predation by foxes peaking for mammals of ca. 280 g and by cats at ca. 130 g. For non-flying mammals, threatened species had a higher relative likelihood of predation by foxes than non-threatened species. Using trait-based modelling, we estimate that many now-extinct Australian mammal species had very high likelihoods of predation by foxes and cats, although we note that for some of these species, extinction likely pre-dated the arrival of foxes. These two predators continue to have compounding and complementary impacts on Australian mammals. Targeted and integrated management of foxes and cats is required to help maintain and recover the Australian mammal fauna. [ABSTRACT FROM AUTHOR]