Distinctive diets of eutherian predators in Australia

Introduction of the domestic cat and red fox has devastated Australian native fauna. We synthesized Australian diet analyses to identify traits of prey species in cat, fox and dingo diets, which prey were more frequent or distinctive to the diet of each predator, and quantified dietary overlap. Nearly half (45%) of all Australian terrestrial mammal, bird and reptile species occurred in the diets of one or more predators. Cat and dingo diets overlapped least (0.64 ± 0.27, n = 24 location/time points) and cat diet changed little over 55 years of study. Cats were more likely to have eaten birds, reptiles and small mammals than foxes or dingoes. Dingo diet remained constant over 53 years and constituted the largest mammal, bird and reptile prey species, including more macropods/potoroids, wombats, monotremes and bandicoots/bilbies than cats or foxes. Fox diet had greater overlap with both cats (0.79 ± 0.20, n = 37) and dingoes (0.73 ± 0.21, n = 42), fewer distinctive items (plant material, possums/gliders) and significant spatial and temporal heterogeneity over 69 years, suggesting the opportunity for prey switching (especially of mammal prey) to mitigate competition. Our study reinforced concerns about mesopredator impacts upon scarce/threatened species and the need to control foxes and cats for fauna conservation. However, extensive dietary overlap and opportunism, as well as low incidence of mesopredators in dingo diets, precluded resolution of the debate about possible dingo suppression of foxes and cats

Reptiles as food: Predation of Australian reptiles by introduced red foxes compounds and complements predation by cats

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

Counting the bodies: Estimating the numbers and spatial variation of Australian reptiles, birds and mammals killed by two invasive mesopredators

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

Impact and response: a review of the effects of fire on the Australian avifauna

The literature concerning the impact of fire on avian communities and the response of birds to fire is reviewed for the Australian continent. There are few detailed long-term studies of the effects of fire on avian communities, but there is sufficient information on fire effects from a broad cross-section of Australian habitats to identify patterns of response to individual fires and to predict likely long-term effects. Some birds respond immediately to fire, taking advantage of temporarily increased availability of food. These birds include predators that are attracted to fires to feed on exposed, disoriented and fire-killed prey and seed-eaters that congregate in burnt habitats to feed on seeds released by the fire or on the seeds of rapidly maturing post-fire ephemerals. At least in eucalypt forests, there is an increase of arthropod abundance on the rapidly regenerating vegetation that may lead to increased abundances of some bird species. Depending on the severity of the fire and the amount of vegetation killed, most avian communities recover rapidly following single fires regardless of fire intensity. However, such fires may pose a significant threat to species with a restricted distribution, limited reproductive potential, poor dispersal ability and/or narrow habitat requirements. Birds persisting in fragmented habitats are particularly at risk. However, of greatest significance as a threatening process to avian communities are increases in fire frequency. Of the threatened species in Australia whose relationships with fire have been comparatively well-documented, almost all show a clear preference for less frequent fires. Detrimental fire regimes contributed to the extinction of two of the three bird species and three of the four subspecies which have disappeared from Australia since European colonization. Inappropriate fire management is now a factor in the threatened status of at least 51 nationally recognized threatened Australian bird taxa. In many environments (notably heath and mallee), inappropriate fire regimes are the main threat to declining bird species. In temperate eucalypt forest and woodland, as well as in heathlands, control burning is widely used to reduce the threat of wildfire. While, in general, the immediate impact of controlled burns is less than that of wildfire, the frequency of these fires can lead to floristic and structural changes in the vegetation. Although not well-documented, these vegetative changes adversely affect the avifauna. In Australia, the most detailed long-term studies suggest that frequent, low-intensity fires may lead to the decline and loss of some species which are now perceived as common and little affected by mild fires

Declines in the mammal assemblage of a rugged sandstone environment in Kakadu National Park, Northern Territory, Australia

There has been marked recent decline in the terrestrial mammal fauna across much of northern Australia, with most documentation of such decline for lowland areas. Here we report changes in the assemblage of small mammals in a rugged sandstone environment (Nawurlandja, in Kakadu National Park) over intermittent sampling between 1977 and 2002. Four native mammal species were commonly recorded in the original sampling: sandstone antechinus (Pseudantechinus bilarni), northern quoll (Dasyurus hallucatus), Arnhem rock-rat (Zyzomys maini) and common rock-rat (Z. argurus). Trap success rates declined significantly for the northern quoll, Arnhem rock-rat and all species combined, but increased for the common rock-rat. Despite being recorded commonly in the initial (1977–79) study, no Arnhem rock-rats were recorded in the most recent (2002) sampling. Trap success rates for northern quoll declined by ~90% from 1977–79 to 2002. The reasons for change are not clear-cut. Notably, all sampling occurred before the arrival of cane toads (Rhinella marina), a factor that has caused severe decline in northern quoll numbers elsewhere. Fire was more frequent in the sampling area in the period preceding the 2002 sampling than it was in the period preceding the initial (1977–79) sampling, and this may have contributed to change in mammal abundance.The 1994 resampling was funded by the Australian National University and a Commonwealth Postgraduate Research Award (to MO)

Evaluating the status of species using Indigenous knowledge: novel evidence for major native mammal declines in northern Australia

A small series of recent monitoring studies has reported major declines for many native mammal species in localised regions in northern Australia. However, the broader spatial context of these studies is uncertain. This study aims to assess the extent and timing of change in mammal status across a broad area of northern Australia (the monsoonal tropics of the Northern Territory). Indigenous information about terrestrial native mammal fauna (excluding bats) was compiled from a large series of interviews conducted across Indigenous communities. A collection of mammal skins was used to help facilitate discussions and verify identifications. The resulting information was analysed with non-parametric statistics to test for changes in mammal status across different time periods, between different regions, and between different groups of mammal species. Declines were reported as extending from the earliest memory of Indigenous participants, but the rate of decline has increased recently. These changes were reported across all five regions within the broad study area and were greater for "critical weight range" species than for other species. Indigenous participants suggested several factors were associated with the changing status of species. The study's results reveal a pattern of widespread decline in the mammal fauna of the monsoonal tropics of northern Australia, thereby corroborating the conclusions of recent more local wildlife monitoring studies. The study also demonstrates the value and capability of Indigenous ecological knowledge to complement and corroborate more intensive and local scientific studies. The results reinforce concern for the conservation status of the mammal fauna of northern Australia

Evaluating the status of species using Indigenous knowledge: Novel evidence for major native mammal declines in northern Australia

A small series of recent monitoring studies has reported major declines for many native mammal species in localised regions in northern Australia. However, the broader spatial context of these studies is uncertain. This study aims to assess the extent and timing of change in mammal status across a broad area of northern Australia (the monsoonal tropics of the Northern Territory). Indigenous information about terrestrial native mammal fauna (excluding bats) was compiled from a large series of interviews conducted across Indigenous communities. A collection of mammal skins was used to help facilitate discussions and verify identifications. The resulting information was analysed with non-parametric statistics to test for changes in mammal status across different time periods, between different regions, and between different groups of mammal species. Declines were reported as extending from the earliest memory of Indigenous participants, but the rate of decline has increased recently. These changes were reported across all five regions within the broad study area and were greater for " critical weight range" species than for other species. Indigenous participants suggested several factors were associated with the changing status of species. The study's results reveal a pattern of widespread decline in the mammal fauna of the monsoonal tropics of northern Australia, thereby corroborating the conclusions of recent more local wildlife monitoring studies. The study also demonstrates the value and capability of Indigenous ecological knowledge to complement and corroborate more intensive and local scientific studies. The results reinforce concern for the conservation status of the mammal fauna of northern Australia