Suchergebnisse

Context Predation is one of the key contributors to mortality in freshwater turtles. Confirming the identity of predators is an important step towards conservation management action. Throughout Australia, the red fox (Vulpes vulpes) is suspected to apply significant and unsustainable predation pressure to turtle populations, killing adults and depredating nests; however methods for confirming this are limited. Aims The present study used a range of methods to confirm predation of oblong turtle (Chelodina colliei) nests and adults by the introduced red fox. Methods First, depredated adult carapaces, and turtle egg-shell fragments from excavated nests were swabbed and analysed for trace DNA. Second, we used artificial turtle nests, monitored by camera traps, to analyse seasonal changes in the behaviour of foxes around sites where turtle nests are present, including over the nesting season. Last, we used scat analysis to identify the prevalence of turtle remains in fox diet. Key results Predominantly fox DNA was recovered from both adult carapaces and depredated eggs. In addition, camera traps recorded only foxes depredating artificial nests. Despite this evidence that foxes kill adults and excavated nests, we found that turtle remains were only a small part of the diet of foxes at this study site (hatchling or turtle egg shell were present in only 4% of 230 scats sampled). The diet of these foxes was largely anthropogenic-sourced foods, such as fruit (e.g. figs, grapes, melons; 81% of scats), sheep carrion (41%) and rodents (36%). Conclusions We conclude that DNA analysis, camera trapping and scat analysis are effective methods of identifying foxes as predators of adult turtle, and their nests. Furthermore, we found that anthropogenic foods (orchard crops, livestock or synanthropic species) may subsidise greater fox population size than might occur in their absence, thereby increasing potential pressure on these freshwater turtles. Implications Our findings give credence to the argument that foxes are effective predators of turtle adults and nests. In addition, the high proportion of anthropogenic food sources in the diet of foxes, and potential subsidisation, is an important consideration for land managers.

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.