Abstract

The impacts of invasive predators can be amplified by high densities of invasive prey species. In Australia, hyper abundant rabbit populations lead to high densities of feral cats and correspondingly high impact of cats on native species, especially small mammals. Therefore, it would be expected reducing rabbits could also reduce abundance of cats, and thereby alleviate predation on native small mammals. However, cats might respond to the loss of rabbits by prey-switching to native small mammals, resulting in increased predation on those species. Our aim was to understand the short-term effects of an experimental reduction of rabbit abundance on feral cats and their small-mammal prey in arid South Australia. We reduced the rabbit population in a 37 km² experimental enclosure by ~ 80%, while monitoring an adjacent unmanipulated area as a control. Cat activity and survival of VHF-collared cats in the enclosure decreased by 40% following the rabbit reduction. Surviving cats increased their consumption of reptiles, birds and invertebrates, but they nevertheless evinced hunger by increased intake of experimentally-supplied sausages. There was no change in either the proportion of cat scats that contained remains of small mammals, or the rate at which video-collared cats were recorded killing small mammals, even though the activity of small mammals declined. Our results demonstrate that individual feral cats prey-switch in response to removal of their primary prey. However, we also show that survival and overall activity of cats decreased, which could result in net, long-term benefits for native prey threatened by cats. Management of feral cats using food lures or baits would also be more effective when introduced prey are scarce, as cats are more likely to eat novel food.

中文翻译：

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野猫对兔子种群减少的短期反应：替代性本地猎物是否更有风险？

摘要

入侵性掠食物种的高密度可以扩大入侵性掠食者的影响。在澳大利亚，过高的兔子种群导致高密度的野生猫科动物以及相应的猫科动物对本地物种（尤其是小型哺乳动物）的高影响。因此，可以预期，减少兔子的数量也会减少猫的数量，从而减轻对本地小型哺乳动物的捕食。但是，猫可能会通过将猎物切换到本地小型哺乳动物来应对兔子的损失，从而导致对这些物种的捕食增加。我们的目的是了解在干旱的南澳大利亚，实验性减少兔子的数量对野猫及其小型哺乳动物猎物的短期影响。我们在37 km ^2内减少了兔子的数量实验围栏约80％，同时监控相邻的未操纵区域作为对照。兔子减少后，围场中有VHF领猫的猫的活动和存活率降低了40％。幸存的猫咪增加了对爬行动物，鸟类和无脊椎动物的消费，但是通过增加实验提供的香肠的摄入量却可以消除饥饿感。即使小型哺乳动物的活动减少了，包含小型哺乳动物遗体的猫粪的比例也没有变化，或者记录有视频的猫杀死小型哺乳动物的比率没有变化。我们的结果表明，单个野猫的猎物会根据其主要猎物的去除而进行切换。但是，我们还表明，猫的生存率和总体活动能力下降，这可能导致猫的净 受猫威胁的本地猎物的长期利益。当猎物稀少时，使用食物诱饵或诱饵管理野猫也将更为有效，因为猫更容易吃新食物。