Data from: Prey responses to foxes are not determined by nativeness

Introduced predators are thought to be responsible for the decline and extinction of their native prey. The prey naivety hypothesis provides a mechanism for these declines, suggesting that native prey are vulnerable to introduced predators as their coevolutionary history is insufficiently long for antipredator behaviours to fully develop. The prey naivety hypothesis thus predicts that prey will be less responsive to introduced predators than to native predators. Australia's endemic small mammals are thought to be vulnerable to predation by red foxes because they are less responsive to – or naive to – a predator with whom they have only co-occurred since the 19th century. To test whether nativeness determines antipredator behaviours we compared small mammal behavioural responses to fox scent outside (Australia) and inside the foxes' native range (North America and Israel). We conducted giving-up density experiments in the deserts of these three regions and evaluated small mammal anti-predator responses to fox scent. To place these results in a broader context, we then integrated our results into a meta-analysis of studies assessing prey responsiveness to fox scent. All small mammals similarly increased their vigilance in response to fox scent, regardless of their coevolutionary history with foxes. Australian small mammals responded with greater wariness to fox scent, by decreasing time at food patches in response to fox scent more than Israeli and American small mammals did. However, we found no evidence that this behaviour influenced foraging as nut consumption was unaffected. Our meta-analysis revealed that globally, small mammals respond with similar wariness to fox scent regardless of whether foxes are their native predator. We found no evidence that Australian small mammals respond in a maladaptive manner, compared to the foxes' native prey. Our results suggest that animals can develop antipredator behaviours to introduced predators to the same magnitude as native prey.

外来捕食者被认为是导致本土猎物种群衰退乃至灭绝的关键因素。猎物幼稚假说（prey naivety hypothesis）为这类种群衰退提供了理论机制：本土猎物与外来捕食者的协同演化历史过短，尚未演化出完整的反捕食行为，因此极易受到外来捕食者的攻击。据此，猎物幼稚假说预测，相较于本土捕食者，猎物对外来捕食者的响应程度会更低。澳大利亚特有小型哺乳动物被认为极易受到赤狐的捕食，因为它们仅在19世纪才与该捕食者产生共存关系，因此对赤狐的响应程度较低，甚至对其完全陌生。为验证猎物是否会因与捕食者的本土共存关系差异而呈现不同的反捕食行为，本研究对比了赤狐原生分布区（北美与以色列）与非原生分布区（澳大利亚）内小型哺乳动物对赤狐气味的行为响应。我们在上述三个区域的荒漠生境中开展了放弃密度（giving-up density）实验，以此评估小型哺乳动物对赤狐气味的反捕食响应。为将本研究结果置于更广阔的学术语境中，我们将实验数据整合至一项针对猎物赤狐气味响应的元分析中。所有受试小型哺乳动物均会因赤狐气味提升警戒水平，且该响应不受二者协同演化历史的影响。但澳大利亚小型哺乳动物对赤狐气味表现出更强的警惕性：相较于以色列与北美小型哺乳动物，它们会在有赤狐气味的食物斑块中停留更短的时间。不过，研究未发现该行为会对觅食活动产生影响，因为坚果取食量并未发生显著变化。元分析结果显示，全球范围内的小型哺乳动物对赤狐气味的警惕性响应均无显著差异，无论赤狐是否为其本土捕食者。相较于赤狐的本土猎物，我们未发现澳大利亚小型哺乳动物的响应存在适应不良的情况。本研究结果表明，动物可以对外来捕食者演化出与本土猎物同等程度的反捕食行为。