Australia's wildlife is being considerably impacted by introduced mammalian predators such as cats (Felis catus), dogs (Canis lupus familiaris), and foxes (Vulpes vulpes). This is often attributed to native wildlife being naïve to these introduced predators. A systematic review of the literature reveals that native metatherians (body mass range 0.02–25 kg) do not recognise, and show relaxed antipredator behaviours towards, native and some introduced mammalian predators. Native eutherians (all with body mass < 2 kg), however, do appear to recognise and exhibit antipredator behaviours towards both native and introduced predators. Based on our findings, we propose a novel theory, the ‘Relaxed Predation Theory’. Our new theory is based on the absence of large mammalian predators leading to reduced predation pressure in Australia during the past 40000–50000 years, and on three key differences between Australian metatherians and eutherians: size, sex, and brains. In light of this Relaxed Predation Theory, we make a number of recommendations for the conservation of Australian wildlife: (i) predator avoidance training of suitable species; (ii) exclusion fencing to exclude some, but not all, predators to facilitate the development of antipredator behaviours; (iii) captive breeding programs to prevent the extinction of some species; and (iv) reintroduction of Australia's larger predators, potentially to compete with and displace introduced predators. A more detailed understanding of the responses of Australian mammals to predators will hopefully contribute to the improved conservation of susceptible species.

中文翻译：

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宽松的捕食理论：大小、性别和大脑很重要

澳大利亚的野生动物正受到引入的哺乳动物捕食者的极大影响，例如猫 (Felis catus)、狗 (Canis lupus熟悉) 和狐狸 (Vulpes vulpes)。这通常归因于本地野生动物对这些引入的捕食者的幼稚。对文献的系统回顾表明，本地的后兽类动物（体重范围 0.02-25 公斤）不识别本地和一些引入的哺乳动物捕食者，并表现出放松的反捕食者行为。然而，本土真兽类动物（体重均小于 2 公斤）似乎确实能够识别并表现出对本土和外来掠食者的反捕食行为。基于我们的发现，我们提出了一种新的理论，即“放松捕食理论”。我们的新理论基于在过去 40000-50000 年间澳大利亚没有大型哺乳动物捕食者导致捕食压力降低，以及澳大利亚超兽类和真兽类之间的三个主要差异：体型、性别和大脑。根据这种宽松捕食理论，我们为保护澳大利亚野生动物提出了一些建议：(i) 适当物种的捕食者回避训练；(ii) 排除围栏以排除一些（但不是全部）捕食者，以促进反捕食者行为的发展；(iii) 防止某些物种灭绝的圈养繁殖计划；(iv) 重新引入澳大利亚较大的食肉动物，有可能与引入的食肉动物竞争并取代它们。