Can native predators be used as a stepping stone to reduce prey naivety to novel predators?

Predator naivety negatively affects reintroduction success and this threat is exacerbated when prey encounters predators with which they have had no evolutionary experience. While methods have been developed to inculcate fear into such predator-naïve individuals, none have been uniformly successful. Exposing ontogenetically- and evolutionary-naïve individuals firstly to native predators may be an effective stepping stone to improved responses to evolutionarily novel predators. We focused on greater bilbies (Macrotis lagotis) and capitalised on a multi-year mammalian recovery experiment whereby western quolls (Dasyurus geoffroii) were reintroduced into parts of a large fenced reserve that contained a population of naïve bilbies. We quantified a suite of antipredator behaviours and measures of general wariness across quoll-exposed and quoll-naive bilby populations. We then translocated both quoll-exposed and quoll-naïve individuals into a large enclosure that contained feral cats (Felis catus) and monitored several behaviours. We found that bilbies can respond appropriately to quolls but found only limited support that experience with quolls better prepared bilbies to respond to cats. Both populations of bilbies rapidly modified their behaviour in a similar manner following their reintroduction to a novel environment. These results may have emerged due to insufficient prior exposure to quolls, inappropriate behavioural tests or insufficient predation risk during cat exposure. Alternatively, quolls and cats are only distantly related and may not share sufficient similarities in their predatory cues or behaviour to support such a learning transfer. Testing this stepping stone hypothesis with more closely-related predator species and under higher predation risk would be informative.

捕食者经验缺失（predator naivety）会对物种重新引入的成功率产生负面影响，当猎物遭遇与其未曾经历协同进化的捕食者时，这一威胁还会进一步加剧。尽管已有研究开发出向此类缺乏捕食者经验的个体灌输恐惧反应的方法，但尚未有方案能实现普适性成功。先让个体发育与进化层面均缺乏捕食者经验的个体接触本土捕食者，或许是提升其应对进化性陌生捕食者反应能力的有效阶梯式策略。
本研究以兔耳袋狸（Macrotis lagotis，英文俗名greater bilby）为研究对象，依托一项多年期哺乳动物恢复实验开展工作：该实验将西袋鼬（Dasyurus geoffroii，英文俗名western quoll）重新引入一处大型围栏保护区的部分区域，该保护区内栖息着一群缺乏捕食者经验的兔耳袋狸。研究人员量化了接触过西袋鼬与未接触西袋鼬的兔耳袋狸种群的一系列反捕食行为，以及一般性警惕性指标。随后，研究人员将接触过西袋鼬与未接触西袋鼬的兔耳袋狸个体分别转移至一处栖息有流浪猫（Felis catus，英文俗名feral cat）的大型围栏圈养区域，并对其多项行为进行监测。
研究结果显示，兔耳袋狸能够对西袋鼬做出恰当的反捕食反应，但关于接触西袋鼬能够帮助兔耳袋狸更好应对流浪猫这一假说，本研究仅提供了有限的支撑证据。两类兔耳袋狸种群在被重新引入全新环境后，均以相似的模式快速调整了自身行为。出现上述研究结果的原因可能包括：对西袋鼬的预暴露时长不足、行为测试方案不够恰当，或是在流浪猫共存阶段的捕食风险强度不足。另一种可能性是，西袋鼬与流浪猫的亲缘关系较远，二者在捕食信号或行为模式上缺乏足够的相似性，无法支撑这种学习迁移效应。后续可选用亲缘关系更近的捕食者物种，并在更高捕食风险条件下对该阶梯式策略假说开展验证，以获得更具参考价值的结论。