Data from: Fear and lethality in snowshoe hares: the deadly effects of non-consumptive predation risk

Predators play a critical, top-down role in shaping ecosystems, driving prey population and community dynamics. Traditionally, studies of predator-prey interactions have focused on direct effects of predators, namely the killing of prey. More recently, the non-consumptive effects of predation risk are being appreciated; e.g., the Ecology of Fear. Prey responses to predation risk can be morphological, behavioural, and physiological, and are assumed to come at a cost to prey fitness. However, few studies have examined the relationship between predation risk and survival in wild animals. We tested the hypothesis that predation risk itself could reduce survival in wild-caught snowshoe hares. We exposed female snowshoe hares to a simulated predator (a trained dog) during gestation only, and measured adult survival and, in surviving females, their ability to successfully wean offspring. We show for the first time in a wild mammal that the risk of predation can itself be lethal. Predation risk reduced adult female survival by 30%, and had trans-generational effects, reducing offspring survival to weaning by over 85% - even though the period of risk ended at birth. As a consequence of these effects the predator-exposed group experienced a decrease in number, while the control group substantially increased. Challenges remain in determining the importance of risk-induced mortality in natural field settings; however, our findings show that non-lethal predator encounters can influence survival of both adults and offspring. Future work is needed to test these effects in free-living animals.

捕食者在生态系统塑造中发挥着至关重要的自上而下调控作用，驱动猎物种群与群落动态变化。传统上，捕食者与猎物的相互作用研究多聚焦于捕食者的直接效应，即猎杀猎物的行为。近年来，捕食风险带来的非消耗性效应（non-consumptive effects）逐渐受到学界重视，例如恐惧生态学（Ecology of Fear）。猎物对捕食风险的响应可表现为形态、行为与生理层面的改变，且这类响应通常被认为会以降低猎物适合度为代价。然而，目前鲜有研究探讨野生动物的捕食风险与存活率之间的关联。本研究针对"捕食风险本身可降低野生美洲兔（snowshoe hare）存活率"这一假说展开验证。研究仅在妊娠期为雌性美洲兔施加模拟捕食者（经训练的犬只）的刺激，并监测其成体存活率，同时统计存活雌性个体成功抚育幼崽至断奶的能力。本研究首次在野生哺乳类动物中证实，捕食风险本身即可致死。捕食风险使雌性成体存活率下降30%，并产生跨代际效应：即便风险暴露期在幼崽出生时即结束，幼崽断奶前的存活率仍降低了85%以上。受上述效应影响，捕食风险暴露组的种群数量出现下降，而对照组种群数量则显著上升。尽管在自然野外环境中量化风险诱导死亡率的重要性仍存在挑战，但本研究结果表明，非致死性的捕食者接触事件可同时影响成体与幼崽的存活率。未来仍需在自由活动的野生动物中验证此类效应。