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，捕食者与猎物互作的研究多聚焦于捕食者的直接效应，即直接捕杀猎物的行为。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）相关研究。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，目前针对野生动物中捕食风险与存活率间关联的研究仍较为匮乏。本研究针对"捕食风险本身即可降低野生雪兔（snowshoe hare）存活率"这一假说开展验证：研究团队仅在雌性雪兔的妊娠期内，使其暴露于模拟捕食者（经训练的犬只）环境中，并分别测定成年个体存活率，以及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动物中证实，捕食风险本身即可具有致死性。实验结果显示，捕食风险使成年雌性雪兔的存活率降低了30%，且产生了跨代际效应：即使风险暴露期在幼崽出生时即结束，幼崽断奶前的存活率仍下降了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增长。尽管在自然野外环境中量化风险诱导死亡的重要性仍存在挑战，但本研究结果表明，非致命性的捕食者遭遇可同时影响成年个体与幼崽的存活率。未来仍需针对自由活动的野生动物开展相关实验，以验证上述效应。