Does fear beget fear? Risk-mediated habitat selection triggers predator avoidance at lower trophic levels
Does fear beget fear? Risk-mediated habitat selection triggers predator avoidance at lower trophic levels
复制标题
恐惧会引发恐惧吗？
作者：
C. Blubaugh;Ivy V. Widick;I. Kaplan
捕食者的非消耗性效应在食物网中普遍存在，并在多个层次上对营养级联产生了详细的影响。然而，将NCE与其他捕食者介导的相互作用，如intraguild捕食，以及特定环境的栖息地因素，形状自上而下的压力，仍然是一个挑战。重点介绍了两种常见的种子捕食者，小鼠（Peromyscus spp.）和步甲甲虫（鞘翅目：步甲科），我们量化的营养和行为后果的捕食风险和避难所植被的可用性intraguild捕食者（小鼠）和intraguild猎物（甲虫）。在为期2年的实地实验中，我们操纵避难所栖息地（红三叶草），小型哺乳动物访问，和月光，小型哺乳动物使用的捕食风险的间接线索。我们发现，避免捕食风险的小鼠在模拟月光减少步甲活动密度在植被中暴露的栖息地相比，高达50%，但没有级联效应的种子捕食。我们通过观察甲虫觅食活动，将现场观察到的模式与行为机制联系起来，发现暴露于间接和直接的脊椎动物捕食者线索减少了50%的运动，与现场观察到的捕食者介导的活动减少一致。然而，捕食风险增加了43%的步甲种子消费。因此，弱的影响，捕食风险种子去除在外地可以解释由超补偿种子喂养甲虫。这项工作表明，捕食者引起的反应，级联在多个营养水平，触发行为的变化，在物种的食物链较低。这些行为介导的级联控制的时空背景下，有重要的下游影响捕食者-猎物动态。
Non-consumptive effects (NCEs) of predators are ubiquitous in food webs with well-detailed impacts on trophic cascades over multiple levels. However, integrating NCEs with other predator–mediated interactions, like intraguild predation, as well as context-specific habitat factors that shape top–down pressure, remains a challenge. Focusing on two common seed predators, mice (Peromyscus spp.) and carabid beetles (Coleoptera: Carabidae), we quantify trophic and behavioral consequences of predation risk and availability of refuge vegetation on both intraguild predators (mice) and intraguild prey (beetles). In a 2-year field experiment, we manipulated refuge habitat (red clover), small mammal access, and moonlight, which small mammals use as an indirect cue of predation risk. We found that avoidance of predation risk by mice in simulated moonlight reduced carabid activity density in vegetation by up to 50% compared to exposed habitat, but had no cascading effects on seed predation. We linked patterns observed in the field with behavioral mechanisms by observing beetle foraging activity, and found that exposure to both indirect and direct vertebrate predator cues reduced movement by 50%, consistent with predator–mediated activity reductions observed in the field. However, predation risk increased carabid seed consumption by 43%. Thus, weak effects of predation risk on seed removal in the field may be explained by overcompensatory seed feeding by beetles. This work demonstrates that predators elicit responses that cascade over multiple trophic levels, triggering behavioral changes in species lower on the food chain. These behavior-mediated cascades are controlled by their spatiotemporal context and have important downstream impacts on predator–prey dynamics.