Data from: Do the antipredator strategies of shared prey mediate intraguild predation and mesopredator suppression?

Understanding the conditions that facilitate top predator effects upon mesopredators and prey is critical for predicting where these effects will be significant. Intraguild predation (IGP) and the ecology of fear are hypotheses used to describe the effects of top predators upon mesopredators and prey species, but make different assumptions about organismal space use. The IGP hypothesis predicts that mesopredator resource acquisition and risk are positively correlated, creating a fitness deficit. But if shared prey also avoid a top predator, then mesopredators may not have to choose between risk and reward. Prey life history may be a critical predictor of how shared prey respond to predation and may mediate mesopredator suppression. We used hierarchical models of species distribution and abundance to test expectations of IGP using two separate triangular relationships between a large carnivore, smaller intraguild carnivore, and shared mammalian prey with different life histories. Following IGP, we expected that a larger carnivore would suppress a smaller carnivore if the shared prey species did not spatially avoid the large carnivore at broad scales. If prey were fearful over broad scales, we expected less evidence of mesopredator suppression. We tested these theoretical hypotheses using remote camera detections across a large spatial extent. Lagomorphs did not appear to avoid coyotes, and fox detection probability was lower as coyote abundance increased. In contrast, white-tailed deer appeared to avoid areas of increased wolf use, and coyote detection probability was not reduced at sites where wolves occurred. These findings suggest that mesopredator suppression by larger carnivores may depend upon the behavior of shared prey, specifically the spatial scale at which they perceive risk. We further discuss how extrinsic environmental factors may contribute to mesopredator suppression.

明确能够促进顶级捕食者（top predator）对中捕食者（mesopredator）与猎物产生调控效应的条件，对于预测此类效应的显著作用场景至关重要。种内捕食（intraguild predation, IGP）与恐惧生态学（ecology of fear）是用于阐释顶级捕食者对中捕食者及猎物物种产生影响的两大核心假说，但二者对于生物体的空间利用模式存在截然不同的假设。IGP假说预测，中捕食者的资源获取效率与被捕食风险呈正相关，进而造成适合度赤字。但若共享猎物同时也会主动规避顶级捕食者，则中捕食者无需在捕食风险与收益回报之间做出权衡。猎物的生活史特征或许是预判共享猎物如何响应捕食压力、并介导中捕食者受抑制程度的关键因素。我们采用物种分布与丰度的层级模型（hierarchical models of species distribution and abundance），通过两组独立的、涵盖大型食肉动物、小型集团内食肉动物（intraguild carnivore）与具有不同生活史特征的共享哺乳类猎物的三角捕食关系，对IGP假说的理论预期进行验证。依据IGP假说，若共享猎物在大空间尺度上未对大型食肉动物产生空间规避行为，则大型食肉动物会对小型集团内食肉动物产生抑制效应；若猎物在大尺度范围内表现出恐惧规避行为，则观测到中捕食者受抑制的证据将相对薄弱。我们依托大范围空间尺度内的远程相机监测（remote camera detections）数据对上述理论假说开展检验。结果显示，兔形目动物（Lagomorphs）未表现出对郊狼（coyotes）的空间规避行为，且随着郊狼丰度提升，狐类的物种检测概率显著降低。与之形成鲜明对比的是，白尾鹿（white-tailed deer）会规避狼活动频率较高的区域，而在狼存在的样地中，郊狼的检测概率并未出现下降。上述研究结果表明，大型食肉动物对中捕食者的抑制效应，或许取决于共享猎物的行为模式，尤其是它们感知捕食风险的空间尺度。我们还进一步探讨了外在环境因素如何对中捕食者的抑制效应产生调控作用。