Data from: Fatal attraction? Intraguild facilitation and suppression among predators

Competition and suppression are recognized as dominant forces that structure predator communities. Facilitation via carrion provisioning, however, is a ubiquitous interaction among predators that could offset the strength of suppression. Understanding the relative importance of these positive and negative interactions is necessary to anticipate community-wide responses to apex predator declines and recoveries worldwide. Using state-sponsored wolf (Canis lupus) control in Alaska as a quasi-experiment, we conducted snow track surveys of apex, meso-, and small predators to test for evidence of carnivore cascades (e.g., mesopredator release). We analyzed survey data using an integrative occupancy and structural equation modeling framework to quantify the strengths of hypothesized interaction pathways, and we evaluated fine-scale spatiotemporal responses of non-apex predators to wolf activity clusters identified from radio-collar data. Contrary to the carnivore cascade hypothesis, both meso- and small predator occupancy patterns indicated guild-wide, negative responses of non-apex predators to wolf abundance variations at the landscape scale. At the local scale, however, we observed a near guild-wide, positive response of non-apex predators to localized wolf activity. Local-scale association with apex predators due to scavenging could lead to landscape patterns of mesopredator suppression, suggesting a key link between occupancy patterns and the structure of predator communities at different spatial scales.

竞争与抑制是塑造捕食者群落结构的主导性驱动力。然而，通过腐食资源介导的促进作用是捕食者类群中普遍存在的种间相互作用，可抵消抑制作用的强度。明确这两类正负相互作用的相对重要性，对于预测全球范围内顶级捕食者种群衰退与恢复所引发的群落级响应至关重要。本研究以阿拉斯加地区官方主导的狼（Canis lupus）防控项目作为准实验平台，针对顶级捕食者、中型捕食者与小型捕食者开展雪面足迹调查，以检验食肉动物级联效应（carnivore cascades，例如中型捕食者释放效应（mesopredator release））是否存在。本研究采用整合占据率模型与结构方程模型的分析框架对调查数据进行解析，以量化假说中各相互作用通路的强度；同时基于无线电项圈监测得到的狼活动集群数据，评估了非顶级捕食者的精细尺度时空响应模式。与食肉动物级联效应假说相悖的是，在景观尺度下，中型与小型捕食者的占据率模式均显示，非顶级捕食者类群整体对狼种群丰度变化呈现负响应。但在局域尺度上，非顶级捕食者类群整体对局域狼活动则呈现近乎全面的正响应。由于食腐行为带来的与顶级捕食者的局域关联，可能会在景观尺度上形成中型捕食者抑制的格局，这表明占据率模式与不同空间尺度下捕食者群落结构之间存在关键关联。