Trophic cascades reportedly structure ecological communities through indirect species interactions. Though the predator–herbivore–autotroph relationship has received much attention, mechanistic evidence supporting intraguild trophic cascades is rare. We established 348 remote camera sites (1 August–5 September 2019) across seven study areas of varying wolf (Canis lupus) density including one study area where wolves were absent in northern Michigan, USA. Using multi-species occupancy modeling at species-relevant spatial scales, we evaluated the hypothesis that increased wolf occurrence suppresses coyote (C. latrans) occurrence with corresponding increased red fox (Vulpes vulpes) occurrence mediated by land cover edge density, human presence, and temporal partitioning. Remote cameras recorded >600,000 images and included 6,370, 10,137, and 4,876 detections of wolves, coyotes, and foxes, respectively. Fox occupancy probability was more than three times as high (0.29) at camera sites where wolves were present, relative to sites wolves were absent (0.09). Pairwise species interactions supported expected size-based dominance patterns among canids and insignificant effects were directionally consistent with reported reduced strength of top-down effects in peripheral wolf range. Increased edge density also increased co-occurrence of coyote and wolves, likely a function of increased prey availability and refugia for coyotes. Though foxes occurred in spatial proximity to wolves, competition was limited by greater temporal partitioning than observed between coyotes and foxes that were spatially segregated. Collectively, our results provide marginal support for the reported trophic cascade among wolves, coyotes, and foxes wherein top-down effects may be reduced near the edge of current wolf distributions. As predators continue to recolonize portions of their historic range, knowledge of the effects on intraguild predators has implications for species management and predicting prey population responses.

中文翻译：

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边缘狼范围内同域犬科动物营养级联的边际支持

据报道，营养级联通过间接物种相互作用构建生态群落。尽管捕食者-食草动物-自养生物的关系受到了很多关注，但支持公会内营养级联的机制证据很少见。我们在七个不同狼（犬狼疮）密度的研究区域建立了 348 个远程摄像头站点（2019 年 8 月 1 日至 9 月 5 日），其中一个研究区域在美国密歇根州北部没有狼。在物种相关的空间尺度上使用多物种占用模型，我们评估了狼出现的增加抑制土狼（C .  latrans）出现与相应增加的红狐（Vulpes vulpes）的假设) 由土地覆盖边缘密度、人类存在和时间分区介导的发生。远程摄像机记录了超过 600,000 张图像，分别包括对狼、土狼和狐狸的 6,370、10,137 和 4,876 次检测。相对于没有狼的站点 (0.09)，在有狼的摄像机站点，狐狸的占用概率高出三倍以上 (0.29)。成对的物种相互作用支持犬科动物中预期的基于大小的优势模式，并且微不足道的影响在方向上与外围狼范围内自上而下影响强度的降低一致。边缘密度的增加也增加了土狼和狼的共同出现，这可能是土狼的猎物可用性和避难所增加的功能。虽然狐狸在空间上接近狼，与在空间上隔离的土狼和狐狸之间观察到的时间分区相比，竞争受到更大的时间分区的限制。总的来说，我们的结果为狼、土狼和狐狸之间报告的营养级联提供了边际支持，其中自上而下的影响可能会在当前狼分布的边缘附近减少。随着捕食者继续重新殖民其历史范围的部分地区，了解对行内捕食者的影响对物种管理和预测猎物种群反应具有影响。