Data from: Dynamic occupancy modeling reveals a hierarchy of competition among fishers, grey foxes, and ringtails

1. Determining how species coexist is critical for understanding functional diversity, niche partitioning and interspecific interactions. Identifying the direct and indirect interactions among sympatric carnivores that enable their coexistence are particularly important to elucidate because they are integral for maintaining ecosystem function. 2. We studied the effects of removing 9 fishers (Pekania pennanti) on their population dynamics and used this perturbation to elucidate the interspecific interactions among fishers, grey foxes (Urocyon cinereoargenteus), and ringtails (Bassariscus astutus). Grey foxes (family: Canidae) are likely to compete with fishers due to their similar body sizes and dietary overlap, and ringtails (family: Procyonidae), like fishers, are semi-arboreal species of conservation concern. We used spatial capture-recapture to investigate fisher population numbers and dynamic occupancy models that incorporated interspecific interactions to investigate the effects members of these species had on the colonization and persistence of each other’s site occupancy. 3. The fisher population showed no change in density for up to three years following the removals of fishers for translocations. In contrast, fisher site occupancy decreased in the years immediately following the translocations. During this same time period, site occupancy by grey foxes increased and remained elevated through the end of the study. 4. We found a complicated hierarchy among fishers, foxes, and ringtails. Fishers affected grey fox site persistence negatively but had a positive effect on their colonization. Foxes had a positive effect on ringtail site colonization. Thus, fishers were the dominant small carnivore where present and negatively affected foxes directly and ringtails indirectly. 5. Coexistence among the small carnivores we studied appears to reflect dynamic spatial partitioning. Conservation and management efforts should investigate how intraguild interactions may influence the recolonization of carnivores to previously occupied landscapes.

1. 阐明物种共存机制，对于理解功能多样性（functional diversity）、生态位分化（niche partitioning）以及种间相互作用至关重要。明确同域食肉动物之间助力其共存的直接与间接相互作用尤为关键，因为这些相互作用对于维持生态系统功能不可或缺。
2. 本研究通过移除9只渔貂（Pekania pennanti），探究其对渔貂种群动态的影响，并利用这一扰动实验阐明渔貂、灰狐（Urocyon cinereoargenteus）与蓬尾浣熊（Bassariscus astutus）之间的种间相互作用。灰狐隶属于犬科（Canidae），因其体型与渔貂相近、食性存在重叠，大概率与渔貂存在种间竞争；而蓬尾浣熊与渔貂同属半树栖的具有保护意义的物种，二者均隶属于浣熊科（Procyonidae）。本研究采用空间捕获-重捕法（spatial capture-recapture）估算渔貂种群数量，并构建纳入种间相互作用项的动态占用模型（dynamic occupancy models），以分析这三类物种种群成员对彼此位点占用的定殖与存续过程的影响。
3. 用于迁地保护的渔貂移除实验完成后的三年内，渔貂种群密度未发生显著变化。与之相反，渔貂的位点占用率在迁地移植后的数年内出现下降。与此同时，灰狐的位点占用率持续上升，并在整个研究周期内维持在较高水平。
4. 本研究揭示了渔貂、灰狐与蓬尾浣熊之间存在复杂的种间等级关系：渔貂对灰狐的位点存续具有负向调控作用，却对其位点定殖存在正向影响；灰狐则对蓬尾浣熊的位点定殖具有正向作用。由此可见，在分布区内渔貂为优势小型食肉动物，可直接抑制灰狐种群，并间接影响蓬尾浣熊种群。
5. 本研究涉及的小型食肉动物之间的共存模式，似乎通过动态空间分区得以实现。未来的保护与管理工作应深入探究同营养级种间相互作用如何影响食肉动物对既往占据生境的重新定殖过程。