Broad-scale influence of abiotic and biotic drivers of carnivore occupancy in Washington state

Travis Wade King

In Washington, the threatened Canada lynx (Lynx canadensis) is a sensitive indicator species at risk to the impacts of climate change. Despite this threat, our understanding of current lynx distribution in Washington is incomplete. To gain a better understanding of the impact of biotic and abiotic drivers on large-scale lynx occupancy patterns, we conducted the largest systematic survey of lynx in Washington to date, utilizing a camera-trapping array covering 7000 km2 of predicted lynx habitat. We used the resulting broad-scale database to develop single-season occupancy models that indicate the influence of abiotic and biotic drivers on current statewide patterns of lynx occupancy. Our results show lynx occupancy in Washington is restricted and dictated largely by abiotic factors, disturbance regimes, and distance from source populations in Canada. Future predictions demonstrate a substantial northward retraction of lynx range in Washington by 2100. Our results help inform state and federal discussion of lynx status, and our methodology could form the basis for a long-term monitoring framework for this species. Biotic interactions may influence species distribution patterns, though the scale to which these interactions act is in debate. The biological paradigm is that over broad spatial extents abiotic covariates dominate species distribution while biotic interactions act primarily at local scales. However, the majority of field studies are conducted over fairly small spatial or temporal scales, limiting strength of inference. Using our 7000 km2 camera trapping study on lynx in Washington, we examined the the relative influence of biotic vs. abiotic drivers on distribution patterns of seven carnivore species across a broad spatial extent, and at two different spatial grains using rigorous single and two-species occupancy models. Our single season results demonstrate that at broad spatial extents distributions are largely dictated by abiotic factors and that as grain size of analysis is increased the importance of biotic factors relatively decreases. However, in the majority of the two-species models, interspecific carnivore interactions still impact occupancy and detection patterns regardless of grain size. Our work demonstrates the need for the consideration of interspecific interactions in broad-scale distribution models, at least in regards to mammalian carnivores.

Broad-scale influence of abiotic and biotic drivers of carnivore occupancy in Washington state

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