Temperature driven density gradients of two congeneric felids reveal contrasting responses to climate change at a range margin.

Climate change causes divergent range shifts in cold versus warm-tolerant species, potentially reshuffling biotic interactions at range margins. Yet, outside of coarse distributional metrics, little information exists regarding the ecology of species along range peripheries. Here, we use camera traps and spatially-explicit-capture-recapture (secr) modeling to examine how climatic gradients influence current and future patterns of density, abundance, and density overlap between two congeneric felids - cold-adapted Canada lynx (Lynx canadensis) and warm-adapted bobcats (Lynx rufus) - at a range margin in Washington, United States. Temperature drove density patterns along the range margin, with lynx densities declining and bobcat densities increasing as a function of temperature. Future abundances, obtained via projection of current-day models onto future climate scenarios, declined for lynx but were stable for bobcats, with both species experiencing upward elevational shifts. Areas of the landscape with high-lynx and low-bobcat densities declined in the future, but areas with low-lynx and high-bobcat densities increased, with only limited high-elevation refugia for lynx from expanding bobcat populations. Our approach reveals how temperature gradients shape density patterns of cold and warm-tolerant mammals and could be applied to other species and montane systems to better understand mammalian population trajectories and spatial associations at range edges.