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Recolonization of the Cascade Range in southern British Columbia, Canada, and Washington, USA, by wolverines ( Gulo gulo (L., 1758)) is an ongoing process whose ultimate outcome is unknown. A reliable species distribution model for the wolverine in the Cascades (i.e., their first-order habitat selection) is urgently needed to help inform management and conservation strategies. Using Argos location data obtained on 10 resident adult wolverines (six females, four males) from 2008 to 2016, we generated a multi-covariate species distribution model for the wolverine in the Cascades. Our final model included three climatic covariates and their quadratic terms: Proximity to the Transitional Zone Near Alpine Tree Line, Number of Frost-free Days per Year, and Annual Precipitation as Snow. Model validations indicated that our model was robust and could identify areas of potential wolverine distribution in the Cascades reliably. Our model provides evidence that wolverine distribution in the Cascades is constrained by climatic conditions and that snowy and cold environments define the geographic areas that are overwhelmingly associated with resident wolverines. In addition, our model provides a reliable basis for monitoring the direct effects of climate change on wolverines in the Cascade Range and for predicting the extent to which climate change may impact their populations under various scenarios.

We propose a fundamental geographic distribution for the wolverine ( Gulo gulo (L., 1758)) based on the hypothesis that the occurrence of wolverines is constrained by their obligate association with persistent spring snow cover for successful reproductive denning and by an upper limit of thermoneutrality. To investigate this hypothesis, we developed a composite of MODIS classified satellite images representing persistent snow cover from 24 April to 15 May, which encompasses the end of the wolverine’s reproductive denning period. To investigate the wolverine’s spatial relationship with average maximum August temperatures, we used interpolated temperature maps. We then compared and correlated these climatic factors with spatially referenced data on wolverine den sites and telemetry locations from North America and Fennoscandia, and our contemporary understanding of the wolverine’s circumboreal range. All 562 reproductive dens from Fennoscandia and North America occurred at sites with persistent spring snow cover. Ninety-five percent of summer and 86% of winter telemetry locations were concordant with spring snow coverage. Average maximum August temperature was a less effective predictor of wolverine presence, although wolverines preferred summer temperatures lower than those available. Reductions in spring snow cover associated with climatic warming will likely reduce the extent of wolverine habitat, with an associated loss of connectivity.