Grizzly Bear Connectivity Mapping in the Canada-U.S. Transborder Region

Fragmentation is a growing threat to wildlife worldwide and managers need solutions to reverse its impacts on species’ populations. Populations of grizzly bears (Ursus arctos), often considered an umbrella and focal species for large mammal conservation, are fragmented by human settlement and major highways in the trans-border region of southern British Columbia, northern Montana, Idaho, and northeastern Washington. We sought to predict preferred linkage habitats for grizzly bears across settled valleys with major highways in the fragmented transborder region to improve prospects for bear movement among 5 small fragmented subpopulations. We estimated a resource selection function (RSF) to identify high quality backcountry core habitat and to predict front-country linkage areas using global positioning system (GPS) telemetry locations from 27 grizzly bears. We used RSF models and data on human presence (building density) to inform cost surfaces for connectivity network analyses identifying linkage areas based on least-cost path, corridor, and circuit theory methods. We identified 60 trans-border (Canada–USA) linkage areas across all major highways and settlement zones in the Purcell, Selkirk, and Cabinet Mountains encompassing 24% of total highway length. We tested the correspondence of the core and linkage areas predicted from models with grizzly bear use based on bear GPS telemetry locations and movement data. Highway crossings were relatively rare; however, 88% of 122 crossings from 13 of our bears were within predicted linkage areas, indicating bears use linkage habitat that could be predicted with an RSF.