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Data from: Steep and deep: Terrain and climate factors explain brown bear (Ursus arctos) alpine den site selection to guide heli-skiing management

Citation

Crupi, Anthony; Gregovich, David; White, Kevin (2020), Data from: Steep and deep: Terrain and climate factors explain brown bear (Ursus arctos) alpine den site selection to guide heli-skiing management, Dryad, Dataset, https://doi.org/10.5061/dryad.dr7sqv9vm

Abstract

Winter recreation and tourism continue to expand worldwide, and where these activities overlap with valuable wildlife habitat, there is greater potential for conservation concerns. Wildlife populations can be particularly vulnerable to disturbance in alpine habitats as helicopters and snowmachines are increasingly used to access remote backcountry terrain. Brown bears (Ursus arctos) have adapted hibernation strategies to survive this period when resources and energy reserves are limited, and disturbance could negatively impact fitness and survival. To help identify areas of potential conflict between helicopter skiing and denning brown bears in Alaska, we developed a model to predict alpine denning habitat and an associated data-based framework for mitigating disturbance activities. Following den emergence in spring, we conducted three annual aerial surveys (2015–2017) and used locations from three GPS-collared bears (2008–2014) to identify 89 brown bear dens above the forest line. We evaluated brown bear den site selection of land cover, terrain, and climate factors using resource selection function (RSF) models. Our top model supported the hypothesis that bears selected dens based on terrain and climate factors that maximized thermal efficiency. Brown bears selected den sites characterized by steep slopes at moderate elevations in smooth, well-drained topographies that promoted vegetation and deep snow. We used the RSF model to map relative probability of den selection and found 85% of dens occurred within terrain predicted as prime denning habitat. Brown bear exposure to helicopter disturbance was evident as moderate to high intensities of helicopter flight tracking data overlapped prime denning habitat, and we quantified where the risk of these impact was greatest. We also documented evidence of late season den abandonment due to disturbance from helicopter skiing. The results from this study provide valuable insights into bear denning habitat requirements in subalpine and alpine landscapes. Our quantitative framework can be used to support conservation planning for winter recreation industries operating in habitats occupied by denning brown bears.

Methods

Brown bear den sites were located by aerial survey where latitude and longitude coordinates were collected on handheld GPS. Additional den sites were located by brown bears instrumented with GPS collars. Habitat factors were extracted from the IfSAR dataset and standardized (x-͞x /SD(x)) prior to analysis. To estimate resource availability, we generated randomly distributed locations at the scale of the study area (second-order selection) [82, 83] at a mean density of 500 locations per km2 [84].

Usage Notes

Den Data

Brown bear (Ursus arctos) den site locations in Haines, Alaska, U.S.A. (2008-2017). The data file includes fields that were included in the analysis of the resource selection function models.  Response of 1 indicates a den site and 0 indicates an available point. We describe the year and geographic mountain range where the den was located, the lifezone (alpine, subalpine), elevation (dtm), slope (slope), topographic position index (tpi), vegetation height index (vhi), vector ruggedness measure (vrm), solar radiation (solrad), terrain wetness index (twi), and snow load (snowload). We calculated a snow load factor as the product of two elements, elevation scaled (0–1) across the entire range of elevations, and a bearing exposure component that was at a maximum opposite from the prevalent wind bearing [66]. These habitat factors were scaled (_s) and squared (_sq) for analyses.

Specific bear den locations are confidential under Alaska state law (AS 16.05.815(d)), hence we only depict generalized locations.

References available in the published research article.

Funding

U.S. Fish and Wildlife Service, Award: AKW-10-4.43

Alaska Department of Fish and Game, Award: AKW-10-4.43