Polar bear (Ursus maritimus) maternity denning habitat in western Hudson Bay: a bottom-up approach to resource selection functions

Abstract

We examined habitat characteristics of 101 polar bear (Ursus maritimus Phipps, 1774) den sites and 83 adjacent unoccupied sites in western Hudson Bay, Canada, between mid-August and early October 2001 and 2002. Bears denned almost exclusively in peat banks (n = 100) along the edges of creeks, rivers, and lakes adjacent to open lichen tundra sites. Den sites differed from unoccupied sites by having greater tree cover (P = 0.002), less moss cover (P < 0.001), and less herbaceous cover (P = 0.005). The presence of tree roots improved substrate stability, providing support to den structures. Den entrance azimuths were weighted toward a southeasterly aspect (P < 0.005), away from the prevailing northwest winds. To identify habitats with the greatest relative probability of having a den, a resource selection function (RSF) model was developed using remote sensing imagery and 1245 known den locations. High normalized difference vegetation index and brightness values derived from Landsat imagery, which were in close proximity to water, corresponded well with polar bear den sites. Identification of critical denning areas through the use of RSF will provide resource managers with a valuable tool for ensuring the protection of denning habitat, and consequently female bears and their young.

Mapping resource selection functions in wildlife studies: Concerns and recommendations

“…For example, predicting a species’ distribution has been used to inform endangered species management and habitat conservation efforts (Dzialak et al, 2013; Dzialak, Olson, Harju, Webb, & Winstead, 2012; Fortin, Courtois, Etcheverry, Dussault, & Gingras, 2008; Richardson, Stirling, & Hik, 2005; Roever, Van Aarde, & Leggett, 2013). As one example, such modeling has been employed to address concerns including the evaluation of conservation networks for African elephants ( Loxodonta africana oxyotis ;(Roever et al, 2013).…”

Polar bear denning distribution in the Canadian Arctic

“…1). While most denning occurred on land (e.g., Clark et al 1997;Richardson et al 2005), there were numerous records of denning on pack-ice in the Beaufort Sea (e.g., Durner et al 2010;Rode et al 2018), and on land-fast ice throughout the Canadian Arctic Archipelago (e.g., Stirling et al 1978;Ferguson et al 2000).…”

Barents Sea polar bears (Ursus maritimus): population biology and anthropogenic threats

“…Most maternity dens are located on land, although a few are made in multi-year sea ice off the Alaskan coast (Harington 1968;Lentfer 1975;Amstrup & Gardner 1994;Fischbach et al 2007). In Hudson Bay, polar bears den in earth dens that can be up to 80 km from the coast, but bears move into snow dens as snow accumulates in autumn (Jonkel et al 1972;Richardson et al 2005). Denning philopatry among female polar bears has been shown in Hudson Bay (Ramsay & Stirling 1990), in Svalbard (Zeyl et al 2010) and the Beaufort Sea (Amstrup & Gardner 1994).…”