Modeling the spatial and temporal dynamics of land‐based polar bear denning in Alaska

Abstract

Although polar bears (Ursus maritimus) of the Southern Beaufort Sea (SBS) subpopulation have commonly created maternal dens on sea ice in the past, maternal dens on land have become increasingly prevalent as sea ice declines. This trend creates conditions for increased human-bear interactions associated with local communities and industrial activity. Maternal denning is a vulnerable period in the polar bear life cycle, and den disturbance could lead to den abandonment, cub mortality, and negative population impacts. We used published long-term data to parameterize a Bayesian hierarchical model of annual land den abundance during 2000-2015, in 4 regions of northern Alaska, USA, with current or potential future oil and gas activity. We also estimated long-term shifts in the spatial distribution of land dens within and among regions using kernel density estimation and assessed the influence of local and regional sea ice and snow conditions on den site selection using a random forest resource selection function. Our objectives were to quantify current den distribution and abundance, test for distributional shifts over time, and investigate if those shifts could be attributed to environmental variables related to den habitat. We estimated that between 2000 and 2015, the SBS contained a median 123 dens in a typical year, of which 68 occurred on land. The region between the Colville and Canning rivers, where most current oil

The post-emergence period for denning Polar Bears: phenology and influence on cub survival

“…Climate change has resulted in spatiotemporal reductions in the quantity and quality of sea ice habitat for polar bears ( Stern and Laidre 2016 ; Durner et al 2019 ), which in turn has led to increases in summer land use in the Southern Beaufort Sea (hereafter, SB) and Chukchi Sea (hereafter, CS) subpopulations ( Rode et al 2015 ; Atwood et al 2016 ), increases in denning on land in the SB ( Fischbach et al 2007 ; Olson et al 2017 ), and since 2000 a westward shift of land denning on the Alaska Beaufort Sea coastal plain ( Patil et al 2022 ). This increase and westward shift in land denning has coincided with an escalation of anthropogenic activity in the Alaska Arctic ( Wilson et al 2014 ; Rode et al 2018a ), increasing the potential for disturbance to denning polar bears ( Atwood et al 2017 ; Wilson and Durner 2020 ).…”