Den-site characteristics and selection by brown bears (Ursus arctos) in the central Brooks Range of Alaska

Abstract

Selection and use of dens is a critical behavioral adaption of bears (Ursus spp.) to survive extended periods of resource limitation. We analyzed selection of den sites by brown bears (Ursus arctos) in an arctic montane environment from 2014 to 2017. We used GPS data from 51 instrumented bears to physically locate, identify, and describe den sites (n = 33) and to quantitatively model the selection of denning habitat (n = 65 dens over 3 yr). We conducted an analysis of den-site selection at the home range (third order) scale using variables describing topographic, vegetative, and spatially-explicit fish and wildlife models. We hypothesized four main factors influence den-site selection by brown bears: (1) physiography, (2) proximity to food resources, (3) thermal insulation, and (4) den-area fidelity. We used kernel density estimates to define space use and conditional logistic regression to estimate den selection within individual home ranges. Brown bears selected den sites on steep slopes (>31°) with high snow load potential near their previously used den site. Our results supported our hypothesis that den selection by brown bears was related to thermal insulation, structural stability, drainage, and den-area fidelity.