Cougar den site selection in the Southern Yellowstone Ecosystem

Abstract

Den sites are critical resources that ultimately influence the population dynamics of many species. Little is known about cougar den selection, even though dens likely play important roles in cougar fitness and kitten survivorship. Thus, we aimed to describe cougar den site selection in the Southern Yellowstone Ecosystem (SYE) at two scales (third- and fourth-order resource selection) and within an ecological framework that included environmental characteristics, as well as some measure of prey availability and anthropogenic landscape features. We documented 25 unique dens between 2002 and 2013, and gathered data on microsite characteristics and paired random points for 20 dens. The timing of dens was clumped in summer, with 56 % of 25 dens beginning in June or July. Unexpectedly, female cougars in our study system exhibited third-order selection for den areas in less rugged terrain, but did not exhibit selection for greater or lesser access to hunting opportunity, roads, water, or specific habitat classes, as compared with the remainder of their home ranges. Instead, our findings suggested that third-order selection for den areas was much less important than fourth-order selection: cougar den sites were characterized by high concealment and substantial protective structure. Therefore, our results provided evidence in support of land practices that promote and protect downed wood and heavy structure on forest floors—these will best provide opportunities for cougars to find suitable den sites and maintain parturition behaviors.