Fine-scale habitat selection by female forest-dwelling caribou in managed boreal forest: Empirical evidence of a seasonal shift between foraging opportunities and antipredator strategies

Abstract

Forest harvesting is a major cause of habitat alteration negatively affecting forest-dwelling caribou (Rangifer tarandus caribou) in the boreal forest. In order to identify female caribou habitat requirements, we conducted a fine-scale habitat selection analysis in a managed forest of eastern Canada. Five land-cover types used by 8 female caribou during 2 periods (winter and snow-free) were considered to characterize structural attributes, ground cover, and lichen abundance at 320 GPS locations and at 200 random points within home ranges. Because caribou rely on a limited food supply in winter, we predicted that they would select sites of higher biomass of terrestrial and/or arboreal lichens. Since female caribou (especially those with calves) are more vulnerable to predation during the snow-free period, we predicted that they would select sites where predation would be reduced by a denser hiding cover (i.e., high basal area, shrub height, and/or lateral cover) or by a lower forage availability for alternative prey (i.e., low shrub density). Within each land-cover type, comparisons between used and random sites were conducted using an exploratory PCA analysis followed by conditional logistic regressions. Our results demonstrated that, in winter, female caribou selected sites with higher terrestrial lichen biomass or ericaceous shrub cover in old spruce stands and old cutovers. During the snow-free period, female caribou did not select sites of denser hiding cover. However, well-regenerated shrub layer was avoided during both periods, suggesting that caribou avoided sites containing abundant forage attractive to moose and, consequently, wolf. At a fine scale, forest management should focus on protecting sites or stands with a high biomass of terrestrial lichens. Silvicultural practices that prevent cutovers from regenerating into areas with abundant moose forage should also be favoured.