Scale-Dependent Habitat Selection by Mountain Caribou, Columbia Mountains, British Columbia

Abstract

Mountain caribou, an endangered ecotype of woodland caribou (Rangifer tarandus caribou) are associated with late-successional forests, and protecting their habitat conflicts with timber extraction. Our objectives were to describe seasonal scale-dependent caribou-habitat relationships and to provide a means for their integration with forest planning. Between 1992 and 1999, 60 caribou were radiolocated 3,775 times in the north Columbia Mountains of British Columbia. We analyzed caribou selection for multiple forest overstory and terrain attributes across 4 nested spatial scales, comparing successively smaller and closer paired landscapes (used and random). Seasonal habitat selection varied with scale for most attributes. During early winter, caribou preferred broad landscapes of low elevation, gentle terrain, high productivity, high canopy cover, and old and young forests of species indicative of a relatively mild, dry climate. Finer-scale preferences were for old western hemlock (Tsuga heterophylla) and western redcedar (Thuja plicata) stands, high canopy closure, high productivity, and southern aspects. During late winter, caribou preferred broad landscapes of high elevation, northern aspects, and old Engelmann spruce (Picea engelmanii) and subalpine fir (Abies lasiocarpa) stands. Overstory preferences were similar at fine scales, coupled with low canopy closure and productivity, high elevations, and gentle terrain. During spring, caribou preferred broad landscapes of young and old closed canopy cedar, hemlock, and spruce forests of high productivity at low elevations, Preferences were similar at finer scales but included gentle slopes. Summer preferences included closed canopy, old spruce and subalpine fir forests of high productivity across scales, north and east aspects at broad scales, and gentle terrain at fine scales. Of the variables considered, linear combinations of subsets could explain and predict seasonal habitat selection across scales (P < 0.001), Our results confirm the close association of mountain caribou with old-growth forests, and describe relationships that can be accounted for in spatially explicit habitat-timber supply forecast models.