Winter habitat ecology of mountain caribou in relation to forest management.
Abstract
During winter, mountain caribou Rangifer tarandus caribou live in late successional and old growth coniferous forests, where they feed almost exclusively on arboreal lichens. Because some of these forests are also valuable to the forest industry, caribou ecology and forest management remains a central conservation issue in British Columbia. To improve our understanding of caribou habitat use in relation to forest management, we investigated the winter habitat selection patterns of mountain caribou at a range of spatial scales between 1988 and 1993 in the northern Cariboo Mountains, British Columbia. Within winter ranges, caribou selected forest stands dominated by subalpine fir (>80% Abies lasiocarpa) and with moderate slopes (16-30%) during early winter (November-December). Although stands with moderately high timber volumes (201-300 m3 ha-1) were used the most during early winter, caribou used these stands in proportion to their availability. Caribou primarily used open canopy subalpine fir stands (i.e. parkland) later in the winter (January-March), where low stocking and inoperable timber volumes (<100 m3 ha-1) reduced direct conflicts with forest harvesting. Characteristics of subalpine forests at early winter caribou foraging areas did not differ significantly from random sites for most variables measured. However, a multivariate analysis indicated that sites used by caribou had slightly less total basal area, more moderate slopes and slightly heavier lichen loads than unused sites. Within early winter foraging areas, caribou chose foraging paths with more trees and greater accessible lichen biomass per standing tree compared with random paths. Although windthrown trees and lichen litterfall were encountered infrequently, caribou rarely rejected these sources of lichen when encountered. The relatively low basal area (27 m2 ha-1) and minor component of economically valuable Engelmann spruce Picea engelmannii (<20%) at early winter caribou foraging areas suggests less conflicts with forestry compared with other caribou populations in southern British Columbia and Idaho. Selection silvicultural systems may provide solutions to caribou forestry conflicts, particularly in mid-elevation subalpine fir stands (1325-1525 m) that may have both operable timber volumes and high caribou numbers.