Factors limiting woodland caribou populations and their interrelationships with wolves and moose in southeastern British Columbia

Abstract

Caribou (Rangifer tarandus caribou), wolves (Canis lupus), and moose (Alces alces) were radio-collared and monitored in two areas of southeastern British Columbia to determine predator–prey interactions. Throughout the year, wolves and moose used similar areas and habitats, and moose were the primary prey of wolves. In winter most caribou used high-elevation habitats and were spatially separated from wolves and moose living in valley bottoms. In summer, caribou, wolves, and moose at Quesnel Lake used similar areas and habitats, whereas in Wells Gray Park most caribou migrated to rugged, mountainous areas, which kept them spatially separated from wolves and moose. The Quesnel Lake caribou population had a high adult mortality rate (29%/year), wolf predation being the major cause. Calf survival to October was low (2.5/100 adult females) when wolves were present and uncontrolled in the area, but was significantly greater (39/100 adult females) when wolves were reduced or absent. The Quesnel Lake caribou population was found to be declining by about 25%/year, and wolf predation appeared to be the major limiting factor. Caribou in Wells Gray Park had a low adult mortality rate (8%/year) and comparatively high calf survival to October (37/100 adult females). The Wells Gray caribou population was found to be slowly increasing, apparently because its migratory behavior kept it separated from wolves and moose throughout the year, resulting in low wolf predation on the caribou.