Twenty-four woodland caribou (Rangifer tarandus caribou) in the mountains and foothills of west central Alberta were radio collared to obtain information on seasonal movements, location and extent of seasonal ranges, rutting and calving areas, and population status. The study was conducted from December 1979 to June 1984 (fall composition surveys continued to 1986). Two populations of woodland caribou resided in the foothills winter range: a migratory mountain variety that moved west to the mountains in spring and returned in fall, and a more sedentary woodland variety that remained year round in the forested foothills. Calving and rutting grounds of the two populations were widely separated (minimum of 60 km). The mountain population ranged over a much larger area (11 000 km2) than the woodland population (4000 km2). Woodland caribou were fewer (maximum estimate 50) than the mountain caribou (maximum estimate 200). Population sex–age structure of the mountain caribou population, based on six surveys during the rut (October), averaged 54 males: 100 females: 27 calves (15% calves). Annual minimum adult mortality was 22% for the mountain and woodland populations, and both populations appeared to be declining. Predation, primarily by wolves, was strongly implicated in adult mortality, but causes of calf mortality were not determined. Human-caused mortality was an additional factor. Intensive management is required to ensure the viability of these caribou populations in the face of increasing industrial and recreational development. A short-term wolf reduction program and long-term public education, law enforcement, and habitat protection programs are recommended.
Probabilistic Performance Assessment vs. the Safety Case Approach
