Widespread Declines in Woodland Caribou (Rangifer tarandus caribou) Continue in Alberta

Nowhere across Canada is the continued persistence of woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)) more uncertain than in Alberta due to widespread industrial development. A recent Government of Canada critical habitat review determined that habitat conditions within all Alberta boreal ecotype caribou ranges are unlikely or very unlikely to allow for self-sustaining caribou populations. This habitat-based assessment was based only indirectly on empirical population trends. Here, we estimated empirical population trend and growth rate (λ) for 13 of Alberta’s 16 remaining woodland caribou populations (plus one adjacent population from Saskatchewan) from 1994 to 2012 using demographic monitoring of adult female survival and calf recruitment. We captured and radio-collared a total of 1337 adult female caribou in 14 populations and estimated the mean annual adult female survival across all populations as 0.851. We conducted 158 late-winter calf recruitment surveys across the 14 populations classifying 20 872 caribou and estimated mean recruitment of 0.154 calves/cow (i.e., 0.077 female calves/cow). We then combined annual estimates of adult female survival and female calf recruitment within each population in a simple age-structured population model to estimate population trend. Annual population growth rate across caribou populations averaged 0.918, and was significantly declining, λ < 1.0, for 10 of the 14 caribou populations. Our results confirm that woodland caribou are declining rapidly (with a realized decline of approximately 50% every 8 years) across Alberta, and support conclusions from previous habitat-based assessments that the population viability of caribou is currently compromised, supporting development and implementation of recovery actions to reverse trends.