Declines in Populations of Woodland Caribou

Abstract

We summarize the demography of woodland caribou (Rangifer tarandus caribou) inhabiting 6 ranges in northeast Alberta, Canada, from 1993 to 2002. Among ranges, mean annual survival of radiomarked adult females averaged 0.88 (range: 0.86-0.93). Predation by wolves (Canis lupus) and other predators was implicated as the most common cause of death for adult caribou in northeast Alberta. Pregnancy rates (90-100%) and calf production (75-95%) were relatively high in all caribou ranges; however, mean annual recruitment was near or below 20 calves per 100 cows in most ranges (x = 17.1, range = 11.4-22.7). Caribou populations in 3 ranges have declined at average rates exceeding those that would lead to a 50% decline from initial population size over 3 generations; another population is declining at half this rate. Populations of caribou in 2 ranges appear to be stable, declining marginally since inception of our study. The current distribution, intensity, amount, and type of human activity in and near caribou ranges is likely compromising the integrity of caribou habitat. Treatment of declines will require new land-use guidelines that promote caribou conservation.