Dynamics of woodland caribou populations at the southern limit of their range in Saskatchewan

• Published in: Canadian Journal of Zoology
• Main Authors: Rettie, W James, Messier, François
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1998
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Canis lupus; caribou; Rangifer tarandus
• Online Access: http://dx.doi.org/10.1139/z97-193; http://www.nrcresearchpress.com/doi/pdf/10.1139/z97-193

Woodland caribou (Rangifer tarandus caribou) in central Saskatchewan are aggregated into several spatially disjunct populations. Historical data indicate that some local populations were eliminated and that the regional metapopulation declined during the 1970s. Proximate causes of decline may have included hunting, severe winter weather, and the end of predator control, though the ultimate causes may relate to road construction and logging activity, which expanded after 1966. There has been no sport hunting since 1987, yet the caribou populations in the region appear to be declining. Based on serum progesterone levels, first conception by females occurred at 16 months and the overall pregnancy rate was 94%, and in addition the minimum parturition rate was 86%, all of which indicate adequate nutrition. The annual survival rate of adults was 84%, which is comparatively low, though similar to results from other studies on woodland caribou. We observed a low rate of calf recruitment (28 calves : 100 cows), which we suspect was due to predation. Wolves (Canis lupus) have long been thought to limit woodland caribou populations while subsisting on other ungulate prey, but we speculate that black bear (Ursus americanus) predation may be an important cause of poor calf survival.