Demography of decline of the Red Wine Mountains Caribou Herd

The causes of decline of woodland caribou (Rangifer tarandus caribou) populations remain incompletely understood. We compared population characteristics of woodland caribou of the Red Wine Mountains Herd (RWMH) in central Labrador before (1981-88) and during a population decline (1993-97). During the 1980s, population estimates were 751 (no error estimation) animals in 1981, 736 ± 172 (x ± SE) in 1983, 610 ± 9 in 1987, and 741 ± 165 in 1989. By 1997, the herd declined to 151 animals (95% CI = 65-251). The decline was not associated with changes in parturition rate or in mean age of >1-year-old females, but the decline was associated with significantly lower recruitment, a greater proportion of females in the >1-year-old population, increased mortality of >1-year-old females, and emigration to the parapatric George River Caribon Herd. Throughout the study. predation by gray wolves (Cauis lupus) remained the most frequent cause of mortality of >1-year-old caribou. We hypothesize that wolves may mediate the population dynamics of sed entary woodland caribon when associated with high densities of moose (Alces alces) and migratory caribon, but that the management implications of such a triad remain unclear.