Demography of decline of the Red Wine Mountains caribou herd

The causes of decline of woodland caribou (Rangifer taranuds caribou) popul ations remain incompletely understood. We compared population characteristi cs of woodland caribou of the Red Wine Mountains Herd (RWMH) in central Lab rador before (1981-88) and during a population decline (1993-97). During th e 1980s, population estimates were 751 (no error estimation) animals in 198 1, 736 +/- 172 ((x) over bar +/- 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 significan tly lower recruitment, a greater proportion of females in the >1-year-old p opulation, increased mortality of >1-year-old females, and emigration to th e parapatric George River Caribou Herd. Throughout the study, predation by gray wolves (Canis lupus) remained the most frequent cause of mortality of >1-year-old caribou. We hypothesize that wolves may mediate the population dynamics of sedentary woodland caribou when associated with high densities of moose (Alces alces) and migratory caribou, but that the management impli cations of such a triad remain unclear.