Climate influences body condition and synchrony of barren-ground caribou abundance in Northern Canada

Large-scale climate oscillations may contribute to the observed dramatic fluctuations and regional synchrony in Rangifer abundance. Here, we test this hypothesis using long-term abundance and physical condition datasets to investigate the relationships between broad climate patterns, summer-range quality, and population dynamics in three barren-ground caribou herds in northern Canada. We found that positive intensities of the Arctic Oscillation (AO) in the summer were associated with warmer temperatures, improved growing conditions for vegetation, and better body condition of caribou. Over this same period, the body condition of female caribou was positively related to fecundity. We further identified that population trajectories of caribou herds followed the direction of the AO: herds increased under positive AO intensity, and decreased under negative AO intensity. Our findings suggest that the AO influences barren-ground caribou population dynamics through effects on summer-range quality, caribou physical condition, and herd productivity.