What do caribou eat? A review of the literature on caribou diet

Historically, the study of caribou and reindeer (Rangifer tarandus (Linnaeus, 1788)) diet has been specific to herds and few comprehensive circumpolar analyses of Rangifer diet exist. As a result, certain diet items may play an outsized role in the caribou diet Zeitgeist, e.g., lichen. We challenge this notion and test the relevant importance of various diet items within the context of prevailing hypotheses. We provide a systematic overview of 30 caribou studies reporting caribou diet and test biologically relevant hypotheses about spatial and temporal dietary variation. Our results indicate that in the winter caribou primarily consume lichen, but in warmer seasons and when primary productivity is lower, caribou primarily consume graminoids and other vascular plants. In more productive environments, where caribou have more competitors and predators, consumption of lichen increase. Overall, our description of caribou diet reveals that it is highly variable, but in circumstances where caribou can consume vascular plants, then they will. As climate change affects Boreal and Arctic ecosystems, the type and volume of food consumed by caribou have become an increasingly important focus for conservation and management of caribou.