Seasonal changes in the composition of the diets of Peary caribou and muskoxen on Banks Island

Abstract

Caribou and muskoxen are the only ungulate species occupying Arctic tundra environments. We analysed plant fragments found in fresh (< 4 hr old) samples of faecal material to determine the diets of Peary caribou (Rangifer tarandus pearyi) and muskoxen (Ovibos moschatus) on Banks Island, Canada. Willow was a major component of the diets of both animals, dominating the caribou diet during summer and representing substantial proportions of the muskoxen diet during at least seven months of the year. The diet of caribou was more diverse than that of muskoxen and was dominated by sedge, willow (Salix arctica), legume (Astragalus spp., Oxytropis spp.) and Dryas integrifolia. The diet of muskoxen was dominated by sedge and willow. There was substantial overlap (up to 70 %) in the diets of these herbivores with the similarity more pronounced in areas of high muskox density (ca. 1.65 animals/km2). We discuss herbivore diets in relation to foraging behaviour and forage availability.