Factors Influencing the Seasonal Diet Selection by Woodland Caribou (Rangifer tarandus tarandus) in Boreal Forest in Ontario

We used remote video cameras over a two-year period to assess seasonal diet composition of 23 woodland caribou at three areas across the boreal forest of Ontario. Diet varied by season, land-cover types, study areas and between managed and unmanaged landscapes. Caribou consumed lichens in winter and in summer but, in the summer, consumed less of the higher protein green plants than we had expected. This suggests that factors other than nutrition, such as predator avoidance, influenced their choice of diet. We conclude that woodland caribou require habitats that supply lichens in abundance. Lichen species are grazed selectively and only the top one or two centimetres are consumed, so the total available biomass is much smaller than what has been considered previously. As some stands become functionally unavailable owing to disturbances or the presence of predators in disturbed landscapes, it is possible that lichen availability may well become limiting in a synergistic manner with other factors that restrict habitat use.