Factors influencing the distribution of Bathurst barren-ground caribou (Rangifer tarandus groenlandicus) during winter.

Across the circumpolar north, many herds of Rangifer have decreased in abundance. In the Canadian central Arctic, the Bathurst herd of barren-ground caribou (Rangifer tarandus groenlandicus) declined from 472,000 ± 72,900 (± 95% confidence interval) caribou in 1986 to 31,900 ± 10,900 caribou in 2009 ...A reduction in winter forage due to forest fires has been suggested as a factor contributing to the decline. I employed a multi-scale study design to identify the influence of vegetation, fire history, snow cover, and predation risk on the occupancy of winter habitats by Bathurst caribou. Between 2008 and 2009, I collected forest stand and understory data at habitats used by caribou, as well as paired control sites. At a larger spatial scale, I used animal location data recorded from 1996 - 2009 to characterize the spatial and temporal distribution of Bathurst caribou on the winter range. At the scale of the feeding patch, caribou foraged in habitats with a high-percentage ground cover, high biomass of lichen, and few or small trees. Similarly, the consensus among the models of habitat selection was that collared caribou avoided areas of the winter range with a high density of burns and favoured older patches of forest characterized by a high percentage of ground cover of lichen and herbaceous forage and a close proximity to lakes and rivers. However, there was considerable use of habitats adjacent to the burn boundary, and some caribou occupied early-seral habitats significantly more than expected. Although the abundance of fruticose (having branched, shrubby thalli) lichens was relatively high (2464 kg/ha) in areas burned within the last 43 - 264 years, my results suggest that an increased incidence and severity of forest fires due to climatic warming could cause a temporary decrease in the habitat available to the Bathurst caribou herd during winter. In the event that reduced lichen availability becomes a limiting or regulating factor for caribou, fire suppression may be necessary to mitigate