Social and seasonal risk assessment by woodland caribou: responses to habitat openness, fire, and roads

Caribou ( Rangifer tarandus (Linnaeus, 1758)) throughout the boreal forest move and select habitat in a manner that ought to maximize benefits while mitigating costs. Boreal forests, however, are undergoing rapid changes that may be affecting cost:benefit ratios, including expanding linear features and climate-induced increased wildfire activity. These costs and benefits may further vary seasonally and by social context. To test the effects of season and social context on caribou movement and selection of potentially risky habitats, we used a socially informed integrated step selection analysis (iSSA). We tested responses to two forms of putative risk in Terra Nova National Park, NL: roads and areas burned 2–75 years prior. We also tested how season and social context affected selection for forested versus open habitats. Caribou avoided areas near roads irrespective of season. Burned area avoidance varied by season and burn age. Caribou selected more open habitats only when in proximity to another collared individual, but social facilitation did not appear to mitigate risks associated with roads or burned habitats. As the most at-risk populations of woodland caribou exist at low density in highly disturbed landscapes, our results affirm the importance of considering sociality in maintaining access to resources.