A uniform 3☌ temperature increase reduced male mortality during a 180 day fast from 18% to 15%. Our results illustrate how environmental conditions, variation in animal properties, and thermoregulation processes may impact survival during extended fasts because polar bears were predicted to require additional energetic expenditure for thermoregulation during a 180 day fast.

When the fast extended to 180 days, Niche Mapper predicted mortality of up to 18% for males. Niche Mapper predicted that all but the poorest condition bears would survive a 120 day fast under current climate conditions. Predicted weight loss for a 120 day fast typical of the 1990s was comparable to empirical studies of the population, and the model was able to reach a heat balance at the target metabolic rate for the entire fast, supporting use of the model to explore the impacts of climate change on polar bears. The model uses a steady state heat balance approach, which calculates the metabolic rate that will allow an animal to maintain its core temperature in its particular microclimate conditions. In this study we tested the ability of a mechanistic model (Niche Mapper™) to accurately model adult, non-denning polar bear ( Ursus maritimus) energetics while fasting during the ice-free season in the western Hudson Bay.

Eq polar bear skin