Endurance

Winter in Yellowstone National Park is extreme. Across Yellowstone recorded low temperatures may drop to -66°F with average snowfalls being greater than 600 inches. Food is scarce. Energy must be conserved. Bison adapt by lowering their metabolic rate, requiring less energy and forage. The Bison's dense fur offers exceptional insulation (which is why snow can accumulate on a bison's insulated back without melting). These and many more adaptations make bison extremely tolerant to cold, in fact -40°F is the bison's lower critical temperature - the temperature at which it must increase its metabolism to maintain body temperature.
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Here a bull bison stoically endures a blizzard on a bitter winter morning. Titled Endurance, it is a good example of a wonderful and cooperative subject. First, ensure your presence is not distressing the animal. In this case, we used our vehicle as a blind and photographed him from over 50 yards away, watching for any signs of stress. Satisfied, I am now happy to stay and photograph him until I either freeze or my clients threaten mutiny. In this instance, I shot video, portrait, landscape, fast shutter speed, slow shutter speed and with blowing snow and without.