Bears Hibernate Without Deep Body Cooling

During winter dormancy, brown and black bears reduce metabolism and heart rate, but their body temperature falls much less than that of many small mammals entering deep torpor. In studied black bears, metabolism fell to about one quarter of basal levels, while body temperature shifted from roughly 37–38 °C to an average near 33 °C. A bear can respond to a stimulus and restore normal function in a relatively short time. Fat stored before winter supplies energy through the food-free season.