Big Bruins and Little Kings: Surviving Montana's Winters

For warm-blooded animals, the ability to maintain relatively constant body temperatures, called “homeothermy”, is critical to life. Regardless of outside temperatures, body temperatures must be maintained within a relatively narrow range. When outside temperatures drop below internal temperatures, body heat is lost. To counteract this heat loss, animals may increase heat production (increasing fuel), decrease heat loss (improving insulation), or lower internal temperature needs (adjusting the thermostat). Biologists refer to these responses as maintaining energy balance.

The biology of energy...