The hibernating dormouse
A hibernatingdormouse (Glis glis) is spherical, with its head tucked into its stomach, its soft furry tail wrapped around itself. In this posture the amount of heat that seeps away from the body is reduced. Its heart beat slows considerably and the breathing becomes so shallow and infrequent that it is difficult to detect. The muscles stiffen and the whole body feels cold, since body temperature is reduced to save energy. In this state of suspended animation, the body's food demands are so low that the fat store can provide enough to keep essential processes ticking over for months. Extreme cold, however, will waken the animal to prevent it being frozen alive. When awakened the animal begins to shiver violently, warming itself by burning fuel in its muscles. It may even, in an emergency, squander some of its remaining reserves of fat by trotting about until the worst of the cold is past and it can go back to sleep again. Normally it is only the warmth of spring that brings the dormouse and other winter sleepers out of their hibernation. Their appetites are now huge and urgent, for during the winter, they may have lost as much as half of their body weight.