THERE are various way of coping with the rigours of the winter months. Some insects, for example, simply die, as if in acquiescence to the practical impossibility of over-wintering. Before they do so, however, they mate, and lay their eggs, trusting the continuation of their species to the succeeding generation. Many birds, on the other hand, migrate for the duration to a warmer climate where they hope that food will be more plentiful. Neither of these expedients, however, is available to animals and reptiles, so after laying up a store of fat within their tissues, many of them retire to winter quarters and simply fall asleep. They hibernate.
Hibernation is a dormant or torpid state which allows animals to survive for several months while using very little energy. It is necessitated by lack of food throughout the winter season, rather than by the winter cold per se. Instead of using scarce resources to maintain body temperature at an unsustainable level, the creature allows it to drop to conform more closely with that of the surrounding air.
Burning less fuel, as it were, the animal consumes less oxygen, so breathing becomes slow and irregular, heart and pulse rates drop dramatically, and various other reflex functions stop completely. As bats doze into hibernation, their heart-beat drops in a very short time from 180 beats per second to about three per minute. They breathe only eight times every minute as opposed to the normal eight per, second. Huddling together in large colonies, their collective body heat conserves further energy for the individual to allow it to survive the hungry period.
Other animals like bears and many squirrels, do not hibernate in the strict physiological sense, but spend longer periods asleep in wintertime than in the summer. On relatively warm and pleasant days they may wake and emerge into the open - in the latter case having already provided for such excursions by laying up a secret cache of nuts and grain to which they can resort before resuming sleep.
Activity returns with the rising temperature and waxing fertility of spring - although the timing here can vary. Indeed, legend has it that the badger creeps from his den at noon on Candlemas to see if he can find his shadow. If there is no shadow, he stays out - but if the sun is shining he returns to his den and snoozes there for six further weeks until the inevitable spell of cold, wintry weather, still to come, has passed away.