Many Ways to Cope With Winter

Animals that overwinter in cold climates have adapted to the rigorous conditions of snow, ice, and cold in one of three ways. 1) They migrate, sometimes hundreds of miles to a more plentiful food supply, a few hundred yards to a protected area such as the winter deeryards, or even a few inches to the underside of a rotting log. 2) They may hibernate or enter periods of dormancy through the coldest parts of the winter or 3) they may remain active, foraging and feeding as best they can. Temperature is a key factor for overwintering animals. Until late December the earth continues to retain some of its summer heat, but even so the ground may freeze to a depth varying from a few inches to many feet. The lowest level of freezing is the frost line, below which many animals try to burrow to reduce the chances of freezing to death. Snow helps to hold the earth's warmth by forming a protective insulating layer for the plants and animals underneath it. Absence of snow can cause severe damage and hardship. One study showed that Hibernation or dormancy is the alternative to the temperature of the soil two inches below the migration for animals that cannot remain active in surface was 1.4°F where the ground was bare, and winter. Specific physical adaptations that include, for 30.2°F where soft snow covered the ground, both at instance, a build-up of fat in vertebrate animals and a the same air temperature. Even more dangerous to buildup of an antifreeze type substance in many hibernators, especially insects are intermittent warm insects, enable animals to sleep relatively safely and cold spells. Ideal conditions are steady cold with through all or much of the winter. True hibernators insulating snow cover. breathe slowly and unevenly, their heartbeats slow Migration is not the survival device used by most down, their temperatures drop way down, and they mammals, but on a small scale, downward migration remain in this state throughout the winter months. is how many insects and spiders, reptiles and Three true hibernating mammals are the woodchuck, amphibians arrive at their winter quarters. little brown bat, and jumping mouse. Overwintering insects and spiders who have The bodily processes of dormant animals also summered in bushes and trees descend to weeds and slow way down and the animals become inactive and grass roots. Ground-dwelling insects, snails, “sleep” for part of the winter, but their body earthworms, and salamanders hide under leaf litter temperatures remain higher than those of and in rotten logs; toads burrow into the soil below hibernators, and they may either venture forth during the frost line. Pond creatures creep down into the mild spells or wake and eat some of their stored food. mud or swim to deeper water, which is usually about The skunk, raccoon, and chipmunk are common 39°F. Some amphibians such as leopard frogs and dormant mammals; there continues to be differences pickerel frogs return to the pond in winter. Many of opinion as to whether the bear hibernates or is snakes migrate to their winter quarters, the same dormant. group usually on about the same date each year. The most obvious migrators, of course, are the birds who From Hands-On Nature By J. Lingelbach must move to insure having Vt. Institute of Natural Science 1986 adequate food supplies. Thus warblers and swallows go south to find active insects, water birds seek open water with available food, and sparrows look for uncovered seeds. Hibernation does not happen all of a sudden. Ivy Creek's Mammals in Winter Periods of drowsiness and wakefulness alternate until profound lethargy takes over. A study of DEER will feed all winter although in this area woodchucks showed a variation of from three they will lose 25% of their body weight. Bucks days to a month interval between full activity and will be solitary or in small groups. Does, fawns, deep sleep. Although hibernating animals merely and yearlings tend to group together. look asleep, they are really in quite a different state. The body position of the majority of SQUIRRELS are usually active all winter, eating hibernating mammals is curled up with the hind stored caches of nuts, seeds, and acorns. legs covering the head so the eyes are hidden. RABBITS are active all winter, living in heavy They are motionless, often for days at a time, and brush patches eating bark, twigs, & sedges. breathe very slowly, as little as once per minute. FOX are active, eating mice, rabbits, insects, fruit, Body temperatures fall; a woodchuck's and carrion. hibernating temperature may be as low as 37.4°F, while his summer temperature is around 96.8°F. MICE AND VOLES stay active but may tend to The heart beats slowly and irregularly during gather more in groups for warmth. hibernation, for a woodchuck averaging four to BEAVERS stay active, sometimes holing up in five times per minute, as opposed to 160 times their lodge during cold spells living off of young per minute when active. Awakening from branches which they long ago stored underwater hibernation seems to start with accelerated in preparation for winter. heartbeat followed by a rise in temperature. Finally, the animal opens its eyes, uncurls, RACCOONS will be less active in winter with stretches, and rises to its feet. some long periods of sleep during cold spells. The third, and among mammals most Raccoon, beaver, muskrat and mink are all common, way of coping with winter is to remain trapped in winter as that is when their fur is active. Many active over-wintering animals go thickest and therefore favored. through physiological changes to prepare for OPOSSUMS AND SKUNKS are more inclined to winter. Fat accumulates and fur thickens on most dormancy although their sleep is light and body mammals; a white-tailed deer's winter coat is temperatures only slightly lowered. They come actually composed of hollow hairs to trap extra out to forage during warm days. body heat. Some animals’ feet change in the GROUNDHOG AND CHIPMUNKS are true winter to make walking on the snow easier; for hibernators but may show less pronounced example, scaly projections on the toes of grouse reductions in temperature and activity in VA's and extra fur on the feet of snowshoe hares. The temperate climate. greatest challenge is to find enough food to provide energy for hunting or foraging lvy Creek BATS are all insectivorous and and for keeping warm. Some, like the mink, therefore must migrate to warmer climates or weasel, deer, and rabbit must hunt their hibernate in cracks, trees, & old buildings food daily, having no instinct to store food. lowering their body temperature Others, such as red squirrels and mice, rely on considerably and staying completely caches of hidden seeds and nuts. inert until spring.