Take Me Outside: Who does what in winter?
** ADVANCE FOR WEEKEND EDITIONS APRIL 4-5 ** A snowshoe hare makes an appearance during a "Snowshoe Ecology Walk" in this photograph taken on March 4, 2009, in Rocky Mountain National Park outside Estes Park, Colo. (AP Photo/Loveland Reporter-Herald, Christopher Stark)
Deer cross a snow-covered field in West Campus of the University of Kansas in Lawrence, Kan., Saturday, March 23, 2013. A winter storm warning is in effect for the area. (AP Photo/Orlin Wagner)
This winter has been a mix of unseasonably warm days followed by bone chilling temperatures. If you have had trouble deciding whether to wear your raincoat or down jacket before heading outside, imagine what it must be like for wild animals.
Some creatures are oblivious to the cold and wind because they are hibernating underground or in some sheltered space. Their bodies have shut down and entered a period of suspended existence, just short of death. In our area only the woodchuck, some bat species, meadow and woodland jumping mice and black bear are considered to be true hibernators. What they have in common is that their prime food becomes scarce or nonexistent in winter. This is the case with the woodchuck, which eats herbaceous plants, and bats, who feed on insects.
True hibernators go through a dramatic metabolic change. During hibernation they do not eat, drink, defecate or urinate. Their heart and breathing rates drop drastically. The woodchuck’s heart rate declines from 100 beats per minute in summer to about 15 during the winter. In most cases hibernators also have a very low body temperature. The black bear is one exception to this rule, making its classification somewhat controversial. Black bears’ heart and breathing rates decline during the winter, but their core body temperature only drops a few degrees from normal. As the definition of true hibernation has broadened, black bears have been added to the list of hibernators.
Though bear behavior may be hard to define, several species of mammals can definitely be labeled as dormant or “sleepers.” Raccoons, skunks, opossums and chipmunks sleep for extended periods without experiencing a major metabolic change. Food storage is a key adaptation for them. Chipmunks cache their food in burrows, where they can access it during the winter without going outside.
The strategy employed by raccoons and skunks is to add body fat during the fall. This acts as insulation but is also a source of energy when they are sleeping for weeks at a time. However when the weather is mild they emerge in search of food to augment what they have stored. During a recent warm spell my yard was crisscrossed with skunk tracks heading for an easy buffet at the compost pile. But with the return of colder weather, fresh tracks will be left only by the truly active creatures.
Mammals that stay active throughout the season make up the majority of our native populations. Squirrels and most of the rodents (including beaver and porcupine), rabbits and hares, coyotes and foxes, bobcats and lynx, all of the weasels (except the skunk), deer and moose have other adaptations that help them survive the cold and reduced food availability.
Deer and moose change their diet from herbaceous to woody plants. Beavers store food under water near their lodge. Squirrels make stashes of seeds and retrieve them when other food becomes harder to find.
Many of these creatures also put on a winter coat. Under-fur will thicken, creating cozy protection from the winter cold. The outer layer of guard hairs are usually hollow, able to trap and hold the body heat generated by the animal and block the outside cold from penetrating. Snow may actually build up on the backs of deer without melting because their fur creates a layer of air between their warm bodies and the snow. In the case of the snowshoe hare, long- and short-tailed weasel or ermine, winter fur also provides camouflage as they turn white to blend in with snow.
Behavioral changes may also include congregating together to share warmth or reduce energy needed to move around: Raccoons will den together; deer congregate in “yards” under evergreen trees, where the snow is not as deep; squirrels gather in tree cavities or leaf nests; and beaver families stay together in their underwater lodges.
It is a marvel to observe how New Hampshire’s wildlife is adapted to the challenges of winter. Why not bundle up with your own strategies for keeping warm and go in search of some of these intrepid neighbors.
There are plenty of animals who aren’t hibernating or hunkered down, and winter is a wonderful time to discover their tracks and signs.