Those Left Behind!

Old Man Winter has arrived, bringing cold temperatures, blustery winds and a few chilling snowfalls. Even the first and second graders who visit our parks know that birds migrate and bears hibernate when it gets cold. Actually, the story is a bit more complicated than that.

Many of our local wildlife residents are left behind by the migrators and hibernators to fend for themselves in the cold, often harsh weather. Their keys to survival are finding adequate food sources, adapting to the fallen temperatures and seeking shelter.

Mammals follow a winter survival strategy of adapting their diets to an available food and finding shelter from the severe weather. For example, the omnivorous raccoon switches from insects, fruit and crayfish to acorns, frozen berries and even rabbits. Raccoons will find a hollow tree to sleep in and they are also known to stay in abandoned woodchuck burrows. Gray squirrels busy themselves by searching for nuts that they buried in the fall. White-tailed deer switch from greenery and fruit to bark and nuts. Deer will make beds in the fields where they sleep despite the snow and cold. They are able to keep warm because the hairs of heir fur coats have tiny air bubbles that serve as insulation for these gentle animals. Some mammals seem better able to tolerate hunger than others and may “hole up” for several days during a deep snow cover or very cold period. Chipmunks spend wintertime sleeping underground with occasional awakenings to snack on stored food. Groundhogs, which usually feed on greenstuffs, and insect-eating bats survive by becoming dormant in sheltered areas, their body temperatures, respiration and other body functions fall drastically. Although they do become dormant, bears and skunks are not considered hibernators because their body temperatures do not drop significantly as do the body temperatures of true hibernators such as groundhogs and bats.

Birds, however, have high metabolic rates and need to eat quite often. The nectar-eating hummingbird, fruit and inset-eating orioles and aquatic birds such as ducks and geese tend to migrate before their food supplies die out or freeze up. However, migration is not an all or none proposition. Hickadees, cardinals and song sparrows are able to keep warm as long as there is enough food to fuel heir internal “furnances.” Many overwintering birds feed mostly on seeds, a food source that ripens in the fall and stays edible for a long time. Birds ay be observed visit artificial feeders in great numbers before a snowstorm. Woodpeckers survive the cold by digging beneath the bark of trees to eat inactive insects, while raptors such as hawks and owls feed on the small birds and mammals that remain active through the old months.

Reptiles and amphibians are too slow to migrate and are unable to generate enough body heat to stave off the cold. As the outside temperature drops, so does their body heat. Most reptiles and amphibians must find a place to hide to prevent freezing to death and to avoid being eaten by active mammals and birds of prey. Zoologists call the winter sleep of cold-blooded creatures “brumation.” Some species will bury themselves in the mud at the bottom of a lake or pond, while land-based reptiles will burrow in loose soil or under leaf litter. Quite often, when there are not enough shelter spots available, snakes of different species will al group together in one place. In recent years, herpetologist have discovered that several species including garter snakes and wood frogs, can actually survive body temperatures below freezing for varying periods of time.

While all these different approaches make it difficult for us to keep track of an animals winter habits, they also make the outdoors much more interesting.

To learn more about winter wildlife activity, join the Naturalist for “Nature in Winter” at Farbach-Werner Nature Preserve on Sunday, January 6 at 2 p.m.