Winter for the Warm Blooded

Winter for the Warm Blooded

As the depths of winter descend on the Pocono region, and we have taken our fill of friends and family, consumed more turkey, ham, kielbasa, seafood and desserts than one should in a month’s time, and watched old movies and football games cozied up by the fire, we settle in for three more months of cold, damp weather. Meanwhile, our fuzzy wild friends survive outside in the coldest of these months. Unable to fly south, like the birds, mammals have ingenious ways of dealing with the harshness of Pennsylvania winters, and we shall take a peek at some of them this month. Curl up on the sofa and be happy you have a blanket!

Black bears have some of the most interesting adaptations to deal with winter of any creature in the world. They spend all summer preparing for a fast that will last up to five months. (I can’t imagine going 5 days without food…..). They can eat upwards of 20,000 calories a day from late summer into the autumn, which is about ten times what an adult male person eats in a day. As the days get shorter and colder, the bear may have accumulated four inches of fat, and added to three to four inches of fur becomes a heavily insulated bruin. The bear stops eating, and when the digestive system is cleared, finds a place to den for the winter. Bear dens include small rock crevices, under homeowners crawlspaces, on the leeward side of a downed tree (called a “blow-down”), or even inside a culvert pipe. They do not hibernate, but do “slumber”, reducing their metabolism and breathing .They can’t shut down completely because in January the sows give birth to from 1 to 5 tiny cubs while in the den. Why in January? These cubs are among the tiniest babies for the mother’s size in the animal kingdom weighing a mere 12 ounces, and are blind, deaf, and almost naked. They need mom’s heat to grow and develop over the next three months until its warm enough and they are big enough to venture from the den with mom in March. Bears do not eat, drink or go to the bathroom for up to five months. Scientists have studied bears’ ability to recycle metabolic wastes to avoid kidney failure and cycle calcium from blood to bone and back to blood to prevent osteoporosis to seek treatment or prevention of human disorders.

A great example of a true hibernator is the groundhog, who settles into a deep den, after feeding and growing fat. The den, or hibernaculum. is sealed to prevent drafts, and the groundhog falls asleep. Once torpor (hibernation) has begun, the heartrate drops to 5 per minute and breathing slows to 4 per minute. Curled up in a ball, they are difficult to rouse, and with a body temperature of a mere 40 degrees F, they are truly in a “death-like” state. In internal clock tells the groundhog when it is time to wake up, and a special layer of “brown fat” is burned while the groundhog shivers to wake and warm up. Food is then a priority, but so are females, and mating takes place early in spring. Sleeping groundhogs are not completely safe, as we have had them delivered for care, still asleep, or at least groggy, having been excavated by heavy equipment or nosy digging dogs.

Both Snowshoe hares and ermine change to a white coat in winter. The obvious purpose of the white is to prevent detection by predators, in the case of the hare, and prey, for the ermine. But, the white hair actually lacks pigment which creates “hollow hair”, which insulates better than solid hair, creating a second benefit. These seldom-seen hares are northern relatives of the cottontail rabbits we see so often, but are residents of swamps and forests. They are bigger and have larger feet and ears.

The short-tailed weasel, or ermine, is, despite its small size (just under a foot plus a three inch tail), a voracious predator. Many residents of the Poconos have never even seen a weasel, and seeing one with a white winter coat may be harder still! These small weasels eat not only mice, voles, shrews, and chipmunks but can catch and kill prey as large as rabbits and squirrels!

White-tail deer have several amazing adaptations to help them survive winter.
They shed their short, brown summer coat and grow a longer, thicker, but hollow, grayish coat. Deer also change their diet during the winter, shifting from a diet of grazing, leaf-eating and acorn-munching, to browsing mainly on buds and twigs. Appetizing, huh? Their four-parted stomach is full of microorganisms that digest the roughage (cellulose) that no mammal can break down on its own, and the microorganisms, in turn, produce the nutrition needed by the deer.

Sadly, many people do not realize this, and as winter progresses and snows deepen decide to embark on a feeding program to “help out” the deer. Unaccustomed to the change in diet, the microorganisms may be severely harmed, making the deer sick or even killing him or her. In addition to the dangers of the change in diet, gathering animals in artificially high numbers can transmit diseases not only among the deer, but through attracting rodents to the feed, which can harbor infectious agents. Want to help deer? Cutting browse (tree limbs) can provide extra nourishment by allowing deer to feed on natural foods that would have been unreachable.

Deer lose their antlers because of winter, as well. Unlike horns, which are made out of fingernail or hairlike material, antlers are growing bone, complete with an external blood supply and skin, called velvet. If deer maintained their antlers year-round, they’d lose a lot of body heat with from exposing all that surface area to the cold.

Raccoons and some skunks will pile into communal dens and snooze the winter away on and off, venturing out on warmer evenings but not becoming very active again until mating season in very early spring. Denning in groups saves a lot of body heat. Soft, dense fur and heavy fat layer allow these creatures to survive for months in the cold. The feet of these two mammals, though, are bare on the bottom, and they can get quite chilly if they venture for too long in the snow.

Opossums will den communally, but they are simply not made for winter survival, and can lose parts of their paper-thin ears, and nearly hairless toes and tails to frost-bite.

Luckily for these lone North American marsupials, they will eat practically anything, and rarely starve to death. They actually carry leaves and bedding in their tails to line and warm a denning area.

Gray squirrels are seen all winter. They do not hibernate or even sleep for long periods during the winter. A thick coat and stored fat from eating high-calorie nuts in the fall keep these rodents warm. Squirrels “scatter-hoard”, which means that they bury nuts all over the place, rather than in one stockpile. Evidently, squirrels utilize a very good sense of smell, rather than memory to find many of these nuts as needed. Those not found become new trees for a future generation of squirrels to use. In addition to tree cavities, Gray squirrels make nests in trees in which to protect themselves from the elements. The winter “drey” is built from small ends of branches nipped from trees with their leaves woven together in the fork of a tree and lined with leaves, grasses and hair. Cozied up in a drey with its furry tail curled over his face, gray squirrels can tolerate the worst winter can deal, spending the sunnier days of winter foraging for the nuts he stored during warmer times.

Enjoy the warmth of home this winter, but don’t forget to bundle up and spend some time enjoying nature in the great outdoors of northeastern PA.

Katherine Uhler
Pocono Wildlife Rehabilitation and Education Center

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