3 minute read
How Does Wildlife Survive Winter?
How Does Wildlife Survive Winter?
By Jennifer Riley
Bundling to brave winter weather, are you also concerned about the local wildlife that lives outdoors year-round?
Not to worry. These species have evolved to survive and thrive in these freezing-cold temperatures.
For most, food availability is the main factor that makes winters such a challenge. Those with a constant winter food supply may stay active. These warm-blooded mammals may protect against the cold by growing thicker coats or bulking up during the plentiful spring and summer months.
Foxes, raccoons, squirrels, and others rely on these methods. Those who no longer have a food supply, such as groundhogs that rely on large volumes of plant material, or the bats that count on large insect populations, torpor or hibernation is the best option.
Torpor is a low-energy state where breathing, heart rate, and body temperature are lowered so that metabolism slows and the animal requires less energy. Bats enter torpor when temperatures drop too low. Animals in torpor will awaken occasionally throughout the winter to hunt or forage, urinate and defecate, and perform other functions as needed.
Alternatively, some mammals, like groundhogs and chipmunks, are true hibernators. Hormones and declining daylight hours induce hibernation in these species and metabolism is reduced to between one to five percent of normal. These animals lower their temperatures and heart rates significantly and cannot be easily roused.
Reptiles and amphibians have their own type of dormancy called brumation, which is similar to torpor. Because they cannot regulate their body temperatures, they begin seeking shelters or burrows as the weather cools. As temperatures approach freezing, they shut down many of their physiological functions.
When weather warms, even if just on a sunny winter day, these brumators may take that opportunity to drink water and catch some rays.
Birds often take a different route than mammals or reptiles –they just leave.
Birds who do not have natural foods readily available in winter can migrate short or long distances until they reach their wintering grounds where resources are more plentiful. Some birds stay put. They may have a steady food supply (such as birds of prey) and others stay year-round and are able to adapt their diets to seeds or berries that are produced in winter.
For birds that stay through the winter, packing on body weight in the spring and summer is important, but their feathers also play an important role. They trap pockets of air close to the body, creating a layer of insulation, which is why feather down is a commonly used as insulating material.
You may see birds “fluff up” in the winter as they try to trap the maximal amount of warm air in their feathers. Birds keep their feathers well-conditioned and waterproof using oil from their uropygial gland (over their rump) so that the feathers can continually provide this essential service.
In the cold, birds also tuck their feet up or their beaks into their back feathers. These featherless body parts get cold quickly and tucking them into the warmer core-area keeps those parts comfortable. The cold hard truth: Our native wildlife handle winter in many different ways, but rest assured, they’re just fine out there.
Details: Jennifer Riley, DVM, is the hospital director at the Blue Ridge Wildlife Center in Millwood, the only dedicated wildlife hospital in Northern Virginia. It assists more than 3,000 native wildlife annually. Visit www.blueridgewildlifectr.org.
