Mammals use a variety of techniques to survive the colder months. Some migrate to warmer climates where food is more readily available. Others remain in their home range, growing thick winter coats and altering their diets. Some mammals, like squirrels will do “pre-season preparation” where they create large caches of foods in the fall that can last them through the winter.
Although there are still some migratory mammals in the United States, none are live in the DC area. Migratory mammals are generally large herd animals like elk or predators like mountain lions.
Few mammals are completely active during the winter. Most, such as Virginia Opossums, Eastern Grey Squirrels, and Eastern Cottontails, build warm nests to protect them during the colder winter days and venture out to hunt for food when the weather is milder. They may become dormant (less active) for short periods but they cannot go for extended periods without food or water.
True hibernators, such as Eastern Chipmunks, Woodchucks, and other ground squirrels, spend most of the winter in their dens where they curl up, cool down, and remain completely inactive, or torpid. While hibernating, animals do not eat. Instead, fat stores are converted into energy to maintain the body’s vital functions.
The length of a hibernation depends on the animal’s ability to store fat. Even some of “true hibernators,” such as Eastern Chipmunks, are not be able hibernate for the entire winter because they cannot store enough fat. Their winter hibernation, therefore, can take the form of many shorter hibernation periods, where they wake periodically to eat. If the weather is mild and enough food is available, Chipmunks may stay awake or forgo hibernating all together.
Woodchucks, on the other hand, store considerably more fat and can sleep much longer. In fact, Woodchucks developed the ability to store more fat because they needed to hibernate longer. Since their diet consists primarily of plants, waking too early in the season could be disastrous. If there isn’t enough food for them to eat they might starve to death.
Adaptations, like the Woodchucks ability to store fat and the Chipmunks ability to store food in cheek pouches so that they can carry and cache food, are essential to winter survival. Be sure to stay tuned for our next blog post, “Where Are They In The Winter: Where are they in the Winter: Reptiles and Amphibians,” to learn about how reptiles and amphibians adapt to colder climates.