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Wildlife In Winter | | Wolves are the perfect example of adaptation to the elements. They grow a thick layer of under-fur to trap warm air and heat close to their bodies. Additionally, their long thin legs allow them to wade through snowdrifts that would hinder other animals. |
Winters in southeastern Oregon are pretty mild compared to other parts of North America, but can still be extremely hard for wildlife. For most animals, energy is harder to obtain and easier to lose in winter than in any other season. Cold, wind, snow, rain, ice, and longer nights can all tax an animal’s energy reserves at a time when replenishing that energy becomes more difficult.
Additionally, the shorter day length combined with the lower angle of the sun, means that photosynthesis stops or slows and most plant growth ceases. Since plants form the base of the food web, this means that there is less energy available for animals ― from insects to birds and mammals.
Animals do many different, amazing things to get through the winter. Wildlife has developed three basic strategies for coping with the austerity of winter: migration, hibernation, or adaptation. Many animals use a combination of these strategies.
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| | | Turkey Vultures one of the most numerous summer residents head south before the snow flies and food gets scarce. |
Adios Muchachos!
Migratory animals move to where they can find a better food supply. Flight is a much more efficient means of long-distance travel than walking. Not surprisingly, then, most of our local migratory animals fly, including many birds, some bats, and a few insects.
How do they know when it is time to leave for the winter? How do they find their way to the same place each year? Scientists are still studying this. Many see migration as part of a yearly cycle of changes that animals goes through. The cycle is controlled by changes in the amount of daylight and the weather. Birds seem to navigate like sailors once did, using the sun, moon and stars for direction. They also seem to have a compass in their brain for using the Earth's magnetic field.
Other animals migrate in their own way. Many fish migrate. They may swim south, or move into deeper, warmer water. Insects also migrate. For example, Monarch butterflies spend the summer flitting around our fields and gardens before saying adios and taking off to Mexico for the winter. However, most migrating insects go much shorter distances. Many, like termites and beetles, move downward into the soil. Earthworms also move down, some as far as six feet below the surface. For these cold-blooded critters, they combine their migration with a reduced metabolism – they migrate AND hibernate.
Naptime in the Woods
Hibernators reduce energy demands by lowering their metabolism. For example, chipmunks reduce their heart rate to a few beats a minute and let their body temperature drop to only several degrees above freezing. Black bears, on the other hand, maintain a relatively high metabolism during hibernation. Other winter-dormant animals allow their body temperature to match the surrounding air. Many reptiles and amphibians choose an over wintering site protected from sub-freezing temperatures, such as an old mammal burrow or the mud at the bottom of a pond.
Stored fat fuels hibernating animals during their dormancy. Smaller hibernating mammals, such as skunks, cannot store enough fat to get them through an entire winter. Female skunks burrow together for their long winter hibernation. Male skunks hibernate alone. They often burrow under houses or barns to stay dry and warm for the winter. They must regularly replenish their fat reserves from food cached in their burrows.
| | Squirrels horde nuts and seeds throughout summer and fall, then huddle together with others for warmth. This is just one of the many tactics small mammals use to endure until spring. There are as many different survival strategies as there are species of animals. |
Fat, Fur, Feathers and Close Friends
Some animals remain in southeastern Oregon and stay active in the winter. They must, however, adapt to the changing weather. Many make changes in their behavior or bodies. Storing fat gives many animals a greater ability to resist winter by providing them with an energy reserve when food is scarce. Fat storage begins in summer when food is more abundant, and most animals can find enough to meet both their daily needs and to store some as fat. Larger animals, such as deer, have an advantage over smaller ones because they can store fat faster than they use it. As a result, they can go longer without eating. Smaller animals need to eat more frequently and many cache a surplus for winter. Squirrels, for example, cache nuts and pine cones.
Nothing beats a good coat for getting through the winter and mammal fur is about the best natural coat around. Fur consists of two layers: long, stiff, coarse outer guard-hairs and finer, shorter, often wavy under-fur. Under-fur traps a layer of air within it which warms up from the animal’s body heat. The trapped, warmed air reduces heat loss to the surrounding cold air.
The avian equivalent of fur is feathers. Soft down feathers concealed beneath a bird’s sleek outer feathers trap a layer of insulating air. To further increase their insulation, birds puff out their feathers in the cold. They also grow additional feathers in winter. However, birds have very high metabolisms, and feathers alone are not enough to maintain their body temperatures. Birds lose significant amounts of heat energy through their thin, poorly insulated legs and can reduce heat loss by tucking one leg up into their feathers while standing on the other. Most birds shiver continuously in cold weather to keep warm when not in flight. Also, chickadees and other small birds can allow their body temperature to drop several degrees below normal during the night.
Animals lose heat through their body surface, and small animals are particularly vulnerable to heat loss due to their greater surface-area to body-volume ratio. Some small mammals and birds overcome this problem by huddling. Huddling effectively makes several small animals into a single, larger animal with a more favorable ratio of surface area to body volume. Nuthatches huddle in tree cavities or nest boxes on cold nights. To try to stay warm, animals like squirrels and mice may also huddle close together.
While we can run down to the grocery store for something to eat and simply turn up the thermostat when we get home to stay warm, our wild friends have had to evolve a myriad of strategies over many millennia simply to survive. The residents of Wildlife Images need our help to get through the winter. Your donations help feed the eagles, bobcats, wolves, owls, raccoons, and our other rehabilitated animals throughout the entire year. Click here to make a donation today.
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