Since the cold icy weather hit North Texas Sunday evening we have been indoors, staying warm, but have been thinking, as we watch birds at the feeders, what about the wildlife in our area?
Some animals migrate while others remain and stay active in the winter. They must adapt to the changing weather. Many make changes in their behavior or bodies. To keep warm, animals may grow new, thicker fur in the fall.
Food is hard to find in the winter. Some animals, like squirrels, mice and beavers, gather extra food in the fall and store it to eat later. Some, like rabbits and deer, spend winter looking for moss, twigs, bark and leaves to eat. Other animals eat different kinds of food as the seasons change. The red fox eats fruit and insects in the spring, summer and fall. In the winter, it cannot find these things, so instead it eats small rodents.
Animals may find winter shelter in holes in trees or logs, under rocks or leaves, or underground. Some mice even build tunnels through the snow. To try to stay warm, animals like squirrels and mice may huddle close together.
Cold-blooded animals like fish, frogs, snakes and turtles have no way to keep warm during the winter. Snakes and many other reptiles find shelter in holes or burrows, and spend the winter inactive, or dormant. This is similar to hibernation.
Water makes a good shelter for many animals. When the weather gets cold, they move to the bottom of lakes and ponds. There, frogs, turtles and many fish hide under rocks, logs or fallen leaves. They may even bury themselves in the mud. They become dormant. Cold water holds more oxygen than warm water, and the frogs and turtles can breath by absorbing it through their skin.
Insects look for winter shelter in holes in the ground, under the bark of trees, deep inside rotting logs or in any small crack they can find. One of the most interesting places is in a gall. A gall is a swelling on a plant. It is caused by certain insects, fungi or bacteria. They make a chemical that affects the plant's growth in a small area, forming a lump. The gall becomes its maker's home and food source.
Every type of insect has its own life cycle, which is the way it grows and changes. Different insects spend the winter in different stages of their lives. Many insects spend the winter dormant, or in "diapause." Diapause is like hibernation. It is a time when growth and development stop. The insect's heartbeat, breathing and temperature drop. Some insects spend the winter as worm-like larvae. Others spend the winter as pupae. (This is a time when insects change from one form to another.) Other insects die after laying eggs in the fall. The eggs hatch into new insects in the spring and everything begins all over again.
On the website for Michigan State University Extension service, we found some additional information on winter adaptations:
- Bergmann's Rule states that northern species of a particular genus or similar class of birds or mammals tend to be larger in size, although this is not always true. Larger body size means a higher body mass-to-surface area ratio. It's easier to retain heat. Polar bears are larger than tropical bears. White-tailed deer in Michigan dress out at higher weights than their counterparts in Texas or Florida.
- Body appendages tend to get smaller in the north, as a heat conservation measure. Snowshoe hares have smaller ears that cottontail rabbits. Mammalian legs and snouts are frequently shorter and stouter.
- Specialized fat, called brown fat, is produced during the food-rich seasons and expended during cold seasons. This is also the kind of fat that most hibernators use for arousal and many migrators use for fuel.
- Various "heat exchange" mechanisms can be found in animal circulatory systems that reduce heat loss to body extremities.
- Certain fish and herptiles produce chemicals within and between cell walls that can lower their freezing temperature a few degrees. In sheltered environmental niches, these few degrees can mean the difference between life and death.
- Some mammals, such as flying squirrels and small rodents, will occupy collective dens to conserve body heat, even though some species are non-colonial during the warm season. This is part of the reason that some species of snakes will do the same thing.
- Food preferences change with the season. Some browsers, such as white-tailed deer, have changes in digestive enzymes to cope with the different food sources. This is one of the reasons why biologists argue against winter deer feeding. If not done correctly, a deer can starve to death with a belly full of corn.
- Aquatic mammals, such as otter and mink, grow thick layers of insulating fat and have specialized fur. Similarly, ducks, geese, and swans have feathers and oil glands that keep water away from the skin. Some have efficient circulatory heat exchangers between the body and the feet. It's usually not the cold that causes waterfowl to migrate. It's more a matter of food shortages.
- Birds and mammals undergo seasonal changes in feathers and pelage. Trappers know that winter pelts are the highest quality because they are thicker and have different kinds of hair.
- Muskrats and beaver construct shelters, partly for protection from severe weather. A number of animals dig burrows, such as groundhogs, foxes, chipmunks, and moles.
- Many species of birds can adjust their internal body temperature downward to reduce the temperature gradient with environmental temperatures, thus reducing heat loss. They also tend to shiver a lot to maintain body temperatures.
From the website, Earth Gauge we learn that:
Prior to the actual onset of winter, animals that resist winter stresses have physiological responsesthat are cued in by the reduced daylight hours. Less daylight triggers a response that isregistered in the “master control” gland (hypothalamus) in the brain. The hypothalamus thensecretes hormones that activate other systems throughout the animal’s body. Animals react invarious ways. Moose, elk and deer begin to rut. The interval between the mating season and givingbirth ensures the young will be born in the spring when food is abundant. Another reactionto shorter days is the urge to eat more thus building up layers of fat that will help animals make itthrough winter. Beavers and red squirrels cache extra food. Animals that remain active all winterwill grow a thicker coat of fur. Deer, elk and moose have winter coats comprised of hollowhairs that trap air for better insulation. Other animals develop thick undercoats.
Even though we may be winter-ready, we are still eager for Spring!
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