When the temperature drops, we put on a coat. When our home becomes a bit uncomfortable, we adjust the thermostat or put another log on the fire. You get the idea…but what about the wild creatures of the Tennessee fields and forests? How do they make adjustments to changing condition? Let’s look at a few examples in our southeast Tennessee area……
Small mammals like squirrels, mice, voles, weasels, and chipmunks stay active during the winter. Mortality rates, especially in the young, can be high…especially in particularly cold winters. For nutrition, they rely primarily on previously hidden stored nuts and grains during the tough times of winter. The Raccoon and the Opossum (our only Marsupial) are good examples of Tennessee survivors. As many homeowners know, they will eat almost anything at any time….from the refuse in your garbage can to the sunflower seeds in your bird feeders. Studies show some small mammals show a significant reduction in body mass in winter to reduce the need for intake of food.
One thing is for sure, birds and mammals that remain active during our winter months must maintain a base internal temperature in order to survive…either through stored body fat or intake of food. The thicker fur common on most mammals in winter helps to achieve the insulation effect. Birds and mammals are known as endothermic (homeotherms)…and for the most part require fuel to keep the motor running through the challenging times of winter! Some mammals, such as the Woodchuck, adapt by going underground…semi-hibernating.
To help with insulation and heat loss, the down feathers of birds become more pronounced in winter. The ‘layered’ arrangement of the feathers, especially the down feathers nearest the body mass, is waterproof. Many birds migrate during winter…an adaptation that usually follows the food supply. Permanent residents in our area include: Chickadees, Titmice, Mockingbird, Eastern Bluebird, and many of the species of Woodpeckers…Red-Bellied, Red-Headed, Pileated, Downy, Hairy, and the Common Flicker. Hint: they love suet cakes in winter. Many of the hawks also stay with us during the winter (Red-Tailed, Sparrow Hawk….)…while others migrate.
Reptiles, the snakes, lizards, and turtles, being ectothermic, or cold-blooded, must adapt in different ways to survive. They are totally reliant on the energy of the sun (and resulting air temperature) to maintain a suitable internal environment necessary for survival. Snakes den underground en masse during late fall/winter. This usually takes place at the base of rock formations with southern exposure. Body activities, including the heartbeat and respiration, reduce almost to zero in hibernating reptiles, drastically reducing the need for energy to keep the engine running. Turtles typically hibernate in the mud at the bottom of a pond, lake or stream. Only when the springtime sun warms the air/soil to desired levels can the Reptilia again continue what we know as normal body activities.
The Amphibia (frogs, salamanders…) adjust to winter similar to the reptiles.
The Whitetail Deer adapts to winter in our area in many ways. From a nutritional standpoint, the deer rely on twigs/buds of various hardwood species, as well as select species of winter grasses. In late summer/early fall, the thin hair of the red-tinted summer exterior coat is replaced by more dense hair of the gray winter coat (see photos). In summary, their coat becomes more dense in late fall and layers of fat become more pronounced beneath the skin, particularly along the spine.
Trees adapt as well. Evergreens are more common in the northern states for a reason…they are better suited with adaptations to the cold temperatures of winter. Deciduous trees shed their leaves in autumn, but that does not mean photosynthesis comes to a stop. This life-giving process slows in winter, but continues in the twigs/buds, simply waiting for the warmth of spring to activate the mitotic division that will eventually provide the new display of millions of leaves. The buds that can be seen on the twigs of deciduous species in winter are covered by a cuticle (or scale)…nature’s protection until conditions are favorable for growth.
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