The Nature Writers of Texas

The best nature writing from the newspaper, magazine, blog and book authors of the Lone Star State . . .

Sunday, January 28, 2007

Wildlife Survival During Extreme Cold
by Ro Wauer

Our recent cold snap, in which we all suffered through colder than normal conditions, also affected our wildlife that lives outdoors all of the time. Some individuals undoubtedly were unable to survive, either because of cold and wet conditions or their inability to find adequate food. Most of the cold blooded adult insects, for example, simply perished, unless they were fortunate to find a protected niche. More than likely all of the butterflies died from either the cold, lack of food, or dehydration. There is at least one exception to this. Although the mourning cloak (butterfly) is extremely rare in our part of Texas, it does occur in most of the remainder of the country. And it is known for finding a protected place during stormy weather, goes into a semi-hibernation, and is able to fly about during warming periods, even when snow cover the ground. The mourning cloak is our longest lived butterfly.

What about our wild mammals and birds? This group of wildlife, of course, is warm-blooded. So they are able to do much better than the cold-blooded creatures during cold weather. Mammals, such as deer and some of our large predators, get along very well so long as they are able to find enough feed. There are, however, records of deer, usually those already weakened by disease or injury that is unable to survive during exceptionally cold and wet periods. And most of the smaller mammals, such as armadillos, skunks, and even smaller species such as mice, that spend most of the daylight hours in a den, usually remain there, cozy and warm, even when temperatures outside the den drop below freezing.

Our wild birds often find cold and stormy conditions more difficult. But even the smaller birds can usually survive unless they have already been weakened by injury or disease. Birds have developed extraordinary methods for survival. For instance, hummingbirds actually go into a state of torpor, in which their body temperatures drop to 50 degrees F. for several hours. But once they awaken they must feed. That is the reason it is so important to maintain hummingbird feeders during the winter. Recent studies suggest that many other birds, besides hummingbirds, swifts and poorwills, can enter shallow torpor for short periods.

As might be expected, birds lose their body heat more through bare surfaces than through their feathered bodies. Bird legs and feet are especially vulnerable, so the warmer body blood circulates, keeping the legs and feet at a safe temperature. Also, a bird can stand on one leg and tuck the other up against it warm body, or it can sit with its legs underneath. In addition, birds can fluff out their feathers to increase the thickness of their insulated "coat."

On sunny days, even during periods of cold, numerous birds warm their bodies by spreading their wings. Some of the better examples of this include the vultures, anhinga, and cormorants. Even roadrunners will sit with their wings partially spread so that their back is fully exposed to the sun. This type of sunbathing occurs in lots of other birds, too, such as grebes, hawks, and even a number of songbirds. And in many bird species their non-feathered patches of skin are dark colored, better for absorbing heat from the sun.

And what about our wild reptiles and amphibians? Because these animals are cold-blooded, like insects and other invertebrates, they must find shelter before a winter storm. Alligators and sea turtles can sink to the bottom of bays and ponds where they enter a torpid state. Other reptiles, such as most snakes, hibernate from late fall until spring, usually in dens or under the soil or rocks. During those periods they are inactive and sometimes almost lifeless. There are records, mostly in the colder regions of the country, where a snake den has been uncovered that contains 100 or more individuals of several species.

Sitting in our heated homes, watching TV or visiting with friends and family during winter storms, we tend to take much for granted. But it is not always so easy on our wildlife neighbors.


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