Reflections in nature: Still a lot to learn about wildlife, winter
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For the past seven years I have been one of the volunteers working at the old Troy Sale Barn. With the financial and volunteer help of many folks in the area, the sale barn is being restored to be used as an event center.
During this past week, we experienced bitter cold weather with temperatures dropping below zero on many nights and never rising out of the teens during the day. On one such day, one of the two boilers in the barn had begun to not work properly.
Then the boiler completely died, causing our water pipes to freeze. As the temperature climbed above 32 degrees the frozen pipes began to thaw, and then, we had water problems.
Cold weather and snow usually bring human activity to a standstill, however, when on a walk in the woods on a frosty day, with snow on the ground, you will see many signs of animal activity.
By reading animal signs in the snow, I find it is almost as if studying the life history of an animal. When following an animal's tracks a person can learn what the animal eats, where it sleeps and how it survives.
During the winter months, the active wildlife keep warm by revving up their internal furnaces, a process known as shivering. Most birds will shiver throughout the winter. There are some birds, such as the goldfinch, that switch from using carbohydrates to fats in their diets. This switch prolongs the time of shivering and also the ability to use only certain muscles for this continuous shivering to preserve some of the fat.
Although humans shiver, our shivering does not increase body temperature. Shivering, which is our body's first response to being cold, aids the body temperature from falling lower and raises our body's metabolic rate. Minor shivering can produce 20% to 25% of the warmth our bodies produce. Violent shivering can increase heat production by as much as 400%.
Although shivering does not make a person feel warmer, it does prevent further heat loss. Shivering does not replace any warmth the body has already lost.
Most humans and animals cannot tolerate icy intrusions in their tissues. If the temperature drops low enough, ice forms in delicate blood vessels, causing the blood vessels to either burst or stretch beyond a point of rebounding. However, hydration is the main problem of frozen tissue. The frozen water is not available to the cells, which actually die of thirst.
Some wild creatures (mostly insects) have the ability to be supercooled and still survive. They have the ability to maintain a body temperature below the freezing point without freezing. For example, the wooly bear caterpillar can spend as many as ten months of the year in a frozen state without any ill effects. Some insects in Alaska are able to resist freezing in temperatures as low as 70 degrees below zero. This is done by ridding their bodies of "seed crystals," such as dust and bacteria, on which ice can form.
The arctic ground squirrel is one mammal that hibernates. During this hibernation, its body temperature drops below freezing without doing any harm to its body tissue. How the arctic ground squirrel is able to do this remains a mystery.
Other animals, such as wood frogs, box turtles and garter snakes, actually freeze solid and still survive. The wood frog survives freezing temperatures by producing a form of sugar, which is known as glucose that floods its body and in turn protects the cells from ice damage. The sugar increase causes the wood frog to go into a type of coma in which its metabolism drops to near zero. The frog freezes and spends the winter in a frozen state. In the spring, as the weather warms, the frog thaws out and hops away.
If we humans were able to pump enough glucose into our bodies to prevent our cells from freezing, our sugar level would be so high we would go into a diabetic coma and die.
The garter snake spends the winter in a hibernation den, where the temperature stays near 40 degrees. During this time, the snake's heart beat drops to a few beats per minute compared to approximately 20 beats per minute on a warm summer day. In early spring, the garter snake will come out of the den. This could be too soon due to the air possibly dropping in temperature below freezing, causing the snake to freeze.
However, a day or two spent in a frozen state does not harm the snake. When the temperature goes above 32 degrees, the snake thaws out and continues on its way.
The painted turtle hibernates under water. The cold water and low oxygen cause the turtle to go into hibernation. The heart beat can go as low as one beat every ten to eleven minutes; whereas, on a warm summer day, the heart beat could be 30 to 40 beats per minute.
If no oxygen is available, the turtle produces an unwanted byproduct known as lactic acid, which is the same chemical that causes cramps in humans. Too much of this lactic acid causes a fatal chemical imbalance called acidosis. The turtle combats this acidosis by using calcium carbonate from its shell, to neutralize the excess acid. The turtle has no ill effects. It's the same process as taking an antacid. When the water temperature rises, the turtle comes out of hibernation and goes about its life cycle.
We still have much to learn about how wildlife survives the winter's cold. It seems that when one question is answered, 10 more take its place. I know we have a long way to go since we humans still haven't been able to solve the problem of keeping our water pipes from freezing, yet alone our bodies.
Bill Bower is a retired Pennsylvania Game Commission Wildlife Officer. Read his blog and listen to his podcasts on the outdoors at www.onemaningreen.com.