OUTDOOR CORNER: SOME ANIMALS GIBERNATE TO CUT HEATING BILL

Bears, bats, and song birds have something in common.

Although odd sounding they make attempts to abandon warm-blooded life for the energy conservative life of cold bloodedness. Many people call this hibernation and the common notion is that it is a deep sleep. Hibernation is more than that and is worth a closer look to see why and how animals deal with winter.

Being warm blooded has a huge price. Lots and lots of food is needed to fuel a body heat furnace. Just like the furnace in a home, a warm-blooded body needs fuel to produce heat. The fuel in the case of a mammal or a bird is food. Food is consumed in large amounts to burn off as heat. A small amount of food is used to perform bodily tasks such as breathing, heart pumping, cell building and so on. A vast majority of the calories eaten though are used for heat.

Being cold blooded on the other hand requires so much less food because body temperature is managed by the temperature of things around. A hot black top road would warm a cold critter while a cool stream in February water will keep it quite cold. This of course means the animal is less energetic when cold because many animals work best at around 98 degrees. If you are colder than that you are sluggish and inactive.

The bonus here is that you are not as hungry! A cold stomach will process food very slowly. A cold body will not use energy very fast. Low energy use means low energy needs, so a cold blooded creature can go without eating for a longer period of time and just sleep the cold weather away.

Think about it! Winter has little food for many animals. So if an animal can go without eating and survive they are better off. The only problem with that idea is that changing your rate of fuel burning (called metabolism) is not a matter of choice. It is a matter of genetic programming. A few animals have managed to have some varying success at trying to abandon their warm bloodedness in favor of energy-cheap cold bloodedness.

Bats are a classic case for hibernation. Flying insects are the only food for all of Missouri's bats and those insects are scarce in winter. Most bats just find a safe place to hang and lower their body temperature. They do this by reducing their fuel burning and therefore use little energy. The result is that eating is not needed. The heartbeat slows tremendously and breathing is just traceable.

Bats are really out of it for a while. To wake up requires burning fat to bring the body back up to working temperatures again. Bats can only do this twice, once to take a winter drink and once to welcome spring time. Unnecessary waking due to disturbance will ensure they do not wake from hibernation in spring.

Bears are famous for hibernation, but few people realize that bears are not capable of hibernation. To truly hibernate an animal must lower its body temperature to just above freezing. That may not sound too hard in winter and it isn't. The problem with bears doing this is that they could never store enough fat to come OUT of true hibernation! They would have to store 6-7 times their body weight in fat to generate enough heat to raise their large body's temperature to operating standards again.

If this sounds odd, consider which is more expensive to heat, a one room shack or a large sports arena? What bears do is called "torpor" and it involves a slight drop in body temperature, relaxed breathing, and slower heart rate. In comparison to a bat it is still quite active.

Birds also try to reduce heating costs. In really cold snaps they will let their body go into short periods of hypothermia.

Hypothermia involves lowering your body temperature below normal rates. For a majority of warm-blooded animals this is not safe and it is the next step to worse things like frostbite, and freezing. But some songbirds can do this for just the night period when it is almost impossible to keep a body heated. The next day brings time to feed and fuel the body heat furnace.

Bear in mind that reducing body heat and food consumption is not a choice an animal makes. Yes it can be a savings to the animal but they do this by instinct and their body has to be able to handle it.

People are not very tolerant of lowered body temperatures. We can endure them but not for long periods. Most warm-blooded animals are bound to those same rules.... eat to stay warm or die. Those animals that can break the rules are rewarded with a lower fuel bill when getting food to burn is scarce anyway!

A.J. Hendershott is an education consultant with the Missouri Department of Conservation.