Dr. Ray L. Winstead
Professor of Biology, Indiana University of
Winter Field Trip
Note the different animal tracks, e.g., deer, grouse, mice, squirrel, fox, rabbit, birds. - - This shows that winter is not a completely dead time in the forest.
Animals respond to a cold, harsh environment with little food in basically three ways:
1) Migrate to a warmer climate, 2) Hibernate, 3) Adapt to the environment.
Adapt to the cold environment:
1: fat layer
brown fat (e.g., in rodents): fat cells provide heat themselves by their own metabolism at that site.
white fat: energy source, nutritive source for rest of body - - also insulates.
2. increase in body metabolism - hormonal response.
3. development of thicker fur or down.
Hibernation (hiber = winter in Latin)
Examples: Woodchuck, Chipmunk (one of the few animals that stores food to eat during winter but is also a true hibernator).
Hibernation is a means of adjusting energy expenditures to food supplies - - triggered by duration of light during the day ("day length") - - not temperature. Animals just "turn down their thermostats" and live with a lower body temperature which conserves energy. Body temperature is lowered to just above freezing. The heartbeat slows (example: ground squirrel normal is 200 - 400 times / minute but when in hibernation it is 7 - 10 times / minute). All metabolism slows. Apparently even aging stops or slows down considerably since hibernators have longer life spans than similar animals that do not hibernate. Arousal is a process of self warming - controlled by a biological clock.
Dormancy: Metabolism and activity go up and down over winter - - animals just sleep for long periods of time (example: Black Bear).
Frostbite = freezing of tissue.
Susceptibles: fingers, toes, nose, cheeks, and ears.
Signs and stages:
1) Intense flushing of area with blood.
2) Gradual loss of blood in area with intense pain (the main signal that there is a problem).
3) Numb but pain goes away (not a good sign).
4) No feeling in area (actually comfortable) = tissue death.
Note: In very cold temperatures there is a normal fluctuation cycle of some flushing with blood into an area to get heat and nutrients and then a period of cutting off blood flow into those areas to conserve body heat. The area will feel cold but without the intense pain characteristic of a stage of frostbite.
The key is to warm the affected area slowly.
For example put a warm hand over the affected area or put an affected hand under the other arm pit.
Don't rub with anything - will destroy tissue and break blood vessels.
Don't overheat - just warm in warm water (100° - 105°F) if possible to return circulation to the area.
Warming process will be painful - a good sign that tissue is not completely destroyed.
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