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How Deer Survive Winter
   We know that in summer and fall, when there is plenty of food, wild animals will eat as much as they can. So, besides the energy spent on maintaining their normal activities, there is some excess. They store the excess in the form of fat, and then in winter when food is scarce, they use these reserves of fat to survive. In addition to this, nature also provides other safeguards for wild animals to survive.
   This is the way through which deer survive winter. Like most wild animals, deer reproduce, grow, and store fat in summer and fall when there is plenty of nutritious food available. A physically mature female deer in good condition who has conceived in November and given birth to two fawns during the end of May or the beginning of June, must get enough food to not only meet her own body’s needs but also to produce milk for her fawns. The best milk production occurs at the same time that new plant growth is available. This is good timing, because milk production is an energy consuming process —it requires a lot of food. The cost can not be met unless the region has ample food resources.
   As the summer progresses and the fawns grow, they become less dependent on their mother’s milk and more dependent on growing plants as food sources. The adult males spend the summer growing antlers and getting fat. Both males and females continue to eat high quality food in fall in order to deposit body fat for winter. Fat reserves are like bank accounts to be drawn on in winter when food supplies are limited and sometimes difficult to reach because of deep snow.
   As fall turns into winter, other changes take place. Fawns lose their spotted coat. Hair on all the deer becomes darker and thicker. The change in the hair coats is usually complete by September and maximum hair depths are reached by November or December when the weather becomes cold.
   But in addition, nature provides a further safeguard to help deer survive the winter. This is an internal physiological response which lowers their metabolism, or rate of bodily functioning, and hence slows down their expenditure of energy. The deer become somewhat slow and drowsy. The heart rate drops. Hibernating animals such as snakes and bears practiced the energy conservation in winter to a greater degree than deer do. Although deer don’t hibernate, they have the same energy saving and spending rhythm to keep in pace with nature’s seasonal changes.
   So, we can see that deer spend more energy and store fat in the summer and fall when food is abundant, and spend less energy and use stored fat in the winter when food is less available. Meanwhile, in winter they reduce their activity, grow a thicker coat of hair, and reduce their metabolism. The reduction in the cost of energy is meant to increase their chances of living. This internal biological response is obtained through thousands of years of evolution. The cruel rule of evolution Survival of the Fittest —will see to it that the deer, as well as any other animal get this gift from nature.
   If the winter has light snow, deer’s survival and productivity in the next spring will be high. But if deep snows come and the weather remains cold for several weeks, then the deer must spend more energy to move about, food will be harder to find, and they must then depend more on their fat reserves to pull them through. If such conditions go on for too long, some will die, and only the largest and strongest are likely to survive. That is the fundamental rule of life for wild, free wandering animals such as deer.