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A good case in point is the white-tailed deer. Like most wildlife, deer reproduce, grow, and store fat in the 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 birthto two fawns during the end of May or first part of June, must search for food for the necessary energy not only to meet her 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.
一个很好的例证是白尾鹿。与大多数野生动物一样，鹿在营养丰富、食物充足的夏秋两季，繁殖、生长并储存脂肪。一只成熟健壮的母鹿，在十一月份怀胎，五月底或六月初生下两只幼鹿，这时，它必须寻找食物以获得必要的能量，这不仅是为了满足自身的需要，而且也是为了给幼鹿生产乳汁。产乳的最佳期也正是植物生长茂盛之时。这个时机选择得很好，因为乳汁生产是一个消耗能量的过程-它需要大量的食物，除非该地区具有丰富的食物资源，否则无法满足这种消耗。
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 the fall in order to deposit body fat for the winter. In the case of does and fawns, a great deal of energy is expended either in milk production or in growing, and fat is not accumulated as quickly as it is in full grown males. Fat reserves are like bank accounts to be drawn on in the winter when food supplies are limited and sometimes difficult to reach because of deep snow.
夏季一天天过去，幼鹿日渐生长，它们变得较少依赖母鹿的乳汁，而更加依靠生长中的植物为其食物来源。雄性成鹿在夏天生长鹿角并养肥身体。在秋天，雄鹿和雌鹿都继续进食高质量食物，贮存体内脂肪，以备过冬。至于雌鹿和幼鹿，由于大量的能量用于产奶或生长，脂肪的积累速度不如完全成熟的雄鹿快。脂肪储备如同银行里的存款，供冬天食物来源不足时和有时由于雪深难以获得时支取使用。
As fall turns into winter, other changes take place. Fawns lose their spotted coat. Hair onall 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.
随着秋去冬来，还会发生其他变化: 幼鹿失去皮毛上的斑纹，所有鹿身上的毛长厚，颜色变深。毛皮的变化通常持续到9月。到11月或12月天气变冷时，毛长得最厚。
But in addition, nature provides a further safeguard to help deer survive the winter - 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. Animals that hibernate practice energy conservation to a greater extreme than deer do. Although deer don't hibernate, they do the same thing with their seasonal rhythms in metabolism. 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.
此外，大自然还为鹿提供进一步的保护以帮助它们度过冬天-体内生理机能作相应调节，放慢新陈代谢，亦即生理活动的速度，从而降低能量的消耗。鹿变得有点动作迟缓、嗜睡。它们的心率减慢。冬眠的动物保存能量的习性胜过鹿。虽然鹿不冬眠，但他们随季节改变新陈代谢节奏的习性则是一样的。夏秋间，食物充裕的时候，鹿消耗较多的能量并储存脂肪。在冬天食物匮乏时，它们则消耗较少的能量并使用储存的脂肪。
