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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.
一個很好的例證是白尾鹿。與大多數野生動物一樣，鹿在營養豐富、食物充足的夏秋兩季，繁殖、生長并儲存脂肪。一只成熟健壯的母鹿，在十一月份懷胎，五月底或六月初生下兩只幼鹿，這時，它必須尋找食物以獲得必要的能量，這不僅是為了滿足自身的需要，而且也是為了給幼鹿生產乳汁。產乳的最佳期也正是植物生長茂盛之時。這個時機選擇得很好，因為乳汁生產是一個消耗能量的過程-它需要大量的食物，除非該地區具有豐富的食物資源，否則無法滿足這種消耗。
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.
夏季一天天過去，幼鹿日漸生長，它們變得較少依賴母鹿的乳汁，而更加依靠生長中的植物為其食物來源。雄性成鹿在夏天生長鹿角并養肥身體。在秋天，雄鹿和雌鹿都繼續進食高質量食物，貯存體內脂肪，以備過冬。至于雌鹿和幼鹿，由于大量的能量用于產奶或生長，脂肪的積累速度不如完全成熟的雄鹿快。脂肪儲備如同銀行里的存款，供冬天食物來源不足時和有時由于雪深難以獲得時支取使用。
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.
隨著秋去冬來，還會發生其他變化: 幼鹿失去皮毛上的斑紋，所有鹿身上的毛長厚，顏色變深。毛皮的變化通常持續到9月。到11月或12月天氣變冷時，毛長得最厚。
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，大自然還為鹿提供進一步的保護以幫助它們度過冬天-體內生理機能作相應調節，放慢新陳代謝，亦即生理活動的速度，從而降低能量的消耗。鹿變得有點動作遲緩、嗜睡。它們的心率減慢。冬眠的動物保存能量的習性勝過鹿。雖然鹿不冬眠，但他們隨季節改變新陳代謝節奏的習性則是一樣的。夏秋間，食物充裕的時候，鹿消耗較多的能量并儲存脂肪。在冬天食物匱乏時，它們則消耗較少的能量并使用儲存的脂肪。
