Unit 2

Is there anything we can learn from deer? During the “energy crisis” of 1973—1974 the writer of this essay was living in northern Minnesota and was able to observe how deer survive when winter arrives. The lesson he learns about the way deer conserve energy turn out applicable to our everyday life.

Deer and the Energy Cycle

Aaron N. Moen

Some persons say that love makes the world go round. Others of a less romantic and more practical turn of mind say that it isn’t love; it’s money. But the truth is that it is energy that makes the world go round. Energy is the currency of the ecological system and life becomes possible only when food is converted into energy, which in turn is used to seek more food to grow, to reproduce and to survive. On this cycle all life depends.

It is fairly well know that wild animals survive from year to year by eating as much as they can during the times of plenty, the summer and fall, storing the excess, usually in the form of fat, and then using these reserves of fat to survive during the hard times in winter when food is scarce. But it probably less well known that even with their stored fat, wild animals spend less energy to live in winter than in summer.

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 give birth to two fawns during the end of May or first part of June, must searched for food for the necessary energy not only to meet her body’s need 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 in 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 source. 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 grow males. Fat reserves are likely bank accounts to be drawn on in the winter when food supplies are limited and sometimes difficult to reach because of deep snow.

As fall turns into winter, other change 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 ——an internal physiological response which lowers their metabolism, or rate of bodily functioning, and hence slow 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.

When the energy crisis first came in 1973—1974，I was living with my family in a cabin on the edge of an area where deer spend the winter in northern Minnesota, observing the deer as their behavior changed from more activity in summer and fall to less as winter progressed, followed by an increase again in the spring as snow melted. It was interesting and rather amusing to listen to the advice given on the radio:

“Drive only when necessary,” were told. “ put on more clothes to stay warm, and turn the thermostat on your furnace down.” Meanwhile we watched the deer reduce their activity, grow a winter coat of hair, and reduce their metabolism as they have for thousands of years. It is biologically reasonable for deer to reduce their cost of living to increase their chances of surviving in winter.

Not every winter is critical for deer of course. If the winter has light snow, survival and productivity 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 a fundamental rule of life for wild, free wandering animals such as deer.

Yes, life — and death, too — is a cycle that goes round and round, and when animals die their bodies become food for other life forms to use by converting them into energy.

And the cycle continues.

[ 862 words ]

译文：有什么是我们能从鹿身上学到的吗？在1973—1974年的“能源危机”期间，本文作者正住在明尼苏达北部，能够观察当冬天来临时，鹿如何生存。他从鹿储存能量的方法上得到经验也能运用到我们日常生活中。

鹿和能量循环

阿伦·N·莫斯

有些人说，爱情驱使世界运转：另一些并不那么罗曼蒂克而更为注重实际的人则说，不是爱情，而是金钱。但真实情况是，能量驱使世界运转，能量是生态系统的货币，只有当食物转变为能量，能量再用来获取更多的食物以供其生长、繁殖和生存，生命才能成为可能。所有生命都维系在这一循环上。

差不多众所周知，野生动物得以年复一年地生存下去，主要依靠在夏秋生长旺季尽量多吃。通常将多余的部分以脂肪的形式储存起来。然后到了冬天食物稀少的艰难时期，就用这些储备的脂肪来维持生命。然而很可能鲜为人知的是，即使有储备的脂肪，野生动物在冬天消耗的能量比夏天要少。

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，生长并存脂肪。一只成熟健壮的母鹿，在十一月怀胎，五月底或六月初生下两只幼鹿，这时，它必须需找食物以获得必要的能量，这不仅仅是为了满足自身的需要，而且也是为了给幼鹿产乳汁，产乳的最佳期也是植物生长茂盛之时。这个时机选择得很好，因为乳汁的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。

夏天一天天过去，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产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。

随着秋去冬来，还会发生其他变化：鹿失去皮毛上的斑纹，所有鹿身上的毛长厚，颜色变深。毛皮的变化通常维持到9月。到11月或12月天气变冷时，毛长的最厚。

此外大自然还为鹿提供了进一步的保护，以帮助他们度过冬天——体内生理机能作用作相应调节，放慢新陈代谢，亦即生理活动的速度，从而降低能量消耗。鹿变得有点动作迟缓、嗜睡。他们的心律减慢。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。他们则消耗较少的能量并使用储存的脂肪。

1973—1974年间，第一次出现“能源危机”的时候，我正与家人住在明尼苏达州北部一处鹿群过冬地方的边缘地带。我们住在一个小小的屋里，观察鹿的生活习性，观察他们如何随着冬季来临从夏秋的活动频繁状态而变得少动的，而到春暖雪融时，他们的活动又是如何增多起来的。

当时广播电台常告诫我们：“没有必要开车，”“多穿衣服好保暖，并请调低锅炉上的恒温器。”这些话听起来既有趣又逗笑。因为与此同时，我们一直注视着鹿减少活动，长出越冬的厚毛，并减缓新陈代谢。几千年来，它们一贯如此，鹿减少生存所需的能耗以增加越冬的机会，从生物学的角度来看是合情合理。

当然，对鹿来讲，并非每个冬天都处于危难之中。如果冬天下雪得少，存活率和次年春天的繁殖力就高。但如果雪积得很深，天气连续数周寒冷，鹿活动起来就得花费较多的能量，觅食会更难，这时他们就得更多地依赖其脂肪储备过寒冬。如果这种情况持续太久，有些鹿就要死亡。只有体型最大的最壮的，才有可能存活。对于像鹿这样四处自由奔走的野生动物来说，这是一条根本性的生存规律。

的确，生命——还有死亡——周而复始，循环不已。当动物死亡的时候他们的尸体转化为能量，变成食物，供其他生命形式使用。

如此循环，永不止息。