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Narrator: Listen to part of a lecture in a biology class.

教授：詹姆斯，你说你去过缅因州，是吗？

Professor: Now, James, you said you've been to the State of Maine, right?

男学生：是的，其实我在十六岁以前一直都住在缅因州西部。

Male Student: Yeah, actually I lived in western Maine till I was about sixteen.

教授：好的，你能告诉我们一下那儿的冬天是怎样的吗？

Professor: Great. So why don’t you tell everybody what it's like there in the winter?

Male Student: In the winter? Well, it's, it's cold.

许多雪，雪之厚，令人难以想象。

And there’s lots of snow, you wouldn’t believe how much snow we used to get.

我在那儿做过野外实地调查，待过几个冬天。

I did field research up there a couple of winters.

那儿的环境真实令人难以置信。

And it really is an incredible environment.

要在那样的环境下生活，动物们必须得随着环境进化。

And to survive in that sort of environment, animals have to adapt, to evolve in response to their surroundings.

你们应该记得物种的进化，即在它们的行为或肢体上为在某个环境下生存和繁衍做出的改变。

As you'll recall, an adaptation is any feature, um... physical or behavioral feature of a species that helps it survive and reproduce.

为了适应极端的气候地带的生存环境，譬如缅因州的冬天，动物们以各式各样的方式进化，其中有一些非常有趣。

And in adapting to extreme climates, like Maine in the winter time, animals can evolve in pretty interesting ways.

这里我们就以缅因州的白靴兔为例谈谈这些进化吧。

好的，白靴兔，顾名思义，当然是一种野兔。

Ok, the snowshoe hare, and of course, that’s H-A-R-E, like a rabbit.

虽然，野兔与我们一般的兔子，严格地说，是有区别的，虽然它们很相似。

Although I probably should mention that technically a hare is not exactly the same as a rabbit, even though it is very similar.

野兔与家兔的主要区别是，家兔出生时是看不见东西的，而且没有胎毛，野兔出生时能够见物，且全身都有胎毛覆盖。

The primary difference is that a rabbit’s young are born blind and without fur, while a hare’s babies are born with a full coat and able to see.

现在，同学们，你们想一想，白靴兔到底在哪些方面发生了进化，从而能够在缅因州的冬天生存下来？

Now, the snowshoe hare, tell me, what sort of adaptations do you think it has developed that help it survive the Maine winters?

白靴兔充裕的食物主要来源是植物的细枝。

The hare actually has abundant food in the small twigs it finds.

我的意思是，我们曾在冬季远足的时候到处找这些兔子，但在雪里面根本找不到它们。

I mean, I know we used to try to look for those rabbits, eh... hares, when we went hiking in the winter, but it was often hard to find them in the snow.

教授：是的。实际情况是这样的。

白靴兔在冬季最大的顾虑是它的捕食者。

The major concern of the snowshoe hare in the winter is predators.

所以，它最基本的一项进化就是伪装。

So one of its adaptations is basically camouflage.

换句话说，它的毛色，从夏天的灰色变成了冬天的白色，这使得捕食者很难从雪地里找到它。

In other words, its coat, its fur, turns from brown in the summer to white in the winter, which makes it harder for the hare’s predators to see it against the white snow.

男学生：是的，但我发誓我记得有几回我在雪地里看到过白靴兔，它们的颜色是棕色的。

Male Student: Yeah, but I could swear I remembered seeing rabbits in the snow a couple of times, I means hares, that were brown.

教授：嗯，你看到的很可能是真实的。

变色的时机是很重要的，但白靴兔并不能一直都把时机把握好。

Timing is really important, but the snowshoe hare doesn’t always get it exactly right.

如果它们能在第一次降雪的时候变成白色，这对它们的生存无疑是最为有利的。

Its chances for survival are best if it turns white about the time of the first snowfall.

And it’s the amount of daylight that triggers the changing of the hare’s coat.

当白天变短的时候，即太阳高悬在天空中的时间越来越短的时候，白靴兔开始长出白毛，棕毛脱落。

As the days get shorter, that is, as the Sun is up for a shorter and shorter time each day, the snowshoe hare starts growing white fur and shedding its brown fur.

白靴兔一向把握时机的本领都很强，但是有时降雪时间或早或晚，它的颜色就在雪里面显露出来了。

The hare does a pretty good job with its timing, but sometimes when there’s a really early or late snow, it stands out.

而且，从开始脱毛刀棕毛完全脱尽需要花费一个月的时间。

Plus, it takes about a month for the snowshoe hare’s coat to completely change color.

这样的话，假如一场雪来得早了，白靴兔的毛可能还没有完全变白。

So if there’s a particularly early snowfall, it’s very likely that the hare’s fur would not yet be totally white.

这段时间对于它们来说是非常为危险的。

And that would make this a particularly dangerous time for the hare.

女学生：嗯，这种兔子叫做“白靴兔”，顾名思义，是不是它的脚能够起到保暖的作用？

Female Student: Well, it’s called the snowshoe hare, so are its feet somehow protect it from the cold?

教授：嗯，这种动物得名，确实与它双脚的适应性有关。

Professor: Well, this animal’s name does have to do with an adaptation of its feet.

然而，并不像它有温暖的毛靴子使它保持温暖。

Uh... though, not like it has warm furry boots or something to keep its feet from getting cold.

我们可能从来都不需要雪地靴。

You’ve probably never needed to wear snowshoes.

但是，雪地靴并不是那种很厚实的保暖靴，实际上这它很薄，但很宽。

But, well, snowshoes are not like thick furry shoes designed to keep the feet warm, they are actually quite thin, but very wide.

它的作用是把脚面展开，从而把身体重量施加给雪面的压力减小。

What they do is spread out the weight of the foot coming down on the snow.

大家都知道吧，在雪地里行走，麻烦就在于你每走一步，脚可能就陷下去一次。

See, the problem with walking on snow is that you sink in with every step.

但是，一旦穿上了雪地靴，你就不会陷下去，就能够在雪面上行走了。

But with snowshoes, you don’t sink in, you walk on top of the snow.

穿上它，在缅因州的乡村道路上行走就容易得多了。

It makes walking through the Maine countryside in the winter much easier.

总之，白靴兔有一项进化，原理与雪地靴差不多。

Anyway, the snowshoe hare has an adaptation that plays on the same idea.

它的脚部有肉垫，与雪地靴的功能相似。

It has hind feet that act like snowshoes.

它的脚掌很宽，使得白靴兔能够在雪的表面上疾速奔跑。

I mean, its paws are wide and they allow the hare to hop and run just at the surface of deep snow.

这对其捕食者而言，是一项很大的优势，它们捕食者总是在雪地行动时陷入雪地里面。

And this is a huge advantage for the snowshoe hare since by contrast, the feet of its predators usually sink right down into the snow.

这项进化带来的另一项优势是，白靴兔可以保持身体姿势的倾斜，负重低。

Now, another advantage related to this is that unlike many animals in winter, snowshoe hares can stay lean and light weight.

有同学能想到这是怎么回事吗？

Female Student: They don’t eat very much?

教授：嗯，对。但这并不是因为它们能找到的食物不够。

Professor: Well, yes. But not because there isn’t enough food around.

这是因为，如我前面讲的，它们的食物随时触手可及，因此它们无须在严酷的冬季储食。

It’s because, like I said, food is almost always within reach, and they don’t have to store up a lot of food energy for the harsh winters.

According to the professor, what causes the snowshoe hare's fur to begin turning white?

Why might an early snowfall be a particular dangerous time for the snowshoe hare?

The professor implies that the snowshoe hare has an advantage over other animals because of its unusual feet. What is that advantage?

The professor explains that the snowshoe hare's supply is available year-round. What does the availability of the food allow the snowshoe hare to do?

Narrator 
Listen to part of a lecture in a biology class. 
Professor 
Now, James, you said you had been to the State of Maine, right? 
Student 
Yeah, actually I lived in western Maine until I was about sixteen. 
Professor 
Great. So why don’t you tell everybody what is like there in the winter? 
Student 
The winter? Well, it’s cold. And there’s lots of snow, you wouldn’t believe how much snow we 
used to get. 
Professor 
Actually I would. I did field research up there a couple of winters. And it really is an incredible environment. And to survive in that sort of environment, animals have to adapt, to evolve in response to their surroundings. As you recall, an adaptation is any feature, um... physical or behavioral feature of a species that helps it survive and reproduce. And in adapting to extreme climates, like Maine in the winter time, animals can evolve in pretty interesting ways. Take, for example, the snowshoe hare. 
Ok, the snowshoe hare, and of course, that’s H-A-R-E, like a rabbit. Although I probably should mention that technically a hare is not exactly the same as a rabbit, even though it is very similar . The primary difference is that a rabbit’s young are born blind and without fur , while a hare’s babies are born with a full coat and able to see. 
Now, the snowshoe hare, tell me, what sort of adaptations do you think it has developed that help it survive the Maine winters? I’ll give you a hint. Food isn’t an issue. The hare actually has abundant food in the small twigs it finds. 
Student 
Well, I don’t know. I mean, I know we used to try to look for these rabbits, eh... hares, when we went hiking in the winter, but it was often hard to find them in the snow. 
Professor 
Yes. That’s exactly right. The major concern of the snowshoe hare in the winter is predators. And now that includes humans. So one of its adaptations is basically camouflage. In other words, its coat, its fur, turns from brown in the summer to white in the winter , which makes it harder for the hare’s predators to see it against the white snow. 
Student 
Yeah, but I could swear I remembered seeing rabbits in the snow a couple of times, I means hares, that were brown. 
Professor 
Well, you may very well have. Timing is really important, but the snowshoe hare doesn’t always get it exactly right. Its chances for survival are best if it turns white about the time of the first snowfall. And it’s the amount of daylight that triggers the changing of the hare’s coat. As the days get shorter, that is, as the Sun is up for a shorter and shorter time each day, the snowshoe hare starts growing white fur and shedding its brown fur. The hare does a pretty good job with its timing, but sometimes when there’s a really early or late snow, it stands out. Plus, it takes about a month for the snowshoe hare’s coat to completely change color. So if there’s a particularly early snowfall, it’s very likely that the hare’s fur would not yet be totally white. And that would make this a particularly dangerous time for the hare. 
OK. What else? Other adaptations? Susan? 
Professor 
Well, you may very well have. Timing is really important, but the snowshoe hare doesn’t always get it exactly right. Its chances for survival are best if it turns white about the time of the first snowfall. And it’s the amount of daylight that triggers the changing of the hare’s coat. As the days get shorter, that is, as the Sun is up for a shorter and shorter time each day, the snowshoe hare starts growing white fur and shedding its brown fur. The hare does a pretty good job with its timing, but sometimes when there’s a really early or late snow, it stands out. Plus, it takes about a month for the snowshoe hare’s coat to completely change color. So if there’s a particularly early snowfall, it’s very likely that the hare’s fur would not yet be totally white. And that would make this a particularly dangerous time for the hare. 
OK. What else? Other adaptations? Susan? 
Student 
Well, it’s called the snowshoe hare, so are its feet somehow protect it from the cold? 
Professor 
Well, this animal’s name does have to do with an adaptation of its feet. Uh... though, not like it has warm furry boots or something to keep its feet from getting cold. You’ve probably never needed to wear snowshoes. But, well, snowshoes are not like thick furry shoes designed to keep the feet warm, they are actually quite thin, but very wide. What they do is spread out the weight of the foot coming down on the snow. See, the problem with walking on snow is that you sink in with every step. But with snowshoes, you don’t sink in, you walk on top of the snow. It makes walking through the Maine countryside in the winter much easier . 
Anyway, the snowshoe hare has an adaptation that plays on the same idea. It has hind feet that act like snowshoes. I mean, it’s paws are wide and they allow the hare to hop and run just at the surface of deep snow. And this is a huge advantage for the snowshoe hare since by contrast, the feet of its predators usually sink right down into the snow. 
Now, another advantage related to this is that unlike many animals in winter, snowshoe hares can stay lean and light weight. They accumulate essentially no body fat. Can anyone guess why this is so? 
Student 
They don’t eat very much? 
Professor 
Well, yes. But not because there isn’t enough food around. It’s because, like I said, food is almost always within reach, and they don’t have to store up a lot of food energy for the harsh winters. 
Professor 
Yes. That’s exactly right. The major concern of the snowshoe hare in the winter is predators. And now that includes humans. So one of its adaptations is basically camouflage. In other words, its coat, its fur, turns from brown in the summer to white in the winter , which makes it harder for the hare’s predators to see it against the white snow. 
Student 
Yeah, but I could swear I remembered seeing rabbits in the snow a couple of times, I means hares, that were brown.