[00:00.00]Narrator: Listen to part of a lecture in a biology class.
[00:05.57]Female Professor: Now James, you said you've been to the state of Maine, right?[00:09.98]Male Student: Yeah, actually, I lived in western Maine till I was about 16.[00:13.82]Female Professor: Great. So why don't you tell everybody what it's like there in the winter.[00:18.16]Male Student: In the winter? Well, it's cold … [00:21.37]and there's lots of snow. You wouldn't believe how much snow we used to get.
[00:25.34]Female Professor: Actually, I would. [00:26.85]I did field research up there a couple of winters, [00:29.41]and it really is an incredible environment. [00:32.18]And to survive in that sort of environment, animals have to adapt … to evolve in response to their surroundings.
[00:39.86]As you'll recall, an adaptation is any feature—uh, physical or behavioral feature—of a species that helps it survive and reproduce. [00:50.36]And in adapting to extreme climates—like Maine in the wintertime—animals can evolve in pretty interesting ways.[00:58.04]Take, for example, the snowshoe hare.
[01:01.41]OK, the snowshoe hare—and of course that’s “H-A-R-E,” like a rabbit … [01:08.47]though I probably should mention that technically a hare is not exactly the same as a rabbit, even though it is very similar. [01:16.83]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.[01:26.83] Now, this snowshoe hare … tell me … what sort of adaptations do you think it's developed that help it survive the Maine winters? [01:36.96]I’ll give you a hint. [01:38.40]Food isn't an issue. [01:40.65]The hare actually has abundant food in the small twigs it finds.[01:44.52]Male Student: Well, I don't know. [01:45.95]I mean, I know we used to try to look for those rabbits, … uh hares, when we went hiking in the winter, but it was often hard to find them in the snow.[01:54.05]Female Professor: Yes, that's exactly right. [01:56.30]The major concern of the snowshoe hare in the winter is predators, [02:00.61]and now that includes humans. [02:02.96]So one of its adaptations is basically camouflage. [02:06.93]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.
[02:18.53]Male Student: Yeah, but I could swear I remember seeing rabbits in the snow a couple of times … I mean hares … that were brown.
[02:25.04]Female Professor: Well, you may very well have. [02:27.07]Timing is really important, but the snowshoe hare doesn’t always get it exactly right. [02:32.71]Its chances for survival are best if it turns white about the time of the first snowfall. [02:37.81]And, it’s the amount of daylight that triggers the changing of the hare’s coat. [02:42.66]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.
[02:53.27]The hare does a pretty good job with its timing, but sometimes—when there’s a really early or late snow—it stands out. [03:01.86]Plus, it takes about a month for the snowshoe hare's coat to completely change color, [03:07.04]so if there's a particularly early snowfall, it's very likely that the hare’s fur would not yet be totally white. [03:13.75]And that would make this a particularly dangerous time for the hare. [03:17.85] OK, what else? Other adaptations? Susan?
[03:23.34]Female Student: Well, it’s called a hare. So are its feet somehow protected from the cold?[03:29.87]Female Professor: Well, this animal's name does have to do with an adaptation of its feet, [03:34.67]though not like it has warm furry boots or something, to keep its feet from getting cold. [03:40.11]You’ve probably never needed to wear snowshoes, [03:43.41]but … well, snowshoes are not like thick furry shoes designed to keep the feet warm. They’re actually quite thin, but very wide.
[03:52.75]What they do is spread out the weight of the foot coming down on the snow. [03:57.13]See, the problem with walking on snow is that you sink in with every step. [04:01.83]But with snowshoes, you don't sink in, you walk on top of the snow. [04:06.49]It makes walking through the Maine countryside in the winter much easier.[04:10.40]Anyway, the snowshoe hare has an adaptation that plays on this same idea—[04:15.43]it has hind feet that act like snowshoes. [04:18.59]I mean, its paws are wide, and they allow the hare to hop and run just at the surface of deep snow. [04:25.01]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.[04:33.78]Now, another advantage related to this is that, unlike many animals in winter, snowshoe hares can stay lean and lightweight—[04:43.66]they accumulate essentially no body fat. [04:46.69]Can anyone guess why this is so?[04:48.92]Female Student: They don't eat very much?[04:50.48]Female Professor: Well, yes. But not because there isn't enough food around. [04:54.37]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.
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