【英语时差8，16】天生爱游荡
时间：2015-11-03 08:12:53
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（单词翻译）
When you've been to the zoo have you noticed how some of the animals pace around a lot? In this Moment of Science Don and Ya?l discuss one explanation for this behavior. D: Ya?l, I went to the zoo yesterday, and boy, the polar bear just kept pacing in circles, and don't even get me started about the lions. I guess they must really miss hunting, huh?
Y: You know, Don, that's what scientists used to think too, and so zoos worked hard to
compensate1 for this by focusing on
stimulating2 hunting behavior. But now scientists think the problem might be that the animals miss the freedom to roam.
D: That makes sense. After all, a polar bear's natural range is about the size of South Carolina.
Y: Right--and the typical zoo habitat is about one millionth of that.
D: No wonder some animals spend about a quarter of their time pacing. But how did scientists figure out that this was the problem?
Y: Well, researchers at
Oxford3 studied the pacing behavior of thirty-five captive species using data from the over one thousand scientific articles published since the 1960s. And when they
analyzed4 this data--which represented more than five hundred zoos worldwide--they
determined5 that the deciding factor for pacing was range size. That also explains why stay-close-to-home species like snow
leopards6 tend to thrive in zoos.
D: So what happens now?
Y: Well, one option is for zoos to build larger, more
varied7 habitats, and switch enclosures periodically to simulate roaming. But a better option might be to phase animals like polar bears out of zoos, and focus instead on those animals that do well in
captivity8. The problem is that this is a double-edged sword: these animals' natural habitats are increasingly threatened as well.
D: Depressing.
Y: No kidding.
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