英語聽力文摘 動物也愛散步？

When you’ve been to the zoo have you noticed how some of the animals pace around a lot?

Scientists think the problem might be that the animals miss the freedom to roam. That make sense. After all, a polar bear’s natural range is about the size of South Carolina. Right. And the typical zoo habitat is about one millionth of that.

Researchers in Oxford studied the pacing behavior of thirty-five captive species using data from over one thousand scientific articles published since the 1960s. When they analyzed this data–which represented more than five hundred zoos worldwide–they determined that the deciding factor for pacing was range size.

That also explains why stay-close-to-home species like snow leopards tend to thrive in zoos. So what happens now?

Well, one option is for zoos to build larger, more varied 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 captivity.

The problem is that this is a double-edged sword: these animals’ natural habitats are increasingly threatened as well.

你去動物園的時候有沒有注意到，有些動物喜歡到處走動?

科學家認為這可能是因為它們被剝奪了散步的自由。有道理。一只北極熊自然分布范圍為整個南卡羅萊納州。對。而一般動物園的大小只是南卡羅萊納州百萬分之一。

牛津的研究人員調查了從20世紀60年代發(fā)表了一千多篇科學論文里的數據，是關于35個圈養(yǎng)物種的散步習性。他們對這些數據研究后發(fā)現：這些數據代表了世界上500多個動物園，他們因此確定散步習性的決定因素是動物的分布范圍。

那就可以解釋：為什么留守家園附近的物種像雪豹在動物園很多了。現在呢?

一個選擇就是把動物園建大一點，更多樣化和定期變換圍墻促進動物們散步。但還有一個更好的選擇就是將那些像北極熊的動物走出動物園，多關注那些能夠圈養(yǎng)的動物。

問題在于這是把雙刃劍：這些動物的自然習性會受到很大的影響。