英语听力：2012-01-27 从南极到北极 From Pole To Pole—5

（单词翻译）

 They are constantly on the move. New-born calves¹ have to be up and running the day they are born. But the vast herds³ do not travel alone. Wolves. Packs of them, eight to ten strong, shadow the migration⁴. And they are hungry. It’s the newly born calves that they are after. Running directly at the herd², it’s a ploy⁵ to generate panic. The herd breaks up. And now it’s easier to target an individual. In the chaos⁶, a calf⁷ is separated from its mother. The calf is young, but it can outrun the wolf if only it manages to keep its footing. At this stage, the odds⁸ are even—either the caribou⁹ will make a mistake or after a mile, the wolf will give up.