英语听力：探索发现 2012-11-28 美洲大平原 American Serengeti—14

（单词翻译）

 13,000 years ago, the ice age cheetah¹ was the pronghorn's greatest enemy. And pronghorn would have needed all their amazing speed. The American cheetah was larger than its African cousin. But it had the same Achilles' heel. A cheetah's high-performance muscles overheat in minutes, and unlike pronghorn, they can't switch to cruising speed. So if the pronghorn managed to outrun the cheetah for the crucial first few hundred meters, it would probably survive. The cheetah hasn't roamed the plains of North America for thousands of years, but pronghorn are still prime for the chase.