英语听力:探索发现 2012-12-02 美洲大平原 American Serengeti—16(在线收听

 So let's go back in time, back 13,000 years to relive one day in the life of North America's great ice age plains.

 
It's early morning at the end of a long, hot summer. Even major rivers are beginning to run low. Colombian mammoth herd follows the river valley. They can't risk being far from the water. Once they’ve quenched their thirst, the next priority is food. They head out to the nearby meadows where they’ll graze most of the day, processing mountains of dry grass.
 
Autumn is mating season. And a couple of nomadic males have started shadowing their herd. By sparring, they decide who will have access to the females coming into heat, who will father the next generation. Most power struggles are resolved through ritual intimidation. But if two evenly matched males cross parts, this posturing can escalate into a full-blown fight.  Both of these opponents have a broken tusk, letting them get closer to each other during combat. Suddenly a free clash leaves them in a deadlock, inextricably entwined. If they can't free themselves, they will both end up the losers.  
 
As a constant source of food and water, even when there’s been no rain for months, this valley draws thousands of other grazers.
  原文地址:http://www.tingroom.com/lesson/yytltsfx/2012/244994.html