英语听力:自然百科 北极熊 冰上间谍 Spy_Bear—12(在线收听

 They continually chatter away to each other. It's all about keeping aggression under control.

 
Their massive claws rake the skin like knives, cutting it into strips. 
 
At two years old, this bear is testing his status, standing up to other bears. Sharing food helps everyone survive in an environment where prey is usually hard to come by. 
 
As summer progresses, the temperature creeps above freezing and the larger ice sheets fragment into ever smaller plates. To avoid being trapped on shrinking ice floes, the cubs must get used to an endless polar assault course.
 
Rolling is clearly fun, but it also has a purpose. It squeezes out water trapped in the fur. Her cubs are growing fast and are full of energy.  But to keep them fit, she must keep them fed. A male has killed a bearded seal. For the sake of her cubs, she needs to be cautious. Burying the carcass will help reduce its odor, concealing it from other bears.
  原文地址:http://www.tingroom.com/lesson/zrbaike/2010/259539.html