英语听力:自然百科 北极熊 冰上间谍 Spy_Bear—8(在线收听

 This new and ever-changing world requires a different spy-camera, iceberg-cam. It effortless steers between ice sheets and its turret rotates to follow the bears. 

 
The bear's lives are now governed by the state of the drifting ice and the movement of the seals. The cubs are expected to keep up, but their mother knows their limits, avoiding long, hazardous swims. But all awhile, she keeps them on the move, tracking the seals that gather around the leading edge of ice.
 
Back on land, iceberg-cam follows the one-cub family. With the seals gone, beachcombing is her best option to find food. He practices his climbing skills, but it's early days. She's found something just below the surface. She checks how deep she has to dive, then takes the plunge.
  原文地址:http://www.tingroom.com/lesson/zrbaike/2010/259376.html