【英文】BBC纪录片行星地球Planet Earth 1-3
For now though it's still minus thirty degrees and the cubs must have the shelter of the den. It's six days since the bears emerged and spring is advancing rapidly. But even now blizzards （暴风雪） can strike without warning. Being so small, the cubs are easily chilled and they will be more comfortable resting in the den. But their mother must keep them out and active. She's becoming weak from hunger and there's no food on these nursery slopes. The sea ice still holds firm, but it won't last much longer.
Day 10, and the mother has led her cubs a mile from the den. It's time to put them to the test. They've grown enormously in confidence, but they don't have their mother's sense of urgency. At last it seems that they're ready for their journey and they're only just in time, for a few miles from the coast the ice is already splitting. Now the mother can start hunting for the seals they must have, but she's leading her cubs into a dangerous new world. Nearly half of all cubs die in their first year out on the ice.
