PLANET EARTH Mountains

A puma - the lion of the Andes. Pumas are usually solitary（独居） and secretive. To see a group walking boldly in the open is extremely rare. It's a family - a mother with four cubs. She has just one brief summer in which to teach them their mountain survival techniques. Rearing four cubs to this age is an exceptional feat, but she does have an excellent territory, rich in food and water.



Although the cubs are now as large as their mother, they still rely on her for their food. It will be another year before the cubs can hunt for themselves. Without their mother's skill and experience they would never survive their first winter. Battered by hurricane force winds, these slopes are now lifeless.



Further north, they hold other dangers. Moving at 250 miles an hour, an avalanche（雪崩） destroys everything in its path. In the American Rockies a 100,000 avalanches devastate the slopes every winter. This huge mountain chain continues the great spine that runs from Patagonia to Alaska（阿拉斯加）.
The slopes of the Rockies, bleak though they are, provide a winter refuge for some animals. A mother grizzly emerges from her den after six months' dozing underground. Her two cubs follow her and take their first steps in the outside world. These steep slopes provide a sanctuary for the cubs.