But each year over 50,000 demoiselle cranes set out on one of the most challenging migrations on Earth. 可是 5万多只蓑羽鹤每年都会 进行一场地球上最具挑战性的迁徙
It'll be a year before it has the strength and skill to kill for itself on these difficult slopes. 它至少需要一年时间才能有足够的技巧和力量 在这些艰险的峭壁上独自狩猎
At this time of the year bears should be fattening up for the winter. 在每年的这个时候 熊必须为越冬储备脂肪
It will be another year before the cubs can hunt for themselves. 小狮至少还需要一年时间 才能学会独自狩猎
and they're growing bigger every year. 而且面积每年都在增大
and their strength is more or less constant all year round. 全年始终或多或少地 受到这种影响力的控制
The cub is a year old and still dependent on its mother. 小豹已有一岁大了 仍旧依靠着它的母亲
Some herds travel over 2,000 miles a year in search of fresh pastures. 有的鹿群一年得走上2000多英里 才能到达新鲜草场
Every year three million caribou migrate across the Arctic tundra. 每年 300万迁徙的北美驯鹿 都将穿越北极苔原