They've been searching for days without a sign. 这些狼虽觅食多日 但一无所获
It's a long way to travel, but for a short period, the tundra is the ideal place for a grazer. 北极的苔原虽然路途遥远, 但仍有短短的一段时间是食草动物的天堂
As soon as couples arrive, they must stake a claim to a nesting patch. 一对雪雁来了之后就必须取得自己的筑巢地
It's a desolate, silent wilderness. 虽然此时是万籁俱寂,一片荒凉的景象
A frozen no-man's land at the end of the Earth. 那是地球边缘 天寒地冻 人迹罕至
But for a short time each year, the long, dark winter releases its grip. 每年却总有短短的一阵日子 漫长阴暗的冬天也会放松它的钳制
0ne and a half billion swarm across the savannahs of Africa. 以15亿的数量聚集在非洲的稀树大草原上
Because it grows from a protected part at the base of its stems, 草茎的基部有很强的自我保护能力
Predators also have a hard time raising their young on open grassland. 掠食动物在这片空旷的草地上繁衍后代也并不轻松