It must get to grips with its new ice world, 它们必须适应这个冰雪世界
The calf must stay close to its mother to avoid getting lost in the sudden blizzard. 小牛必须紧跟着母亲 才能避免在突如其来的暴风雪中迷路
The ducks must quickly prise the mussels free before the tide starts to turn. 绒鸭必须赶在潮流转向之前迅速采食
so the transfer must be done quickly 所以交接过程必须迅速完成
But first, each must find a mate. 但是 首先每只企鹅必须找到自己的配偶
First, though, valuable nesting places must be defended from property thieves. 不过先得保护好来之不易的筑巢地 免得被其他鸟类占据
they must be in position before the thaw starts. 企鹅们必须赶在解冻期结束前做好就位的准备
they must have wondered what unearthly sights lay in store. 他们必曾感慨于地球上竟有如此别样的地方存在
which tell others in the group that they must move on. 提醒蝗群中的其它成员它们应该动身了
and when it happens they must make the most of it. 一旦发生 它们必须尽可能地利用它