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The herd has long since moved on,
鹿群早已走远
but her maternal instinct is so strong
但它在强烈母性本能的驱使下
she'll stay to search for her missing calf for days.
独自留下来 花好几天寻找自己的宝宝
The reindeer are free from flies for now,
驯鹿群暂时逃离了可恶的苍蝇
but with no food on these high slopes,
但是高地上没有食物
they will eventually be forced to descend to find new pastures
它们迟早要回到山下的草原
and face the biting swarms once more.
再度面对苍蝇大军
No animal makes a longer migration across the lands of the earth
这些哺乳动物的迁徙距离之长 在动物王国里
than these mammals.
无人能出其右
Other mammals have found a more economic way
另一种得长途迁徙的哺乳动物
of travelling huge distances and at greater speed.
找到了更经济，更快速的方法
They go by air.
它们用飞的

重点解释

The herd has long since moved on,鹿群早已走远

move on:继续前进；离开

The soldiers shouldered their kit and moved on.

士兵们背起行装，继续前进。

Now let's move on to the next item.

让我们讨论一下吧。

she'll stay to search for her missing calf for days.独自留下来花好几天寻找自己的宝宝

search for:搜寻； 寻找

He searched for work at various stores.

他在各家商店寻找工作。

The reindeer are free from flies for now,驯鹿群暂时逃离了可恶的苍蝇

free from:不受； 免于

He is free from any sense of responsibility.

他丝毫没有责任感。

they will eventually be forced to descend to find new pastures它们迟早要回到山下的草原

be forced to:被迫(不得不)

I was forced to sign the agreement against my will.

我被迫违心地在协议上签了字。

The truck was forced to lie by for repairs.

卡车不得不停下来修理。

descend to:向下延伸到；

The mountain path descends to a small river.

那条山间小路向下延伸到一条小河。