原文视听

A bite to the back of the neck and a kill.
它咬住兔子的后颈 成功扑杀
The incredible agility of the stoat, practised since it was a kit,
白鼬自小锻炼得来的惊人敏捷性
was just enough to swing the balance.
足以让它扭转乾坤
There are times when mere physical powers
有时光是体力 还不够让猎人
are not enough to give the hunter an edge.
取得优势
Then mammals must deploy their most sophisticated weapon - their brains.
这时哺乳动物就必须 动用最精密的武器，那就是智慧
Strange patterns are visible in the mud of Florida Bay,
佛罗里达湾的泥泞海底 出现奇特图案
a faint hint of a unique hunting tactic.
这是一种 独特猎捕策略的模糊提示
The perpetrators...
始作俑者就是它们
..bottlenose dolphins.
这是瓶鼻海豚
And they're on a mission - a mission to catch fish.
它们正在出任务 它们要去捕鱼
The fish here are very difficult to catch
这里的鱼很难抓到 在这样的浅水处
and in such shallow water they ought to be safe.
鱼群应该很安全
Yet the dolphins have a plan.
但这群海豚早有计划

重点解释

And they're on a mission - a mission to catch fish.它们正在出任务，它们要去捕鱼

on a mission执行(某一)任务, 肩负(某一)使命

We are not on a vacation, we're on a mission.

我们不是在度假,我们是在执行任务。

The French teenager became man on a mission.

这位法国的年轻人身上的担子重了。

catch fish扑鱼, 抓住鱼

He led the whole family out to sea to catch fish.

他带领全家出海捕鱼。

You catch fish with a fishing rod.

你可以用钓竿逮鱼。

in such shallow water they ought to be safe.在这样的浅水处鱼群应该很安全

ought to be应当

That ought to be enough food for all of us.

那些该够我们大家吃的了。

The child with the cough ought to be in bed.

这患咳嗽的孩子应该睡在床上。