It's time to go again to the A Moment of Science mailbag. A listener writes:
又到了再次查看科学一刻来信的时候了。一位听众朋友写到：
Dear A Moment of Science,I know that gorillas and chimpanzees can learn sign language and use it to communicate.
亲爱的科学一刻：我知道大猩猩和黑猩猩能够学习手势并用它进行交流。
But can other animals use sign language, too?
但是其他动物呢，它们也会使用手语么？
Good question. And the answer is, maybe.
问得好。答案是：可能会。
To be clear, gorillas and chimps are the only animals that have so far been taught to use human sign language.
明确的说，大猩猩和黑猩猩是迄今为止被教授使用人类手语的仅有的两种动物。
But some other animals do seem to use a form of sign language, or at least use gestures to communicate with other species.
但是某些其它动物似乎也在使用一种形式的手语进行交流，或是至少能使用手势与同类进行交流。
Like, for example, fish.
比如说：鱼类。

Really? How can fish use sign language?
真的么？鱼怎么能使用手语呢？
You know how some fish hunt in cooperation with other types of fish?
你知道一些鱼是如何与其它种类的鱼共同合作捕猎的么？
Scientists have found that these animals have ways of using gestures to communicate during a hunt.
科学家发现这些动物在猎食的过程中会使用手势来进行彼此间的交流。
For example, when grouper and eels are on the prowl, grouper will sometimes position themselves where prey is hiding.
例如，石斑鱼和鳗鱼在来回游动的时候，石斑鱼会不时地在猎物的躲藏处停下。
And they do a sort of headstand and shake their head in the direction of the hidden prey.
接着它们会做一个头倒立的姿势并朝着猎物躲藏的地方不断摇头。
Taking the signal, eels then slither in and flush out the prey.
收到信号后，鳗鱼就会滑行过去并把猎物驱赶出来。
Trout do something similar with octopuses.
鳟鱼也会同章鱼进行类似的合作捕食。
That's cool, but does it really qualify as sign language?
这太酷了！不过这种行为真的能称之为一种手语么？
It depends how you define it.
这取决于你如何定义手语。
But typically, scientists define a referential gesture as one that's directed toward an object, isn't used for an immediate mechanical purpose, is aimed at a recipient, and is then used by that recipient to do something like chase or catch prey.
但是通常来说，科学家认为，当一种姿势在指向某个物体的时候，就可以把它看作一种具有参考意义的手势。它并不是用于一种即时的无意义的目的，而是指向接受者的。接受者再通过这一手势所传达的信息来追赶或捕获猎物。