時差N小時:瞪大眼睛和旋轉脖子

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瞪大眼睛和旋轉脖子

Ask any gradeschooler to imitate an owl andyou'll probably get one of two responses: the giant,staring eyes or that amazingly swivel-prone neck. Asit turns out, these two characteristic features arerelated; they are part of an overall system owlshave for catching prey.

讓任何小學生模仿貓頭鷹，他們大概都會有這兩種反應：瞪大眼鏡，拼命地旋轉脖子。事實證明，這兩種動作是有聯(lián)系的;都是貓頭鷹完整捕獵系統(tǒng)中一部分。

To understand the connection, remember that owls are nocturnal birds: they hunt forfood at twilight and even in the dark. Food for an owl may be something as large as a rabbit oras small and hard to see as a field mouse. Not only is this kind of meal difficult to spot, it alsohas a tendency to bolt away quickly at the slightest sound.

要弄懂這種聯(lián)系，須知道貓頭鷹是夜行動物。他們在黃昏甚至是黑夜里尋找食物。貓頭鷹有時捕食像兔子一樣大的獵物，有時捕食如地鼠一般又小又難看見的獵物。這些獵物不僅很難被發(fā)現(xiàn)，而且聽到一點風吹草動就會迅速消失得無影無蹤。

The owl overcomes these difficulties by having evolved a visual system that works even atgreat distances and in low light. This is partly the result of having large eyes that are set on arelatively flat face, thus increasing binocular vision. However, those big eyes don't move muchin their sockets, and the owl's total visual field is therefore reduced. At any given time, it onlysees about one third as much as birds with eyes on either side of their heads.

貓頭鷹視覺系統(tǒng)不斷進化，使它在很遠或者很黑的情況下看清物體，這樣就克服了那些困難。由于貓頭鷹面部相對扁平，再嵌上一雙大眼睛，這樣就增強了雙眼視力。然而大眼睛不易在眼窩里轉動，因此貓頭鷹的整個視野范圍受到限制。它的視野只有其它眼睛長在頭兩邊的鳥類的三分之一。

That means the only thing to do is to be able to turn those staring eyes in any direction,without the noise that would be caused by actually getting up and moving. And now you cansee how the staring eyes and swiveling neck work together: the owl's super-flexible spineallows it to remain silent while it scans 180 degrees on either side. Yes indeed -- from aforward-facing position, an owl can look entirely backwards.

這意味著貓頭鷹唯一能做的就是，將瞪大的眼睛轉向各個方向，并避免因跳上跳下，來回走動而發(fā)出聲響?，F(xiàn)在你明白瞪大的眼鏡和旋轉的脖子是怎樣合作的：貓頭鷹的脊梁超級靈活，可以兩邊180度角地快速偵查環(huán)境而不發(fā)出任何聲響。雖然眼睛長在前方，但貓頭鷹確實可以看清后面。