時差N小時:海洋生物有趣的睡覺習慣

Many people know that marine mammals, likewhales, porpoises and dolphins, breathe air, likewedo.

大多數人都知道些海洋哺乳動物，比如鯨魚，鼠海豚和海豚。它們和我們一樣都要呼吸空氣。

But, many people don't know that marine mammalshave developed some interesting sleepinghabits inorder to accommodate their regular trips up to thesurface for air.

但是大多數人都不知道這些哺乳動物已經養(yǎng)成了一些有趣的睡眠習慣，以配合來回水面呼吸空氣。

Today, A Moment ofScience looks at what its like to sleep with the fishes.

今天，科學一刻將探究一下，這些哺乳動物是如何像魚類一樣睡覺的。Unlike our own breathing, which doesnot require conscious effort, marine mammals mustconsciously go to the surface of the waterto breathe through a blowhole on top of their heads.

與人類“無意識”呼吸不同，這些動物必須到水面，通過頭頂的氣孔，進行“有意識”的呼吸。

Because of this, marine mammals don't sleep for a solid 8 hours a night, the way we do.

因此，它們不像我們，每晚能夠穩(wěn)定的睡上八小時。

Some marine mammals sleep while swimming.

有些海洋哺乳動物邊睡覺邊游動。

Whales nap for brief periods while swimmingalongside an alert friend who guides them.

對于鯨魚，只要有同伴放風，并引導著，他們就會邊游邊打會個盹。

In fact, young whales must sleep alongside their motherbecause the mother's slipstreamactually pulls the calf along: it will sink if the mother stops.

實際上，幼鯨必須在母鯨身邊睡覺，因為母鯨游動時產生的水流可以推動幼崽向前：如果母鯨停止游動，幼崽就會沉下去。

Other marine mammals, like dolphins, sleep while floating on the surface of the water or takeshortcatnaps while floating below the surface.

而其它海洋哺乳動物，像海豚，睡覺的時候是浮在水面上，打盹的時候就浮在水面下。

Researchers claim that while marine mammals sleep theirbrain is always partially alert.

研究表明，海洋哺乳動物睡覺時，他們部分大腦依然保持警覺。

Aside from these brief naps, dolphins are active most of the night.

海豚在晚上，除了打盹，其余時間都處于活躍狀態(tài)。

Of course, marine mammals are equipped to handle underwater sleeping.

當然，也有些海洋哺乳動物具備水下睡覺的能力。

They haveproportionately larger lungs, exchange air more fully at each breath, and carry moreoxygen intheir blood than we do, so they can hold their breath long enough to sleep with thefishes.

相應地，他們的肺都很大，每次呼吸都能換進更多的空氣。他們的血液中的含氧量就比我們的高，這樣他們就能長時間屏息，像魚類一樣睡覺。