Marine Animals Have Interesting Sleeping Habits
Many people know that marine mammals, like whales, porpoises and dolphins, breathe air, like we do. But, many people don’t know that marine mammals have developed some interesting sleeping habits in order to accommodate their regular trips up to the surface for air. Today, A Moment of Science looks at what its like to sleep with the fishes.
No Sleep Tonight
Unlike our own breathing, which does not require conscious effort, marine mammals must consciously go to the surface of the water to breathe through a blowhole on top of their heads. Because of this, marine mammals don’t sleep for a solid 8 hours a night, the way we do.
Some marine mammals sleep while swimming. Whales nap for brief periods while swimming alongside an alert friend who guides them. In fact, young whales must sleep alongside their mother because the mother’s slipstream actually pulls the calf along: it will sink if the mother stops.
Dolphin
Other marine mammals, like dolphins, sleep while floating on the surface of the water or take short catnaps while floating below the surface. Researchers claim that while marine mammals sleep their brain is always partially alert. Aside from these brief naps, dolphins are active most of the night.
Of course, marine mammals are equipped to handle underwater sleeping. They have proportionately larger lungs, exchange air more fully at each breath, and carry more oxygen in their blood than we do, so they can hold their breath long enough to sleep with the fishes.
海洋生物有趣的睡覺習(xí)慣
大多數(shù)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。但是大多數(shù)人都不知道這些哺乳動物已經(jīng)養(yǎng)成了一些有趣的睡眠習(xí)慣，以配合來回水面呼吸空氣。今天，科學(xué)一刻將探究一下，這些哺乳動物是如何像魚類一樣睡覺的。
今夜無眠
與人類“無意識”呼吸不同，這些動物必須到水面，通過頭頂?shù)臍饪�，進(jìn)行“有意識”的呼吸。因此，它們不像我們，每晚能夠穩(wěn)定的睡上八小時。
有些海洋哺乳動物邊睡覺邊游動。對于鯨魚，只要有同伴放風(fēng)，并引導(dǎo)著，他們就會邊游邊打會個盹。實際上，幼鯨必須在母鯨身邊睡覺，因為母鯨游動時產(chǎn)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。
海豚
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。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。海豚在晚上，除了打盹，其余時間都處于活躍狀態(tài)。
當(dāng)然，也有些海洋哺乳動物具備水下睡覺的能力。相應(yīng)地，他們的肺都很大，每次呼吸都能換進(jìn)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。
