英语听力文摘 English Digest 692 海洋生物有趣的睡觉习惯

Marine¹ Animals Have Interesting Sleeping Habits

Many people know that marine mammals, like whales, porpoises² 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 calf³ 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 partially⁴ 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 fully⁵ 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.

1 marine   

adj.海的；海生的；航海的；海事的；n.水兵

参考例句：

• Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
• When the war broke out,he volunteered for the Marine Corps.战争爆发时，他自愿参加了海军陆战队。

2 porpoises   

n.鼠海豚( porpoise的名词复数 )

参考例句：

• A shoal of porpoises are well on the feed. 一群海豚正在吞食。 来自辞典例句
• In 1928 some porpoises were photographed working like beavers to push ashore a waterlogged mattress. 1928年有人把这些海豚象海狸那样把一床浸泡了水的褥垫推上岸时的情景拍摄了下来。 来自辞典例句

3 calf   

n.小牛，犊，幼仔，小牛皮

参考例句：

• The cow slinked its calf.那头母牛早产了一头小牛犊。
• The calf blared for its mother.牛犊哞哞地高声叫喊找妈妈。

4 partially   

adv.部分地，从某些方面讲

参考例句：

• The door was partially concealed by the drapes.门有一部分被门帘遮住了。
• The police managed to restore calm and the curfew was partially lifted.警方设法恢复了平静，宵禁部分解除。

5 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。