Sleep is an important biological process for people and animals.

睡眠对于人和动物来说都是一个重要的生理过程。

However, much remains unknown about the process.

然而，关于这一过程仍有许多未知之处。

Humans spend about one third of their lives sleeping.

人的一生中大约三分之一的时间都在睡觉。

But some mammals, like the northern elephant seal, survive with much less sleep.

但一些哺乳动物，如北象海豹，睡眠时间要少得多。

Researchers in a new study described the unusual sleep pattern of these ocean animals.

研究人员在一项新的研究中描述了这些海洋动物不寻常的睡眠模式。

They found that when these mammals go to feed on trips that can last seven months, they sleep just two hours.

他们发现，当这些哺乳动物在长达七个月的觅食旅行时，它们只睡两个小时。

Those two hours of sleep are made up of short moments of rest lasting only 10 minutes each as they dive deep to avoid predators.

这两个小时的睡眠是由短暂的休息组成的，每次只持续10分钟，因为它们会潜入深海躲避捕食者。

The only other mammals known to get so little sleep are African elephants.

其他已知睡眠时间如此之少的哺乳动物只有非洲象。

The seals' sleep time during ocean trips is different from the 10 hours a day they spend sleeping on the coast during mating season at places like California's Ano Nuevo beach.

海豹在海洋旅行时的睡眠时间与交配季节在加利福尼亚州的ano Nuevo海滩等地每天睡在海岸上的10个小时不同。

The researchers placed a head covering with sensors on the heads of the seals that they studied.

研究人员在他们研究的海豹头上配戴了带有传感器的头罩。

The sensors recorded sleep signals created by the seals' brains and heart rate.

传感器记录了海豹大脑和心率产生的睡眠信号。

The sensors also recorded the animals' location and depth beneath the sea.

传感器还记录了这些动物在海底的位置和深度。

The researchers studied female seals because they go out on long open-ocean trips while males feed in coastal waters.

研究人员之所以对雌性海豹进行研究，是因为它们会进行长距离的远洋旅行，而雄性海豹则在沿海水域觅食。

During dives lasting about 30 minutes, the seals went into a deep sleep called slow-wave sleep while keeping a controlled downward movement.

在持续约30分钟的潜水中，海豹进入一种称为慢波睡眠的深度睡眠，同时保持可控制的向下运动。

When they then experienced rapid-eye-movement (REM) sleep, a condition where voluntary movement while sleeping stops, the seals fell into a turning pattern.

当他们进入快速眼动(REM)睡眠时，海豹会进入一种旋转模式。在这种状态下，睡眠中的自主运动停止了。

They sometimes ended up without movement on the seafloor.

海豹有时会在海底静止不动。

Jessie Kendall-Nar of the University of California San Diego's Scripps Institution of Oceanography is the lead writer of the study published this week in Science.

加州大学圣地亚哥分校斯克里普斯海洋学研究所的杰西·肯德尔-纳尔是本周发表在《科学》杂志上的这项研究的主要作者。

She said, "Then, at the deepest point of their sleeping dive - up to 377 meters deep - they wake up and swim back to the surface."

她说：“然后，在海豹沉睡的最深处——深达377米——它们醒来并游回水面。”

The northern elephant seal is the world's second-largest seal.

北象海豹是世界第二大海豹。

Only the southern elephant seal is bigger.

只有南象海豹比它大。

Male northern elephant seals may reach four meters long and weigh up to 2,000 kilograms.

雄性北方象海豹可达4米长，体重可达2000公斤。

Females reach about three meters in length and 590 kilograms.

雌性北方象海豹长约3米，体重590公斤。

The seals eat sea animals like fish and squid.

海豹以鱼类和鱿鱼等海洋动物为食。

Even with their large size, predators like sharks and killer whales are still a threat.

即使海豹体型庞大，鲨鱼和虎鲸等掠食者对它们来说仍然是一个威胁。

Terrie Williams is a scientist at the University of California at Santa Cruz who helped write the study.

特里·威廉姆斯是加州大学圣克鲁兹分校的一名科学家，她帮助撰写了这项研究。

She said, "It is remarkable that a wild animal will fall into deep, paralytic REM sleep when there are predators on the hunt."

她说: “当有掠食者在捕猎时，野生动物会陷入深度的、麻痹性的快速眼动睡眠，这是非同寻常的。”

She added that the seals solve this problem by going into deep sleep in the deep parts of the oceans where predators usually do not hunt them.

她补充说，海豹通过在海洋深处进入深度睡眠来解决这个问题，因为捕食者通常不会捕杀它们。

Williams said the brain's ability to control awakening the sleeping seals at a depth before they drown is also a discovery about how mammalian brains work.

威廉姆斯说，大脑在海豹溺水前控制唤醒熟睡海豹的能力也是对哺乳动物大脑工作方式的一项发现。

She commented on this saying that it shows the survival control of the seals' brains.

对此，她评价说：“这显示了海豹大脑的生存控制能力。

I'm Gregory Stachel.

格雷戈里·斯塔切尔报道。