Sleep is an important biological process for people and animals.
睡眠对人和动物来说都是一个重要的生物过程。
However, much remains unknown about the process.
然而，这一过程仍有许多未解之谜。
Humans spend about one third of their lives sleeping. But some mammals, like the northern elephant seal, survive with much less sleep.
人类一生中大约有1/3的时间都在睡觉。但一些哺乳动物，如北象海豹，睡眠很少也能生存。
Researchers in a new study described the unusual sleep pattern of these ocean animals. They found that when these mammals go to feed on trips that can last seven months, they sleep just two hours. 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. The only other mammals known to get so little sleep are African elephants.
研究人员在一项新的研究中描述了这些海洋动物不同寻常的睡眠模式。他们发现，当这些哺乳动物在长达7个月的觅食之旅时，它们只睡两个小时。这两个小时的睡眠是由每次只持续10分钟的短暂睡眠组成的，它们会深潜以躲避捕食者。其他已知睡眠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.
海豹在海洋之旅中的睡眠时间跟交配季节它们在加州安诺纽沃海滩等地每天10小时的睡眠完全不同。
The researchers placed a head covering with sensors on the heads of the seals that they studied. The sensors recorded sleep signals created by the seals' brains and heart rate. The sensors also recorded the animals' location and depth beneath the sea.
研究人员在他们研究的海豹头上戴上了一个附传感器的头罩。传感器记录了由海豹大脑和心率产生的睡眠信号。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.
研究人员对雌性海豹进行了研究，因为它们会进行长时间的公海旅行，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. When they then experienced rapid-eye-movement (REM) sleep, a condition where voluntary movement while sleeping stops, the seals fell into a turning pattern. They sometimes ended up without movement on the seafloor.
在持续30分钟的潜水过程中，海豹会进入一种被称为慢波睡眠的深度睡眠，同时保持可控的下潜运动。然后，当它们经历快速眼动睡眠时，这时睡眠中的自主运动会停止，它们进入螺旋下沉模式。它们有时候最终会落到海底不再移动。
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. 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."
加州大学圣地亚哥分校斯克里普斯海洋研究所的杰西·肯德尔·纳尔是这项本周发表在《科学》杂志上的研究的主要作者。她说：“然后，在他们睡眠下潜的最深处——高达377米——它们醒过来，再游回海面。”
The northern elephant seal is the world's second-largest seal. Only the southern elephant seal is bigger. Male northern elephant seals may reach four meters long and weigh up to 2,000 kilograms. Females reach about three meters in length and 590 kilograms.
北象海豹是世界第二大海豹。只有南象海豹体型更大。雄性北象海豹身长可达4米，体重可达两吨。雌性身长约3米，体重590公斤。
The seals eat sea animals like fish and squid. Even with their large size, predators like sharks and killer whales are still a threat.
海豹以鱼类和鱿鱼等海洋动物为食。即使体型巨大，鲨鱼和虎鲸等食肉动物对它们来说仍然是一种威胁。
Terrie Williams is a scientist at the University of California at Santa Cruz who helped write the study. She said, "It is remarkable that a wild animal will fall into deep, paralytic REM sleep when there are predators on the hunt." 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.
特里·威廉姆斯是加州大学圣克鲁斯分校的一名科学家，她帮助撰写了这项研究。她说：“当有捕食者在狩猎时，野生动物进入深度、麻痹性的快速眼动睡眠是很异常的。”她还表示，海豹通过在通常不会有捕食者的深海进入深度睡眠来解决这个问题。
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. She commented on this saying that it shows the survival control of the seals' brains.
威廉姆斯说，大脑能够在熟睡的海豹溺水前将其唤醒，这也是对哺乳动物的大脑如何工作的一个发现。她就此发表评论说，这表明了海豹大脑的生存控制。
I'm Gregory Stachel.
我是格雷戈里·斯塔切尔。(51VOA.COM原创翻译，请勿转载，违者必究！)