美国国家公共电台 NPR--Think you're tired? This animal goes for months with only two hours of sleep a day

Think you're tired? This animal goes for months with only two hours of sleep a day

Transcript¹

Maybe you didn't get enough sleep last night, but chances are you're still doing better than the typical northern elephant seal.

Scientists have discovered the massive creatures — so named because the males sport a distinctive² trunk-like nose — are often getting less shut-eye than most others in the animal kingdom.

Everything about the animals is "pretty much extreme," says Chris McKnight, an ecophysiologist at the Sea Mammal Research Unit in Scotland.

Adult females weigh upwards³ of 1,300 pounds, while adult males tip the scales at more than two tons.

And it's not just their size that sets them apart.

For months at a time, they go on long voyages where they migrate thousands of miles off the Pacific coast and back again as they forage⁴ for food. While out at sea, they're constantly diving more than 3,000 feet underwater.

"So there's a bit of a conundrum," explains McKnight. "If you're diving all the time, if you're spending 90% of your time at sea underwater without access to air, when the hell do you sleep?"

A study published on Thursday in the journal Science now offers an answer: Northern elephant seals rely on short power naps during those deep dives, which altogether add up to about two hours of sleep per day, says Jessica Kendall-Bar, the study's lead author and an ecophysiologist at Scripps Institution of Oceanography.

"And they do that while holding their breath very deep below the ocean surface," she says.

The new findings mean that northern elephant seals now rival African elephants who currently hold the world record for the shortest daily sleep time among mammals.

Peering into the brain of a sleeping seal

To study how northern elephant seals sleep, Jessica Kendall-Bar first had to deal with the challenge of measuring their brain activity underwater at extreme pressures.

She retrofitted a device used on birds and then refined it on herself by heading to a local surf spot in Santa Cruz, California where she applied⁵ the electrodes to her scalp. "So really channeling what it would be like to be a seal with this instrument attached to me," she says.

Kendall-Bar then waterproofed⁶ those electrodes and recorded her own brain activity while pretending to take naps underwater.

Her design incorporated the same electrodes used in sleep clinics to study humans struggling with insomnia⁷, narcolepsy, obstructive sleep apnea and other sleep disorders⁸, she says. In addition, she incorporated movement sensors⁹ and a heart rate monitor.

After some test runs, she was ready to attach it to wild animals at A?o Nuevo State Park on the coast of central California.

Because of their size, "they can be quite dangerous," Kendall-Bar says. So she and her team sedated¹⁰ the animals through an intramuscular injection. Once they woke up, the elephant seals were "pretty chill about it," she says.

"They'll wake up and basically 'galumph'" — this is the actual technical term the scientists use to describe the seals' undulating motion on land — "and then they'll usually just go right back to sleep."

Next, Kendall-Bar and her team were able to wire up two young females hauled out on the beach, place them on a truck and release them some 60 miles south in Monterey.

"For an elephant seal, it's kind of like picking someone up and dropping them at the end of their driveway and being like, 'OK, let's see you find your way home,'" she says. "So they'll get in the water and then they'll have this strong urge to come back to the colony."

Colossal¹¹ leviathans, sinking with grace

With the data in hand, Kendall-Bar studied the seals' brain waves and high-resolution movements while they were out at sea. Soon, a clear pattern emerged.

They'd begin their dive, and after a period of time, they'd start to nap by switching to slow wave sleep, "a time when the brain activity slows down and becomes more synchronous," she explains.

And then at some point — after about a minute — the seals would transition to REM sleep, a stage that, in humans, is associated with our most vivid dreams. Sleep paralysis¹² would take over.

The blubbery giants would float hundreds of feet downwards¹³ gracefully¹⁴.

"Just like in humans, they seem to lose control of their body," she says. "They flip¹⁵ upside down and they start this sleep spiral where they spin 360 degrees while sinking towards the ocean floor just like a falling leaf."

In fact, one animal (that they nicknamed "Fatigued¹⁶ Fiona") completed her nap while lying upon the seafloor.

Unlike up at the surface, deeper underwater where it's darker, elephant seals are less vulnerable to predators¹⁷. After about five to ten minutes, the animals would wake up and swim up to the surface.

Kendall-Bar compared these movements to data collected from 334 adult female elephant seals that had been tagged over the last 20 years. This analysis showed that while spending months at sea, elephant seals sleep in total about two hours per day, divvied up across multiple ten minute naps.

And once they return to land, the same elephant seals seem to play catch up, spending up to 14 hours per day asleep.

"[The researchers have] done an exceptional job," says Chris McKnight who wasn't involved in the study. He says it would've been nice to see brain scans from more animals, "but I think they've got as much as was probably physically¹⁸ possible. You've only got access to those animals for a short period of time when they're on land."

Kendall-Bar also found that northern elephant seals prefer to sleep near the coast while underwater, which will help inform the habitat that can be safeguarded. "We can build protected areas that conserve¹⁹ not only the areas that are really important for the animals to feed," she says, "but also those areas that they might go to to sleep."

These are the places where you might find these animals sinking through the water motionless, adrift in sweet seal slumber²⁰.

1 transcript   

n.抄本，誊本，副本，肄业证书

参考例句：

• A transcript of the tapes was presented as evidence in court.一份录音带的文字本作为证据被呈交法庭。
• They wouldn't let me have a transcript of the interview.他们拒绝给我一份采访的文字整理稿。

2 distinctive   

adj.特别的，有特色的，与众不同的

参考例句：

• She has a very distinctive way of walking.她走路的样子与别人很不相同。
• This bird has several distinctive features.这个鸟具有几种突出的特征。

3 upwards   

adv.向上，在更高处...以上

参考例句：

• The trend of prices is still upwards.物价的趋向是仍在上涨。
• The smoke rose straight upwards.烟一直向上升。

4 forage   

n.(牛马的)饲料，粮草；v.搜寻，翻寻

参考例句：

• They were forced to forage for clothing and fuel.他们不得不去寻找衣服和燃料。
• Now the nutritive value of the forage is reduced.此时牧草的营养价值也下降了。

5 applied   

adj.应用的；v.应用，适用

参考例句：

• She plans to take a course in applied linguistics.她打算学习应用语言学课程。
• This cream is best applied to the face at night.这种乳霜最好晚上擦脸用。

6 waterproofed   

v.使防水，使不透水( waterproof的过去式和过去分词 )

参考例句：

• Waterproofed 100% leather upper, with a light, durable polyurethane molded sole. 有一亮，持久聚氨基甲酸乙酯的使能防水100%皮革鞋帮塑造脚底。 来自互联网
• The outer covering of the egg is waterproofed to prevent the embryo from drying out. 鸡蛋的外壳是不透水的，防止胚胎失水。 来自互联网

7 insomnia   

n.失眠，失眠症

参考例句：

• Worries and tenseness can lead to insomnia.忧虑和紧张会导致失眠。
• He is suffering from insomnia.他患失眠症。

8 disorders   

n.混乱( disorder的名词复数 )；凌乱；骚乱；（身心、机能）失调

参考例句：

• Reports of anorexia and other eating disorders are on the increase. 据报告，厌食症和其他饮食方面的功能紊乱发生率正在不断增长。 来自《简明英汉词典》
• The announcement led to violent civil disorders. 这项宣布引起剧烈的骚乱。 来自《简明英汉词典》

9 sensors   

n.传感器，灵敏元件( sensor的名词复数 )

参考例句：

• There were more than 2000 sensors here. 这里装有两千多个灵敏元件。 来自《简明英汉词典》
• Significant changes have been noted where sensors were exposed to trichloride. 当传感器暴露在三氯化物中时，有很大变化。 来自辞典例句

10 sedated   

v.使昏昏入睡，使镇静( sedate的过去式和过去分词 )

参考例句：

• She's sedated,but she's probably scared out of her mind. 她很安静，但是她可能已经吓疯了。 来自电影对白
• Are you telling me the porn actually sedated you? 你是要告诉我，那毛片的确让你镇静下来吗？ 来自电影对白

11 colossal   

adj.异常的，庞大的

参考例句：

• There has been a colossal waste of public money.一直存在巨大的公款浪费。
• Some of the tall buildings in that city are colossal.那座城市里的一些高层建筑很庞大。

12 paralysis   

n.麻痹(症)；瘫痪(症)

参考例句：

• The paralysis affects his right leg and he can only walk with difficulty.他右腿瘫痪步履维艰。
• The paralysis affects his right leg and he can only walk with difficulty.他右腿瘫痪步履维艰。

13 downwards   

adj./adv.向下的（地），下行的（地）

参考例句：

• He lay face downwards on his bed.他脸向下伏在床上。
• As the river flows downwards,it widens.这条河愈到下游愈宽。

14 gracefully   

ad.大大方方地；优美地

参考例句：

• She sank gracefully down onto a cushion at his feet. 她优雅地坐到他脚旁的垫子上。
• The new coats blouse gracefully above the hip line. 新外套在臀围线上优美地打着褶皱。

15 flip   

vt.快速翻动；轻抛；轻拍；n.轻抛；adj.轻浮的

参考例句：

• I had a quick flip through the book and it looked very interesting.我很快翻阅了一下那本书，看来似乎很有趣。
• Let's flip a coin to see who pays the bill.咱们来抛硬币决定谁付钱。

16 fatigued   

adj. 疲乏的

参考例句：

• The exercises fatigued her. 操练使她感到很疲乏。
• The President smiled, with fatigued tolerance for a minor person's naivety. 总统笑了笑，疲惫地表现出对一个下级人员的天真想法的宽容。

17 predators   

n.食肉动物( predator的名词复数 )；奴役他人者（尤指在财务或性关系方面）

参考例句：

• birds and their earthbound predators 鸟和地面上捕食它们的动物
• The eyes of predators are highly sensitive to the slightest movement. 捕食性动物的眼睛能感觉到最细小的动静。 来自《简明英汉词典》

18 physically   

adj.物质上，体格上，身体上，按自然规律

参考例句：

• He was out of sorts physically,as well as disordered mentally.他浑身不舒服，心绪也很乱。
• Every time I think about it I feel physically sick.一想起那件事我就感到极恶心。

19 conserve   

vt.保存，保护，节约，节省，守恒，不灭

参考例句：

• He writes on both sides of the sheet to conserve paper.他在纸张的两面都写字以节省用纸。
• Conserve your energy,you'll need it!保存你的精力，你会用得着的！

20 slumber   

n.睡眠，沉睡状态

参考例句：

• All the people in the hotels were wrapped in deep slumber.住在各旅馆里的人都已进入梦乡。
• Don't wake him from his slumber because he needs the rest.不要把他从睡眠中唤醒，因为他需要休息。