VOA慢速英语--研究表明海象为了保持脂肪做了大量努力

A new study has found that elephant seals have to work very hard to stay fat.

The research represents the most complete study to date of the feeding behavior of northern elephant seals. Scientists paid special attention to females of the species during difficult two-month trips, or migrations², in the northeastern Pacific Ocean.

The seals were found to spend up to 20 hours every day - and sometimes a full 24 hours - in continuous deep-diving to feed on fish. They fed 1,000 to 2,000 times daily to gain the body fat necessary for reproduction and warmth in the cold waters.

Taiki Adachi of the University of St Andrews in Scotland led the study, which recently appeared in the journal Science Advances.

"It is not easy to get fat," Adachi said.

Researchers studied 48 female elephant seals from Año Nuevo State Park in California as they traveled large ocean distances. Their entire trip was around 6,000 kilometers.

Scientists based their findings on data collected in 2011 and 2018. They used three small removable devices.

One device, attached under the jaw³, counted the number of times the seals fed and measured their depth. A second satellite-linked device, attached to the head, followed the seals' ocean movements. The third device was a "smart" video camera with an infra-red LED light and another depth sensor⁴. It was also attached to the head.

Elephant seals get their name from the large noses of the males. These noses look like an elephant's trunk. There are two species - the northern elephant seal and the slightly larger southern elephant seal. The two are the world's biggest seals and the largest ocean mammals other than whales.

Male northern elephant seals can grow up to 4 meters long and weigh up to 2,000 kilograms. Females are smaller, getting up to about 3 meters in length and 590 kilograms. The males feed only in coastal⁵ waters.

Some large marine⁶ mammals depend on deep dives to get enough food to support their large bodies. Sperm⁷ whales, for example, hunt for large prey⁸ like giant squid.

Female elephant seals -- which are large, but not as big as sperm whales -- have a different solution. They eat huge amounts of small fish. But it is difficult for them to catch enough small fish to meet the energy needs of their large bodies.

Adachi said about the female elephant seals:

"They continuously dive, for long periods of time - 20 minutes on average and about 100 minutes at maximum - and deep - 500 meters on average and about 1,500 meters at maximum - with only a few minutes breathing at the surface."

Adachi noted⁹ that the seals do not come back to land for their two-month trip, or migration¹. "The sleeping hours in at-sea animals is not fully¹⁰ understood. But, based on our record of extreme foraging¹¹, their available time for sleeping should be less than 20 percent of the day," he added.

Foraging is a term that means looking for food.

Northern elephant seals live on the Pacific coast of the United States, Canada and Mexico. They generally give birth in California and Baja California, usually on offshore¹² islands, from December to March. During their mating season, they do not eat. During this period they lose about a third of their body weight.

Words in This Story

species – n. biology : a group of animals or plants that are similar and can produce young animals or plants : a group of related animals or plants that is smaller than a genus

jaw – n. either one of the two bones of the face where teeth grow

prey – n. an animal that is hunted or killed by another animal for food

1 migration   

n.迁移，移居，（鸟类等的）迁徙

参考例句：

• Swallows begin their migration south in autumn.燕子在秋季开始向南方迁移。
• He described the vernal migration of birds in detail.他详细地描述了鸟的春季移居。

2 migrations   

n.迁移，移居( migration的名词复数 )

参考例句：

• It foundered during the turmoils accompanying the Great Migrations. 它在随着民族大迁徙而出现的混乱中崩溃。 来自辞典例句
• Birds also have built-in timepieces which send them off on fall and spring migrations. 鸟类也有天生的时间感应器指导它们秋春迁移。 来自互联网

3 jaw   

n.颚，颌，说教，流言蜚语；v.喋喋不休，教训

参考例句：

• He delivered a right hook to his opponent's jaw.他给了对方下巴一记右钩拳。
• A strong square jaw is a sign of firm character.强健的方下巴是刚毅性格的标志。

4 sensor   

n.传感器，探测设备，感觉器（官）

参考例句：

• The temperature sensor is enclosed in a protective well.温度传感器密封在保护套管中。
• He plugged the sensor into a outlet.他把传感器插进电源插座。

5 coastal   

adj.海岸的，沿海的，沿岸的

参考例句：

• The ocean waves are slowly eating away the coastal rocks.大海的波浪慢慢地侵蚀着岸边的岩石。
• This country will fortify the coastal areas.该国将加强沿海地区的防御。

6 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。

7 sperm   

n.精子，精液

参考例句：

• Only one sperm fertilises an egg.只有一个精子使卵子受精。
• In human reproduction,one female egg is usually fertilized by one sperm.在人体生殖过程中，一个精子使一个卵子受精。

8 prey   

n.被掠食者，牺牲者，掠食；v.捕食，掠夺，折磨

参考例句：

• Stronger animals prey on weaker ones.弱肉强食。
• The lion was hunting for its prey.狮子在寻找猎物。

9 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

10 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。

11 foraging   

v.搜寻（食物），尤指动物觅（食）( forage的现在分词 )；（尤指用手）搜寻（东西）

参考例句：

• They eke out a precarious existence foraging in rubbish dumps. 他们靠在垃圾场捡垃圾维持着朝不保夕的生活。 来自《简明英汉词典》
• The campers went foraging for wood to make a fire. 露营者去搜寻柴木点火。 来自辞典例句

12 offshore   

adj.海面的，吹向海面的；adv.向海面

参考例句：

• A big program of oil exploration has begun offshore.一个大规模的石油勘探计划正在近海展开。
• A gentle current carried them slowly offshore.和缓的潮流慢慢地把他们带离了海岸。