054 聪慧的海狸

旁白 neutral

Beavers once lived all over Europe and North America

海狸曾经遍布欧洲和北美。

旁白 neutral

But because they have beautiful fur, people hunted them to make warm coats

但是因为它们有美丽的皮毛，人们猎杀它们来制作保暖的外套。

旁白 neutral

As beavers started to disappear, scientists became worried and decided to learn more about them

随着海狸开始消失，科学家们变得担忧，决定更多地研究它们。

旁白 neutral

The first thing scientists studied was a beaver's body

科学家们首先研究的是海狸的身体。

旁白 neutral

Beavers are part of the rodent family, which means squirrels and rats are their cousins

海狸属于啮齿动物家族，这意味着松鼠和老鼠是它们的表亲。

旁白 neutral

Their front teeth are very long, and beavers use them to cut wood and pull off bark

它们的前牙非常长，海狸用它们来切割木头和剥树皮。

旁白 neutral

Like a hamster or rat, a beaver's teeth grow and grow and grow for its whole life!

就像仓鼠或老鼠一样，海狸的牙齿在一生中不断生长，长啊长！

旁白 neutral

However, beavers are bigger than all of their cousins

然而，海狸比所有的表亲都大。

旁白 neutral

Most beavers weigh fifteen to thirty-one kilograms, and are almost 117 centimeters long!

大多数海狸体重十五到三十一公斤，身长几乎有117厘米！

旁白 neutral

Even though beavers have fur, they like to be in water instead of on land

尽管海狸有皮毛，它们喜欢待在水里而不是陆地上。

旁白 neutral

Beavers are very beautiful swimmers, but they look silly when they try to walk

原文>

旁白 neutral

Their heavy tails make walking very difficult

原文>

旁白 neutral

A beaver tail is the size of a computer keyboard, and it helps a beaver stand, balance heavy logs, and steer in the water

原文>

旁白 neutral

And, if an enemy comes too close, one beaver will warn other beavers by slapping its tail on the water

原文>

旁白 neutral

When a beaver dives into the water, two important changes happen

原文>

旁白 neutral

First, it closes its eyes, nose, and mouth

原文>

旁白 neutral

Beavers have two kinds of eyelids:

原文>

旁白 neutral

the inside one is clear — like goggles — and the outside one is black

原文>

旁白 neutral

When a beaver is underwater, it protects its eyes by using the goggle-like eyelids to see where it's swimming

原文>

旁白 neutral

The beaver's nose also has special skin inside which closes to keep out water

原文>

旁白 neutral

However, its mouth is even more amazing

原文>

旁白 neutral

A beaver needs its front teeth to grab logs underwater, but it doesn't want a mouthful of water and logs

原文>

旁白 neutral

Amazingly, its lips are behind its front teeth so that it can keep water out and still grab whatever it needs

原文>

旁白 neutral

The second underwater change is when the beaver goes from a walker to a swimmer

原文>

旁白 neutral

On land, a beaver's back feet look like its cousin's

原文>

旁白 neutral

But when it dives into water, the toes pull apart to show a web in between

原文>

旁白 neutral

This webbing helps it swim through water quickly

原文>

旁白 neutral

Most beavers stay underwater for three to five minutes

原文>

旁白 neutral

But some can stay down for as long as fifteen minutes

原文>

旁白 neutral

That's a long time for only one breath — especially since most humans stay underwater for less than sixty seconds

原文>

旁白 neutral

Scientists were very impressed with the beaver's body

原文>

旁白 neutral

Few animals can live in water and on land as well as the beaver

原文>

旁白 neutral

But scientists are still worried

原文>

旁白 neutral

The more that people wear fur coats, the fewer beavers there are in the wild

原文>

旁白 neutral

And the fewer beavers there are in the wild, the more problems scientists see in nature

原文>

旁白 neutral

Now that scientists have learned about a beaver's body, they know more about how a beaver lives

原文>

旁白 neutral

But scientists are still looking for ways to help beavers and humans live together

原文>