How about beavers—ecosystems with beavers in waterways.
海狸怎么样——水道中包含海狸的生态系统。
As an example, let's look at foraging behavior among beavers.
作为一个例子，让我们看看海狸的觅食行为。
Beavers peel off the bark to eat and they also use the branches for building their shelters.
海狸把树皮剥下来吃，它们也用树枝来筑巢。
The coyotes killed a large percentage of the park's red foxes, and completely drove away the park's beavers.
土狼杀死了公园里大部分的红狐，还赶走了所有的海狸。
Beavers live near streams and rivers and they block up the streams and rivers with like logs and sticks and mud.
海狸住在小溪和河流附近，它们用木头、树枝和泥巴堵住小溪和河流。
If water levels fall in summer, as they do in most of North America, then beavers lodge entrances may be exposed.
如果夏季水位下降，就像在北美大部分地区所发生的那样，那么海狸居所入口可能会暴露。
If water levels fall in summer, as they do in most of North America, then beavers' lodge entrances may be exposed.
如果像北美大部分地区一样夏季水位下降，那么海狸的小屋入口就会暴露出来。
There used to be beavers all over the place, something like 200 million beavers, just in the continental United States.
在美国大陆，到处都有海狸，大约有2亿只海狸。
The beavers were hunted a lot, overhunted, they are almost extinct by the 1800s, that meant fewer wetlands, less standing water.
海狸被大量捕杀、过度捕杀，到19世纪它们几乎灭绝了，这意味着湿地和静水变得更少了。
These beavers do know how to build dams, and do so if the need arises, as may occur if they are forced to relocate after felling and consuming all nearby trees.
这些海狸知道如何建造水坝，而且在有需要的时候就会这么做，比如当它们在砍伐和消耗了附近所有的树木后被迫迁移的时候。
Wait, I see where you are heading with this, but before we go into how European settlement affected the ecosystem, tell me this—what kind of environment do beavers live in?
等等，我明白你的意思了，但在我们讨论欧洲人的定居如何影响生态系统之前，告诉我，海狸生活在怎样的环境中？
It's been shaped by constraints over vast stretches of time, all of which comes down to the fact that the best foraging strategy for beavers isn't the one that yields the most food or wood.
它是由长时间的约束形成的，都指向一个事实，就是对海狸来说最好的觅食策略不是产出最多食物或木材。
Beavers also help make flooding less, scientists say.
科学家说，海狸还能帮助减少洪水的发生。
Beavers build dams along the river.
河狸沿河筑坝。
Many plants are growing near the beavers.
许多植物生长在海狸群附近。
Beavers aren't the only animals that are being reintroduced to the wild!
海狸并不是唯一一种被重新引入野外的动物！
The beavers' dams slow down the speed of the river, especially after heavy rain.
河狸筑的水坝减缓了河水的流速，尤其是在大雨之后。
It was a big surprise, wild beavers hadn't lived in England for around 400 years!
这是一个很大的惊喜，英国大约有四百年没有发现过野生海狸了！
In 2015, the government allowed the beavers to stay there as part of a trial.
2015年，政府允许海狸留在那里以作试验。
Some scientists from the University of Exeter already say the beavers help the wildlife in the area.
埃克塞特大学的一些科学家已经表示，海狸对该地区的野生动物有益。
Over ten years ago, a family of beavers turned up in a part of the river Otter, in Devon.
十多年前，德文郡水獭河中出现了一个海狸家族。
Beavers build dams and birds make nests.
海狸筑水坝，鸟筑巢。
Beavers use ash trees only for construction.
海狸只将灰树用于筑巢。
I concede the innocence and creativity of beavers.
再认可海狸的无辜和创造力。
Beavers live and work together in family groups.
河狸以家庭为群，一起生活和工作。
Within an hour, some of the beavers returned to land to continue eating.
不到一小时，一部分海狸回到岸上继续进食。
Finally I pledge we'll find a way to preserve our P.C.D.S without, in the future, harming beavers.
最后，我保证今后基地会找到一种方法，既能保护污染处理设备又不会危害海狸。
Keepers were feeding the beavers and hooded mergansers (a species of duck) when the earthquake hit.
地震来袭时，饲养员正在喂海狸和镜冠秋沙鸭(一种鸭子)。
The beavers stopped eating, stood on their hind legs and looked around, then got into the water, too.
海狸停止进食，用后腿站立，环顾四周，然后也跳到了水里。
The beavers stopped eating, stood on their hind legs and looked around, then got into the water, too.
海狸停止进食，用后腿站立，环顾四周，然后也跳到了水里。
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