海狸筑水坝，鸟筑巢。
作为一个例子，让我们看看海狸的觅食行为。
As an example, let's look at foraging behavior among beavers.
海狸把树皮剥下来吃，它们也用树枝来筑巢。
Beavers peel off the bark to eat and they also use the branches for building their shelters.
去年秋天，一只海狸搬进了我家旁边的小溪里。
Last fall a beaver moved into the small stream beside our house.
继续像海狸一样咀嚼，你最终会实现你的目标的。
Keep chewing like the beaver, and you will achieve your goal in the end.
土狼杀死了公园里大部分的红狐，还赶走了所有的海狸。
The coyotes killed a large percentage of the park's red foxes, and completely drove away the park's beavers.
没人会相信一只海狸能有意识地去权衡每个要素的利弊。
No one believes a beaver consciously weighs the pros and cons of each of these elements.
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。
Beavers live near streams and rivers and they block up the streams and rivers with like logs and sticks and mud.
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。
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.
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。
The beavers were hunted a lot, overhunted, they are almost extinct by the 1800s, that meant fewer wetlands, less standing water.
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。
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.
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？
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?
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。
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.
许多植物生长在海狸群附近。
为什么科学家关心海狸鼠？
科学家说，海狸还能帮助减少洪水的发生。
2015年，政府允许海狸留在那里以作试验。
In 2015, the government allowed the beavers to stay there as part of a trial.
海狸鼠会伤害当地大小像猫的动物。
海狸并不是唯一一种被重新引入野外的动物！
Beavers aren't the only animals that are being reintroduced to the wild!
十多年前，德文郡水獭河中出现了一个海狸家族。
Over ten years ago, a family of beavers turned up in a part of the river Otter, in Devon.
几十年来，毛皮贸易一直控制着海狸鼠的数量，但在20世纪80年代末，海狸鼠毛制品市场崩溃，导致这种猫大小的动物的数量疯涨。
The fur trade kept nutria in check for decades, but when the market for nutria collapsed in the late 1980s, the cat-sized animals multiplied like crazy.
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！
It was a big surprise, wild beavers hadn't lived in England for around 400 years!
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。
Some scientists from the University of Exeter already say the beavers help the wildlife in the area.
猎人们每年能猎得超过30万条海狸鼠尾巴，所以这几天穆顿的部分工作内容就是大力推广皮毛。
Hunters bring in more than 300,000 nutria tails a year, so part of Mouton's job these days is trying to promote fur.
设计师詹妮弗·安德森承认，她花了一段时间才改变她的观点，即在她的作品中使用海狸鼠的皮毛是合乎道义的。
Designer Jennifer Anderson admits it took her a while to come around to the opinion that using nutria fur for her creations is morally acceptable.
皮草正义项目的总监克里·麦克里说：“如果你不知道海狸鼠每年都在破坏大量的湿地，那么说使用皮草没有愧疚感听起来会很疯狂。”
"It sounds crazy to talk about guilt-free fur unless you understand that the nutria are destroying vast wetlands every year", says Cree McCree, project director of Righteous Fur.
海狸鼠会严重破坏生态系统。
海狸只将灰树用于筑巢。
海狸怎么样——水道中包含海狸的生态系统。
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