Why are beavers obsessed with dams? - Glynnis Hood

翻译人员: Lihua Jin 校对人员: Yuwei Wu

Nestled in the remote forests of northern Canada

在加拿大北部偏僻的丛林深处

sits the world’s longest beaver dam.

坐落着世界上最长的河狸水坝。

Curving around the water like a castle wall,

它像城墙一样围水而建，

this 850-meter-long structure is large enough to be seen in satellite imagery.

850 米的长度使它在 卫星图像里清晰可辩。

The dam and the generations of North American beavers that maintain it

大坝和世世代代 维护它的北美海狸极大地

have dramatically transformed the region,

改变了该地区，

creating a pond containing roughly 70,000,000 liters of water.

创造了一个容纳大约 7000 万升水的池塘。

This is a suitably sizable home for the creators of this woodland kingdom.

为这些建筑师们 创造了面积可观的栖息地。

But even dams 1/100th the size of this one

即使是比这小一百倍的水坝

can have huge impacts on their environment.

也会对周围环境产生极大的影响。

So how exactly do beavers redesign the forest,

那么，河狸到底是如何改造森林，

and how do they build these impressive structures in the first place?

又是怎样完成这项辉煌工程的呢？

Consider this beaver in the northwestern US.

这只河狸生活在美国西北部。

Standing just under 2 feet tall,

身高不到两英尺的他，

he’s a proud representative of the world’s second largest rodent species.

是世界第二大啮齿动物的优秀代表。

While he’s at risk to predators on land, once he’s built a lodge,

在陆地上，他面临着被捕食的危险 但只需建一个小屋，

he’ll have a massive moat to keep him safe.

周围的护城河就可以保障他的安全。

But he can’t just build a dam anywhere.

然而，水坝的选址可不能随便。

Following the sounds of running water,

河狸一路寻着水声，

our beaver searches heavily wooded areas

在草木茂密的地方搜索

to find a medium-sized stream that’s not too steep or too deep.

就为找到一处水流平缓， 深度合适的小溪。

After abandoning one construction site due to its rocky floor,

此处巨石太多， 作为工地并不理想，

he finds a stream with a soft, muddy bottom.

这里水底充满淤泥，就合适多了。

Combining vegetation, mud, and sticks,

他用草木、淤泥和树枝，

he creates a small bank along the stream’s edge.

沿着溪边建起一个小河堤。

Then, using a bite almost 3 times stronger than any other mammal of this size,

然后用比他大三倍的哺乳动物 才能使出的力量，

our beaver chews nearby logs into sturdy sticks.

将周边的树干啃成坚固的木棍。

He then rolls them into the water and spikes them down into the soft streambed.

这些木棍随后被滚动到水中， 竖直插进河床。

Beaver dams come in several shapes,

河狸水坝的形状有很多种，

but our beaver opts for a concave dam to dissipate the forceful flowing water,

但为了抵御水流冲击， 这只河狸选择了凹面设计，

and layers in large rocks to reinforce areas

并用石头层层加盖

where water flows the strongest.

从而加固水流最大的地方。

Depending on a dam’s length, the stream’s speed,

工程受水坝长度、水流速度，

and the number of beavers on the job,

以及参与施工的河狸数量的影响，

these devoted architects can build shockingly fast.

这些河狸建筑师们可谓效率惊人。

In some cases where humans tried to remove dams,

有几次人们试图拆除水坝，

beavers have rebuilt them overnight—

而河狸们一夜之间 就把它们建了回来——

sometimes rebuilding larger than they were before.

有时新建的比之前的还大。

Like most dams, our beaver’s project

和大多水坝一样

is just a couple meters long.

这位河狸的杰作只有几米长。

And working alone, this dam could take several days to complete.

他独自作业，要好几天才能完成。

But once the structure spans the channel, his watery home begins to fill up.

但他的工程一旦横阻于 溪流上栖息地就会开始蓄水。

As the pond grows,

水量越积越多，

he’ll extend the dam to block water flowing around the sides.

他要扩大水坝，以防止漏水。

However, some is permitted to leak downstream,

然而，有些地方漏水也没关系，

releasing pressure on the dam and regulating the pond’s water levels.

这样可以减轻水坝压力， 调节池塘水位。

The larger the pond, the larger the beaver’s territory.

池塘面积越大， 河狸的地盘也就越大。

And since they can hold their breath for up to 15 minutes,

他们可以在水中 憋气长达 15 分钟，

beavers can easily access food along the shorelines.

这也使他们能轻松地 吃到岸边的食物。

Throughout the fall, our beaver builds up an impressive supply for winter—

这只河狸努力了一整个秋天 为过冬囤积了大量的食物——

while also looking for someone to share it with.

同时，他也在找伴侣 和他分享这一切。

Beavers are fiercely territorial, but they also bond for life.

河狸有很强的领地意识 但也对伴侣极为忠诚。

When the pond freezes over,

等到水塘封冻时，

our new beaver couple splits their time

这对夫妇就开始两头忙活

between making trips to the food cache with their lodge’s private entrance

一边要往返于食物的藏匿地 和小屋的隐蔽入口

and starting a family.

一边要生育小河狸。

Come summertime, the juveniles will help reinforce and expand their dam,

到了春天，小河狸们会帮忙 加固、扩建水坝，

gather food, and watch their younger siblings.

储存食物，照顾弟弟妹妹。

After 2 to 3 years,

两到三年后，

these young beavers will disperse to find territory and mates of their own.

小河狸们会各自离开家， 找到自己的领地和伴侣。

But their ancestral dam can last for decades.

但祖上的这座水坝会屹立几十年。

Maintenance work is continued by descendants of the original colony,

由后代们不断修缮，

or new beavers that move in when the reigning family leaves.

如果原来的家族离开了， 则由新居民们负责养护。

There’s certainly no shortage of neighbors—

他们从不缺少邻居——

some regions have as many as 40 beaver dams per kilometer of stream.

在有些地区，每千米小溪 有多达 40 个河狸水坝。

This is great news for surrounding wildlife

这对周围一些野生物种来说 是个好消息

that rely heavily on these semi-aquatic engineers.

半水生的河狸工程师们 是这些物种赖以生存的依靠。

Lodges can serve as nesting sites and refuges for various species of waterfowl.

多种水鸟在小屋上筑巢。

Beaver channels also connect bodies of water,

水渠连接多处水体，

increasing the biodiverse areas between water and land.

从而扩大了水陆间的生物多样区域

Humans benefit from beaver construction projects too.

人类也是河狸水坝工程的受益者。

Their ponds help replenish groundwater stores,

水塘增加了地表水面积，

in part by creating large expanses of surface water.

也从而补充地下水储备。

And just like their manmade counterparts,

和人类建造的水坝一样，

beaver dams slow floodwaters.

河狸水坝可减小洪水流速。

So just by following their natural instincts,

这些生态工程师们只是靠本能做事，

these ecosystem engineers create huge impacts downstream.

却极大地影响着环境。