They gnaw through bark to eat the sugary layer underneath.

牠們會咬穿樹皮，去吃底下的糖分。

They've been gnawing through forests for 20 million years.

牠們已經這麼做兩千萬年了。

Felling trees with your teeth takes great strength, skill, and patience.

用牙齒砍伐樹需要很多力量、技術和耐心。

One technique is to slice halfway through and let the wind do the rest.

其中一項方法，是從中間啃一半，讓風自然把樹吹倒。

The beavers' incisors are strengthened with iron, which makes them orange.

海狸的門牙含有鐵質，導致它們是橘色的。

They grow continuously and even self-sharpen.

它們會不斷增長，甚至會自動變利。

The pond makes it easier to move around the heavy logs they need to build their dams.

在池塘裡，海貍更方便移動沈甸甸的木塊去牠們的築水壩。

Out of the water, it's a struggle.

離開水後，一切就變困難了。

Stones help weigh down the base.

石頭可以幫忙穩固基地。

The whole family works together, carefully interlocking the timber.

整個海狸家庭同心協力，小心地把木塊堆疊。

They dredge mud from the pond bottom to seal the dam.

他們撈取池塘底部的泥土，把水壩封住。

Each pond traps several inches of sediment every year so there's plenty of it.

池塘每年都會留有幾吋的沈積物，所以泥土是夠用的。

The young act as apprentice builders, learning the tricks of the trade.

年幼的海貍便像建築師的學徒，學習著築水壩的秘訣。

The final results are impressive.

最終結果相當驚人。

In the Rocky Mountains beaver dams slowly filter billions of tons of water.

在洛磯山脈，海狸的水壩正慢慢過濾上億噸的水。

The ponds build up soil and nutrients and help prevent floods and droughts.

泥土和養分在池塘裡緩緩累積，幫助預防洪水和乾旱。

(Leave it to Beavers, Wednesday, May, 8/7c on PBS)

(交給海狸吧！五月的每週三，PBS 上的 8/7c )