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。