Beavers and their dams play an important role in nature. Because of the dramatic effects their dams have on surrounding ecosystems, these mammals are considered a keystone species. By constructing dams they create wetlands -- lush environments which attract fish, ducks, frogs and other creatures. However, beavers can become a big headache for farmers and landowners -- a problem we'll examine later in this article.
A long, long time ago, lemurs lived all over the world. But something happened to kill them off -- everywhere except in Madagascar. How did the island protect them from extinction?
Loners might seem intriguing, but they lead dangerous lives -- a least those in the wolf world do. Lone wolves are outsiders, relying only on themselves to survive without a pack.