Object: Something to make the children think of beavers, even if it is simply a picture of a dam

Good morning, boys and girls. One of nature's most amazing animals is the beaver. What do beavers do? They cut down trees with their teeth and use them to build dams to dam up rivers, and they build houses for themselves and their families out of wood and they even build canals. Why canals? If they can't find enoug…