Lisa Flaherty, age 9, of St. Paul, Minn., for her question:

HOW DO BEAVERS MOVE TREES?

Beavers are tremendously smart engineers. They may cut down a tree that is far away from the location where they plan to build a dam. But they can make the move with not too much trouble.

Beavers often dig canals so they can move logs easily and quickly from one spot to another. Canals are usually from 12 to 18 inches deep and may be more than 700 feet long. The canal may run from a wooded area to a lake or riverbank. A beaver canal may even cut across a piece of land that sticks out into the water.

Some great engineering work is done by beavers. Dams can be more than 1,000 feet long. Beavers also build fancy lodges for their families.