Beaver

 
 

The largest North American rodent (up to 4.5' long), easily distinguished by its size, webbed hind feet, and large horizontally flattened tail.  The broad tail is furred at the base, but the rest is covered with leathery scales.  Uniformly dark brown above, a bit lighter below.  Beaver live throughout North America in wetland habitats such as streams, marshes, and lakes.  They often live within stream banks in areas where flooding is unpredictable, but in some areas they will build lodges made of wood and sticks.  Beaver are also known to build dams of wood and sticks to regulate water levels.  They can cut down large trees by gnawing them at their base, and then can then pull the trees into the water; thus, beaver are extremely strong.  Usually they prefer to cut smaller trees and branches.  Beaver often have a significant impact on community structure in places where they can dam streams.  They feed on both woody and non-woody vegetation.  Their pelts were the original reason that many settlers journeyed west and north; it is still an important source of fur.