THE MAMMALS 



217 



Their webbed, hind feet and broad, flat tail adapt them for 

 their semi-aquatic habits. One of their most remarkable 

 performances is the construction of dams across streams. 

 This is accomplished by cutting down trees which are cut 

 into pieces and dragged into the water where they form 

 the basis about which the industrious animals gather 



FIG. 168. A beaver. (After Baker.) 



stones, sticks and various other materials, thus damming 

 up the water. In the water thus backed up the beavers 

 usually construct their mounds, or lodges, which sometimes 

 rise three feet above the surface. These lodges are formed 

 of sticks and stones plastered together with mud and are 

 entered only through the water. In these retreats the 

 beaver passes the winter in security from ordinary enemies. 



