THE BEAVERS OF NORTH AMERICA 63 



to subsist on them, and to the severity of the winter 

 in each neighbourhood. Some piles are fully 

 thirty-five or even forty feet across and con- 

 tain a fairly closely-packed mass of browse and 

 wood from five to about ten feet in depth. Very 

 Uttle use is made of this store, or what remains of 

 it, after the ice melts, for then the beaver prefers to 

 cut fresh material for food. The water-soaked 

 mass of brush is generally left at the bottom where, 

 by rotting, it gradually settles lower and lower, and 

 often forms a foundation for a new house or anchor- 

 age for the next season's cuttings. Occasionally trees 

 are dropped into the water, more particularly in 

 rivers, so that the tops as well as a large part of the 

 branches are submerged. The beaver leave them 

 there, knowing full well that they can come when- 

 ever they wish during the winter and cut off what 

 they need under water. It is usually noticeable 

 that when a tree is used in this way the animals 

 cut off much of the bark around the thicker portion 

 of the trunk, whether it is exposed or beneath the 

 water, and they also trim the tree of most of the 

 branches which project above water. 



When the lodges are built in places where there 

 is a swift current, few trees of any size are ever cut 

 below the lodges. Well do the animals know that 

 swimming with heavy branches against the stream 

 is hard work and usually quite unnecessary, so 

 they do practically all their wood-cutting above 

 stream and often let the heavier logs drift down 



