Yellowstone Beaver 20J 



and the house well plastered with mud, it also begins to lay in a 

 stock of provisions, in the shape of logs and branches of trees upon 

 whose bark it feeds. Where aspens are available, these are the pre- 

 ferred sort, and willows and alders are likewise used, but the alders 

 seem to be third choice. Where they are found, maple and birch are 

 also made use of, and are much liked. Whatever species are used, 

 the wood is taken to the pond and stored in the water. The small 

 logs or poles are carried to the bottom and forced into the mud 

 sufficiently to hold them until more is piled on them. While green 

 aspen does not sink, as I have seen stated in a recent popular article 

 on the beaver, but floats, it is very heavy, and doubtless after a time 

 becomes waterlogged, though one often sees freshly peeled green 

 sticks floating in the pond where they have been discarded. 



These food piles are usually at the lodge or close by. When the 

 pond is covered with ice the owner comes out under water, cuts off 

 a length and carries it indoors, where the bark is eaten, the peeled 

 stick being carried out and left in the water. In Colorado I found 

 a mass of stored willow brush extending 100 feet along the shore, 

 in water four feet deep, and piled up to the surface (figure 55). 

 These willows were from three to eight feet long, and it will readily 

 be seen that they represent much work as well as a large amount of 

 food. 



Beaver Engineering 



Dams. Beavers use four different types of construction : dams, 

 lodges, burrows and canals; but not every beaver uses them all, 

 many living only in burrows, and probably are as well or better off 

 for that. This happens when they are living on a stream too deep 

 or swift for dams or lodges. 



A dam is begun by laying twigs and branches on the bottom, butt 

 ends upstream, and very likely forced into the bottom. These are 

 covered with gravel or mud dug from the upstream side, stones also 

 often being used. More twigs are then laid on top and covered, and 

 thus the dam is built up until its top appears above the surface and 

 a pond begins to form. The dam is carried up to the required height 

 and the top is plastered with mud. The builders keep close watch 

 on it, and are continually making repairs and additions. A beaver 

 dam is never finished while the pond is occupied, its owners con- 

 tinually adding something to it. Perhaps the water may flow around 

 the end. That is stopped with mud or sticks, whereupon the water 

 in the pond rises so that the main dam has to be added in order to 



