MAMMALS. 65 



were found along the edges of Elizabeth, Crossley, and (jlenn Lakes 

 in the Belly Eiver valley, and the banks of Belly Eiver were in many 

 places, where beavers were inhabiting the bank dens, conspicuously 

 marked near the deep water by large beaver houses or by aspens that 

 had been freshly cut and were to be dragged into the river for food 

 or building material. Many of the small side streams along this 

 valley had been dammed up by the animals for ponds as gcfod 

 building sites for their houses. 



On Belly Eiver near the park line a huge old beaver came out one 

 evening near our camp and worked for a half hour before the dark- 

 ness closed in and hid him from view. He would go to the shore 

 and cut willow branches and carry them to some shallow beach 

 where he could sit in the water and trim the leaves and bark from 

 the branches for his supper. He would then swim to another place, 

 often with loud splashes of his tail, and gather more willows. Again 

 he would come out on the grassy bank and graze like a cow for some 

 time in the meadow, and in many places I found where the grass had 

 been thus eaten down all along the shores until it was as closely 

 cropped as if by horses or cattle. On a steep bank high above the 

 river this beaver had been cutting asjDen trees the previous night and 

 dragging the logs down the steep slope into deep water where they 

 could be floated around the bend to his house or sunk to the bottom 

 of the river for winter food. No dam crossed the river at this point, 

 but the water was deep and permanent, and a large beaver house had 

 been built on the bank. The house was not surrounded by water as 

 those in beaver ponds usuallj' are, but the burrows entered from 

 deep under the bank and came up to the nest cavity inside. The 

 thick walls of the house, built of sticks laid at all angles and firmly 

 plastered with mud, afforded ample protection from all enemies 

 except man, and even man armed with ax and spade has hard work 

 to dig through such walls. During the winter when heavy ice covers 

 the water and the beaver houses are frozen solid the animals are 

 especially safe and comfortable and enjoy the even temperature to 

 which they are adapted. They have usually stored up ample food 

 for the winter's supply in the bark of trees cut and sunk to the 

 bottom of the ponds, but the myriads of tender roots which penetrate 

 the banks of streams and are always accessible from under water 

 apparently form a large part of their food in winter as well as in 

 summer. 



As their destruction of timber for building and food purposes is 

 limited almost entirely to small cottonwoods, aspens, and willows of 

 no particular value, the claim that they are doing damage to the 

 forest is generally without foundation, while their dams and ponds 

 are often a great benefit to the country in storing water, providing 

 51140°— IS 6 



