BEAVER HABITS, BEAVER CONTROL, AND BEAVER FARMING. 9 



The inner chamber is a simple cavity about 3 to 5 feet wide and 

 1| to 3 feet high. It is partly cut out and shaped from the inside, 

 all sticks being cut off flush with the surface on the inner wall, and 

 if more room is needed the chamber is enlarged from within. A 

 semidry bed of grass, twigs, leaves, or shredded wood is made 2 or 

 3 inches above the water level and close to the water hole. One and 

 occasionally two large holes in the floor enter the water and come 

 out under the bottom edges of the house 15 to 40 feet away, form- 

 ing safe means of entrance and exit to and from the living room. 

 If alarmed in the house the beavers dive into the water hole and 

 may not show themselves at the surface within a quarter or half 

 mile of the house, but usually a line of air bubbles escaping from 

 their fur shows their course as they leave the vicinity of the house 



BREEDING. 



Beavers apparently begin breeding when 1 year old, as one or 

 two embryos are often found in females of 25 or 30 pounds, but some 

 may not breed the first year. At 2 years old, when weighing 40 or 

 45 pounds, they may have 4 young and this seems to be the normal 

 number for most beavers. There are a few records of 6 young and 

 two or three of 8 embryos found in large, old females; but as the 

 females have only two teats on each of the two large mammary 

 glands, more than 4 young must be abnormal. So far as we can tell, 

 the sexes are about evenly divided in numbers. 



The young are born in May and a few late litt«rs apparently in 

 June. There seems to be no evidence of more than one litter in a 

 season, and there is no more than time for one litter to grow up 

 and get ready for winter between May and November. The time 

 of mating and the period of gestation are not definitely laiown. 



The mother beaver takes good care of the young and brings them 

 tender plants and rootlets before they are old enough to leave the 

 house. The father apparently remains away while the young are 

 small, but in a large house in August I found 2 females, 1 male, and 

 6 good-sized young. Like all rodents, beavers are polygamous, and 

 the fact that fights among the males take place indicates that the 

 older ones strive for supremacy. 



DAMAGE BY BEAVERS. 



The trees cut by beavers for food^ and building material are 

 generally of little value, mainly aspens, cottonwoods, birches, and 

 pin cherries, or such shrubby woods as willoAvs, alders, bush maples, 

 azels, and smaller bushes. However, some choice trees are oc- 

 casionally cut along lake or stream fronts, or in orchards situated 



2 Foi- food habits, see pp. 6—7. 

 102637°— 22 2 



