THE BEAVER IN NORWAY 249 
said, is carried out in autumn. Spring and autumn floods 
also frequently submerge the lodges, from which large 
portions are loosened and swept away. From twenty to 
thirty years is the probable period during which a lodge 
is habitable. 
On the bank of the river in the neighbourhood of the 
lodge numerous burrows are met with, a few of which are 
in connection with the lodge, although most are entirely 
separate. Burrows are the first refuges formed by the 
beaver when taking possession of a fresh spot, and they 
may accordingly be likened to the rude sheds erected by 
workmen employed on building a mansion. Probably 
each lodge is tenanted only by a single couple and their 
young family, the young beavers, when able to do without 
parental assistance, either settling down temporarily in 
burrows in the immediate neighbourhood, or wandering 
away to found new colonies. Small lodges constructed in 
a kind of jerry-building fashion appear to be run up by 
bachelor beavers who have not yet ventured to take upon 
themselves the responsibilities of a wife and family. There 
may, however, be also spinster beavers to whom such 
accommodation is also necessary—it is to be hoped only 
temporarily. 
Dams are constructed where beavers have quartered 
themselves by the sides of gently flowing streamlets, or 
small ponds through which a current runs, in order to 
obtain water of sufficient depth and maintaining a constant 
level. The dam is substantially built and difficult to 
demolish. One examined in 1895 was constructed at the 
outflow of a small stream through a forest-marsh; and 
where there was formerly but a small shallow pool, a 
pond or lake of some few hundred yards in diameter soon 
resulted from the labours of these indefatigable rodents. 
