RODENTS 83 



with grass or reeds. Here it spends the day at rest, feeding and working 

 only during the night. 



Besides its underground dwelling, the beaver builds up more or 

 less artistic structures in the water out of the trunks of trees, branches 

 and brushwood. How is it enabled to do this ? 



(a) By means of the powerful incisor teeth, which in felling trees serve 

 it as an axe. If it wishes to fell a tree, it gnaws round the trunk, 

 especially on the side facing the water, until it bends and falls ; trees of 

 as much as 2 feet in diameter have been felled in this manner. The 

 trees are cut in pieces for use in building, unless they are too strong, 

 when the branches are stripped off. The bark and leaves serve as food, 

 the bark of willows, poplars and aspen being specially preferred. 



(&) While engaged in building the beaver sits erect on its hind-feet, 

 the broad tail serving as an additional support. 



(c) By means of the fore-paws, which, not being webbed, can be used 

 as hands, it holds tight the branches which it detaches from the tree or 

 from which it is gnawing the bark. 



The structures erected by the beaver are of four kinds : (1) If the 

 surface of the water sinks so low as to expose the opening of the passage 

 which leads to its dwelling, the beaver covers it with an interlacing 

 meshwork of brushwood, by which contrivance it is enabled to reach the 

 water without being observed. ( k 2) If in consequence of a heavy fall of 

 rain the thin roof of earth above its chamber should fall in, it covers the 

 opening thus formed with a heap of branches from 7 to 10 feet in height, 

 and in shape resembling a charcoal kiln. (3) Where beavers live in 

 large companies, as is still the case in North America, they erect what 

 are known as "beaver castles" at shallow spots of rivers or lakes. 

 These consist of mounds or heaps shaped like a baker's oven, from 

 7 to 10 feet in height, and about 10 or 11 feet in breadth, and composed 

 of tree-trunks and branches roughly piled together. These structures 

 are then covered over with sand, mud, earth, reeds and pieces of turf, 

 which the animals carry up in their mouths. In their interior we find, 

 besides the animals' dwelling-places, also store-chambers for the winter, 

 in which they hoard up pieces of bark and all sorts of roots. The 

 European beaver, also, when driven out of its home by floods, builds on 

 land structures similar to these, though much less extensive. (4) If the 

 level of the water of a brook or stream sinks so low that the beaver can 

 no longer move without hindrance in the shallow water, it builds a dam 

 for stemming back the water. Similar structures are erected in lakes 

 and ponds for the purpose of damming up the inflow water. These 

 dams consist of tree-trunks bound together with reeds, osiers, etc., and 

 cemented with mud, clay, etc. It must increase our wonder to learn 



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