BEAVER DAMS. 373 



elevated ground on which the deciduous trees are found, over 

 the uneven but generally descending surface to the pond. . . . 

 After one of these cuttings has been transported to the water, 

 a beaver, placing one end of it under his throat, pushes it before 

 him to the place where it is to be sunk. 



The sinking is no doubt partly effected by mere soaking ; 

 but there is also some evidence to show that the beavers 

 have a method of anchoring down their supplies. Thus 

 they have been observed towing pieces of brush to their 

 lodges, and then, while holding the large end in their 

 mouths, ' going down with it to the bottom, apparently to 

 fix it in the mud bottom of the pond.' A brush-heap 

 being thus formed, the cuttings from the felled trees are 

 stuck through the brushwork, without which ' protection 

 they would be liable to be floated off by the strong currents, 

 and thus be lost to the beavers at the time when their 

 lives might depend upon their safe custody.' 



Lastly, as a method whereby the beavers can save 

 themselves the trouble of cutting, transporting, and 

 anchoring all at the same time, they are prone, when cir- 

 cumstances permit, to fell a tree growing near enough to 

 their pond to admit of its branches being submerged in 

 the water. The animals then well know that the branches 

 and young shoots will remain preserved throughout the 

 winter without any further trouble from them. But of 

 course the supply of trees thus growing conveniently near 

 a beaver-pond is too limited to last long. 



We have next to consider the most wonderful, and I 

 think the most psychologically puzzling structures that are 

 presented as the works of any animal ; I mean, of course, 

 the dams and canals. 



The object of the dam is that of forming an artificial 

 pond, the use of which is to afford refuge to the animals 

 as well as water connection with their lodges. Therefore 

 the level of the pond must in all cases be higher than that 

 of the lodge- and burrow-entrances, and it is usually 

 maintained two or three feet above them. 



As the dam is not an absolute necessity to the beaver for 

 the maintenance of his life his normal habitation being rather 

 natural ponds and rivers, and the burrows in their banks it is, 



