Adirondack Beaver iju 



The time required by a beaver to fell a tree of given size is not 

 positively known, for only rarely has the operation been actually 

 observed and recorded. Seton says, "Two beavers can cut down a 

 three-inch sapling in three minutes and a six-inch tree in an hour or 

 two. Three are the most that have been seen working on the same 

 tree at once." Their work, however, is often erratic and subject to 

 many interruptions ; many partly cut and abandoned trees may be 

 found in most beaver-inhabited localities (figure 31). 



Photographs by Dugmore ('14) and Shiras ('21) show that the 

 beaver stands erect upon its hind feet, supported by the tail, and 

 rests its fore feet upon the trunk when gnawing off a tree. 



Trees up to about four inches in diameter are usually cut into 

 sections of various lengths and dragged to the ponds ; in the case of 

 larger trees only the branches are removed. 



The amount of food eaten by a beaver in a year is not known. 

 We ought to know how much an average colony or lodge needs in 

 order to know the potential productive capacity of a given area of 

 forest for beaver. Aspens (Weigle and Frothingham, '11, pp. 16- 

 17) and paper birch (Dana, '09, pp. 19, 36) grow rapidly and 

 yellow birch more slowly (McCarthy and Belyea, '20, pp. 19, 42, 

 49). It probably requires from 10 to 20 years for the aspens and 

 paper birches to become three or four inches in diameter at the 

 level where the beaver cuts them, and of a size to attract it. 



Beaver Architecture 

 Character of Ponds and Streams Favored. It is a familiar 

 fact that beavers usually choose for their dam building operations 

 small, shallow streams with sluggish current. Running water seems 

 to be the stimulus that sets the dam-building instincts in motion. 

 During dry periods when the water in creeks forms only a series 

 of interrupted pools of still water, damming operations usually 

 cease. A pond that has no stream entering or leaving it but is fed 

 by seepage from springs, and drains off by underground channels, 

 suffers no damage from dams, except occasionally indirectly from 

 neighboring sources. Streams whose water averages more than 

 about 2.5 or 3 feet in depth are rarely dammed, although if shallow 

 rapids occur much deeper streams may be dammed at such places. 

 The width of a stream alone does not easily discourage the beaver 

 and even a swift current is often overcome by anchoring the dam 

 against various obstacles that may be found in the stream. 



