2 BULLETIN 1078, U. S. DEPARTMENT OF AGRICULTURE. 



floods and extensive erosion, in increasing the stream flow in dry 

 weather, and in improving the fishing resources of streams and lakes. 

 In such places they would not only enrich our forests and parks 

 with a unique and intensely interesting form of wild life, but would 

 also add' much valuable fur to our decreasing supply. 



Even in the mountains and remote wildernesses, however, there are 

 many localities where beavers, if allowed unrestricted freedom, would 

 surely destroy much valuable timber, ruin many of the most attrac- 

 tive lake and stream borders, destroy trails and roads, and even en- 

 danger railroad beds and human lives. While interesting, desirable, 

 and valuable animals in their place, they must be controlled to a 

 certain extent or they will become exceedingly troublesome and 

 destructive. 



Beavers at one time produced fur of greater value than that of any 

 other fur-bearing animal of North America. During the period 

 when the fur traders dominated a vast region in the West and Xorth, 

 the beaver skin was the unit of value used in the traffic between the 

 Indians and the white trappers. Through unrestricted trapping 

 beavers were exterminated over great areas and for a time threatened 

 with complete extinction, but with the protection given them in recent 

 years they are now returning to many parts of their former range. 



The necessar}' control of beavers in any part of the country need 

 not be difficult, but must be based on a thorough knowledge of the 

 animals and their habits. Controlling them under semidomestic con- 

 ditions, in beaver farming as a business enterprise, has not yet been 

 satisfactorily tested, but with our present knowledge of the habits 

 of beavers there is every reason to believe that this may develop into 

 a successful industry. 



DISTRIBUTION. 



Beavers originally occupied the streams of most of the continent 

 of Xorth America from the mouths of the Rio Grande and Colorado 

 Eivers and northern Florida north to Labrador, Alaska, and the 

 mouth of the Mackenzie, well within the Arctic Circle (Fig. 1). 

 Over this enormous area they are exposed to a great variety of cli- 

 matic and environmental conditions, which have produced numerous 

 geographic races, or subspecies. These vary somewhat in size and 

 proportions, but far more in the color, quality, and value of the fur. 

 Generally they are paler in the south and darker in the north, but 

 the darkest, most beautiful, and most valuable fur is found along the 

 southern shore of Lake Superior. 



DESCRIPTION. 



Beavers have been directly responsible, in the construction of dams, 

 for holding water in storage, preventing erosion, and profoundly af- 



