50 RODENTS OF IOWA 



whose land is infested with these animals would see to it that the 

 numbers are reduced and held in check the situation could be much 

 improved without the expenditure of county funds. The animals 

 can also be shot without difficulty, the principal prerequisite on 

 the part of the hunter being a fair degree of ' ' watchful waiting. ' ' 



BEAVERS. 



Family CASTORID^E. 



This family is made up of but a single genus, represented in 

 North America by one species, of which there are five recognized 

 geographical races. 



Beavers are the largest of the North American rodents, varying 

 from thirty to fifty pounds in weight, and excepting the capybara 

 of South America, are the largest of existing rodents. The ani- 

 mals are semi-aquatic and the arms and hands are small and adapted 

 for burrowing as well as for holding substances between them. 

 Beavers were and still are in localities where they are sufficiently 

 plentiful, hunted and trapped for their skins which are of great 

 commercial value. In addition, the anal glands of the animal con- 

 tain an oily, yellowish, sticky, and strongly-scented fluid called 

 castoreum which is used by trappers as a bait ; it is also used in the 

 manufacture of perfumes, and is furthermore asserted to have 

 medicinal properties. 



The beaver, as a type, is one of the oldest living mammals, and 

 has been contemporaneous with many now extinct species. His 

 prolificacy, semi-aquatio habits, rugged strength, and food habits 

 have fitted him for successful maintenance in his struggle for exist- 

 ence. However, the competition with avaricious man has been too 

 great, and in many places where he was formerly abundant the 

 beaver is now entirely extinct. In both the United States and Can- 

 ada governmental protection has in recent years, been given this 

 animal, and its numbers are now somewhat on the increase. 



BEAVER. CANADIAN BEAVER. 



Castor canadensis camadensis Kuhl. 



Castor canadensis Kuhl, Beitr. z. Zool., 64, 1820. 



Description. — General color brown ; hairs of upper part dark 

 brown at base and tipped with chestnut ; top and sides of head and 

 neck, rump and thighs chestnut; under parts paler than upper 



