10 



THE MUSKRAT. 



CLASSIFICATION AND DISTRIBUTION. 



The muskrat belongs to a group of rodents known technically as 

 the Microtina?. The group has been separated into two divisions, 

 the lemmings and the field mice, the latter including the common 

 short-tailed meadow mouse (Microtus) of the Northern Hemisphere. 

 The muskrats are very closely related to the field mice, but are larger, 

 and have fur, feet, and tails more highly specialized for a life in 

 the water. They differ from field mice of the genus Microtus par- 

 ticularly in having long, narrow, rudder-like tails, which are nearly 

 naked, about as long as the body without the head, and thickest along 

 the middle line. 



Five species and eight subspecies (geographic races) of muskrats 

 have been described.^ 



Muskrats are distributed over the greater part of North America, 

 from the southern border of the United States to the barren grounds 

 of northwest Canada and from the Atlantic to the Pacific. They seem 

 to be absent from the coastal parts of South Carolina, Georgia, Ala- 

 bama, and Texas; and from Florida and nearly the whole of Cali- 

 fornia. Of course they do not occur in parts of the interior plateau 

 that are devoid of streams or lakes. 



DESCRIPTION. 



The common muskrat when full grown is about four times as large 

 as the ordinary brown rat. In general form it resembles the com- 

 mon meadow mouse {Microtm pennsylv aniens) ^ but its tail is rela- 

 tively very much longer and of different shape. The animal has a 

 blunt muzzle, a short and hardly noticeable neck, and a stout body. 

 The tail is characteristic of the genus, about two-thirds as long as 

 the head and body, compressed, thickest along the middle line, and 

 tapering to a rather acute point; the thinly scattered hairs do not 



"The list of these forms follows: 



Fiber rnacrodon Merriam. Type from Lake Driimmond, Dismal ywami), 

 Virginia. 



F. ohscurus Bangs. Type from Codroy, Newfoundland. 



F. occipitalis Elliott. Type from Florence, Oreg. 



F. spatulatus Osgood. Type from Lake Marsh, Yukon, Canada. 



F. zihethicus (Linn.). Type from eastern Canada. 



F. z. aquiloniiis Bangs. Type from Rigoulette, Hamilton Inlet, Labrador. 



F. z. hndsonins Preble. Type from Fort Churchill, Keewatin, Canada. 



F. z. mergens Hollister. Type from Fallon, Nev. 



F. z. osoyoosensis Lord. Type from Lake Osoyoos, Washington. 



F. z. pallidus (Mearns). Type from Fort Verde, Ariz. 



F, z, ripensis Bailey. Type from Carlsbad, N. Mex. 



F. z. rivalicius Bangs. Type from Burbridge, La. 



F. z, zalophus Hollister. Type from Bercharof Lake, Alaska. 



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