194 Department of Conservation of Louisiana 



while smaller than the common eastern muskrat, the Lou- 

 isiana species exceeds in size the Newfoundland, Northwest- 

 ern, Alaskan Peninsular, Arizona, Pecos, and Great Plains 

 species, being exceeded in size only by the Rocky Mountain 

 muskrat, Maryland black, and the common eastern species. 

 It averages about the same size as examples from Labrador 

 and Nevada. 



The sexes are identical, it being rather difficult to tell 

 the boar from the female; when handling adult live animals 

 the determination of sex is not an easy matter, even when 

 using a "sexing box," as a conical instrument for holding 

 the muskrat upside down, so that the posterior parts can 

 be examined, is called. 



Molts 



According to Hollister, the Louisiana muskrat "appar- 

 ently molts twice a year, approximately spring and fall." 

 This is a very important matter if proved to be so, but, 

 it must be freely confessed no evidence has been found that 

 this is so, but we are continuing our investigations. 



The authority on the muskrats of the North American 

 continent in general goes on to say, when discussing the 

 muskrat's pelage, that "Aside from conspicuous cases of 

 dichroism [that property of being differently colored], the 

 color of all specimens in comparable pelage from any given 

 locality is remarkably uniform. The great variation fre- 

 quently noticed in a large series from one region is due 

 mainly to age and season and the degree to which the black 

 overlying hairs have appeared. Sexual variation is so abso- 

 lutely wanting that it was found useless to distinguish be- 

 tween the sexes in skin or cranial measurements. 



"Skulls in a large series from any particular water 

 are remarkably alike in shape and size, but a slight varia- 

 tion between series from nearby localities is frequently 

 noted." 



This distinguished biologist and authority on muskrats 

 said that since no two forms occur in the same locality and 

 that the characters separating the geographic races are fre- 

 quently relative, it was obvious that an artificial key to the 



