genious device, the muskrat can be 

 held firmly by gentle pressure on 

 the plunger, the ears pulled through 

 the wire netting, and the tag quickly 

 attached, without, unduly squeezing 

 or bruising the animal a^nd without 

 risk to the operator. A small, num- 

 bered eartag, made of aluminum or 

 preferably Monel metal, is in gen- 

 eral use. 



Identification of Sex 



For efficient management and re- 

 stocking, recognition of the sex of 

 the muskrat is essential. No valid 

 criteria of color or size exist for the 

 sexes, but the sex of an adult musk- 

 rat can be determined by palpation. 

 The animal is picked up by the tail 

 and lowered until its front feet rest 

 on a firm surface such as a board or 

 table. Held in this position for a 

 few moments, it usually calms down 

 (extreme caution is necessary in 

 handling the muskrat, for it is very 

 agile and will turn and bite 

 quickly). The sex can then be de- 

 termined by palpating the genitalia. 

 A protuberance, or urinary sheath, 

 is present in both sexes; it lies on 

 the ventral midline, anterior to the 

 anus, and covers the penis in the 

 male and the anterior rim of the 

 vaginal entrance in the female. 

 The relatively long and solid penis 

 of the adult male can be felt within 

 the sheath. The protuberance in 

 the male is long and somewhat 

 rounded; in the female it is less 

 conspicuous, more pointed, and 

 comparatively short. The vaginal 

 opening is often difficult to see in 

 nonbreeding females ; it may be cov- 

 ered by a vaginal closure mem- 

 brane. In adult females during 



the breeding season the vaginal 

 opening is prominent. 



The most convenient criteria for 

 determining sex in muskrats are 

 (1) distance between the anus and 

 the protuberance, and (2) presence 

 of hair over a portion of this area 

 which is known as the perineum. 

 In the male the perineum is long 

 and is covered with hair; in the fe- 

 male it is short and the anterior 

 part is hairless. 



Shipping Live Animals 



The shipper of live muskrats 

 must see that the animals are well 

 crated to insure arrival at their 

 destination in a good condition. 

 Shipping crates should be made of 

 20-gage sheet metal or of wooden 

 boxes lined with hardware cloth or 

 netting to prevent the muskrats 

 from gnawing their way out (fig. 

 53). Each muskrat should be 

 shipped in a compartment of ap- 

 proximately 101/2 X 81/2 X 101/2 

 inches. Separating the animals 

 keeps them from injuring each other 

 by fighting, which results from in- 

 compatibility and the excitement 



Figure 53. — Metal cages such as these 

 have proved very satisfactory for 

 shipping live muskrats. 



39 



