Identification of sex in live muskrats

One problem in the management and breeding of muskrats is the difficulty in determining the sex of the living animal. No valid criteria as to color or size exist, so it is necessary to examine the external genitalia and the region between the genitalia and anus. In the meager literature available on the subject a "sexing funnel" for holding the animal has been recommended by Hodgson (1930) and others (1929). When large numbers of animals must be examined such devices are usually difficult or impractical to use. This paper reports a simple method for examination that has been used successfully at the United States Fur Animal Field Station, Blackwater National Wildlife Refuge, Cambridge, Md. The sex of an adult muskrat can be