14 



THE MUSKRAT. 



I lis statoinonts are based on information obtained from the company's 

 Indian hunters, who are keen observers. 



Some of the foregoing testimony has little weight. Also, we should 

 be slow to accept conclusions based on the number of kit " musk- 

 rats found occupying a winter house, for they may be either more or 

 fewer than a full litter. The close relationship existing between this 

 animal and the common field mouse {Microtus) suggests that a simi- 

 larity of breeding habits is to be expected ; and the investigations of 

 the Biological Survey show that such resemblance actually exists. 



Field naturalists of the survey have made two records of actual 

 litters of muskrats. A female taken June 18, 1895, by Vernon 

 Bailey, at Summit, Mont., contained 13 large embryos. Another, 

 taken June 8, 1893, by J. A. Loring, at Ward, Colo., contained 8 

 embryos. A specimen in the United States National Museum, col- 

 lected by Dr. E. A. Mearns at Newport, R. I., April 19, 1900, contained 

 C) small f(]etuses. 



The w^riter, in March, 1909, talked with a considerable number of 

 muskrat trappers in Dorchester County, Md., about the breeding 

 habits of the animals. The best informed of these men state that 

 from three to five litters (normally but three) are produced, and 

 that the number of young in a litter varies from 3 to 12 or even more, 

 the average being probably 6 to 8. 



In mild winters sporadic breeding occurs. Thus, in the open 

 season of 1908-9, in January one trapper found a female that had 

 recently suckled young, and on the same day found young near by 

 that were only about one-third grown. Another trapper in Feb- 

 ruary captured a female that contained 3 embryos, and still another, 

 a Mr. Insley, on March 6 took a female that had 3 embryos. In dis- 

 cussing the date in spring at which trapping should cease, the 

 trappers stated that each year before March 15 a number of preg- 

 nant females are caught, and that trapping should not be continued 

 later than that date. The early spring litters, they stated, are usually 

 below the average in size, 3, 4, and 5 being the more common num- 

 bers. The young of these early litters are said to breed the same 

 fall. 



I am indebted to R. J. Slacum, of Cambridge, Md., for a detailed 

 account of his observations during many years while residing near 

 the marshes and trapping in them. He confirmed the statements of 

 the more intelligent trappers as to the number of litters and number 

 of young; and made the interesting statement that most of the 

 young muskrats in Dorchester County marshes are born, not in 

 burrows, for there are few places where burrowing is possible, nor yet 

 in winter houses, although this is occasional, but in new nests which 

 the female builds of grasses and dry plants, but without roots or 



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