THE MUSKEAT. 



13 



water. They often rise to within a few inches of the surface of the 

 ground and are frequently protected above by roots, or by trees and 

 shrubs, or by thickly matted turf. These tunnels extend 10 to 50 

 feet into the bank and terminate in a roomy chamber which sometimes 

 contains a bulky nest composed of dried vegetation. Usually two 

 tunnels lead from the nest to the water, and often a tunnel has two 

 branches or outlets. 



When burrows are available, muskrats occupy them in winter and 

 summer; but in shallow ponds and marshes, and especially in north- 

 ern latitudes, the entrances are often closed by ice in winter. In 

 such situations and Avhen banks suitable for burrows are wanting, 

 houses become a necessity. But they are seldom seen along the 

 borders of deep ponds and canals, and, except in extensive swamps 

 unbroken by hillocks, they are not found in the southern parts of 

 the muskrat's range. 



As cold weather approaches, muskrats are very active, adding to 

 their old winter houses, building new ones, and deepening channels 

 that lead to houses and burrows. The animals do not hibernate, and, 

 aside from the vegetation of which their houses are made, they seem 

 to make little provision for winter. However, some of the surplus 

 food collected may be found in their burrows at almost any time. 



BREEDING HABITS. 



Published accounts of the muskrat's breeding disagree so widely 

 that the habits of the animals might be supposed to differ in different 

 sections of the country. Harlan states that the female brings forth 

 5 or 6 young annually.^ Richardson, on the other hand, says : " In 

 latitude 55° the musquash has three litters in the course of the season 

 and from three to seven young in a litter." ^ Audubon and Bachman, 

 and many zoologists since their time, repeat Richardson's statement, 

 with slight variations that show no original research. Amos W. 

 Butler, writing of the muskrat in Indiana, states that he is con- 

 vinced that in his vicinity the animals breed but once a year, though 

 he admits the probability of exceptions. He gives the number of 

 young as 4 to G and the period of gestation as about six weeks.^ 

 Roderick MacFarlane, a chief factor of the Hudson Bay Company, 

 in writing of the mammals of the Mackenzie River region, states 

 that the female has two litters the first and three each succeeding 

 season, and that the number of young at times varies from 8 to 20.^ 



« Fauna Americana, p. 133, 1825. 



^ Fauna Boreali-Americana, p. 117, 1829. 



^ American Field, XXIV, 537, 1885. 



<^Proc. U. S. Nat. Museum, XXVIII, 738, 1905. 



396 



