180 



Order RODENTIA 





Fig. 98.— Muskrat. 



dwelling and some for feeding, from materials that are readily 

 available, such as bulrushes, smartweed, and cattails. A dwelling 

 house usually is dome shaped, several feet in diameter at the base, 

 and the walls are 1 to 2 feet thick. The entrances (usually 

 two) are below the surface of the water. Within the house the 

 muskrat makes its nest, which is above the normal high-water 

 level and usually remains dry. Perhaps half or more of the 

 houses are feeding houses. These are without nests, are smaller 

 than the dwelling houses, and have thinner walls. 



Muskrats that live along rivers and ditches build no houses 

 like those described above but extend burrows back into the 

 banks. The nest chambers are above the surface of the water 

 at its normally highest level, and thus the nests usually remain 

 dry. Entrances are normally below the surface of the water, 

 but at times of low water some of them may be exposed. Run- 

 ways or paths lead from the exposed burrow entrances to the 

 water. Trails visible in shallow parts of a stream may indicate 

 usual routes of travel. 



The muskrat may breed from April to September. A female 

 usually has two litters, occasionally three, per year, and litters 

 average about four young each. At about a month of age, the 

 young are sufficiently grown to shift for themselves. Sometimes 

 there may be room within the parental marsh or along the home 

 bank for these new muskrats to settle down, for an acre of suit- 

 able marsh may accommodate 20 to 40 rats, or a mile of un- 



