Family MURIDAE 181 



grazed ditchbank more than a hundred. At other times, some 

 of the young may have to move long distances to establish homes, 

 and it is during forced migrations overland that many are killed 

 by motor vehicles on highways or by dogs or other predators. 

 Once established in their new homes, the young muskrats may 

 be preyed upon by minks. Extreme fluctuations in water level 

 can be destructive to an entire population of muskrats. 



The muskrat is active during all months of the year. It feeds 

 on roots, tubers, and green material, including cattails, bul- 

 rushes, sedges, pickerelweeds. corn, alfalfa, wild parsnips, wil- 

 lows, and clovers. 



Signs. — Houses in ponds or marshes, fig. 11, runways from 

 water to burrows in the banks of streams or ditches, fig. 12, 

 and feeding platforms among the vegetation in shallow water, 

 fig. 38, are telltale signs of muskrats. Footprints and tail marks, 

 fig. 21, may be evident at the water's edge. The print of a hind 

 foot is about 3i4 inches long; the print of a front foot shows 

 only four toes and is about \]4- inches long. Droppings, fig. 21, 

 are dark brown, oval-shaped, and each a little more than i/? 

 inch long; they are frequently deposited on stones and logs pro- 

 jecting above water. 



Distribution. — The muskrat, found in suitable habitats 

 throughout Illinois, is most common in the northern portion of 

 the state. The Illinois subspecies is Ondatra zibethicus zibethi- 

 cus (Linnaeus). The range of the species includes most of 

 Canada, Alaska, and the United States. It does not include 

 south-central Oregon, most of California, south-central Nevada, 

 southern Arizona, south-central Texas, or the extreme south- 

 eastern United States. 



RATTUS RATTUS (Linnaeus) 



Roof Rat Black Rat 



Description. — The roof rat, fig. 99, generally is a grayish 

 brown on the upper parts and a creamy color on the under parts. 

 The tail is brown all around and longer than the body. The 

 upper sides of the feet are light brown. Occasionally black indi- 

 viduals or families occur. This rat differs from the Norway rat 

 in that it has a slimmer body and a more uniformly colored 

 tail that is longer, rather than shorter, than its head and body. 

 Its ears are larger, more delicate, and less hairy. 



