MAMMALS OF MARYLANI> 



111 



yellow. The dorsxiin, however, is a unifonn glossy black with no hairs 

 banded with red and yellow. Rarely an albinistic individual is encoun- 

 tered, and Dozier (1948&, p. 394) has reported upon a nonalbino white 

 mutation ("Maryland white") occurring in some of the marshes in 

 Dorchester County, and fawn colored mutants from the vicinity of 

 Chestertown, Kent County. 



The muskrat is readily distinguished from other Maryland rodents 

 by the combination of its aquatic habits, large size, and laterally com- 

 pressed tail. The beaver, which the muskrat resembles in aquatic 

 habits, is larger and has a broad, horizontally compressed tail. 



Measurements. — External measurements of an old male and two 

 young adult females from Laurel, Prince Georges County, are as fol- 

 lows: Total length 675, 600, 570; tail 280, 275, 266; hind foot 87, 86, 

 79. Cranial measurements of 11 adults from Laurel are : Condylobasal 

 length 67.6 (63.9-72.2) ; zygomatic breadth 41.8 (39.8-44.5) ; least 

 interorbital breadth 5.9 (5.0-6.6) ; length of maxillary toothrow 16.1 

 (14.9-17.2). 



Dozier et al. (1948, p. 180) found that the average weight of 13,421 

 male muskrats trapped on the Blackwater National Wildlife Refuge, 

 Dorchester County, was 2 pounds 4 ounces, and the average weight of 

 10,090 females was 2 pounds 2 ounces. Adult males varied in weight 

 from 6 ounces to 4 pounds, and females from 6 ounces to 3 pounds 12 

 oimces. 



Habitat and habits. — ^Muskrats are most abundant in the extensive 

 marshes that line the Chesapeake Bay. Elsewhere in Maryland they 

 are found in streams that wind through pastures, and in swamps. 



The muskrat is essentially vegetarian, but occasionally will make 

 use of animal food such as fish, mussels, insects, crayfish, and snails. 

 Martin et al. (1951, p. 236) report that at the Patuxent Research Cen- 

 ter near Laurel, the most important plant material eaten is burreed, 

 cutgrass, arrowhead, waterlily and panicgrass. Smith (1938, p. 12) 

 found that muskrats in Dorchester County would eat, to some extent, 

 almost any plant found in the marshes there. Certain f avorities, how- 

 ever, form their staple diet, and no area lacking these will support a 

 large muskrat population. Three square sedge and broadleaf and nar- 

 rowleaf cattails constitute four-fifths of the animal's diet, and all parts 

 of these plants are eaten at one time or another during the year. Other 

 foods that are at times utilized by the muskrat in the Dorchester 

 marshes are saltmarsh, wild reed, saltgrass, beak-rush, spikerush, big 

 cordgrass, wild millet, and sweet sedge. Also occasionally eaten are 

 saltmarsh fleabane, marshmallow, waterlily, dodder, iris, waxmyrtle, 

 small pine trees, and poison-ivy. Smith found that Dorchester County 

 muskrats sometimes consumed turtles, blue crabs, fish (chiefly sluggish 

 kinds such as carp) , salt-water mussels, and possibly dead birds. 



