MAMMALS OF MARYLANID 



125 



This species probably is of Asiatic origin. It is efficient at climbing, 

 jumping, and swimming; and it will eat and thrive on practically any 

 food that man consumes. Its nest is made of soft materials and is 

 placed in any convenient location, such as in walls, under floors and 

 steps, in bookcases or furniture, and, in the wild, under logs or stones 

 and other convenient recesses. 



The house mouse is very prolific. It attains sexual maturity at the 

 age of 3 months and the breeding season is of long duration. The 

 gestation period is from 19 to 21 days, and the number of young per 

 litter is usually five or six. The young are born blind and naked, but 

 they mature rapidly and are able to leave the mother in about 3 weeks. 



When these mice inhabit houses in large numbers, they do consider- 

 able damage by eating large quantities of food, or tainting it with 

 their droppings. They will consume linen clothing of all types, gnaw 

 on books, and chew holes in the woodwork. In shops, warehouses, grain- 

 eries, and on farms, they are usually abundant and destructive. 



In Maryland, the house mouse is found everywhere, even on marshes 

 and dunes of the Atlantic outer barrier beaches. 



Specimens examined. — Allegany County: Green Ridge, 1; Mount 

 Savage, 7. Anne Arundel County: Annapolis, 3 miles NW, 1. Calvert 

 County: Drum Point, 1; Plum Point, 2; Plum Point, 2 miles W, 6; 

 Scientists Cliffs, 2; Solomons Island, % mile N, 11. Charles County: 

 Nanjemoy Creek, 1; Port Tobacco, 4. Howard Comity: Long Comer, 

 2. Montgomery County: Cabin John Bridge, 2 ; Chevy Chase, 3 ; Forest 

 Glen, 5 ; Gaithersburg, 5 miles NE, 1 ; Kensington, 7 ; Seneca Creek, 

 1 ; Silver Spring, 1 mile N, 2. Prince Georges Covmty: Beltsville, near, 

 1 ; College Park, 1 ; Lanham, 1 ; Laurel, 5 ; Mitchellville, 1 mile W, 9 ; 

 Oxon Hill, 6; River View, 1; sphag-num bog, near District line, 1. 

 Queen Annes County: Parson Island, 1. Washington County: Fort 

 Frederick State Park, 2. Worcester Cownty: Ocean City, 3; Ocean 

 City, 5 miles S, on Assateague Island, 3 ; West Ocean City, 4. DistHct 

 of Columbia: 83. 



Remarks. — Schwarz and Schwarz (1943, pp. 59-72) reviewed the 

 species and suggest that all house mice in the United States are re- 

 ferable to two commensal subspecies M. m. hrevirostris and M. m. 

 domesticus^ the latter being the one that supposedly occurs in Mary- 

 land. In all probability, however, house mice have been introduced 

 into Maryland from many different areas and at many different times. 

 The range of variation in size, tail length, and coloration in Maryland 

 specimens is so great that I am unable to assign them a subspecific 

 name. 



336-897 a— 69 ^9 



