MAMMALS OF MARYLANiD 



97 



hairdii, the incisive foramina of mibiterrae are open and evenly curved, 

 while in noveboracensis they are anteriorly constricted. The teeth in 

 the latter form, even in juvenile animals, are noticeably larger and 

 more robust than in nuhiterrae. 



Measurements. — External measurements of eight adults from Alle- 

 gany County (Dans Mountain State Park, and vicinity of Oldtown) 

 are as follows: Total length 174.4 (170-188) ; tail 76.2 (70-92) ; hind 

 foot 21.1 (20-22) ; ear 15.7 (13-18). Nine adults from the same locali- 

 ties have the following cranial measurements: Greatest length 26.2 

 (26.0-26.7) ; zygomatic breadth 13.4 (12.7-14.0) ; interorbital breadth 

 4.1 (3.9^.3) ; maxillary toothrow 3.6 (3.4-3.8). 



Habitat and habits. — This species is primarily a woodland inhab- 

 itant, but is often found in brushy regions and sometimes in grassy 

 areas that border woodlands. It is one of the most abundant mammals 

 in Maryland. On Assateague Island their tracks have been observed 

 even on the bare sand dunes a few yards from the ocean beach. Usually, 

 however, this mouse will be found not more than 50 feet from woods or 

 forests, of which it seems to prefer the deciduous woods, especially 

 oak-hickory forest. 



Nests are built almost anywhere. Although it apparently does not 

 dig its own burrow, or make a trail, this mouse will utilize burrows 

 or trails of other small mammals. Jackson (1961, p. 218) says that it 

 seems to prefer a tree site for its nest, usually about 6 to 8 feet from 

 the ground, but that he has found them in abandoned squirrel nests as 

 high as 20 feet above ground. He says that often the nest is built in 

 a hollow tree or limb, and that another favorite site is under an old 

 stump or log. The nest itself is composed of soft material such as grass, 

 leaves, or other vegetation. It is usually about 10 or 12 inches in diam- 

 eter and 6 or 8 inches deep. 



Breeding takes place in late February or early March, and the first 

 litter is bom in April. The gestation period is variable, but is usually 

 between 23 and 25 days, and the litter size varies from one to seven, 

 usually three to six, with four the most frequent number. Each female 

 may produce as many as four litters during the breeding season. 



The principal food for the species is seeds of various grasses, weeds, 

 clover, small fruits, and grain as well as acorns and hickory nuts. In- 

 sects form a small portion of the diet as does green herbage. This mouse 

 sometimes occupies houses, where it may be bothersome. On Assateague 

 Island in 1957 and 1958, white-footed mice were inliabiting the houses 

 and outbuildings, while house mice {Mus rmisGulus) occurred in the 

 woods and marshes, but apparently not in the houses. 



Specimens examined. — Allegany County: Dans Mountain State 

 Park, 13; Green Eidge, 4; Mount Savage, 11; Oldtown, 4 miles E, 



