92 



NORTH AMERICAN) FAUNA 66 



DEER MOUSE 

 Peromyscus tnaniculatus (Wagner) 



Hesperomys mamcvZatus Wagner, Arch. Naturgesch., Jahrg. 11, 1 : 

 148, 1845. 



This is a wide-ranging species that occurs over much of North Amer- 

 ica. Numerous subspecies have been described ; of these, two are known 

 to occur in Maryland. They are : 



Peromyscus tnaniculatus bairdii (Hoy and Kennicott) 



Mm hairdii Hoy and Kennicott, in Kennicott. Agricultural Eeport, 

 U.S. Commissioners Patents, 1856, p. 92, 1897. 



Type locality. — Bloomin^on, McLean County, 111. 



General distribution. — Prairie region of the upper Mississippi Valley, from 

 eastern Kansas and Missouri ; north to southwestern Manitoba, Canada ; east- 

 ward through southern Minnesota, Wisconsin, and Michigan to the man-made 

 prairie of central New York, Pennsylvania, Maryland, and northern Virginia. 



Distribution in Maryland. — The distribution of this subspecies 

 within the State is unknown. It has been taken in Maryland only at the 

 Patuxent Eesearch Center, Prince Georges County. (See fig. 34.) 



Distinguishing characteristics. — Teeth 1/1, 0/0, 0/0, 3/3, = 16; 

 coloration of upperparts brownish gray, mixed with darker hairs; 

 underparts white, the basal gray of the underfur often conspicuous; 

 tail short and distinctly bicolored, upperparts brownish black, white 

 beneath; feet white. Immature animals are more grayish dorsally. 



This subspecies is readily distinguished from Peromyscus manicula- 

 tus mjbbiterrwe by its much shorter tail. It is easily confused with 

 Pemmyscus leucopu^s^ but may be distinguished by several characters 

 which are discussed under that species. 



Measurements. — External measurements of two adults from the 

 Patuxent Research Center, Prince Georges County, (a wild-caught 

 female and one of her laboratory-raised offspring) are as follows: 

 Total length 152, 149; tail 63, 59; hind foot 18, 19; ear 13.5, 14.0. 

 Cranial measurements of three adults from the Patuxent Research 

 Center (the wild-caught female and two of her laboratory-raised off- 

 spring) are: Greatest length 23.1, 23.3, 23.0; zygomatic breadth 11.5, 

 12.1, 11.9; interorbital breadth 3.7, 3.9, 3.9; length of maxillary tooth- 

 row 3.0, 3.3, 3.3. 



Habitat and habits. — This subspecies inhabits prairies, open fields, 

 and arable land and is entirely absent from dense forests. It was un- 

 known in Maryland until 1949, when Lucille F. Stickel and Oscar 

 Warbach live-trapped several in crop fields at the Patuxent Research 

 Center. These fields are about 1.9 miles north of Bowie and are situated 

 on a wide bench of sandy clay near the Patuxent River. From May 



