MAMMALS OF MARYIANiD 127 



Figure 42. — ^Distribution of Zapus hudsonius americanus. 



mouse to accumulate a certain amount of fat before it is capable of 

 hibernation (Hamilton 1935, p. 193), and thus those taken in autumn 

 are usually fat. 



Almost invariably, meadow jumping mice hibernate in burrows in 

 which nests are constructed of grass, leaves, or other vegetation. 

 Grizzel (1949, pp. 74-75) found two of these animals hibernating in 

 woodchuck dens at the Patuxent Research Center in January 1948. 

 One animal was found 4 feet from the entrance to the burrow and 

 about 40 inches below the surface of the ground. The second was 

 found in another burrow 5 feet from the entrance and 26 inches below 

 the surface. Both animals were curled up in the center of large leaf 

 nests and well insulated from the cold. 



In the vicinity of Washington, D.C., these mice remain active well 

 into November, and emerge from hibernation in early April. In the 

 Allegheny Mountain section, and the Ridge and Valley section, the 

 hibernation period is more prolonged. Occasionally, during mild spells 

 in midwinter they merge from their burrows and become active. 

 Barbehenn tells me that he collected one jumping mouse in an old 

 orchard with honeysuckle and poison-ivy ground cover near Rock- 

 ville, Montgomery County, on 11 February 1960, in very mild weather. 



During their active part of the year, meadow jumping mice wander 

 freely and seldom make well-defined trails or runways. They con- 



