98 
Rose, Everton, Stankavich, and Walke 
15 years old. As long as grasses remained in the understory, S. c. 
helaletes persisted. Sorex /. fisheri persisted even in mature forests with 
no grasses, but at lower densities than in early serai stages. Reithro- 
dontomys h. humulis were restricted to early serai stages, i.e. those with 
few saplings or shrubs, where they attained densities as great as 25/ ha 
on live-trapping grids (Stankavich 1984). Trapping in areas dominated 
by herbaceous vegetation no doubt contributed to the relatively large 
number of M. p. nigrans compared with previous studies (Table 4). 
Clark et al. (1985), working in and near Carolina Bays and pocosins in 
North Carolina, also reported 3-5 times higher capture success when 
trapping on edges or in fields compared with the interior of pocosins. 
Five species (C. parva, O. palustris, S. hispidus, M. pinetorum, and 
M. musculus ), each represented by one to five specimens, were found 
only in nonforested habitats (Table 2). Except for S. hispidus , all had 
been collected in the past, usually in low numbers, and should be 
considered as minor species in the Dismal Swamp. For example, C. 
parva is most abundant in the region in dry oldfield habitats (Rose 
1983, Everton 1985), habitats that are absent in the Dismal Swamp. 
Although little is known of the ecology of O. palustris , it is highly 
aquatic and therefore well adapted to live in swamps. The decline in 
numbers of O. palustris (Table 4) may be more apparent than real, or it 
could indicate a loss of habitat. Sigmodon hispidus , first reported from 
Virginia (Mecklenburg Co. in 1940) by Patton (1941), has been expanding 
its range throughout the Midwest and East. In Virginia, it has crossed 
the James River near Richmond (Pagels 1977), but its northward path is 
blocked in eastern Virginia by the Chesapeake Bay. As a species that is 
well adapted to the dry grassland of the Southwest, S. hispidus probably 
is poorly adapted to conditions of long-term inundation of its habitat, 
particularly if winters are relatively cold. Furthermore, the species is 
found primarily in habitat dominated by grasses and other herbaceous 
vegetation, and it seems not to tolerate much woody vegetation in its 
habitat. Although patches of suitable habitat may be produced by fires 
or clearcutting, that habitat will probably occur in remote sections of 
the swamp, where it is separated from the closest source populations of 
S. hispidus by large expanses of unsuitable cover. 
The woodland vole, M. pinetorum , also called the pine vole, 
usually is associated with the edge of forest and oldfield. Although M. 
pinetorum sometimes is common in well-drained upland forests in the 
region, it apparently is not common in the seasonally flooded forests of 
the Dismal Swamp. Finally, M. musculus , introduced to North America 
from Europe during colonial times, usually is a commensal of man or is 
restricted to disturbed areas such as recently plowed fields, croplands, 
