Dismal Swamp Small Mammals 47 



and local abundances. Finally, four species — the woodland vole, Micro- 

 tus pine tor um scalopsoides (Audubon and Bachman); the house mouse, 

 Mus musculus domesticus Rutty; the least shrew, Cryptotis p. parva 

 (Say); and the meadow vole — were seldom caught by any collector, 

 which may mean that the habitats required by these species are rarely 

 found in the Swamp (Handley 1979). 



On 23 February 1980, David Harrelson, a senior biology student at 

 ODU, and I began a study of the small mammals of openings in the 

 GDSNWR. The term "openings" refers to any area in which a signifi- 

 cant level of shading provided by tree canopy is absent. These habitats 

 are vegetated predominantly by cane, Arundinaria gigantea; softstem 

 rush, Juncus effusus; sedges; grasses; and herbaceous forbs. Many open- 

 ings also have small trees and shrubs, plus a number of woody vines; the 

 most common of these are red maple, Acer rubrum; blackberry, Rubus 

 allegheniensis; grape, Vitis spp.; and greenbriers, Smilax spp. 



MATERIALS AND METHODS 



Pitfall traps, made of No. 10 tin cans sunk into the ground flush 

 with the soil surface and half-filled with water, were used to collect 

 small mammals. Seven pitfall traps were dug and placed on 23 Febru- 

 ary, but adverse weather, including a record snowfall that covered the 

 area for the first two weeks in March, delayed until 20 March the set- 

 ting of twenty-eight additional traps. All 35 traps were set within 150 m 

 of Jericho Ditch, north of Williamson Ditch, under the 1 10 kv electrical 

 powerline in the northwestern corner of the GDSNWR. 



On 10 April, 10 pitfall traps were placed 9 km away, under the 

 same powerline near East Ditch, also in an area dominated by cane, 

 grasses, and rushes. This area had a higher proportion of standing water 

 than did the Jericho Ditch site. All traps were removed from the ground 

 on 2 May 1980. 



RESULTS 



Only one small mammal, a Microtus pennsylvanicus, was captured 

 in the seven traps from 23 February to 20 March. However, a total of 

 43 small mammals of seven species was trapped during the study period 

 at the Jericho Ditch site (Table 1). At the East Ditch site, three small 

 mammals of three species were caught (Table 1). 



Based on the number of small mammals captured in 100 trap- 

 nights, the relative density of small mammals appeared to be greater in 

 the Jericho Ditch area (2.43) than in the East Ditch area (1.36). (One 

 trap in place for one night equals one trap-night; relative density = 

 N/trap nights X 100.) This difference in density may be due in part to 

 the greater vegetational diversity of the Jericho Ditch site, and to the 

 greater proportion of standing water on the East Ditch site. 



