Small Mammals in Great Dismal Swamp 
95 
Table 3. Comparison of trapping efficiencies for three methods of trapping 
small mammals, expressed as the number of new individuals taken per 1,000 
trap-nights. 
Species 
Live 
trapping 3 
Pitfall 
trapping' 3 
Nest-box 
trapping 0 
So rex longirostris 
0 
0.993 
0 
Blarina brevicauda 
1.133 
1.151 
0 
Crypt otis parva 
0 
0.113 
0 
Oryzomys palustris 
0.008 
0 
0 
Reithrodontomys humulis 
5.747 
0.113 
0 
Peromyscus leucopus 
1.133 
0.158 
4.512 
Ochrotomys nuttalli 
1.781 
0.068 
1.128 
Sigmodon hispidus 
0.016 
0 
0 
Micro tus pennsylvanicus 
1.052 
0.293 
0 
Microtus pinetorum 
0.024 
0.023 
0 
Synaptomys cooperi 
1.052 
0.542 
0 
Mus mus cuius 
0.016 
0 
0 
New individuals 
per 1,000 trap-nights 
11.962 
3.454 
5.640 
a 12,354 trap-nights, 
b 44, 320 trap-nights 
c 7,979 trap-nights. 
several times over a 2-month period on the driest live-trap grid. For the 
first time in this century, O. p. palustris (one specimen in live trap) and 
M. p. scalopsoides (four specimens in live and pitfall traps) were 
collected. No specimens of P. g. gossypinus were collected in these 
studies, and only two have been collected in this century [in 1933 by 
Dice (1940)]. We can conclude that its numbers and distribution have 
declined, and perhaps it is now absent from the swamp forests. The 
largest apparent increases in numbers were for the shrews, because 
pitfall traps were used, and R. h. humulis, most of which were taken in 
live traps. 
