Small Mammals in Great Dismal Swamp 99 
or the earliest successional stages. In general, M. musculus does not 
coexist with native mammals once the latter become well established. 
Because there are no buildings or croplands, there is today relatively 
little disturbed habitat in the Dismal Swamp, except for that resulting 
from an occasional fire or blowdown. Hence, there is little opportunity 
for M. musculus to flourish. Except for S. hispidus, which was not 
found prior to these studies, the five species that we found in lowest 
number (1-5) also were present, but rare to uncommon, in the early 
studies of the Dismal Swamp (Table 4). 
The numbers of different individuals taken by the three methods 
differed substantially in these studies (Table 3). Higher catch rates for 
almost all species were obtained in live traps compared with pitfall 
traps. The exception was B. brevicauda, for which the rates were 
comparable. One thing we learned in the pitfall-trapping study was that 
most of the animals were taken in the first 2-4 weeks. Catch rates 
dropped off sharply thereafter. On grids established midway in the 
study, we placed plastic snap-on lids on the pitfall traps after a month 
of trapping, and weeks later reopened them. These grids had higher 
catch rates, i.e. yielded more animals over fewer weeks of trapping. Had 
we used this technique throughout the study, the catch rates for pitfall 
trapping would have been substantially higher. 
Besides yielding moderate catch rates, live traps are also useful 
because individuals can be trapped repeatedly and marked to obtain 
information on growth, reproduction, and density. The primary advantage 
of pitfall traps is that some species, particularly S. longirostris, rarely 
are taken by any other means. An additional advantage is that, unlike 
live traps, pitfall traps can be checked at irregular intervals, e.g. weekly 
or biweekly, which permits a large amount of information to be obtained 
in relation to the time spent tending the traps. Especially for locations 
deep inside the Dismal Swamp, pitfall traps are useful even though the 
catch rate is lower than for live traps (and based on Wiener and Smith 
1972, much lower than it would be for snap traps). 
The relatively high number of O. nuttalli (22, Table 1) and the 
catch rate for this form in the live-trap grids were surprising, particularly 
because other studies in the swamp have shown it to be less common 
than Peromyscus . We believe our success resulted from the habitat 
sampled, because the powerline right of way provided a large amount of 
ecotone, which seems to be ideal for O. nuttalli (Layne 1958). All but 
one of the O. nuttalli in the nest-box study also were taken at the 
ecotone. These results reinforce Dueser and Shugart’s (1978) suggestion 
that O. nuttalli is a habitat specialist and requires the complex vegetational 
structure provided along the edge of a forest. In the forest proper, 
