32 Mary K. Clark, David S. Lee, John B. Funderburg, Jr. 



plant communities. Interestingly, they suggested that no single factor 

 was responsible, but discussed the impacts of low food availability and 

 flooding. 



The paucity of small mammals in pocosins and related communi- 

 ties can be illustrated by comparing trap-night success in those habitats 

 with success in other habitats. For example, 3,000 trap-nights in pocosin 

 communities (data pooled from Bladen, Hoke and Dare counties) had 

 only a 2.06 percent capture success, and 1,000 trap-nights in mature 

 evergreen bay forest in Bladen County had 1.23 percent success. On the 

 other hand, 2,000 trap-nights in non-pocosin habitats in Currituck 

 County averaged 6.1 percent trapping success, and 365 trap-nights in 

 upland habitats of various types adjacent to Carolina bays in Bladen 

 County yielded 7.12 percent success. The point here is that plant com- 

 munities, not geography, are responsible for the relative densities. 



Pocosin Systems as Refugia 



Lee et al. (1982) discussed the occurrence in pocosin-rich areas of 

 relicts such as Synaptomys cooperi, semi-relicts such as Condylura cris- 

 tata and Marina brevicauda, and species at the limits of their ranges. 

 About 25 percent of the mammals associated with pocosins fall into one 

 or another of these categories. Species that reach their northern distri- 

 butional limits on the Atlantic slope within the Dismal Swamp area 

 include Plecotus rafinesquii, Sylvilagus aquaticus, Peromyscus gossypi- 

 nus, Ochrotomys nuttalli, and to a lesser extent Sigmodon hispidus. 

 Except for fragmented populations of Condylura cristata and saltmarsh 

 populations of Microtus pennsylvanicus that occur farther south, the 

 Dismal Swamp area is also the southern limit for northern species that 

 invade the southeastern Coastal Plain on the Atlantic slope. These 

 include C. cristata, M. pennsylvanicus, and S. cooperi, and possibly M. 

 lucifugus and B. brevicauda. Furthermore, Condylura cristata and 

 Sorex longristris each reach the southern extremes of their ranges in 

 pocosin-like communities, the former in the Okefenokee Swamp, Geor- 

 gia (Paradiso 1959) and the latter in the Green Swamp, Polk County, 

 Florida (Hill 1945). Their southernmost populations appear to be 

 somewhat disjunct from populations to the north. 



Pocosin habitats may have provided refugia for both northern and 

 southern species since Pleistocene times, allowing populations to persist 

 beyond otherwise normal distribution limits. The protective evergreen 

 vegetation and the heat retention of high water tables should buffer the 

 extremes of severe winter weather, while shade and evaporative cooling 

 could be expected to ameliorate extreme high temperatures of Coastal 

 Plain summers. Hibbard (1960) postulated that in the late Pleistocene 

 (ca. 16,000 years ago) a period of climatic equality existed, in which 



