Distribution and abundance of non-native red-eared slider turtles (Trachemys scripta elegans) and native red-bellied turtles (Pseudemys rubriventris)

Habitat destruction and introduction of non-native species are among the greatest threats to the Earth's biodiversity. The threatened red-bellied turtle, Pseudemys rubriventris, historically prevalent throughout the Mid-Atlantic region, is now restricted to a few fragmented wetlands. In addition to destruction of wetland habitat, introduction of the nonnative red-eared slider turtle, Trachemys scripta, may play an important role in the decline of red-bellied turtle populations. Because the niches occupied by these two turtle species overlap, the invasion of red-eared slider turtles represent a threat to the red-bellied turtle as a competitor for limited wetland resources. In 2005 and 2006 we assessed 52 wetlands throughout Southeastern Pennsylvania for the occurrence of red-eared slider turtles in historic red-bellied turtle habitat. Trachemys scripta occurred at 25 of the 52 wetlands. Thus, T. scripta are pervasive within the geographic range of P. rubriventris in Southeastern Pennsylvania. From 2007 to 2009 I used mark-recapture to determine relative abundances of the two species in different wetlands. GIS-based landscape data was used to determine relationships between habitat degradation and relative abundances of both turtle species. I found a negative relationship between our human impact rank and the relative abundance of P. rubriventris. I found a lower relative abundance of red-bellied turtles in wetlands in public parks. There was no significant difference in relative abundance between the two methods, trapping and observation of basking turtles. Four observation visits were sufficient to detect turtles. The data provide wildlife and habitat management agencies important information on the relationship between invasive T. scripta, the state threatened P. rubriventris and wetland characteristics.