Urbanization is a major threat to biodiversity. However, little is known about the mechanism through which urbanization affects the persistence of wildlife. One of the potential threats is the reduced food availability associated with habitat shrinkage and fragmentation. The eastern box turtle (Terrapene carolina) is listed as vulnerable by the IUCN. To determine whether urbanization associated reductions in food availability contribute to the decline of the eastern box turtle, we measured the abundance and body condition of turtles along a gradient of impervious surface cover across 11 sites in the rapidly urbanizing South Carolina Piedmont region. Timed visual searches were performed at each site to locate turtles. The body mass, carapace width and length as well as the sex was recorded for each individual. Body condition was evaluated based on scaled mass index.
Results/Conclusions
Generalized linear models showed that both male and female abundance declined significantly as impervious surface cover increased. Reduced body condition was evident only in urban males; urban females exhibited a comparable body condition to rural females. The apparent lack of body condition decline in urban females suggests that resource availability is not a direct cause of observed population decline. The poorer body condition of males may be attributable to the increased energetic costs of searching for scare females in urban sites. We propose that the observed population decline is not driven by reduced habitat quality per se, but primarily by external sources of mortality such as vehicle strikes, urban predation or poaching. Therefore, conservation efforts should focus on maintaining large interconnected forest patches in order to minimize exposure to these external sources.