Road mortality has detrimental impacts on animal populations, particularly turtles. Diamondback terrapins (Malaclemys terrapin) are thought to be declining throughout their range due to anthropogenic factors, including road mortality on coastal causeways. Populations of terrapins in proximity to causeways are most vulnerable to the effects of road mortality when adult females are struck and killed while searching for nest sites on open, elevated road banks. While causeways may be a broad target for management, defining specific spatial and temporal peaks of mortality along these corridors could facilitate more precise management to reduce impacts on wildlife. Through intensive road surveying in the summers of 2009 and 2010, we performed a case study of the 8.7-km Jekyll Island Causeway in Georgia, USA to 1) determine whether terrapin activity on the causeway was spatially (hot spots) or temporally (hot moments) predictable and 2) determine whether particular habitat features were associated with hot spots.
Results/Conclusions
We documented 636 terrapin crossings (~450 resulted in mortality), and identified both hot spots and hot moments of terrapin activity that were consistent between years. Temporally, we found peaks in activity concentrated around the 3-hr window at high tide. Spatially, 30% of terrapins were observed crossing in 3 hot spots that composed less than 10% (~800 m) of the entire causeway’s length. Three habitat features influenced terrapin activity on the causeway, and the amount of surrounding, unvegetated high marsh had the largest (negative) effect. Our results indicate that terrapin road crossings are spatially and temporally predictable. We suggest that this information could be used to develop more effective warning systems for motorists during hot moments and implement fencing of hot spots to limit terrapin road mortality for this population.