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Road ecology of the northern diamondback terrapin, Malaclemys terrapin terrapin


Diamondback terrapin populations along the East Coast have suffered due to a number of factors since the early 1900’s. Overexploitation from commercial harvesting, drowning in fishing gear, and loss of habitat has had a negative impact on the terrapin (Roosenburg 1991). Terrapins in several areas, specifically in New Jersey, are now threatened by an additional source of mortality, road mortality (Wood and Herlands 1997, Hoden and Able 2003), which could cause further declines in the abundance of this species. Road mortality and ecology of the northern diamondback terrapin, Malaclemys terrapin terrapin, in the Jacques Cousteau National Estuarine Research Reserve was examined and compared to traffic patterns during the nesting seasons (May-July) of 2004 and 2005. Traffic-measuring devices were stationed on sections of Great Bay Boulevard (GBB), an access road through salt-marsh habitat to obtain traffic-volume estimates. A total of 1201 terrapins were observed on the road with 104 road mortalities (8.66%). In 2004, a significantly greater proportion of road kills was found in the section of the road with the highest traffic volume. However, we did not see this same pattern in 2005 as road mortalities across the sections were fairly evenly distributed. There was a positive correlation between road kills and increasing traffic volume throughout the day observed in 2004. Three hundred terrapins were tagged with passive-integrated transponder (PIT) tags over the course of the study. The tagging portion of this study indicated that some females may have been returning more than once in the season to lay multiple clutches along the roadside and demonstrated nest-site philopatry by returning to the area where they were initially tagged. The information gathered suggests that terrapins are attracted to the roadside as it meets the requirements for a suitable nesting habitat. Future mitigation, such as drift fencing and increased patrolling of the roads, is needed to help reduce road mortalities. Fencing will be proposed to be installed in the areas of greatest road mortality and of greatest nesting activity along Great Bay Boulevard for 2006.

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