Evaluating Diamondback Terrapin (Malaclemys terrapin) Nesting and Reproductive Vulnerabilities at Gateway National Recreation Area, Fire Island National Seashore, and Sagamore Hill National Historic Site

Marshall, Kathryn; Hough, Karissa; Berzins, Rebecca; Kirungi, Innocent; Sterrett, Sean

doi:10.36967/2320023

This report evaluates the continued presence, spatial extent and relative number of nesting diamondback terrapins (Malaclemys terrapin; hereafter DT) at Gateway National Recreation Area (GATE) Sandy Hook Unit (SAHO), Fire Island National Seashore (FIIS) and Sagamore Hill National Historic Site (SAHI) from 2023–2024. The study was conducted for basic inventory purposes and to inform park management approaches for DT, a species experiencing regional population declines. DT nesting was documented at all three study sites. GATE SAHO and FIIS both included areas with very high densities of depredated nests. These patterns likely reflect a combination of high-quality nesting habitat and elevated predation pressure, which may be amplified by subsidized predators associated with human activity. At FIIS, the Otis Pike Fire Island High Dune Wilderness sites supported the highest levels of DT nesting activity and were also among the least accessible areas for human recreation. At SAHO, the areas referred to here as “Sandy Spit” and “Plum Island” (project-defined survey units; see Methods for descriptions) supported the highest nesting densities. Little evidence of nesting was found at SAHI, likely due to its relatively small nesting area and high recreational use by humans and their dogs. All three areas had sites where human recreation, including unleashed dogs, may negatively impact successful DT nesting, especially because DT nesting season overlaps with peak park visitation. These findings have important implications for park management. First, DT is still a significant component of beach and dune nesting wildlife in all three areas studied. Second, peak human recreation on National Park Service properties overlaps with peak DT nesting in space and time and, in some cases, suggests a conflict that could be managed with stricter public access restrictions that may align with existing nesting shorebird management and conservation. Lastly, because we found areas with nesting habitat where we would expect DT nesting but did not detect any, we predict that enhancement of shoreline access and maintenance of beach or dune habitat could be beneficial for DT.

Evaluating Diamondback Terrapin (Malaclemys terrapin) Nesting and Reproductive Vulnerabilities at Gateway National Recreation Area, Fire Island National Seashore, and Sagamore Hill National Historic Site

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