Considering diamond-backed terrapin (Malaclemys terrapin) nesting habitat and reproductive productivity in the restoration of Gulf of Mexico coastal ecosystems

Abstract

Diamond-backed terrapins (Malaclemys terrapin) are coastally distributed between south central Texas in the Gulf of Mexico along the Gulf and Atlantic Coast north through Massachusetts. Throughout their range many different biotic and abiotic factors have been shown to influence terrapin abundance, distribution and nesting success. Louisiana Department of Wildlife and Fisheries (LDWF) implemented a multi-year (2013–2015) project which evaluated diamond-backed terrapin nesting ecology along Louisiana's coastline, principally within the Deltaic Plain. We focused on identifying nest site locations, nest predators and predation rates, nest surface characteristics, nest depth, clutch size, egg morphometrics, nest and nest survivorship. Our results indicate that terrapin nesting occurs coast-wide in locations where suitable nesting substrates exist. Nests are laid in open areas and beneath dense vegetative cover with surface slopes in all orientations. Depredation rates range between 50 and 100 percent depending on nesting beach location. Intact clutch size averages 6.5 eggs and varies between one and 15 eggs. Statewide, average egg morphometrics are: mass 10.6 g, length 36.9 mm and width 23.6 mm. Average nest ceiling depth is 7.7 cm and average nest floor depth is 11.8 cm. Seventy-six percent of all nests surveyed were fully or partially depredated. In 2015 we studied in detail 92 nests from a single nesting site; 49% of nests hatched at least 1 egg, 43% of eggs were depredated, 31% of the eggs hatched and 26% had unknown fate. We provide Louisiana's first evaluation of diamond-backed terrapin nesting ecology critical for determining the conservation status of diamond-backed terrapins within Louisiana. Our findings provide natural resource managers with critical life history information that can be incorporated into current and future coastal restoration plans to benefit diamond-backed terrapins.