Understanding movements and habitat use of diamondback terrapins (Malaclemys terrapin) is important for the conservation of the species, however movement studies of the species are limited. Additionally, while head-starting is a common method to bolster populations in turtle conservation, it’s impacts on survival and behavior of individuals post release are poorly understood. We initiated a study of juvenile and adult female terrapin movements in southern New Jersey to better understand impacts of our long-term head-starting program, and fill in gaps in our knowledge of terrapin ecology. Telemetry methods varied by age class, incorporating passive and active telemetry methods using novel technology. Adult female terrapins (n=13) were captured and tracked using solar-powered GPS transmitters from 2018-2019. Transmitters attempted a GPS fix every 8 hours when not submerged in water. Location data were transmitted via radio signal to a receiver over a 3-10 km range. From 2018-2019, 45 (6 wild, 39 head-started) juvenile terrapins were fitted with digital radio transmitters and released in the study area. Signals from these tags were received passively by an array of 20 receiver antennas installed in a 100 m grid across a 24-hectare area of tidal saltmarsh. Relocations made using a hand-held antenna facilitated data collection on behavior and habitat characteristics.
Results/Conclusions
Despite the challenges of telemetry in saltmarshes, location data were received from 11 of the 13 adults tracked, with 16 ± 8.5 locations/individual and mean accuracy of 4.6 ± 2.1 m. Data collection are ongoing, however preliminary results show adult females traveled between 0.4-4.6 km straight-line movement from their home creeks to upland nesting locations, spent significant time in salt pannes, and were active mainly within small areas in tidal creeks. Female terrapins exhibited fidelity to nesting locations within a nesting season, and nested up to three times per season, increasing the occurrence of triple clutches known in our marked population. For juveniles, active tracking produced locations for 33 of 45 terrapins, with mean daily movements 13.4 ± 7.9 m. The extent of movements varied by individual; some juveniles dispersed from release locations continuously and others appeared to settle in a defined area. Juveniles were buried in the mud 38.5% of these observations, a behavior more frequent in the low marsh compared to high marsh habitats. Though telemetry remains challenging in a salt marsh environment, the use of new technologies are proving valuable for increasing our knowledge of terrapin ecology to inform our conservation efforts.