Fine-scale movement patterns of diamondback terrapins (Malaclemys terrapin) on a southeast Louisiana barrier island

Tracking animal movement in brackish water systems poses significant challenges as standard tracking techniques often perform poorly in these environments. The Diamondback Terrapin, a semi-aquatic, estuarine turtle found along the U.S. Atlantic and Gulf Coasts, is one such species with limited knowledge of movement ecology, especially within the Gulf region. We used a novel method to track terrapin movement at fine spatiotemporal scales via an automated radio telemetry system on a barrier island in southeast Louisiana. From August 2022 to May 2023, we captured and tagged 38 terrapins with radio transmitters. We triangulated locations, calculated hourly and daily movement rates, and used generalized linear mixed models to determine factors that influence both hourly and daily terrapin movement. We found that carapace length, time of day, and water temperature were important predictors of hourly movement, and season strongly influenced daily movement. Movement peaked around midday and at moderate water temperatures (24.6 °C). The largest movements occurred early in the active season during mating and nesting activities. Larger turtles moved longer distances at both the hourly and daily scales, indicated by the positive effect of carapace length. The automated radio telemetry system we employed was effective for high accuracy location estimation and fine-scale characterization of terrapin movement patterns. Our findings support prior knowledge of broad-scale seasonal and diel terrapin behaviors but revealed factors influencing fine-scale movement that are challenging to document with traditional tracking techniques. This study demonstrates the importance of movement monitoring for guiding conservation efforts and management decisions for species in dynamic salt marsh systems.