Juvenile Survival and Growth Probability in the Suwannee Alligator Snapping Turtle

The Suwannee Alligator Snapping Turtle (Macrochelys suwanniensis) is confined to the Suwannee River drainage in Florida and Georgia, where it is listed as threatened in both states. It is currently being considered for listing under the Endangered Species Act. Researchers from the University of Florida and the Florida Fish and Wildlife Conservation Commission initiated a capture-mark-recapture (CMR) study in 2011, and a recent population assessment found an “uncertain” population status in the river mainstem in Florida. This finding is likely due to the large amount of uncertainty around estimates of juvenile apparent survival and a low juvenile to adult growth probability. After 12 years of CMR sampling, researchers have recaptured turtles that were marked as juveniles and have since matured into adults. Here, we present a multistate model for M. suwanniensis that could, 1) provide better estimates of juvenile apparent survival, 2) estimate the juvenile to adult growth probability directly from the CMR data, and 3) help clarify this species’ status.

Tracking Turtles, An Overview of SnapperGPS and Potential Applications for Turtle Research and Conservation

Understanding how animals use their environment is an important component of understanding their ecology, and tracking systems are a vital tool to help us study these movements. Perhaps the most common tracking system for turtles is radio and acoustic telemetry, but satellite systems such as GPS are becoming more common. However, many of these tags are too large, too expensive, and are simply not feasible for use on smaller species of turtles and tortoises. Recently, researchers in the Department of Computer Science at the University of Oxford developed a small, affordable, low-power tracking system called “SnapperGPS”. This novel receiver employs “snapshot” GNSS technology that takes advantage of multiple satellite constellations (e.g., GPS, Galileo, BeiDou) to obtain accurate positional data. In addition, the unit can operate for a year on a tiny 40 mAh LiPo battery. We believe this open-source technology possesses enormous potential for better understanding freshwater turtle and tortoise ecology. Here, we present a review of this technology, some modifications for use on turtles, and discuss potential applications for turtle research and conservation.

Effect of Different Bycatch Reduction Devices on diamondback terrapin exclusion in Florida, USA

There is a need to reduce terrapin bycatch mortality in Florida while maintaining the capture of blue crabs. Arendt et al. (2018) used modeling techniques to design and test a 5.1–6.4 x 7.3 cm square shaped bycatch reduction device (BRD), which may be more effective than previous rectangle designs. Here, we examine terrapin exclusion probabilities for discrete BRD designs on a theoretical terrapin population based on reported terrapin body sizes in Florida. Our results agree with Arendt et al. (2018) who designed BRD A based on optimization. Although our results are preliminary, it appears that the square BRD is better at excluding terrapin and allows for the capture of legal sized blue crabs at the same rate as the control. Our research is on going.

The Suwannee Alligator Snapping Turtle in Florida

The Suwannee Alligator Snapping Turtle (Macrochelys suwanniensis) is endemic to the Suwannee River drainage in Florida and Georgia, and little information exists regarding its population status. A previous capture-mark-recapture (CMR) study conducted in 2011–2013 found the population status to be unclear. In 2020, we resumed sampling in three 5-km sites in the main stem Suwannee River. So far, we have captured 78 individuals and had 24 recaptures. Adult males and females maintained high estimates (0.99) of apparent survival (φ), but our estimate for juvenile φ was much higher (0.81) than our previous estimate (0.32). We used these new estimates to update a postbreeding census matrix population model for M. suwanniensis.We used simulations (n=10,000) of the matrix with our measurements of uncertainty to estimate the deterministic population growth rate (λ). The mean λ of simulations indicated a nearly stable population (λ = 1.0), but there is a considerable amount of uncertainty around this estimate (λ = 0.97–1.03). Therefore, we recommend continued research and long-term monitoring of this imperiled species.