All ETDs from UAB

Advisory Committee Chair

Thane Wibbels

Advisory Committee Members

Ken Marion

Scott Rush

Document Type

Thesis

Date of Award

2022

Degree Name by School

Master of Science (MS) College of Arts and Sciences

Abstract

The Diamondback Terrapin, Malaclemys terrapin pileata, inhabits saltmarshes in the Northern Gulf of Mexico including along the coast of Alabama. Due to a variety of factors, this species has declined drastically in Alabama, and it is currently designated as a “species of highest conservation concern”. Understanding the ecology of this species is a prerequisite to the recovery of this population. The current thesis addresses the reproductive and foraging ecology of the Diamondback Terrapin in Alabama. This thesis combines the use of classic ecological methodologies with modern technologies. Between April 2019 to July 2022, wild nesting females were caught at a major nesting beach located on the western border of Cedar Point Marsh in Heron Bay, Alabama. Blood samples were obtained from all of the captured terrapins in order to evaluate the foraging ecology through δ13C and δ15N stable isotope analysis. The variation in δ13C and δ15N exhibited by the samples suggested potential variation in foraging behavior. Additionally, the mean and standard deviation of these values did not overlap with those previously reported for three terrapin populations in southwest Florida. Stable isotope values were also evaluated for a variety of potential prey items and primary producers in the salt marsh habitat. The results revealed significant species-specific and site-specific variation in the stable isotope values of prey and primary producers in both δ13C and δ15N and included an isoscape for the Marsh Periwinkle in the eastern portion of the Mississippi iv Sound of Alabama. An experimental evaluations of stable isotope values in Head Start terrapins indicated that they could provide a model for resources assimilation by wild Diamondback Terrapin. This study represents the first documentation of δ13C and δ15N stable isotope values for the Diamondback Terrapin from a major nesting location in the northern Gulf of Mexico and documents stable isotope values for a variety of prey items in that habitat. The reproductive ecology of the nesting female terrapins was evaluated during the 2021 and 2022 nesting seasons at Heron Bay, Alabama. Captured turtles ranged from 600 to 1385 grams, 67 to 188 mm in plastron length, and 157 to 207 cm in straight carapace length. Gravid females produced an average of 7.7 ± 1.8 eggs. Population estimates revealed that there were 166 individuals during 2021 and 133 individuals during 2022. Radio transmitters were attached to a subset (n = 13 for 2021, and n = 10 for 2022) of these turtles to monitor post-nesting movements. Telemetry results indicate that many of the terrapins that were nesting in Cedar Point Marsh remained in the Cedar Point Marsh area after nesting, and that terrapins captured in the northern portion of Heron Bay continued to inhabit that area for the period they were tracked post-release. To assess the impact of local predators on terrapin nests, Cedar Point Marsh was surveyed for nesting daily for depredated nests during the 2021 and 2022 nesting seasons. No depredated nests were observed during the 2021 or 2022 terrapin nesting seasons which is in distinct contrast to high nest depredation levels in years previous to a racoon removal program in 2020. Collectively, these data document that the salt marshes and associated beaches in the Heron Bay area represent habitat that is critical for successful reproduction of the Diamondback Terrapin.

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