All ETDs from UAB

Advisory Committee Chair

Thane Wibbels

Advisory Committee Members

Ken Marion

David Nelson

Willem Roosenburg

Robert Thacker

Document Type

Dissertation

Date of Award

2011

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

The diamondback terrapin is the only obligate estuarine turtle in North America and is considered an integral member of the salt marsh ecosystem. Unfortunately, many populations throughout the terrapin's range have experienced size declines due to past overexploitation and have been unable to rebound due to current threats including crab trap mortality, habitat degradation, nest predation, and road mortality. The current study was the first comprehensive study examining various population and conservation parameters of Mississippi diamondback terrapins in Alabama. Through various field survey methods conducted in numerous salt marshes along the Gulf Coast of Alabama, it was concluded that Cedar Point Marsh supported the largest aggregation of terrapins in Alabama, and the beach bordering Cedar Point Marsh represented the most important nesting habitat. However, population estimates indicated a significant size reduction from historical levels, and crab trap mortality and nest predation were identified as major threats currently impacting this population. Bycatch reduction devices were shown to be an effective management tool to prevent terrapin entry into crab traps, although decreases in crab capture were observed. Obtaining eggs from nesting females to help offset nest predation allowed investigations of post-emergence migratory behavior of hatchlings and female allocation strategies. Terrapin hatchlings utilized the same orientation cues as sea turtle hatchlings but migrated to the higher marsh areas rather than open water. This underscored the necessity of healthy marsh habitat adjacent to nesting beaches. Larger and older females produced larger eggs and hatchlings, but the advantage of larger hatchling sizes were not detected with the potential fitness indicators examined in this study. The consequences of high levels of road mortality, which would theoretically result in removing older females, were examined, and the Alabama population, which does not experience high road mortality, produced larger eggs than the Georgia population that does suffer from this threat. The major population decline was also reflected in the genetic diversity of the Alabama population, whose low genetic diversity was similar to other sampled terrapin populations. The initiation of this long-term dataset is crucial in developing optimal management strategies in ensuring the future survival of diamondback terrapins in Alabama.

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