Year

2022

Season

Summer

Paper Type

Master's Thesis

College

College of Arts and Sciences

Degree Name

Master of Science in Biology (MS)

Department

Biology

NACO controlled Corporate Body

University of North Florida. Department of Biology

First Advisor

Dr. Adam E. Rosenblatt

Second Advisor

Dr. Eric G. Johnson

Third Advisor

Dr. Joseph A. Butler

Department Chair

Dr. Cliff Ross

College Dean

Dr. Kaveri Subrahmanyam

Abstract

Loggerhead sea turtles (Caretta caretta) are currently listed as “vulnerable” on the IUCN Red List and are experiencing population declines across many parts of their range. These declines are caused by environmental and anthropogenic stressors which impact sea turtle ecology and behavior, including nesting behavior. One nesting behavior sea turtles exhibit is known as “false crawling,” which is when a female sea turtle ascends the beach in an attempt to nest and either abandons the attempt altogether or while in the middle of digging an egg chamber. False crawling, a largely understudied sea turtle behavior, can not only be detrimental to the reproductive output of an individual female but could negatively impact an entire population’s reproductive success if the behavior is widespread. To investigate the different environmental and anthropogenic factors that may affect false crawling behavior in loggerheads we used historical survey data to determine the impact of a large anthropogenic structure (revetment) on a loggerhead nesting beach on Jekyll Island, GA. We then conducted surveys of the same beach for two years to assess the effects of lighting pollution, sand surface temperature, sand subsurface temperature, human presence, anthropogenic obstructions, and marine debris. For the 2008 – 2019 nesting seasons, we found that loggerhead false crawling rates were significantly higher near the revetment than on other parts of the beach, and that loggerheads mostly avoided trying to nest near the revetment at all. For the 2020 and 2021 nesting seasons, we found that sand subsurface temperature, human presence, and location relative to the revetment each significantly affected loggerhead false crawl rates, though sometimes in surprising ways. Overall, these results suggest that on Jekyll Island false crawling by loggerheads has been primarily caused by the presence of a large anthropogenic obstruction, but that other factors can also affect false crawling in context-specific ways.

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