Term of Award
Fall 2023
Degree Name
Master of Science in Biology (M.S.)
Document Type and Release Option
Thesis (open access)
Copyright Statement / License for Reuse
This work is licensed under a Creative Commons Attribution 4.0 License.
Department
Department of Biology
Committee Chair
John Carroll
Committee Member 1
Kathryn Craven
Committee Member 2
Elizabeth Hunter
Abstract
Loggerhead sea turtles nest commonly on the Georgia barrier islands and serve critical roles in human cultures, coastal economies, and multiple ecosystems. However, their global populations are declining and dependent on conservation efforts and informed management of natural and anthropogenic threats. Nesting offers a unique opportunity to research and protect this valuable marine species in terrestrial habitats. Microsatellite DNA sampling from eggshells can consistently identify nesting females from eggshells, allowing tracking of nesting behaviors for large populations over multiple years. Using this novel technology, we compared maternal investment and nest site-selection between first-time nesting neophytes and experienced remigrants. We sampled 110 randomly selected nests throughout the summer nesting season on Ossabaw Island, measuring clutch counts, egg sizes, environmental parameters, and nest placement the morning after deposition, and collecting one egg for genetic identification and water and calorie content analysis. Temperature, tidal washovers, and disturbances were monitored daily throughout incubation, then nests were excavated to determine hatching success and outcomes after hatchlings emerged or 70 days passed. Experienced remigrants averaged 18.4 more eggs per clutch than neophytes, but egg size, water and calorie content, and nesting locations were statistically similar. Clutch and egg sizes decreased significantly for all females during the season as reproductive resources were depleted, and nests later in the season were laid further from the water. Hatching success was most strongly positively correlated with warmer temperatures, greater distance from the water, and fewer washovers. Other variables, including nesting experience, nesting date, and egg mass also showed significant effects on hatching success, but require more investigation into their interactions and importance. Our data support the hypothesis that experienced females have higher relative reproductive rates with larger clutches, but may also show signs of senescence and decreasing hatching success despite using similar nesting behaviors and locations. These findings improve our understanding of the complex factors involved in sea turtle reproduction and the importance of protecting mature reproductive female loggerheads from anthropogenic mortality and habitat destruction. At the same time, they support focusing conservation resources on mitigating pressing environmental threats to incubating eggs, especially sea level rise and climate change.
Recommended Citation
Sundquist, L. (2023). Loggerhead Sea Turtle (Caretta caretta) Nesting Experience, Seasonal Variation, and Hatching Success on a Georgia Barrier Island [Master's thesis, Georgia Southern University]. Digital Commons.
Research Data and Supplementary Material
No
