Year
2025
Season
Fall
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
Committee Chairperson
Dr. Quincy A. Gibson
Second Advisor
Dr. Eric G. Johnson
Third Advisor
Dr. Kris A. Lewis
Abstract
Wildlife population management depends on knowledge of the population’s foraging ecology. A community of resident Tamanend’s bottlenose dolphins (Tursiops erebennus) utilizes the St. Johns River (SJR) in Jacksonville, Florida, and members of the community are regularly sighted emaciated or with skin lesions. Anthropogenic disturbances may contribute to further health decline, therefore Chapter One analyzed SJR foraging dolphin group habitat use before, during, and after a large-scale dredging event known as the Jacksonville Harbor Deepening Project (JHDP). Kernel density estimates (KDEs) of foraging dolphin group sightings were generated to estimate 95% utilization distributions (i.e., foraging home ranges) for three dredging period comparisons for warm and cold seasons: before vs. during, during vs. after, and before vs. after the JHDP. In addition, 50% UDs (i.e., core foraging areas) were identified for each period. The lack of core foraging area overlap between most period comparisons indicated that SJR dolphin foraging habitat use shifted after dredging, most notably with the disappearance of a core foraging area located at the intersection of the SJR and the Intracoastal Waterway. To determine whether significant foraging dolphin group density changes occurred across time, home ranges for each period were compared. Results indicated that foraging dolphin group densities decreased during and after dredging. Although the JHDP is complete, maintenance dredging is ongoing, which may also impact SJR dolphin prey. In Chapter Two, stranded SJR dolphin stomach contents were analyzed to describe the species composition, size, and proportionality of potential key prey species. A novel bottlenose dolphin prey item, the violet goby, was identified as a key SJR dolphin prey item, along with Atlantic croaker and weakfish. This research provides evidence that dredging disturbances impacted the SJR dolphin community and lay the groundwork for identifying prey species that are key to the conservation of the SJR dolphin community.
Suggested Citation
Swinehart, Andrea Leigh, "What’s for dinner? A multi-pronged approach investigating the foraging habits and diet of St. Johns River bottlenose dolphins (Tursiops erebennus)" (2025). UNF Graduate Theses and Dissertations. 1367.
https://digitalcommons.unf.edu/etd/1367