USF St. Petersburg campus Master's Theses (Graduate)

First Advisor

Major Advisor: Alison Gainsbury, Ph.D.

Second Advisor

Co-advisor: Justin Perrault, Ph.D.

Third Advisor

Committee Member: Deby Cassill, Ph.D.

Fourth Advisor

Committee Member: Sarah Hoffmann, Ph.D.

Fifth Advisor

Committee Member: Annie Page-Karjian, DVM, Ph.D.

Publisher

University of South Florida St. Petersburg

Document Type

Thesis

Publication Date

2020

Date Issued

June 24, 2020

Abstract

Anthropogenic threats, such as bycatch, boat strikes, and pollution, account for two to three times more sea turtle mortality events than natural causes. The goals of this study were to: (1) determine prevalence and cause of external traumatic injuries on nesting loggerhead sea turtles (Caretta caretta) in Juno Beach, Florida and (2) conduct an analysis of historical rehabilitation data from Florida Fish and Wildlife Conservation Commission (FWC) to calculate mortality of loggerhead and green (Chelonia mydas) turtles injured by boats. During the 2019 nesting season, 300 loggerheads were tagged and examined for external injuries. All injuries were categorized based on type, condition, and anatomic location. Red light photos from the field and FWC stranding data were analyzed using ImageJ. Case outcome (e.g., died, euthanized, released) and mortality (e.g., died, survived) of turtles entering rehabilitation facilities were analyzed separately. To test for differences in injury prevalence of nesting loggerheads and for differences in the case outcome of rehabilitation patients’ contingency tables were created. To test the association between numeric independent variables (e.g., SCLmin, injury size, number of injuries, and number of injury locations) and mortality, a multiple logistic regression was run. Contingency tables were created to test for differences in mortality according to all other variables. Approximately 24% (N=71) of tagged nesting loggerheads had an external injury. The majority of the identifiable injuries were boat strikes (68%), followed by shark interactions (18%), hook injuries (9%), and entanglements (5%). Additionally, for each unit increase in the number of injured anatomic locations, the odds of the turtle dying during rehabilitation increased by a factor of 5.99 in loggerheads. Green turtles entering rehabilitation facilities had significant differences in case outcome depending on injury area, width, lateral carapace presence, condition, and severity. Injury width and injury severity were significantly related to mortality in green turtles. For each unit increase in average injury width to straight carapace width (SCW) ratio the odds of a green turtle dying in rehabilitation increased by a factor of 217.02. Healed injuries had a significantly lower probability of mortality, when compared with fresh and partially healed injuries in both loggerheads and green turtles. The results of this study provide new insight into the impact that anthropogenic and natural threats have on sea turtles, as the nesting females in this study survived these interactions without veterinary intervention. The results can be used to create/improve upon conservation management plans, such as boat speed restriction zones, and rehabilitation facility triage decisions.

Comments

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Conservation Biology Department of Biological Sciences College of Arts and Sciences University of South Florida Saint Petersburg

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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