Document Type

Event

Start Date

28-3-2014 9:00 AM

End Date

28-3-2014 9:55 AM

Faculty Sponsor

Dr. Frank Paladino

Department/Program

Department of Biology

University Affiliation

Indiana University-Purdue University Fort Wayne

Award Winner

Third

Abstract

Understanding diving behavior in sea turtles is critical for predicting the risks they face and is necessary in the formulation of effective management plans. Many recent studies have suggested that oceanographic features may influence diving behavior and thus diving patterns even in the same species may differ regionally. Hawksbill sea turtles usually spend the internesting interval close to the nesting beach, resting on coral reefs in shallow water (<5m). Sandy Point National Wildlife Refuge, St. Croix (USVI) hosts approximately thirty nesting hawksbills annually, but is an atypical nesting beach for the species because it is not surrounded by coral reefs and deep water (more than 200 meters deep) is located just offshore. We aimed to test the hypothesis that oceanographic features influence diving behavior by examining diving behavior in hawksbills nesting on Sandy Point. We attached time-depth recorders (model LAT 1100 by Lotek) to nesting turtles, obtaining 5 sets of diving data from 7 individuals. The data loggers were removed when the turtles returned to nest, on average 15 days later. Most turtles spent the majority of the internesting interval submerged at a constant depth, which is consistent with seafloor resting. Overall, they spent an average of 86.4% of the internesting interval submerged, with average dive durations of 29 minutes. Although these turtles inhabited mostly shallow water (2-29 meters), we documented 2 turtles that dove to depths greater than 85 meters. These dives are extraordinarily deep for this species, exceeding the maximum published diving depths for hawksbill sea turtles in the internesting interval. These dives, as well as the deepest dives exhibited by each individual, all occurred in the last 3 days before returning to nest. Based off previous studies of movement patterns during the internesting interval, these turtles were likely in the waters just offshore Sandy Point when they attained their deepest dives. Many of these deep dives had constant bottom depths, which is consistent with seafloor resting, the same behavior observed throughout the internesting interval. We suggest that the turtles needed to dive deep to reach the bottom to rest, which resulted in the diving patterns we observed. Our results supported the hypothesis, indicating that oceanographic features may indeed impact diving behavior, especially in cases when turtles are seeking the bottom. We recommend continued investigations into diving behavior at each major nesting ground to account for site-specific differences in behavior.

Keywords

Hawksbill sea turtle, West Indies, sea turtle

Included in

Biology Commons

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Mar 28th, 9:00 AM Mar 28th, 9:55 AM

Do Oceanographic Features Influence Marine Turtle Diving Behavior? Investigations into Hawksbill Sea Turtle (Eretmochelys imbricate) Diving in the West Indies

Understanding diving behavior in sea turtles is critical for predicting the risks they face and is necessary in the formulation of effective management plans. Many recent studies have suggested that oceanographic features may influence diving behavior and thus diving patterns even in the same species may differ regionally. Hawksbill sea turtles usually spend the internesting interval close to the nesting beach, resting on coral reefs in shallow water (<5m). Sandy Point National Wildlife Refuge, St. Croix (USVI) hosts approximately thirty nesting hawksbills annually, but is an atypical nesting beach for the species because it is not surrounded by coral reefs and deep water (more than 200 meters deep) is located just offshore. We aimed to test the hypothesis that oceanographic features influence diving behavior by examining diving behavior in hawksbills nesting on Sandy Point. We attached time-depth recorders (model LAT 1100 by Lotek) to nesting turtles, obtaining 5 sets of diving data from 7 individuals. The data loggers were removed when the turtles returned to nest, on average 15 days later. Most turtles spent the majority of the internesting interval submerged at a constant depth, which is consistent with seafloor resting. Overall, they spent an average of 86.4% of the internesting interval submerged, with average dive durations of 29 minutes. Although these turtles inhabited mostly shallow water (2-29 meters), we documented 2 turtles that dove to depths greater than 85 meters. These dives are extraordinarily deep for this species, exceeding the maximum published diving depths for hawksbill sea turtles in the internesting interval. These dives, as well as the deepest dives exhibited by each individual, all occurred in the last 3 days before returning to nest. Based off previous studies of movement patterns during the internesting interval, these turtles were likely in the waters just offshore Sandy Point when they attained their deepest dives. Many of these deep dives had constant bottom depths, which is consistent with seafloor resting, the same behavior observed throughout the internesting interval. We suggest that the turtles needed to dive deep to reach the bottom to rest, which resulted in the diving patterns we observed. Our results supported the hypothesis, indicating that oceanographic features may indeed impact diving behavior, especially in cases when turtles are seeking the bottom. We recommend continued investigations into diving behavior at each major nesting ground to account for site-specific differences in behavior.