Diving behavior and thermal habitats of gravid hawksbill turtles at St. Croix, USA
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Knowledge of an animal’s behavior during particular life history stages can provide insights into habitat selection, and this can have important conservation implications. Gravid hawksbill turtles spend the internesting interval resting on the seafloor, but their diving behavior has only been previously examined in shallow-water habitats. We examined depth use of gravid hawksbills in a location of variable bathymetry to determine if hawksbills engage in deeper diving if deeper waters are available. We attached archival time-depth recorders onto hawksbills nesting at Sandy Point National Wildlife Refuge, St. Croix, US Virgin Islands, where the neritic zone ends within 500 m of the shoreline. We recorded seven internesting intervals from five individuals. Internesting intervals were characterized by long dives (mean 24.2 ± SD 22.3 min) to a constant depth, consistent with seafloor resting in a spatially restricted residence area. There was little variation in the water temperatures at all depths occupied (mean 29.06 ± SD 0.43 °C). Two turtles attained the deepest recorded dives for gravid hawksbills (95.1 and 84.4 m) and sometimes remained at depths greater than 60 m for up to 30 min. Although we recorded instances of relatively deep diving for the species, the overall pattern of seafloor resting and infrequent diving was consistent with hawksbills in other ocean basins with different offshore habitats. We propose that benthic resting is common behavior for gravid hawksbills globally, and protection of benthic habitats near the nesting beach should be a management priority.
KeywordsGreen Turtle Benthic Habitat Bottom Phase Diving Behavior Dive Depth
We would like to thank Mike Evans and Claudia Lombard of the US Fish and Wildlife Service for logistical support and assistance in obtaining permits (USFWS Special Use Permits 41526-2013-003 and 41526-2012-004, VI DPNR Endangered Species Research Permit STX-031-12). Brian Daley and Jen Valiulis of Geographic Consulting, LLC also aided in the logistics of working on St. Croix. Field assistance was provided by Jake Bryan, Justin Whisante, Scott Perry, Liz Zimmer, Molly Clifford, and Donna Boles. This study was funded by a grant from the Lerner Gray Marine Research Fund, The Leatherback Trust, and by the Schrey Chair in Biology at Indiana University-Purdue University Fort Wayne. Research methods were approved by the Purdue Animal Care and Use Committee (Protocol 1206000656).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Human and animal rights disclosure
All applicable national and institutional guidelines for the care and use of animals were followed. All procedures performed in studies involving animals were in accordance with the ethical standards of the institution at which the studies were conducted.
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