ESR 13:25-31 (2010)  -  DOI: https://doi.org/10.3354/esr00311

Combining stable isotopes and skeletal growth marks to detect habitat shifts in juvenile loggerhead sea turtles Caretta caretta 

Melissa L. Snover1,*, Aleta A. Hohn2, Larry B. Crowder1, Stephen A. Macko

1Duke University Marine Lab, 135 Duke Marine Lab Road, Beaufort, North Carolina 28516, USA
2NOAA, NMFS, SEFSC, 101 Pivers Island Road, Beaufort, North Carolina 28516, USA
3Department of Environmental Sciences, University of Virginia, 291 McCormick Road, Charlottesville, Virginia 22903, USA

ABSTRACT: Understanding the phase and timing of ontogenetic habitat shifts underlies the study of a species’ life history and population dynamics. This information is especially critical to the conservation and management of threatened and endangered species, such as the loggerhead sea turtle Caretta caretta. The early life of loggerheads consists of a terrestrial egg and hatchling stage, a post-hatchling and juvenile oceanic, pelagic feeding stage, and a juvenile neritic, primarily benthic feeding stage. In the present study, novel approaches were applied to explore the timing of the loggerhead ontogenetic shift from pelagic to benthic habitats. The most recent years of somatic growth are recorded as annual marks in humerus cross sections. A consistent growth mark pattern in benthic juvenile loggerheads was identified, with narrow growth marks in the interior of the bone transitioning to wider growth marks at the exterior, indicative of a sharp increase in growth rates at the transitional growth mark. This increase in annual growth is hypothesized to correlate with the ontogenetic shift from pelagic to benthic habitats. Stable isotopes of carbon and nitrogen just interior and exterior to the transitional growth mark, as well as stable isotopes from pelagic and benthic flora, fauna and loggerhead stomach contents, were analyzed to determine whether this transition related to a diet shift. The results clearly indicate that a dietary shift from oceanic/pelagic to neritic/benthic feeding corresponds to a transitional growth mark. The combination of stable isotope analysis with skeletochronology can elucidate the ecology of cryptic life history stages during loggerhead ontogeny.


KEY WORDS: Sea turtle · Caretta caretta · Growth · Skeletochronology · Stable isotopes


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Cite this article as: Snover ML, Hohn AA, Crowder LB, Macko SA (2010) Combining stable isotopes and skeletal growth marks to detect habitat shifts in juvenile loggerhead sea turtles Caretta caretta . Endang Species Res 13:25-31. https://doi.org/10.3354/esr00311

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