Inferring foraging areas of nesting loggerhead turtles using satellite telemetry and stable isotopes

PLoS One. 2012;7(9):e45335. doi: 10.1371/journal.pone.0045335. Epub 2012 Sep 20.

Abstract

In recent years, the use of intrinsic markers such as stable isotopes to link breeding and foraging grounds of migratory species has increased. Nevertheless, several assumptions still must be tested to interpret isotopic patterns found in the marine realm. We used a combination of satellite telemetry and stable isotope analysis to (i) identify key foraging grounds used by female loggerheads nesting in Florida and (ii) examine the relationship between stable isotope ratios and post-nesting migration destinations. We collected tissue samples for stable isotope analysis from 14 females equipped with satellite tags and an additional 57 untracked nesting females. Telemetry identified three post-nesting migratory pathways and associated non-breeding foraging grounds: (1) a seasonal continental shelf-constrained migratory pattern along the northeast U.S. coastline, (2) a non-breeding residency in southern foraging areas and (3) a residency in the waters adjacent to the breeding area. Isotopic variability in both δ(13)C and δ(15)N among individuals allowed identification of three distinct foraging aggregations. We used discriminant function analysis to examine how well δ(13)C and δ(15)N predict female post-nesting migration destination. The discriminant analysis classified correctly the foraging ground used for all but one individual and was used to predict putative feeding areas of untracked turtles. We provide the first documentation that the continental shelf of the Mid- and South Atlantic Bights are prime foraging areas for a large number (61%) of adult female loggerheads from the largest loggerhead nesting population in the western hemisphere and the second largest in the world. Our findings offer insights for future management efforts and suggest that this technique can be used to infer foraging strategies and residence areas in lieu of more expensive satellite telemetry, enabling sample sizes that are more representative at the population level.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animal Migration / physiology*
  • Animals
  • Carbon Isotopes
  • Feeding Behavior / physiology
  • Female
  • Isotopes*
  • Nitrogen Isotopes
  • Telemetry / methods*
  • Turtles

Substances

  • Carbon Isotopes
  • Isotopes
  • Nitrogen Isotopes

Grants and funding

This work was supported by several grants awarded from the Sea Turtle Grants Program (09-055R, 10-020R, 10-023R). The Sea Turtle Grants Program is funded from proceeds from the sale of the Florida Sea Turtle License Plate. Learn more at www.helpingseaturtles.org. Additional funding was provided by Disney’s Animal Programs. Sea turtle monitoring at the Archie Carr National Wildlife Refuge was coordinated through the University of Central Florida Marine Turtle Research Group, with funding from Brevard County, the Florida Fish and Wildlife Conservation Commission, the United States Fish and Wildlife Service, and the United States National Marine Fisheries Service. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.