Stable isotope (carbon and nitrogen) signatures of Pacific green and hawksbill sea turtles in Costa Rica

<p>Investigating niche and diet can reveal competition, and partitioning among sympatric animal species. We investigated niche size, niche overlap, and diet composition in green turtles (black and yellow morphotype <em>Chelonia mydas</em>; 49.5 – 95 cm curved carapace length) and hawksbill turtles (<em>Eretmochelys imbricata</em>; 40 – 83 cm curved carapace length) in a recently described foraging habitat in North Pacific Costa Rica using stable isotope analysis. Whole blood d<sup>13</sup>C values were positively related to curved carapace length in black sea turtles while skin d<sup>15</sup>N values were negatively related to curved carapace length in hawksbill turtles. Using whole blood stable isotope signatures, niche space revealed distinct enrichment in d<sup>15</sup>N isotopic space in black turtles. We also observed significant overlap in niche space between yellow turtles and hawksbill turtles. Our results suggest that black turtles forage at multiple trophic levels, while yellow and hawksbill turtles primarily forage at a lower trophic level. Our analysis of trophic niche and diet composition for these species of sea turtles indicated resource partitioning among these spatially overlapping species. </p>