Stable isotope signatures from green turtles and hawksbills at Buck Island Reef National Monument, U.S. Virgin Islands from 2012-2019

We used stable isotope analysis of nitrogen and carbon turtle epidermal samples to describe the trophic niche of the sampled sea turtle population by portraying δC as a habitat structure variable against δN as a resource gradient axis. We examined isotopic data for hawksbills (n = 64) and green turtles (n = 241) hand-captured across an 8-year time frame (2011-2019) to assess interspecific competition. We use statistical analysis to identify ontogenetic shifts associated with changes in trophic feeding to postulate changes to resource use. Our results indicate that stable environmental conditions around Buck Island Reef National Monument (BIRNM) allow for different trophic strategies across the two species with significantly overlapping foraging niches. Our metrics can further be used to measure change in local conditions and populations, or to make global comparisons of trophic niche for each species.