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ESR 52:265-283 (2023)  -  DOI:

Hawksbill and green turtle niche overlap in a marine protected area, US Virgin Islands

Melissa A. Moorehouse1,2, John D. Baldwin2, Kristen M. Hart3,*

1Department of Geography and Environmental Engineering, United States Military Academy, West Point, NY 19960, USA
2Department of Biology, Florida Atlantic University, 3200 College Avenue, Davie, FL 33468, USA
3U.S. Geological Survey, Wetland and Aquatic Research Center, Davie, FL 33314, USA
*Corresponding author:

ABSTRACT: Studying how species interact with their environment and other co-occurring species are 2 main aspects of ecology. For marine turtles, ocean currents drive migratory routes and may determine the location of surrounding foraging grounds. As a result, circumglobal species like the hawksbill turtle Eretmochelys imbricata and green turtle Chelonia mydas adapt to diverse foraging habitats and employ varied feeding strategies. Dietary specializations may reduce competition for available food and space resources between co-occurring hawksbill and green turtles in US Virgin Island shallow reef habitats. This study analyzed isotopic data from immature hawksbill (n = 49; range: 18.7-49.8 cm straight carapace length [SCL]) and green turtles (n = 225; range: 24.1-69.4 cm SCL) to examine foraging niche. We used nitrogen stable isotope (δ15N) values as an indicator of trophic positioning and carbon stable isotope (δ13C) values as a habitat variable. Turtles were hand-captured across an 8 yr period (2012-2019), which facilitated the distinction of isotopic patterns in both the environment and among individual turtles. Understanding variations in habitat, community dynamics, and dietary consumption allowed us to utilize a 5 point framework to translate isotopic space to foraging niche. We found that the site’s relatively stable environmental conditions allow for isotopic overlap between hawksbill and green turtles despite the specialized feeding strategies each species employs. We also underscore the need to evaluate species-specific tissue turnover estimates as evidenced by the influence of tropical storms on recaptured turtle isotopic signatures. These findings inform our understanding of resource use for these imperiled species at our study site and are useful for future global isotopic comparisons.

KEY WORDS: Eretmochelys imbricata · Stable isotope analysis · Chelonia mydas · St. Croix

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Cite this article as: Moorehouse MA, Baldwin JD, Hart KM (2023) Hawksbill and green turtle niche overlap in a marine protected area, US Virgin Islands. Endang Species Res 52:265-283.

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