Foraging ecology of Kemp’s ridley (Lepidochelys kempii) turtles in the northeastern Gulf of Mexico: insights from stable isotope analysis

An individual’s foraging ecology can affect its growth and survival. Stable isotope analysis has been commonly used to investigate the foraging ecology of marine turtles. However, only a few studies have provided isotopic values for the critically endangered Kemp’s ridley turtle (Lepidochelys kempii). This study presents the first characterization of δ13C and δ15N values from Kemp’s ridley epidermal tissue in the coastal Gulf of Mexico, Florida, USA (28.834953°N, 82.761966°W) and investigates potential size-related differences in foraging ecology. Samples were collected from 64 neritic individuals between 2016 and 2021 and divided into two groups based on straight carapace length (SCL): a smaller (< 40 cm, n = 17) and a larger (> 40 cm, n = 47) size class. When analyzing all the data together, significant correlations were found between SCL and δ13C, but not SCL and δ15N. However, significant differences were found between size classes, with the larger size class exhibiting higher δ13C and lower δ15N values than the smaller size class, which may indicate niche partitioning between size classes. To compliment these findings, an animal-borne camera was deployed on a Kemp’s ridley, and its foraging activity was documented. These results provide insights into the trophic and spatial dynamics of an understudied population and can be used to facilitate future research. Continued stable isotope analysis of Kemp’s ridley epidermis, coupled with dietary studies and satellite telemetry, can expand on these findings to elucidate more about the foraging ecology of Kemp’s ridleys and explore how dietary preferences may differ by individual size, which can guide conservation initiatives for foraging areas.