Ecological niche use varies with sea turtle reproductive age

Understanding an organism’s niche and ecological role in its ecosystem is critical for conservation, especially for species that use multiple habitats at different life stages. The hawksbill sea turtle ( Eretmochelys imbricata ) is one such migratory animal that plays an ecologically important role in imperiled coral reef habitats. Although hawksbill resource use strategies (e.g., generalism vs. specialism) in these foraging grounds are poorly understood, stable isotope analysis of carbon ( δ ¹³ C) and nitrogen ( δ ¹⁵ N) can provide information on the trophic niche and foraging location of consumers. Additionally, when a single sample is taken from a tissue that accretes through time, such as keratin, analyses can reveal information on the long-term foraging patterns of individuals. Here, we evaluate resource use strategies for 98 females within a nesting aggregation of hawksbills in Antigua, West Indies (17.159, -61.756). Stable isotope analysis of scute tissue collected from 2017–2019 revealed population-level generalism and varying degrees of individual specialization. Additionally, older turtles displayed overall smaller ranges in isotope values, indicating a narrowing of resource use with increased reproductive age amongst breeding adult females. These findings provide evidence of high variability in hawksbill diet, illustrate differences in ecological niche use across different ages, and highlight the necessity of evaluating multiple life stages to inform the conservation of this critically endangered species.