Fine-scale intraspecific niche partitioning in a highly mobile, marine megafauna species: implications for ecology and conservation

A species may partition its realized ecological niche along bionomic and/or scenopoetic axes due to intraspecific competition for limited resources. How partitioning manifests depends on resource needs and availability by and for the partitioning groups. Here we demonstrate the utility of analyzing short- and long-term stable carbon and nitrogen isotope ratios from imperiled marine megafauna to elucidate realized niche partitioning in these species. We captured 113 loggerhead (Caretta caretta) sea turtles at a high-use area near Crystal River, Florida, between 2016–2022, comprising 53 subadults, 10 adult males, and 50 adult females. Isotopic analyses indicated that loggerheads partition their realized ecological niche by life stage, along a scenopoetic axis. Most adults likely forage and reside in shallow areas of the study site, with most subadults displaying habitat switching between deeper locations to forage and shallower locations to rest. Some subadults, like adults, also forage and reside in shallow areas, and may display behaviors to avoid intraspecific competition. Analysis of stable isotopes with different turnover rates was critical for this characterization of intraspecific niche partitioning in loggerhead turtles, which has direct implications for ongoing research and conservation efforts for this and other imperiled species.