Body size-related polymorphic foraging strategy in adult green turtles

Abstract

Green turtles (Chelonia mydas) are among the prominent migratory and conservation-needing animals. Missing data on the foraging strategy of green turtles limits effective conservation actions in the Eastern Mediterranean. We applied the stable δ13C and δ15N isotope signatures together with body size to evaluate the foraging ecology of green turtles. Five tissue samples were utilized, including keratin, epidermis, red blood cells, plasma, and whole blood. The samples were retrieved from five major breeding areas in Turkey. Significant correlations were observed between curved carapace length and the δ13C and δ15N values of the green turtles in all the breeding populations except for Alata. The bimodal distribution of δ13C and two clusters based on the δ13C and δ15N values indicated a dichotomy concerning the foraging habitats of the green turtles nesting on the Eastern Mediterranean. The body sizes of the females in the first cluster (with depleted values) were significantly larger than the second cluster (with enriched values). The total niche area of the females in the first cluster was larger than that in the second cluster, which may correspond to the generalist/specialist feeding strategy. The present study gives some novel results about the foraging ecology of green turtles in the Mediterranean. For effective and viable conservation actions, further studies are needed to identify the foraging areas of green turtles in the Mediterranean.