Niche partitioning between sea turtles in waters of a protected tropical island

Juvenile sea turtles recruit in coastal areas where they act as habitat engineers modifying the coastal landscape through feeding. However, little is known about the coexistence of these mega-vertebrates and their potential competition for resources. In this work, diet, food selectivity, trophic niche width and niche overlap of juveniles of two sympatric sea turtle species (Eretmochelys imbricata and Chelonia mydas) were evaluated from gastric lavages and habitat surveys in a tropical island bay of the southwestern Atlantic. The main items selected by E. imbricata were the zoanthid Zoanthus sociatus, the sponge Chondrilla nucula and red algae while C. mydas showed strong selectivity for red algae, mainly Asparagopsis sp. Species diets differed significantly and niche overlap was low; E. imbricata’s recorded niche was 2.5 times larger than that of C. mydas. We conclude that these two species do not compete for food in a well-preserved environment and that their feeding habits provide favorable conditions for local corals and other benthic groups to prosper by means of foraging on coral-competitors.