Regional and local factors determining green turtle Chelonia mydas foraging relationships with the environment

Changes in green turtle Chelonia mydas foraging patterns were evaluated within a latitudinal gradient along tropical and subtropical coasts in the southwestern Atlantic and investigated as to how green turtles responded to regional and local changes in their foraging habitats. In addition, we evaluated how changes in feeding ecology caused populations to be more susceptible to various anthropogenic threats. The literature and original diet data of 427 green turtles were analyzed. Turtles from tropical and subtropical reefs exhibited the classic pattern of herbivorous benthic foraging, turtles from estuarine areas exhibited a more generalist diet and pelagic foraging, and turtles from colder reef areas, located between the winter isotherms of 10 degrees C and 20 degrees C, exhibited an omnivorous diet and pelagic foraging strategy. The amount of ingested animal matter was higher in occurrence and abundance in the green turtle diets in the most southern foraging areas. Foraging ecology was influenced by regional (phycogeographical provinces and water temperature) and local (urbanization and rivers) factors. Green turtles exhibited high foraging plasticity, and their importance to the ecosystem was not restricted to their role as herbivores. Green turtles may also have an important role as second-order consumers in certain areas, mainly in the cooler waters at the extremes of their distribution. Foraging plasticity was observed both in the type of diet item and foraging strategy, which implies that there may be variation in the exposure of populations to threats.