Nest Site Fidelity of Green Turtles Nesting at Rekawa Turtle Rookery, Sri Lanka

Abstract

Marine turtles represent an ancient and a distinctive part of the world's biological diversity. There are seven species of sea turtles living in the world and five of them come to the shores of Sri Lanka. The surveys revealed that one of the most important green turtle (Chelonia mydas) rookery is located at Rekawa, in southern Sri Lanka near Tangalle. Leatherback turtle (Dermochelys coriaceay; Loggerhead turtle (Caretta caretta), Hawksbill turtle (Eretmochelys imbricatai and Olive ridley turtle (Lepidochelys olivacea) also nest at Rekawa. The turtle populations are known to have individuals that display both regular and irregular re-nesting behaviour and it is known green turtles show a high degree of nest site fidelity.

About 2050m stretch of the beach at the project site in Rekawa was marked by wooden posts at 50-meter intervals. When a turtle comes to nest, the nesting site was marked on the data sheet giving the location of the nest between a pair of beach posts. Throughout the project, turtles coming to nest at Rekawa beach were tagged using Dalton plastic tags. A number and the project office address were printed on both side of the tag. About ninety five percent of the nesting green turtles and that re-nested were recorded from September 1996 to September 1999.

The number of turtles that attempted to re-nest within a single fifty-meter interval (distance with two beach post = same location) was counted during the three year project period. Of the five turtle species, only green turtles came to re-nest in the same fifty-meter interval during two weeks intervals. Of the recorded green turtles, 230 individuals nested at least twice in the same location while one green turtle was noted to nest eight times in the same location. This showed that a turtle could identify and remember its nesting location throughout the nesting season (four to six months). Certain of the turtles nested in other locations away from the first nesting site in the beach, during the same nesting season. The close observations made during this study confirm that green turtles show a high degree of nest site fidelity.