Reproductive output and morphometrics of green turtle, Chelonia mydas nesting at the Kosgoda rookery in Sri Lanka

Abstract

Reproductive output provides data fundamental to the conservation and management of sea turtles. Five years of data on the reproductive output of female green turtles was collected from Kosgoda beach, the second largest sea turtle rookery in Sri Lanka. Egg size, clutch size, clutch frequency, female size, hatchling size, hatching success, nest depth, and incubation duration were recorded. A total of 1,492 nests comprising 166,358 eggs were laid by 575 nesting females during the study period. Larger females had a higher reproductive output, laying larger eggs, bigger clutches, and producing a greater number of eggs in total for a season. There was no relationship between clutch size and egg size, and the hatchling size did not depend on the egg size or the female size. The mean hatching success was 77.3% and the mean incubation duration was 50.6 days. Clutch size, egg size, female body size, and nest depth had no effect on hatching success of the green turtles nests laid at Kosgoda rookery. Even though the size of the nesting turtles and clutch size were similar to other green turtle populations, the reproductive output and clutch frequency of green turtle females nesting at Kosgoda rookery were low compared to the population at Rekawa beach in southern Sri Lanka and other green turtle populations worldwide. The shorter stretch of beach (1 km) used to collect data may be a reason for this difference, precluding observation of re-nesting efforts by the female turtles.