Distribution of Nesting Site of Green Turtle (Chelonia mydas) in Sangalaki Island of Derawan Islands, Berau District

Abstract

Population of green turtle (Chelonia mydas) that laid their eggs in the Derawan Islands conservation area was declined due to various factors. The aim of this study was to determine the number of egg that was laid down into the nest for each green turtle parent and its correlation to shade, sandy beach width, and moon phase. The study was conducted from 24 January to 31 March 2015 in the Sangalaki Island. The observation of the broods stock was done by walking down the beach in the night to find out the broodstock that laid the eggs and counted the number. A sign was given to the nest of broodstock that finished laying the eggs. On the following day, nest excavation, egg collection, and the environmental measurement were conducted. Environmental conditions were measured include the depth of the nest, substrate temperature, the distance of the nest site to the shading trees and the border line of lowest tide. Data analysis was done descriptively by counting the number of eggs and environmental parameters. The results show that the average number of egg per nest was 97 items with the range of 45 - 127 items, the length of the carapace was 96 cm with a range of 86 - 107 cm, the average depth of the nest hole was 73 cm with a range of 56 - 87 cm. Broods stock of green turtle that laid more eggs would dig nest hole deeper, but there was no correlation between the carapace length and the number of the laid eggs. The average number of green turtle broods stock that lay eggs in the Sangalaki Island was 486 individual/ month with the range of 168 - 1085 individu/month. The west and east seasons affect the frequency of nesting and the laid eggs. The frequency of spawning occured throughout the year and the highest spawning frequency occured in August which coincides with the peak of the East Season. The frequency of spawning during the East Season was four times higher than during the West season. The frequency of green turtle landing was not affected by the lunar phase. Based on the location of laying egg, the beaches that were selected for laying egg are located in the northwest, northeast, and south parts of the Sangalaki Island. The Green turtle nests were commonly found in the vegetation shading areas (64%) than open sand areas (36%).