VARIATION IN NEST-SITE SELECTION AND HATCHERY MANAGEMENT OF SEA TURTLES IN ALAS PURWO NATIONAL PARK,
BANYUWANGI (EAST JAVA), INDONESIA
Oleh : Risma Illa Maulany
In Alas Purwo National Park (APNP) has operated a hatchery for sea turtles conservation for over 20 years. There are four species using the beaches of APNP to nest: olive ridley (L. olivacea), leatherback (D. coriacea), green (C. mydas), and hawksbill (E. imbricata) turtles. Since hatchery practices around the world have invite many criticisms regarding the success and appropriateness in increasing the population of sea turtles, natural nest always become a priority in conserving sea turtles. However, when nest-site selection by the species has put the natural nest at risks of being lost due predation, erotion, and inundation by tides, egg translocation to the hatchery is needed. Therefore, this study aims to describe nest-site selection of sea turtles within their natural ebvironment, provide information on important nesting sites along the beach, examine current management regimes in a sea turtles hatchery, and predict the relationship between current management practices with reference to their appropriateness and success in maintaining and increasing the sea turtle population.
The field work was carried out along the beaches of APNP (Marengan and Pancur) in Banyuwangi, Indonesia. Primary data on nest-site selection were collected from female adults nesting during the study. Measurements were made on distances of the nest from vegetation, sea water and the highest tide, nest depth, nest diameter, nest temperature, beach slope and the locality of the nest along the beach profile. Sand samples were taken for the purpose laboratory analysis of grain size, sand colour and composition. A 10 m x 10 m plot was establish to examine vegetation cover surrounding a nest.
To obtain data on general characteristics of the nests primary and secondary data were used. Data on beach slope, average temperature and sand colour in each sites along the beach were measured which than integrated with frequency of the turtles nesting to each sites over 3 years to also provide information on nesting pattern and important sites used by the turtles.
Hatchery performance and mechanism were note descriptively. Timing of egg translocation from original sites to the hatchery was also recorded. Natural nests condition was also assessed by recording any tracks or sighting of predators surrounding the nests. Hatchery conditions were also described. Secondary data of population of four species emergences, hatching success and number of hatchlings released over 20 years were obtained from the National Park office.
In general, Marengan beach had a higher temperature, darker sand and lower slope compared to Pancur beach. With those characteristics, Marengan was visited more frequently by the turtles than Pancur in particular by L. olivacea. The observed pattern showed that sea turtles clumped their nest or tend to place their nest relatively close each other or from the previous attempt of nesting during nesting season. Several beach section were always visited by turtles over 3 years with higher frequency compared to other section.
The results revealed that L. olivacea had a high number of nests placed in open areas below the dune slope and the high tide line which may influence the hatching success. Moreover, the sign of predators was also significant in natural nests. Therefore, for this species the hatchery played and importand role in increasing and maintaining their population in the wild which would not be possible under natural conditions.
The overall results suggested that the ongoing hatchery program in APNP had a positive contribution in increasing and maintaining the population of sea turtles over the time. However, limited resources and funding has become a major impediment for improving the hatchery performance and mechanism. Lack of skill and knowledge in appropriate handling during egg translocation, reburial technique, hatchery design, timing and distribution releasing the hatchlings, may influence the hatching success and quality of hatchlings produced from the hatchery which later on, may affect the population of sea turtles nesting in the future.
Mahasiswa Program Pasca Sarjana University of Queensland Australia