Nesting activity and reproductive output of green turtles in Similajau National Park, Bintulu, Sarawak

Abstract

Green turtles (Chelonia mydas) are ecologically important marine megafauna, yet reproductive information from small and understudied nesting sites in Sarawak remains limited. This study provides descriptive baseline characterization of green turtle nesting activity and reproductive outcomes in Similajau National Park (SNP), Sarawak, from 2015–2017 and 2022–2024 using historical nesting and hatchery records. In this study, nest numbers, clutch size, hatching success, apparent incubation duration, and embryo mortality across developmental stages were analyzed using descriptive statistics to evaluate nesting activity and reproductive outcomes. Findings show that nesting activity in SNP was low and inconsistent throughout the study period, with a mean annual nesting number of 3.33 nests, whereas the mean hatching success rate from the study period was 45.47%. In 2024, four nests were successfully relocated, with clutch sizes ranging from 119 to 137 eggs (mean = 129.75 ± 7.72) and apparent incubation durations ranging from 54 to 62 days (mean = 58.5 ± 3.70). Hatching success in 2024 averaged 41.8% (± 26.8), showing substantial variation among nests. Predation, inundation, and delayed nest detection were observed as key challenges affecting nest survival in SNP. This study emphasizes the importance of continued long-term monitoring, habitat protection, and improved nest management strategies. The findings provide baseline reproductive data for this understudied nesting site and may support future conservation planning and targeted management interventions in SNP.