367 / 2024-09-15 11:15:28

Sand temperature fluctuation and risk analysis of female-biased nests at the green turtle nesting ground of Qilianyu, Xisha Islands

Green turtle; Xisha Qundao; Sand temperature; Nest% with female-biased; Climate change

Under the premise of not interfering with the natural incubation of green turtle nests, this study monitored year-round sand temperature near the nests during December 2019 and December 2020 at the green turtle nesting ground of Qilianyu (Xisha Qundao) using HOBO temperature loggers. The results were then combined with nesting date, metabolic heat generated during incubation, and the fitting relationship between air temperature and sand temperature in order to estimate the number of female-biased nests. The results showed that the year-round sand temperature of Qilianyu was from 22.3 (February) to 34.1 ℃ (July). The daily sand temperature range between the highest and the lowest, and its variation range were small throughout the year. There was a significant and positive correlation between the sand temperature and the air temperature (p < 0.05). The rainfall at Qilianyu was mainly concentrated in August to November in 2020, and the monthly sand temperature range between the highest and the lowest was significantly and positively correlated with the rainfall (p = 0.001). The sand temperature fluctuation of the vegetation boundary was more moderate than that of the exposed beach at Bei Dao, the core nesting island, showing a pattern of warmer winter and cooler summer. There were 149 nests found at the green turtle nesting ground of Qilianyu in 2020. Based on the nesting date records, it was confirmed that green turtles could nest nearly throughout the year except January and February, and the nesting peak was from May to September. It was estimated that totally 119 nests were female-biased, mainly laid in May to August, and the whole year nest% with female-biased was 79.9%~92.6% in 2020. Under the general trend of global warming, the hatchlings at Xisha Qundao - the largest green turtle nesting ground in China, would be female-biased. The impacts of climate change on the green turtle population of China merit more attention.