Data from: Empirical evidence for the extent of spatial and temporal thermal variation on sea turtle nesting beaches
Data files
Oct 04, 2024 version files 1.33 MB
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Chagos_TDL_MASTER_FILE_2012-2023.xlsx
16.50 KB
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README.md
2.18 KB
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Temperature_logger_individual_files.zip
1.31 MB
Abstract
Recording sand temperatures has become routine at many sea turtle nesting sites across the world given the impacts of incubation temperatures on hatchling sex ratios. However, the extent of thermal variability found at a nesting site has previously received little attention. Here we examine empirical sand temperature records across five atolls extending 250 km in the Chagos Archipelago, Indian Ocean, between October 2012 and July 2023 and quantify the extent of spatial and temporal thermal variability. Our results suggest that sand temperatures at our study site vary seasonally and inter-annually, between beaches in the archipelago, and within beaches in different nesting habitats. The biggest drivers of thermal variability were seasonal and inter-annual differences, which modulated sand temperatures by up to 3.00°C and 1.03°C, respectively. Intra-beach and inter-beach variability further modulated temperatures by up to 0.56°C and 0.85°C, respectively. In addition, mean monthly sand temperatures were relatively low, suggesting that hatchling sex ratios are fairly balanced. The wide range of sand temperatures recorded at this nesting site suggests that it is likely both male-biased and female-biased clutches are produced during the nesting season. Quantifying thermal variability from a long-term sand temperature time series offers valuable insight into a population with temperature-dependent sex determination and, when possible, should be considered when modelling temperature impacts on hatchling sex ratios.
README: Data from: Empirical evidence for the extent of spatial and temporal thermal variation on sea turtle nesting beaches
https://doi.org/10.5061/dryad.f4qrfj74k
Description of the data and file structure
Sand temperature was recorded using temperature loggers (Tinytag Plus 2 model TGP-4017, Gemini Data Loggers, UK, dimensions 34 x 51 x80 mm and weighing 110g, accurate to less than 0.5 °C) buried in the sand at green and hawksbill turtle nest depths (30, 50, 70 cm) on Diego Garcia, (a 2.8 km Index Beach), Nelson's Island, Ile des Rats, Ile Jacobin, and Petite Ile Coquillage in the Chagos Archipelago. A total of 132 loggers were buried between October 2012 and July 2023 in three different nesting habitats; in the vegetation, in the open beach, and at the spring high water line. Loggers were only deployed at the spring high water line between 2012 and 2014. One logger was buried at 80 cm at all sites partially shaded above the spring high water line to record sand temperature near the maximum green turtle nest depth. This study examines sand temperatures for a total of 83 loggers successfully recovered with downloadable data.
Files and variables
File: Temperature_logger_individual_files.zip
Description: Individual data logger txt files, labelled with logger ID. Each file contains the date (dd/mm/yyyy), time (hh:mm:ss), and sand temperature recorded (°C).
File: Chagos_TDL_MASTER_FILE_2012-2023.xlsx
Description: Master file with metadata for each temperature logger file including the expedition (mm-yr), island, atoll, logger ID, treatment (open, vegetation, HWL = High Water Line), depth (cm), date the logger was deployed and recovered (dd/mm/yyyy), length of time the logger was deployed (days) and the corresponding file name in 'Temperature logger individual files.zip'. NAs in columns 'Date recovered' and 'ts length' (time series length) are used where the date the logger was recovered was not recorded. All loggers that do not have recovery dates had also stopped working upon recovery.
Code/software
All analyses were conducted in the free software R.