DOI: 10.5061/dryad.f4qrfj74k
title: Data from: Empirical evidence for the extent of spatial and temporal thermal variation on sea turtle nesting beaches

description: 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.
description: # 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](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.