99 skewed ratio, with the most conservative estimate at 17.0% of females (Tableau 7). This tendency was observed in all of the three considered nesting seasons. Tableau 7. Observed mean temperature over the full incubation period (total) and over the middle third of the incubation period (2nd third), incubation duration, and estimated female hatchling proportions based on four distinct predictive models. Sex ratio estimates are implemented with the Chu et al. (2008) model (Females A); the Girondot (1999) model (Females B); the Mrosovsky et al. (2002) model with sex ratio as a function of the observed temperature (Females C) and with sex ratio as a function of the observed incubation duration (Females D) for the nests of the RP and the GLS area. n loggers Observed temperature total (°C) Observed temperature 2nd third (°C) Incubation duration (d) Females A (%) Females B (%) Females C (%) Females D (%) RP 25 32.3 ± 1.7 32.1 ± 1.3 51.3 ± 2.2 98.0 97.4 100.0 99.5 2019-2020 9 33.0 ± 1.5 32.9 ± 1.1 50.1 ± 1.8 99.8 98.6 100.0 99.9 2021-2022 8 32.0 ± 1.6 31.8 ± 0.9 51.8 ± 1.8 99.4 97.0 100.0 99.8 2022-2023 8 31.4 ± 1.6 31.1 ± 1.3 52.3 ± 2.5 94.7 96.9 99.8 98.8 GLS 12 28.7 ± 2.1 28.3 ± 1.6 61.3 ± 5.4 52.2 52.3 17.0 12.5 2019-2020 2 27.6 ± 2.2 27.1 ± 1.3 62.5 ± 2.1 39.4 34.0 0.0 0.0 2021-2022 8 29.2 ± 2.1 28.8 ± 1.7 62.5 ± 2.2 57.0 60.0 25.5 18.8 2022-2023 2 28.4 ± 0.8 28.2 ± 0.3 62.5 ± 2.3 46.0 40.0 0.0 0.0 5. Discussion In this study, we compared nest temperature between two important loggerhead turtle nesting areas that show contrasting habitats, yet are used by females from a single, genetically coherent population in New Caledonia (Bourgogne et al. 2024a). Significantly cooler temperatures were measured in the nesting sites of the GLS compared to the RP beach. The average fitted temperature difference of 2.97°C (± 0.83) recorded between the two areas over the study period is consequential, considering that the transitional range of temperature within which the hatchling sex ratio shifts from 100% male to 100% female (or from 100% male to 100% female) is generally less than 2°C (Ewert et al. 1994; Jribi and Bradai 2014). Nest temperature is positively correlated with Sea Surface Temperature (SST) (Fuentes et al. 2024). Since no significant differences in SST were observed between the RP and the GLS area based on data time series available on the French National Research Infrastructure ReefTEMPS network (Varillon et al. 2019), we suggest that the geomorphological differences of the nesting habitats are responsible for this substantial thermal amplitude, both between the
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