Feminization of hawksbill turtle hatchlings in the twenty-first century at an important regional nesting aggregation

Abstract

Projected climate change is forecasted to have significant effects on biological systems worldwide. Marine turtles in particular may be vulnerable, as the sex of their offspring is determined by their incubating temperature, termed temperature-dependent sex determination. This study aimed to estimate historical, and forecast future, primary sex ratios of hawksbill turtle Eretmochelys imbricata hatchlings at an important nesting ground in northeastern Qatar. Incubation temperatures from the Arabian/Persian Gulf were measured over 2 nesting seasons. Climate data from same period were regressed with nest temperatures to estimate incubation temperatures and hatchling sex ratios for the site from 1993 to 2100. Future hatchling sex ratios were estimated for 2 climate forecasts, one mid-range (SSP245) and one extreme (SSP585). Historical climate data showed female-biased sex ratios of 73.2 ± 12.1% from 1993 to 2017. Female biases from 2018 to 2100 averaged 85.7% ± 6.7% under the mid-range scenario and 87.9% ± 5.4% under the high-range scenario. In addition, predicted female hatchling production was >90% from 2054 and 2052 for SSP245 and SSP585, respectively. These results show that hawksbill primary sex ratios in Qatar are at risk of significant feminization by the year 2100 and that hawksbill turtle incubation temperatures in an extreme, understudied environment are already comparable to those predicted in tropical rookeries during the latter half of the 21st century. These results can help conservationists predict primary sex ratios for hawksbill turtles in the region in the face of 21st-century climate change.

Reconstructing past thermal conditions in beach microclimates

“…This conclusion in itself is not new, since reconstructing sand temperatures at sea turtle nesting sites has been widely done using the correlative approach (e.g. Chatting et al, 2021; Fuentes et al, 2009; Hawkes et al, 2007; Hays et al, 2003). However, there has been a debate about which environmental variables are the best predictors of sand temperature and here our work adds value by showing there is little difference in the predictions made by using either sand or air temperature.…”

“…Fuentes et al, 2009). For yet other sites using both air and sea surface temperatures produce best results (Bentley, Kearney, et al, 2020;Chatting et al, 2021).…”

“…Fuentes et al, 2009). For yet other sites using both air and sea surface temperatures produce best results (Bentley, Kearney, et al, 2020; Chatting et al, 2021). We show here that for sites across the globe all these approaches give good predictions of sand temperatures.…”

“…For sea turtles, the correlative approach using either air temperature (AT) and/or sea surface temperature (SST) has been widely used to reconstruct sand temperatures at nesting sites (Bentley et al, 2020; Chatting et al, 2021; Fuentes et al, 2009; Hays et al, 2003; Jensen et al, 2018). However, there has been debate about whether AT or SST provides the best proxy for these sand temperature reconstructions (Bentley, Kearney, et al, 2020; Fuentes et al, 2009; Hays et al, 2021).…”

Biology and conservation of marine turtles in the northwestern Indian Ocean: a review

“…The study found a significant increase in female biases by 2100. Hindcasting of sex ratios (1993−2018) gave approximately 73% female hatchling production and increasing to > 95% from 2075 to 2100 (Chatting et al 2021). Tanabe et al (2020) calculated the expected sex ratio of both green and hawksbill turtles in the Red Sea and showed that sites could already be exceeding thermal maximums and may be vulnerable to rising temperatures.…”