Present and future nesting prospects for loggerhead turtles in the Eastern Mediterranean

OpenAlex İngilizce

The loggerhead turtle Caretta caretta population of the Eastern Mediterranean faces a host of climate change-induced challenges in the future. The sex of hatchlings is determined by incubation temperature during a genital differentiation phase, producing more females at higher temperatures (generalised here to >29°C). Without behavioural change, either by nesting at a cooler time of year or altering microsite selection, there is a risk that climate change-induced female bias may place the population at risk. Through a combination of in situ dataloggers and biophysical modelling, we estimated offspring sex ratios across 8 Mediterranean countries, including established rookeries (>50 nests yr -1 , n = 17 in 4 countries) and smaller rookeries (n = 5) and beaches that do not currently host nesting (n = 9). Here, we provide for the first time a regional estimate of hatchling sex ratio: 74.5% female, which may rise to 91.2% by 2100 per IPCC SSP3-7.0. Of the well-established rookeries, Patara, Türkiye, has the lowest female production (49%), while Alagadi, Northern Cyprus, produces the most females (96%). Several smaller beaches, particularly in North Africa, exhibit male-biased production, including Lake Bardawil, Egypt (19% female), and Kuriat Islands, Tunisia (23% female). Beaches without current nesting activity, such as Qerret, Albania, could provide significant male production (6% female). A phenological shift of 20 d could potentially decrease female hatchling proportion upwards of 60% in areas with rapid mid-summer warming. We present as part of this work an interactive tool to explore these warming and phenological shift scenarios, providing a novel framework to assess the impact of hypothetical phenological and abundance changes on resultant primary sex ratios.