Global warming is affecting the sex ratio of endangered caretta caretta sea turtles, with nearly 90% of hatchlings emerging as females, according to professor Yakup Kaska, director of the Sea Turtle Research, Rescue and Rehabilitation Center (DEKAMER).
This season, around 40,000 hatchlings from 770 nesting sites at Iztuzu Beach, located in the Ortaca district of Muğla, southwestern Türkiye, reached the sea. DEKAMER officials, located near Iztuzu, considered one of Europe’s best caretta caretta conservation and nesting areas, have been conducting protection efforts since 2008, including treating injured turtles and monitoring nests during the egg-laying and hatching periods. Night-long patrols are conducted during critical periods to ensure the safety of eggs and hatchlings.
“This year, 770 nests were placed under protection and from 58,000 eggs, nearly 40,000 hatchlings were released into the sea,” Kaska said. “Our conservation efforts have been continuous since 1988. In the early years, the number of nests was around 200-300. Now, it has reached 770-800, on a beach officially recognized by Europe as the most well-protected open nesting area, where the population increase is most visible.”
Kaska emphasized the importance of protecting injured adult turtles, noting that since only one out of a thousand hatchlings typically survives to maturity, rescuing and rehabilitating a single adult can be equivalent to raising thousands of hatchlings over 25 years. To date, DEKAMER has treated 630 injured turtles and released 380 back into the sea. Some of these turtles are equipped with satellite tracking devices to monitor their movements and survival.
For example, the caretta caretta named “Tuba,” released with a satellite tracker in 2019, returned to Iztuzu Beach and was rereleased, beginning her second journey around the world. Kaska said Tuba has traveled more than 7,000 kilometers (4,349 miles) and is currently near Bodrum, while another turtle released at the same ceremony, “Atlas,” reached the Tunisian coast. “Tracking these turtles demonstrates how successfully we are protecting them,” he added.
Kaska also highlighted the effects of global warming on sea turtles and their nests. “High temperatures lead to female development, which is why recent data show that 90% of hatchlings emerging from nests are female,” he said. “Global warming affects all living species, but male-less sea turtles cannot reproduce. With today’s technology, eggs incubated in shaded or cooler conditions can also produce male hatchlings.”
He explained the biological process of temperature-dependent sex determination: “When eggs develop at high temperatures, the egg cells that determine sex migrate to the ovary and proteins synthesized at high temperatures ensure they remain there. At lower temperatures, these proteins do not form and other proteins are created, favoring male development. The sex of a hatchling developing over 45 days is determined by the temperature of the sand between days 15 and 30.”
