Bhubaneswar: Are rising temperatures skewing the sex ratio in favour of females among Olive Ridley turtle hatchlings in Odisha?
A study claims that a higher number of female hatchlings have been found at Rushikulya River mouth in Odisha’s Ganjam district. The study is based on 15 years of monitoring of the mass nesting of the sea turtles at traditional sites such as Rushikulya.
According to biologists, the sex of hatchlings of reptiles, such as turtles and crocodiles, depends on the temperature around the nests. The higher the temperature, greater is the possibility of the hatchlings being female.
“Over the last 15 years, we have been monitoring nest temperatures and hatchling sex ratios at the Rushikulya rookery. Determining the hatchlings’ sex through gonad histology helps monitor the primary sex ratios of both solitary and arribada nests.” the study report titled ‘Monitoring sea turtles in India 2008-2024’ states.
During these mass nesting events, hundreds of thousands of female turtles get together on a beach within just a few days to lay eggs.
Large Olive Ridley arribadas occur only in Central America and on the east coast of India. The east coast population of Olive Ridleys in India is especially interesting as it is considered to be genetically distinct and the ancestral source of Olive Ridleys around the globe, the study says.
Odisha is home to two of the largest mass nesting sites – Gahirmatha and Rushikulya.
“This data has been instrumental in establishing the pivotal temperature of the population. Sex ratios at Rushikulya are skewed towards females but not to the extent seen in certain global sea turtle populations,” it says.
The study says estimating the sex ratios of hatchlings produced at this rookery was useful for understanding the future impacts of climate warming. It says as global temperatures rise, sea turtle populations might become increasingly feminised.
“The hatchling sex ratio from arribadas at Rushikulya was found to be about 71% female on average. While some years had extremely female-biased sex ratios due to high nest temperatures, a few years produced male-biased sex ratios,” the study has found.
“Our ability to accurately determine sex ratios is limited by the kind of data we can collect at the rookery. Nevertheless, with additional temperature data, we aim to employ embryo growth models to examine the long-term trends in sex ratios of hatchlings from arribadas at Rushikulya,” it has been observed.
Since 2008, Dakshin Foundation and the Centre for Ecological Sciences, Indian Institute of Science, Bangalore, in collaboration with the state forest department have monitored Olive Ridley turtles in Odisha.
“Long-term monitoring and data generated from it can be used to understand trends in populations and predict the future impacts of climate change. They can also guide policy and determine conservation actions. In particular, they can help devise strategies that are inclusive of local communities towards long term benefits for turtles, ecosystems and people,” Kartik Shanker, one of India’s foremost researchers on Olive Ridley turtles told the media.
Since 2008, mass nesting events have occurred almost every year at Rushikulya in the range of between one and two lakh turtles being recorded in many years. This suggests that the Ridley population in this region is either stable or increasing.
