55% Olive Ridley babies in Maharashtra didn’t survive in 2019-20Updated: May 24, 2020 00:56 IST
Only two-fifths of all Olive Ridley turtle hatchlings made their way to the sea in Maharashtra between 2019 and 2020.
According to data collated from different forest ranges by the state mangrove cell and Maharashtra Mangrove Foundation on World Turtle Day (May 23), 12,149 hatchlings survived from 27,254 eggs during 2019-20, which is a survival rate of 44.5%.
In 2018-19, the survival rate was 54.4%, with 12,601 hatchlings that made it to sea from a total of 23,131 eggs.
Sporadic nesting of turtles is reported from an average of 33 sandy beaches across three districts in Konkan – Raigad, Ratnagiri, and Sindhudurg.
While Sindhudurg witnessed a marked improvement in survival rate, from 47.3% in 2018-19 to 74.3% in 2019-20, Ratnagiri observed a decline to 34% in 2019-20 against 57.4% in 2018-19. Raigad also witnessed a drop from 65.4% to 52.2% over two years.
“We must realise that this is preliminary information, and there might be several data gaps since this annual statistical collation from three districts is a relatively new process. We need to study the pattern for at least 10 years to come up with exact trends,” said Virendra Tiwari, additional principal chief conservator of forest (mangrove cell).
Olive Ridley sea turtles are found in warm tropical currents of the Indian and Pacific oceans. A schedule I species under the Wildlife Protection Act, 1972, they travel thousands of kilometres in the ocean, with only the females returning to their original nesting sites within a minimum of two years, to lay eggs.
After a 50 to 60-day incubation period, juvenile turtles break the eggshell, dig through the sand, and crawl to the sea. While females return to their place of birth, males never return to land. “Female turtles use geomagnetic imprinting [navigating to their geographic area of origin using magnetic field] and olfactory [relating to the sense of smell] cues to find their natal areas,” said Harshal Karve, marine biologist, Mangrove Foundation.
Changes in weather patterns are the main reason for the fall in survival rate, said Mohan Upadhyay, livelihood assistant, Mangrove Foundation. “Firstly, nesting was delayed due to a series of extreme weather events including heavy rain coupled with cyclones in the Arabian Sea last monsoon. The winter was much warmer than previous years for coastal districts. Following this, there was a spike in maximum temperatures this year from late February. When temperatures rise, it affects the incubation period, resulting in a lower survival rate,” said Upadhyay.
Independent experts, however, said the survival rate does not depend completely on extreme weather factors. “Hatchling survival is affected by rising beach temperature and prolonged rainy days can damage some nests. But proper management and protection for natural nests can address these issues. However, even a 44% survival rate for natural in-situ nests is not bad. Focused conservation can help improve this,” said Basudev Tripathi, senior scientist, Zoological Survey of India and member of International Union for Conservation of Nature.
Meanwhile, the Mangrove Foundation has commissioned a research study to assess the incubation temperature of nests along the Maharashtra coast. The project is being undertaken by a PhD scholar from the Wildlife Institute of India, Dehradun.
“Atmospheric temperature plays a major role in developing and determining the sex of baby turtles. Temperature data loggers have been deployed at various turtle nesting sites in Ratnagiri and Sindhudurg, and the results will help us understand the nesting ecology,” said Karve.
A similar study undertaken by the Mangrove Foundation – comparing nesting data from 2002 to 2006 and 2014 to 2019 – has shown that the peak nesting period had shifted from winter months (December) to early summer months (February-March). “Many nests which are now being laid along the Maharashtra coast during the February-March period hatch out in the summer months of April-May when the ambient and sand temperatures tend to be on the higher side [above 32 degrees Celsius], which may lead most of the turtle hatchling to be females. Also, higher nest temperature data suggests a lower survival rate for hatchlings,” said Tiwari. “We are therefore developing solutions to ensure that the hatchlings are protected from higher temperatures through the use of sheds, regular monitoring, and litter-free turtle nesting habitats.”
Using some of the results, this year green sheds were installed to cover nesting sites from direct sunlight and high temperatures. “However, the Covid-19 lockdown made material transport difficult,” said Upadhyay.
The state forest department, with local NGO Sahayadri Nisarg Mitra, has been educating local communities on sea turtle conservation. “From locating nesting sites, excavation, relocation of eggs, fencing nets, and preventing poaching and flooding, around two persons per nesting site have been trained. The volunteers have begun collating information about the process from nesting to hatching,” said Karve.
To further boost turtle conservation, earlier this month the forest department introduced an honourarium of ₹15.63 lakh to locals in Ratnagiri, while the Sindhudurg district administration provided ₹6lakh to ₹8 lakh annually under its conservation management plan.