Olive Ridley’s 3,500km journey from Odisha to Maharashtra challenges migration assumptions

Pune: An Olive Ridley's 3,500km journey from Odisha to Maharashtra's Guhagar beach has reshaped researchers' understanding of the turtles' migration patterns, contradicting the idea that east and west coast nesting sites are separate.
Titled "03233", the turtle was flipper tagged by Dr Basudev Tripathy, a senior scientist from Zoological Survey of India (ZSI), on March 18, 2021, at Gahirmatha beach in Odisha during a mass nesting activity.
On Jan 27 this year, to the amazement of researchers, the same turtle was found nesting at the Guhagar beach. She was discovered laying eggs when a team from Maharashtra's Mangrove Foundation was conducting their flipper tagging exercise at night. Upon approaching her after nesting, it was discovered that she was already tagged, with the tag address mentioned on the other side, which led to the discovery of her origin.
The journey of the turtle is estimated to be at least 3,500km from the east to the west coast. While it is established that Olive Ridley turtles nest across multiple beaches from Dec to March, nesting at two beaches in the same period, while also travelling for the same, has been recorded for the first time in history. Researchers said the only possible route she could have taken is from Odisha down to Sri Lanka in their migration pattern, and then across to Ratnagiri in Maharashtra.
"I have tagged 12,000 turtles over the period of three years on Odisha's coast. It is premature to assume that there might be a genetic distinction in the population. But we can say that we might be dealing with different populations moving between the two coasts. This highlights the need to conserve both east and west coasts that are home to these turtles," Tripathi told TOI.
According to Wildlife Institute of India's senior scientist Dr Suresh Kumar, the turtle could have exhibited a dual reproductive strategy, nesting at a mass site in Orissa and then travelling to Maharashtra for solitary nesting as well to ensure maximum reproduction.
"It is very surprising altogether. In the early 90s and 2000s, we have extensive data of the turtles travelling to Sri Lanka and returning. However, there are possibilities in this case that the turtles are mixing up from both migration of east and west coasts and travelling to the other coast as well. Meanwhile, this can also be an effective way for the female to play around with the sex ratio of the hatchlings, which depends on the temperature and moisture," Kumar told TOI.
For decades, researchers thought that the nesting populations for both coasts were different, with no interconnection, as the turtles show high fidelity to their nesting sites. With the new information from flipper tagging, it has been proven wrong, said researchers.
"It is very surprising to see this as there has been a great season for nesting at Odisha this year, so we cannot pinpoint any particular stress situation that could have led to her journey. This is the first time she has been spotted by us, but she might have come many times to this coast over the last few years. This discovery has definitely changed our outlook on the turtle's migration patterns," Kumar said.
The scale of this migration has driven researchers to reevaluate the patterns, considering different possibilities across the coasts, including population complexities, migration patterns, habitat preferences, and climate-driven migrations. "This turtle nesting season, the Wildlife Institute of India and Mangrove Cell, Maharashtra forest deprtmemt has started a programme of flipper tagging Olive Ridley female turtles that come for nesting on the beaches of Ratnagiri and Sindhudurg districts, and going forward," said Manas Manjrekar, deputy director, Mangrove Foundation.
"This programme will reveal more information regarding the Olive Ridley turtle population, their movements along the coast of Maharashtra during the nesting season, and also hopefully some more interesting information regarding Olive Ridley turtles that nest on both the east and west coast of India," he said.
Tamil Nadu-based IAS officer Supriya Sahu, who is the additional chief secretary, Environment Climate Change & Forests, also tweeted on X that it is a "rare migratory feat achieved by 03233," which has thrilled marine researchers to further boost their studies.
Divisional forest officer at Ratnagiri, Kanchan Pawar, said "03233" was first noticed at Guhagar on Jan 31 this year, following which the tag number was forwarded to others to know where it had come from. The Kasav Mitra (friends of turtles) volunteers deployed by Mangrove Foundation ensured the safety of the Olive Ridley, which was safely released into the sea; and between Mar 23 and 26, as many as 107 of its hatchlings were also released in the sea, Pawar said.
WII scientists have completed flipper tagging, a cost-effective tracking method, for 64 turtles across Maharashtra. However, the threat of fishing in nearshore waters haunts the turtles even more now, with certain areas already designated for their congregation. Researchers have demanded strengthened marine fishing regulations during their nesting seasons near the river mouths and basins.
Turtle "03233", who travelled across both coasts, has in the meantime returned to the deep waters, with researchers keeping a watch on her arrival again.
(With inputs from Vijay Singh in Navi Mumbai)