Olive Ridley Turtle's 3,600 Km Journey: A migration marvel

Tagged at Gahirmatha Marine Sanctuary on Odisha coast around four years ago, an Olive Ridley Turtle swam around 3,600 km through the Bay of Bengal before being spotted at a Maharashtra beach, a senior Zoological Survey of India (ZSI) scientist said.

The turtle, which was tagged on March 18, 2021, was located on a beach in Ratnagiri district of Maharashtra, where it had arrived for nesting and laying eggs, the scientist said.

Basudev Tripathy, a senior ZSI scientist, said this was first recorded instance of a turtle that had previously nested on Odisha’s coast migrating such a long distance to lay eggs.

"Generally, turtles tagged at Odisha nesting grounds to study their migration behaviour do not travel such long distances," Tripathy said.

"Earlier, some tagged turtles were rescued from the northern coast of Sri Lanka by fishermen. However, there has been no history of turtles tagged in the eastern statenesting in Sri Lanka," he added.

On migration patterns, Tripathy said sea turtles typically migrate between foraging and nesting grounds.

"Male and female turtles migrate to breeding areas, usually returning to the beaches where they were born," he said.

"To identify and strategise the effective protection of Olive Ridley turtles’ feeding and breeding grounds along the Bay of Bengal, further study and tagging of these delicate marine animals is the need of the hour," he added.

The turtle’s unprecedented nesting in western India has drawn scientific attention.

"Given that a tagged turtle from the Odisha coast was found nesting for the first time on Maharashtra’s coast, a more elaborate scientific study into the behaviour of these itinerant marine species is now in focus," Tripathy added.

"Earlier tagged Olive Ridley sea turtles travelled around 1000 km in the sea to reach north Sri Lanka sea within a month from Gahirmatha Marine Sanctuary. But they did not nest there," they said.

On most occasions, such turtles returned to Odisha for mass nesting. However, the turtle tagged by ZSI in 2021 was found nesting at Ratnagiri beach in Maharashtra.

"This female turtle undertook an arduous journey of not less than 3,600 km to nest at the Maharashtra site," Tripathy added.

Tagging studies have established Odisha as the most favoured nesting destination for Olive Ridley turtles, with 'arribada' (mass nesting) only recorded at Gahirmatha, Rushikulya and Devi river beaches in the state.

"This makes it crucial to undertake large-scale tagging of nesting turtles annually to further understand their behaviour," he said.

The Odisha Forest Department began turtle tagging in 1999, tagging around 1,000 turtles. Two of those were later sighted off the Sri Lankan coast. The initiative was paused for several years before being resumed by ZSI in 2021. Between 2021 and 2024, around 12,000 turtles have been tagged at the Gahirmatha and Rushikulya river mouth nesting sites, according to official sources.

Mass nesting on Odisha’s coast remains impressive. This year alone, around 10 lakh turtles arrived at the state’s nesting beaches for arribada.

"Tagging needs to be conducted on a much larger scale," Tripathy said.

"Currently, around 3,000 turtles are tagged annually. But we believe at least one lakh turtles need to be tagged to gain deeper insight into their reproductive biology, movements, growth rates, migratory routes, and foraging zones," he added.