Turtle Voyages: Tracking Olive Ridley Turtles in the Arabian Sea


The olive ridley sea turtles that nest in Odisha feed in the Bay of Bengal, migrate to the east coast of Sri Lanka and return to the same Indian beaches year after year in the tens of thousands. Data on their movements has helped the Odisha government to enforce protective measures and fishing bans during the mating and nesting season.

There’s another thing scientists have learned about these turtles: they never swim to the other coast and never venture into the Arabian Sea. “This means that the olive ridley sea turtles that visit the west coast of India could be a separate and distinct population,” says Harshal Karve, a marine biologist at the Mumbai-based Mangrove Foundation, an autonomous unit operating under the Maharashtra Forest Department. .

Turtle nesting on the west coast of India does not occur on the same scale as in Odisha, but the numbers are still significant. About 690 olive ridley nests were recorded in Maharashtra during the 2021-22 season. Where did they come from? Where did they go? Did they also return to the same Indian beaches every year?

In an attempt to answer some of these questions, a unique initiative has been undertaken on the west coast. The Maharashtra Forestry Department’s Mangrove Cell, the Mangrove Foundation and the Wildlife Institute of India teamed up to tag five female olive ridleys with satellite trackers, in January and February 2022, before they returned to the ocean.

Two of these turtles, named Prathma and Saavani, were tagged on the beaches of Velas and Anjarle; Vanashree, Lakshmi and Rewa were marked at Guhagar near Ratnagiri.

Satellite trackers are attached to the turtle’s shell using industrial-strength glue, then coated with antifouling paint (also used on the exterior of ships), to keep barnacles and other sea creatures away. (Mangrove Foundation)

Marking a turtle is not as easy as marking a bird or mammal. Fins cannot be fitted with a collar or anklet; these would fall off right away. So a transmitter is attached to the top of the turtle’s shell with industrial-strength glue, and the entire cap is then coated with anti-fouling paint (also used on the exterior of ships), to keep barnacles and other sea creatures.

Transmitters must be able to connect to a satellite for data to be recorded. This link is not possible underwater. “But since turtles are reptiles, they have to keep surfacing to breathe, and that’s when we get an impact on their movement,” Karve says.

In the weeks since the turtles returned to the sea, a pivotal discovery emerged. “Saavani visited a beach only 8 or 9 km from his old nesting site and nested there again. Olive ridley turtles are known to return to the same nesting sites, so it was very interesting,” Karve explains. The researchers were also interested to find that the tagged females moved in different directions, and some did not venture far from the coast of Maharashtra at all.

Unfortunately, the researchers lost contact with the turtles sooner than they expected. In March, the Lakshmi signal went silent, near Ganapatipule in Maharashtra. In June they lost contact with Prathma, Saavani and Rewa in the waters off Maharashtra and Karnataka. In August, the Vanashree signal cooled off the coast of Gujarat.

Manas Manjrekar, deputy director of research and capacity building programs at the Mangrove Foundation, says they’re looking to find out why the transmitters haven’t lasted longer. But already, with their findings, “we are setting the stage for conservation measures that may be needed, say, 10 years from now.”

Turtle watchers also hope that when the turtles return next year, some can be tagged again and tracked for longer and longer this time.


Comments are closed.