WII’s satellite telemetry study on Olive Ridley turtles to track migratory path
The WII study will examine whether there has been any change in the traditional migratory route of the marine turtles from the Odisha coast to Sri Lanka.Updated: Nov 14, 2020, 00:18 IST
Thirteen years after it conducted a satellite telemetry study on biological and behavioural aspects of Olive Ridley sea turtles off the Odisha coast, the Dehradun-based Wildlife Institute of India has proposed another such study next year to find out whether there has been any change in their migratory path.
The study, the third such by the institute, would examine whether there has been any change in the traditional migratory route of the marine turtles from the Odisha coast to Sri Lanka. It would also find out if some of these turtles stay near the Odisha shoreline instead of migrating out after the nesting season is over in March-April.
“We know that one set of the population of Olive Ridleys go to Sri Lanka while another set goes to Myanmar coast off Andaman sea. They travel for about 3,000 km and return to the Odisha coast. Through this new study we want to confirm the presence of some turtles along the Indian coast that don’t migrate out and stay within 100 nautical miles of Indian coast. Though we don’t expect any change in the migratory path, we need to study if there has been any change in their migratory paths and its reason. It’s going to be a very useful study,” said Kuppusamy Sivakumar, scientist in the Endangered Species Management department of WII, Dehradun.
Named after English biologist Henry Nicholas Ridley who first reported the sighting of the turtles in Brazil in 1887, the omnivorous Olive Ridleys are among the smallest of the marine turtle species in the world. They can dive to great depths and are highly migratory, covering thousands of kilometers between foraging and nesting grounds. Their tear-drop shaped carapace has an olive green colour. They grow to an average of 70 cm long while adults weigh approximately 45 kgs.
The most fascinating feature of Olive Ridleys is their mass nesting called ‘arribada’ that happens on the Odisha coast when lakhs of gravid females choose narrow beaches near estuaries to lay eggs. Each adult female lays approximately 100-140 eggs at a time. In India, arribada takes place in the east coast state of Orissa at three nesting grounds Gahirmatha, Devi river mouth and Rushikulya river mouth. Forest department officials estimated that in March this year, around 8 lakh turtles had laid eggs in Rushikulya and Gahirmatha sites.
The first satellite telemetry study on Olive Ridley turtles was done in April 2001, when the WII with Odisha forest department and turtle biologist Jack Frazier of the Smithsonian Institute fitted Platform Transmitter Terminals on four turtles at Devi nesting beach for an online monitoring of migratory routes. Of the four PTT-fitted turtles only one migrated towards Sri Lanka. However, all the four turtles stopped transmitting within two to four months either due to technical problems or trawler-related mortality.
In the second study done between 2007 and 2010 by WII and funded by the Ministry of Petroleum and Natural Gas, 70 PTT were used which showed that the turtles undertook open-ocean migrations in the Bay of Bengal and exhibited migratory corridor between Sri Lanka and nesting sites along the Odisha coast of India. Sivakumar said that the study not just gave a lot of information about their migratory route, but also helped Odisha government firm up its measures on 7-month ban on the coast between November and May to prevent turtle mortalities during mating and nesting season.
“Following our study, the Odisha government announced a one-time notification banning fishing activity off the coast during the 7 months,” said Sivakumar.
He said through the new study using 30 PTTs to be done during the nesting season in April-May, the WII would try to find out the developments in the migratory paths of the turtles and study how turtle tourism can be done in Rushikulya nesting site.
“We need some understanding of the current situation. More and more activities are being planned in Bay of Bengal and a lot of changes are happening in Odisha coast. As many fishermen are not happy due to loss of livelihood during the ban period, we want to know whether we can improve our action plan so that turtles are safe and fisherman can go with their livelihoods. Based on the telemetry studies we would see whether there is a need to reduce the fishing ban period or increase it. We would also see whether any change can be made to the no-fishing zone,” said the WII scientist.
The study would be conducted over a period of three years.
As WII does not have money to fund the studies, it has proposed Odisha government to fund it. Odisha forest and environment secretary Mona Sharma said money would not be an issue. “We are waiting for their proposal,” said Sharma.
Through the studies, the WII would also partner with the Odisha government for undertaking research in the upcoming Sea Turtle Research and Conservation centre that is likely to come up over 5 acres at Gorakhakuda village near Rushikulya turtle nesting site of Ganjam district.