A captive-breeding programme in the Sunderbans has brought back from the brink of
extinction a rare turtle species.
Now, the challenge is to ensure that the animals thrive in the wild, said foresters associated with the project.
More than 200 hatchlings of the northern river terrapins (Batagur baska), found in the Sunderbans and termed critically endangered by the International Union for Conservation of Nature (IUCN), were recorded so far this year at a captive breeding centre at Sajnekhali in the Sundarban Tiger Reserve (STR).
The project — a collaboration between the Bengal forest department and the Indian chapter of the Turtle Survival Alliance, a global organisation that works for captive management of freshwater turtles and tortoises — started in 2012 with only 12 turtles.
“Now, the number is close to 700. In 2025 alone, 223 eggs hatched successfully, compared to 49 in 2024. The numbers are rising every year. At the heart of this effort is the Sajnekhali Wildlife Sanctuary, which serves as the main hub for the Batagur baska captive breeding programme. Complementing it are six additional conservation centres across the STR, where terrapins of different size classes are raised and cared for — ensuring structured growth, genetic health and survival through each life stage,” said Justin Jones, deputy field director, STR.
One of the primary reasons for the dip in their numbers was people killing them for their meat, said forest officials.
“There is very little we know about this animal. Before we could, they were pushed to the brink of extinction,” said Jones.
The forest department looks for natural nesting sites of northern river terrapins at regular intervals.
Till now, the search had not yielded results. It suggests the terrapins are not breeding freely in the wild. “There may be some nesting sites that we may have missed. But the population in the wild is not thriving,” said Jones.
Ten turtles, fitted with manual transmitters, were released in the wild in 2016. But they failed to send any signals.
In 2022, ten more (three males and seven females) were fitted with satellite transmitters and released into the wild.
“Most of the turtles moved to Bangladesh. These terrapins prefer reduced salinity. The Bangladeshi side of the Sunderbans has more freshwater than the Indian Sunderbans. One of the terrapins swam up to Myanmar before coming back, covering a total distance of around 2,000km,” said Jones.
The people at the helm of the project are now gearing up to release the next batch into the wild.
“Last time, we released adults who could travel long distances. This time, we want to release sub-adults, who have restricted mobility and may look for habitats in and around the Indian Sunderbans,” said Shailendra Singh, director, TSA Foundation India.
Northern river terrapins feed on fish, crustaceans and fruits of some mangrove trees. They are important to the mangrove ecosystem because of their role in “seed dispersal”, said Singh.
The animals eat the mangrove seeds at one place and travel hundreds of kilometres and deposit them at other places (through defecation). They also play the role of an indicator to the integration of different systems because the turtles are born in sea water, move into freshwater for foraging and move back to sea water for nesting, he said.
“The northern river terrapins need different gradients of salinity. We hope to collect more information on that aspect as well once the next batch is released into the wild. We want to have more coordination with our Bangladeshi counterparts as well,” he added.