CHENNAI: In a major breakthrough, a healthy breeding population of 31 individuals of elusive Leith’s soft-shell turtle (Nilssonia leithii), which is a critically endangered species protected under Schedule 1 of Wildlife Protection Act, were found in Cauvery river between Mekedatu and Hogenakkal in Tamil Nadu.
These are large freshwater turtle species endemic to peninsular India. So far, only sporadic sightings of this species was recorded in parts of the Thungabhadra, Ghataprabha, Bhavani, Godavari, Krishna, Chalakkudy, Cauvery, and Moyar Rivers.
For the first time, a pilot study was done to estimate their population, in Tamil Nadu, by a group of researchers. The study results were presented at the 3rd annual research conference at Advanced Institute for Wildlife Conservation on Thursday.
The study was received well by the Tamil Nadu forest department, as there has been steady decline in the soft-shell turtle sightings in recent years due to poaching, habitat fragmentation, hydropower projects and to some extent, illegal river sand mining.
Peter Christopher, who is in the process of publishing a research paper along with other researchers from Willdife Institute of India, Natural History Museum in London and the Indigenous Biodiversity Foundation in Pondicherry, told TNIE: “We recorded all the sightings through visual encounter survey method from October 2022 to September 2023. It was a painstaking exercise since the sightings are difficult as these turtles are highly elusive.”
The researchers said that the presence of turtles was confirmed when they were seen surfacing for breathing, basking on rocks, and through spoor marks on the riverbanks.
“Visual encounter surveys were carried out 24 times in the Cauvery river between the Tamil Nadu–Karnataka border and Hogenakkal. During this survey, 31 individual sightings were recorded, including adults, females and hatchlings, in the study area. The findings confirm the presence of Nilssonia leithii in little or completely undisturbed stretches of the river,” Christopher said.
He said a comprehensive study should be carried out to better understand their population status, feeding and breeding behaviour and threats.
“We need in-situ conservation and captive breeding programme to maintain sustainable population in the wild,” he said.
The Nilssonia leithiis have distinctive physical characteristics. When young, these turtles possess distinct ocelli on their carapace, which tend to fade as they grow. Adults exhibit an olive green or greyish hue on their carapace, while their plastron is white or cream-colored. Notably, many adults display a captivating head pattern with black stripes near the lips and interlaced red blotches. Although limited studies have been conducted, most information available about this species remains anecdotal.
Their diet includes mosquito larvae, crabs, freshwater molluscs and fish. They grow up to 700-1000mm.