Turtle Survival Alliance Foundation India and Assam Forest Department, with financial support from the Disney Conservation Fund and Turtle Survival Alliance, rewilded hatchlings of the Critically Endangered black softshell turtle Nilssonia nigricans in the Brahmaputra River within Kaziranga Tiger Reserve, Assam, from late November 2023 to mid January 2024. The hatchlings were approximately 5 months old. They were head-started from 368 eggs sourced from 27 nests protected at Nagshankar temple, Biswanath district, Assam.
The black softshell turtle is threatened by overexploitation and fisheries bycatch. Endemic to Brahmaputra basin, the species was thought to be extinct in the wild and confined to Bostami shrine in Bangladesh until recent sightings in the Brahmaputra River drainage and records from a few temple ponds in north-east and east India.
Assam's temple ponds are known to hold a number of threatened turtle species. The ponds have recently gained prominence as semi-captive conservation facilities, and the Turtle Survival Alliance Foundation India project team has been helping two temple ponds with husbandry improvements, nest protection and rear and release programmes since 2018. Artificial incubation of the eggs of the black softshell turtle at optimum temperature and humidity conditions resulted in 64% hatching success in 2023. The newly emerged hatchlings were fed live fish fingerlings, maintained in a heated indoor environment and regularly moved into the sun for basking.
Pre-release habitat suitability surveys were conducted at eight potential sites in the Brahmaputra floodplains. Two sites were chosen that would allow released turtles to acclimatize over the winter before dispersing into the mainstream as the river floods during the monsoon. After primary health screening, a total of 150 black softshell turtle hatchlings were released on three occasions in the two locations. Approximately 35 hatchlings from 2023 have been retained in the semi-captive facility until they weigh 1 kg, to allow them to be fitted with acoustic telemetry devices prior to release. This will allow us to investigate their survival and dispersal after release.
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