Unlocking the Key to Diapause Increases Hatching Success for the Crowned River Turtle

By Arunima Singh, Shailendra Singh, Rishika Dubla, and Jordan Gray

A total of 68 hatchling Crowned River Turtles (Hardella thurjii) recently hatched at the Kukrail Gharial Rehabilitation Centre (KGRC) in Lucknow, India, as part of a joint project between Turtle Survival Alliance (TSA) / Wildlife Conservation Society (WCS)-India and the Uttar Pradesh Forest and Wildlife Department.

The Crowned River Turtle is a large freshwater turtle found in the watersheds of the Ganges, Brahmaputra, and Indus river systems across Bangladesh, India, Nepal, and Pakistan. It is the single representative from the monotypic genus Hardella. Listed as Endangered by the IUCN Red List, extensive hunting and habitat degradation have severely depleted populations throughout its range.

Until recently, knowledge on the ecology and remarkable incubation adaptation of this principally aquatic species has been limited. In light of the paucity of species knowledge, as well as the contradictory information available, TSA-India continues to conduct a study in the Saryu River of northern India. One objective of this field research is to elucidate reproductive aspects key to its conservation breeding and incubation success.

In November 2018, nine nests totalling 84 eggs were collected from the banks of the Saryu and transported to the joint TSA India Program/Endangered Project/Uttar Pradesh Forest Department's Laboratory for Aquatic Biology (LAB) at the KGRC for incubation. Because wild nests of the species are commonly inundated by flood waters during the monsoon season, the incubation period often includes a diapause, or arrest in development. To increase hatching success, our program simulates these natural conditions by inducing a diapause during artificial incubation. On 22 May 2019, after nearly 8-months incubation, the first of the 68 hatchlings pipped their eggs, with all viable eggs completing hatching by 30 May 2019. By unlocking the key to the parameters of their diapause, our hatching success has increased from 50 to 80%.

The goal of this project is to not only better understand the reproductive particularities of this marginally understood species, but to also improve ex-situ breeding for future supplementation of the dwindling wild population. This year’s cohort of hatchlings will be retained at the LAB for several months before 75% are released into the wild at the same site from which the eggs were collected. The remaining 25% will be kept in captivity to bolster the gene pool of our assurance breeding colony for the species.

This project could not have been possible without the unwavering and continued support from the officers and frontline staff of the Uttar Pradesh Forest and Wildlife Department, and financial support from the WCS John Thorbjarnarson Fellowship for Reptile Research.