In less than two decades, the crowned river turtle (Hardella thurjii), one of the least studied and investigated species of hard-shelled turtles, jumped from being “Vulnerable” to “Endangered” on the IUCN’s Red List. Sadly, the name rarely sparks any recognition. So it follows that its diminishing numbers hardly triggered any anxiety. Except, of course, among those racing to turn back the clock on this species.
These beautiful creatures are found in large deep pools of slow-flowing rivers and are endemic across India, Nepal, Pakistan, and Bangladesh. They have a dark head with 2-3 yellow-orange lines running from nostril to tympanum, giving the distinctive crown, which is how it earned its name. And yet, it is a barely understood species, with very little known of its reproductive ecology and unique behaviour.
“They are found scattered across the Gangetic and Brahmaputra river systems. They require very specific conditions — deep river pools but not fast-flowing water, proper vegetation where they can forage and the right conditions for nests. A 100-km stretch of the Sarju-Ghagra river system in the Terai area on the Indo-Nepal border at the foothills of the Himalayas offers all these conditions and three large, robust adult populations, of over 500 females, are found here,” says Dr Shailendra Singh, director at the Turtle Survival Alliance-India, who spearheads the conservation programme. Dr Singh began studying these turtles around 2003, but they became the centre of attention around 2012-13 when robust populations were discovered.
Pointing out the characteristics of the species, he says it exhibits clear sexual dimorphism: the carapace (shell) of adult females measures 55-60 cm and weighs 18-20 kg which is about 3-4 times the size of the average male (15-17 cm, 6-7 kg). They are completely herbivorous and believed to live up to 60-70 years, but that is still to be verified since studies on them have only been on for three decades.
The researchers realised they had very little information on their breeding behaviour. They found hatchlings and yearlings but no intact nests, and the females were not seen and seemed to disappear. Sustained efforts led to some remarkable discoveries. “When we cast nets to catch them for studying, we caught both males and females in May, which happened to be the breeding season. But around September-October, we caught very few males. So we believe the males migrate between groups, but the females are tied to the habitat,” he says.
The significant discovery was that these turtles are underwater nesters, a characteristic not found in any other Indian freshwater turtle. “We found that the females would make a body pit near the edge of the water when the water level went up and entangle the nest with weeds and other debris. This would also safeguard it from predators. In the cold months and when the water level goes down, they go into development arrest (stop growing temporarily). The eggs only hatch once the water goes up again, sometime in May-June. Their behaviour is fascinating,” Singh says. Besides, these turtles were found to be entirely aquatic with very rare instances of basking, leading to the assumption that they had developed a sophisticated system of thermoregulation.
Around 2012-13, biologist Arunima Singh joined the Turtle Survival Alliance as Project Coordinator (Ex-situ Conservation). “The main aim was to understand the population dynamics. This included identifying the population differences over the years and their nesting ecology in the wild,” she says.
Arunima began collecting turtle eggs and transporting them to the Laboratory for Aquatic Biology in Lucknow, where hatching was induced, and the juveniles studied for various aspects before being released back into the Sarju river. “We’ve had 90 per cent success rate with hatchlings, and their survival and dispersal rate has also been good. But it has only been four years since we have been doing this. It will take at least four more years of study for proper data collection,” she stated.
For all its uniqueness, the crowned river turtle is in a precarious state. It is estimated that about 1,000 turtles live in the entire 200 km of the river system and a total of about 10,000-15,000 across India, Pakistan, Nepal and Bangladesh. “It is extensively hunted for its meat, which is considered a delicacy.” Since a single female turtle yields more than 15 kg of meat, it is highly coveted. It is also prized as a pet in the illegal pet trade. According to Dr Singh, other threats the turtle faces are inadvertently getting caught in fishing nets and their habitat being in constant danger due to unpredictable water release from dams.
Dr Singh says they have been working with local fishing communities, conducting education and awareness programmes, and designing and implementing special nets with funnel technology that allows the turtles to escape. He says they were also working with the local government and communities to protect the turtle populations and showcase them as a unique species. What makes the task daunting is that the river is unprotected, making the turtles extremely vulnerable.
Dr Singh points out that though we know some facts about adults, there is very known little about the juveniles, the characteristics of their habitat, and the way congregations develop and behave. Nothing, for instance, is known about where they go at some times of the year and where the males migrate to when the females are nesting. Adding that, “Overall, we know only 8-10 per cent of the life and behaviour of the crowned river turtle; there’s so much more to study.”