However, unfazed by the casualties, Principal Chief Conservator of Forests and Wildlife, Uttar Pradesh, D N S Suman, has decided to release 40 ghariyals into the river. While this was to initially take place on January 24, it has now been decided that the ghariyals will be released later due to the prevailing cold conditions. The temperature at the National Chambal Sanctuary (NCS) is currently hovering around two degrees Celsius mark.

A crisis management group formed by the Central Government to look into the sudden deaths is likely to visit the sanctuary on January 28. Among other things, it will monitor the movement and activities of the ghariyals to be released. The management group will be accompanied by officials of the World Wildlife Fund For Nature (WWF).

The latest possible clue to what is killing the rare reptiles is an unknown parasite that scientists found in the dead ghariyals’ liver and kidneys, according to Dr A K Sharma of the Indian Veterinary Research Institute.

“We can say that the liver and kidneys of these gharyials were badly damaged,” said Sharma. “They were swollen and bigger than their usual size.”

Others believe the ghariyals may have gotten sick and died after eating contaminated fish from the polluted Yamuna river, which joins the Chambal in Uttar Pradesh. Pathological tests confirmed lead and cadmium in the bodies of the animals, said Suman. “The Chambal river has clear water, free from heavy metals. The only possibility seems to be that these ghariyals might have migrated from the Yamuna.”

Conservator of Forests Eva Sharma says ghariyals below the age of three years would be released.

Defending the decision, she says: “The NCS informed us that only those ghariyals already in the Chambal river had died. None of the ghariyals sent from the Kukrail Ghariyal Rehabilitation Centre (KGRC) were found dead.”

The KGRC has been releasing ghariyals into the Chambal river since 1970. It chops the tail of the animal to ensure that it can be spotted easily.

Conservationists believe there are only about 1,500 ghariyals left in the wild, many of them in the Chambal, one of the few unpolluted rivers in India. The Chambal contains the largest of three breeding populations in the world.

The ghariyal was on the verge of extinction in the 1970s, when a government breeding programme that has released several hundred into the wild raised their numbers.