for National Geographic News
Invasive fish carrying industrial chemicals likely triggered the recent die-off of 110 critically endangered reptiles known as gharials in a central Indian river sanctuary, scientists announced last week.
But the bulk of reptile fatalities occurred along a 22-mile (35-kilometer) stretch near the Chambal's confluence with the Yamuna, considered to be of the dirtiest rivers in the world.
Researchers therefore think an unidentified substance might be seeping into the Chambal and affecting the gharials' food supply.
Autopsies of the animals revealed evidence that they perished from gout, a painful metabolic disease, after ingesting polluted fish.
"Gharials that are already infected with the toxin will continue to die," said Ravi Singh, secretary general and CEO of the India branch of WWF.
The international conservation group is coordinating efforts by the government, other animal-welfare groups, veterinarians, and state departments to conduct an investigation and contain the crisis.
"If this mass die-off has truly stemmed from ongoing pressures on the habitat, people should know that there's no short-term fix."
Conservation groups say that no more than 1,400 gharials are left in the wild, living in pockets of India and Nepal.
More than 300 of these individuals live in the National Chambal Sanctuary along the Chambal River, which contains the largest of the world's three breeding populations.
When the reptiles began to wash up dead in December, post-mortem examinations revealed chemical-laced lesions on the animals' kidneys.
SOURCES AND RELATED WEB SITES