Dead gharials began washing up on the banks of India’s Chambal River in December 2007. Over the following weeks, the body count grew. By mid-January, the dead reptiles—some the length of two tall men, lined up end to end—numbered in the dozens. By March, more than 110 of the skinny-snouted creatures had been found dead, most along a 30-kilometer (18-mile) stretch of river.

At the time, there were thought to be just 200 to 250 breeding-age gharials (Gavialis gangeticus) left in the world.