Nepal, June 20 -- Every spring, tens of thousands of people gather on the ancient streets of Patan to witness the Rato Machindranath Jatra, started in the 7th century. The towering chariot is hand-built from bamboo and wood, and is slowly pulled through the city by hundreds of devotees. Flowers and water sprinkles from rooftops. The people chant: "Let the rain come".

For most visitors, the jatra is a deeply moving spectacle of faith and tradition. For a small group of scientists studying the DNA of the Himalayan pangolin, the jatra became a symbolic clue to their laboratory results about the species' sharp decline.

An animal hard to see

The Himalayan pangolin (Manis aurita) is a seldom-seen animal. It comes out at night. It curls into ...