Nearly 41 percent of amphibian species are threatened with extinction, compared with 26.5 percent of mammals, 21.4 percent of reptiles, and 12.9 percent of birds. Through laborious fieldwork, they have documented more than 100 new frog species across India, Sri Lanka, and other parts of the subcontinent. According to the Nature study, which evaluated more than 8,000 amphibian species worldwide, two out of every five amphibians are now threatened with extinction. Frogs, says Biju, are excellent model organisms to study evolution and biogeography because of the extreme diversity of traits they acquired over millennia. She has done extensive fieldwork in India, Sri Lanka, the Western Ghats, the Himalayas, and Indo-Burma.