Among the smallest frogs in the world, they live on the forest floor and make insect-like calls at night.
Three larger species were also found, bringing to seven the number of night frogs discovered in the Western Ghats.
The mountain range, which runs parallel to the western coast of India, is home to hundreds of threatened plants and animals.
Scientists discovered the new species after several years of exploration in the forests of Kerala and Tamil Nadu.
Secretive habits
