They are as small as a five-year-old child’s thumbnail; and leap out of their daytime hideouts after sundown to croak to life the Western Ghat jungles with their signature cricket-like chirps.
They are among seven new species of frogs, some of the tiniest in the world that were discovered by Indian scientists. These nocturnal amphibians measure between 12.2mm and 15.4mm.
The discovery makes the rich but eco-sensitive Ghats the second-largest global amphibian hotspot after Brazil’s Atlantic Forest, a research paper reported on Tuesday.
Named after the place of discovery such as Sabarimala and Athirappilly in Kerala, the paper said they were found inside “damp tree leaf litter or marsh vegetation” -- unlike night frogs that predominantly reside along streams. That was a probable reason why these elusive frogs were out of sight until the 21st century.
“The miniature species are locally abundant and fairly common, but they have probably been overlooked because of their extremely small size, secretive habits and insect-like calls,” said Delhi University research scholar Sonali Garg, the paper’s lead author.
Locals knew about these frogs, but never thought they make sounds like crickets, explained SD Biju, a Delhi University taxonomy professor who guided the five-year research.
The first of the new discoveries was sighted in 2012, but differentiating their genre using DNA sampling and analysing their unique calls took time, he said.
The paper stressed that more studies were required to understand the “evolutionary advantages of miniaturisation and adaptation to terrestrial life” within the Nyctibatrachidae family, comprising largely robust torrential frogs.
Most of these frogs are endemic to the Western Ghats and represent an ancient group that diversified on the Indian landmass approximately 70-80 million years ago, according to a statement by peer reviewed open access journal, PeerJ, which published the study.
“Once the extinction risk is assessed and we can better understand the realities of each species, this would allow for the tailoring of both research and conservation actions accordingly,” said Ariadne Angulo, co-chair of a specialist group on amphibians at UN’s wildlife monitoring authority, International Union for Conservation of Nature (IUCN).
With the discovery, the number of night frog species found in the region has gone up to 35, of which 20% are extremely tiny.
Of the 103 amphibian species discovered in the Ghats since 2006, Biju’s team has discovered close to 80 as part of a collaborative effort with the Central government and taxonomy institutes in Europe.
“Many more are still to be found,” he said.
What worries biologists is the increasing anthropogenic interference in the Ghats, where most amphibians reside outside protected areas and are in direct conflict with humans.
For instance, researchers found Radcliffe’s Night frog and Kadalar Night frog inside state-owned plantations are facing threats because of habitat loss and disturbance. Similarly, Athirappilly Night frog was found in close vicinity to the Athirappilly waterfalls, a tourist spot, and Sabarimala Night frog near the pilgrimage centre by that name.
“Over 32%, that is one-third, of the Western Ghats frogs are threatened by climate change and other environmental factors. Of the seven new species, five require immediate conservation efforts,” Biju said.