Wildlife & Biodiversity

After 89 years, frog endemic to the higher altitudes of Western Ghats ‘rediscovered’

A more detailed description of the ‘near threatened’ species & its habitats will bolster conservation efforts 

By Preetha Banerjee
Published: Friday 03 March 2023
After 89 years, frog endemic to Western Ghats ‘rediscovered’
Jerdon’s narrow-mouthed frog (Uperodon montanus) photographed by zoologists recently. Photo: Amit Hegde Jerdon’s narrow-mouthed frog (Uperodon montanus) photographed by zoologists recently. Photo: Amit Hegde

The Jerdon’s narrow-mouthed frog (Uperodon montanus) could once be spotted leaping over slippery pebbles or peeping from behind rocks in the shallows of streams in the upper reaches of the Western Ghats.

But since it was last studied in 1934 by a British scientist, the species faded into oblivion, rarely spotted by residents and researchers or wrongly identified as other ambhibians that look similar.

This changed last year when a group of zoologists photographed 40 tadpoles of the species in the biodiverse Western Ghats, in the same stages of development they were last identified 89 years ago, according to a new report published February 26, 2023.

The frogs have a longish snout, which gives it its name, and shiny brown skin with darker brown, red and golden spots on the back and head. They are found in rock pools or tree holes filled with rainwater.

This frog is considered a montane species and is restricted to higher altitude ranges of 800-1,700 metres, according to the report published in the Journal of Threatened Taxa.

They are distributed from near Wayanad south across the Palghat and the Shencottah gaps to the Agasthyamalai hills, it added.

“The previous record of altitude limit for the species was 1,700 m (Garg et al. 2018) but our studies extend much higher altitudinal range of 1,916 m from Vaguvarai, Idukki, Kerala,” the authors wrote.

It is classified as ‘Near Threatened’ in the International Union for Conservation of Nature Red List of Threatened Species. But researchers have been campaigning for it to be put under the ‘Endangered’ group of species to aid conservation. 

Its tadpoles are free-swimming and exotrophic, which means they feed on other species.

Uperodon montanus tadpole. Photo: Amit Hegde

“During one of our regular field visits to Coorg, Western Ghats, we surveyed small rock pools beside the mountain streams in which tadpoles were observed,” wrote the researchers who studied the spawning grounds and tadpoles of different stages.

From the samples studied, “37 tadpoles were of Gosner stage 25 and three tadpoles
were of Gosner stage 40 in the rocky pools characterised by 80 cm in length, 50 cm in width and 15.5 cm depth in the steep slopes”.

In November (post-monsoon), the tadpoles were seen in the rock pools beside the mountain streams of the evergreen forests, according to the report. “Most of these pools / pockets had organic debris, leaf litter and aquatic insects.”

“Change in the tadpole body colouration was observed during the day and night. In the daytime, they looked comparatively darker and at night they were slightly transparent,” the researchers noted.

The study was a joint effort by the researchers of Breeding Behaviour and Bioacoustics Lab, department of Zoology, Karnatak University in Dharwad, Karnataka and Zoological Survey of India in Pune, Maharashtra.

A majority of the amphibians have two different stages: Water-independent adult stage (feeding and breeding) and the aquatic larval stage (feeding) known as tadpoles.

These tadpoles / larvae have completely different morphological appearance, feeding, habitat and ecology which is totally different from adults.

“As a kid, we studied in textbooks that there are several species found only in Western Ghats and are defined as endemic to Western Ghats,” Amit Hegde from Karnatak University and co-author of the report wrote in a press note. “But now from various studies we know that within Western Ghats they are restricted to certain small biogeographical area and within that they are known from only certain elevations (mountain ecosystems) and in that they are seen in only certain specific micro habit.”

The finer details of habitat and ecosystem preference of the frog as described in the new report will bolster conservation efforts, according to KP Dinesh from the Zoological Survey of India, Pune and co-author.

Apart from the British Zoologist HW Parker’s small description during colonial times in 1934, this is the second report on the tadpoles of this species roughly after 89 years, the authors pointed out in the press release. 

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