Thirty-eight species of frogs have been recorded in Dibang basin of Arunachal Pradesh where big hydel projects are being planned.

The study, done by researchers Jayanta K. Roy, Ramie H. Begum and M. Firoz Ahmed from 2014-17 across the river basin, recorded 38 species of amphibians belonging to 17 genera in six families.

Of 38, six species have been recorded in new areas across the river basin. The study has been published in the current issue of Journal of Threatened Taxa.

The frog species include Nanorana chayuensis, Odorrana chloronota, Hydrophylax leptoglossa, Minervarya pierrei, Minervarya syhadrensis, Theloderma moloch and Rhacophorus tuberculatus among others.

A single individual of genus Oreolalax was recorded from Ikindi at 3,235 metres in Dibang. It was observed in the night on an elevated tree trunk covered with moss in a rhododendron forest.

Ahmed, an expert of herpetofauna research and conservation division, Aaranyak, a wildlife NGO, said the study also observed that unscientific developments, including establishing large hydroelectric projects and building roads in the study area, would have an irreversible impact on the river basin’s ecology in the next few decades.

Roy and Begum are researchers on Assam University’s Diphu campus.

The Dibang river basin is situated in the foothills, flanked by the eastern Himalayas. It covers two districts of Arunachal — Lower Dibang Valley and Dibang Valley — with a total geographic area of 13,029 square kilometres.

The basin is a mountainous tract. Its altitude ranges from 200 metres to 4,900 metres and its rocky headwater streams with thick canopy cover provide a suitable habitat for rare amphibian species.

The survey across the river basin covered the altitudes from 200 metres to 3,500 metres. Systematic surveys were conducted along different streams and in forested habitats.

The study says that nearly 50 per cent of the 38 species have not been evaluated yet and further evaluation is required to find out their conservation status.

The river basin approach has helped plan long-term ecological study on amphibians. Long-term ecological studies in the river basin would help experts understand the factors that influence and limit distribution of species and effect of weather change in the Himalayan mountain ranges and mid-elevation foothills on them.