Assam keelback snake registers presence after more than a century

[ Abhijit Das ]
129 years ago, the centre of the Ahom dynasty, Sivasagar district of Upper Assam, would have had impenetrable evergreen forest teeming with wildlife. It’s the massive tea plantation that took its toll first, and perhaps during that time, Samuel Edward Peal, a British tea planter based in upper Assam, collected two specimens of a small 50 cm long brown-coloured snake and deposited in the museum.
In the year 1891, William Lutley Sclater, a British zoologist, formally described the snake as a new species in a half-page description and named it after the collector (Edward Peal) and commonly after the place where it was found.
Of the two original specimens, one was kept in the Zoological Survey of India, Kolkata, and the other in the Natural History Museum, London. This species has never been reported since then; nobody knew where it lived and how it looked, and everyone considered it a lost species.
In September 2018, a team from the Wildlife Institute of India (WII), Dehradun, retraced the steps of the century-old iconic Abor Expedition to Arunachal Pradesh. We initiated our survey from the Poba reserved forest, located at the interstate boundary between Assam and Arunachal Pradesh, from 30 September, 2018. This relict patch of lowland Brahmaputra Valley tropical wet forest is characterized by a three storied appearance with >30 m canopy with numerous, small, slow-moving perennial streams and rivulets in the forest interior.
While following one of these muddy-bottomed streams in the forest interior, at around 10:30 h, we recorded this harmless snake coiling under the submerged leaflitter of a stream. The snake was difficult to spot among leaflitter due to its dark-brown colour, but its belly contrasted it with brown spots on a yellow background – and that’s what caught my attention.
To confirm the identity and evolutionary relationships of this rare find, collaboration came from the Natural History Museum, London, where original the specimen was kept intact, unlike the one in the Zoological Survey of India, Kolkata. Subsequently, we identified this species as the Assam keelback (Herpetoreas pealii), based on morphological and molecular comparisons.
The discovery of the Assam keelback from a slow-flowing stream inside a forest indicates the need to prioritize conservation of ‘special habitats’ to safeguard microhabitat specialized species.
The Assam keelback is the real ‘Khilongia of Upper Assam region’ as this species is found nowhere else in the world. Poba, at the interstate boundary between Assam and Arunachal Pradesh, is a reserved forest with a ‘least protection’ status. The structure and composition of this forest have been highly modified as a result of past logging events and fragmentation by a highway and a village road.
During two days of post-monsoon fieldwork in September 2018, rare species, such as the slow loris (Nycticebus bengalensis) and at least 20 herpetofaunal species were also seen, perhaps signifying that better protection measures are required for this area. As we photographed the snake in its habitat, we appreciated the value of such remnant patches as a Noah’s ark for covert biodiversity.
We feel that this discovery is significant for the fact that we have discovered a first female individual of the species, and a natural habitat where this rare snake exists. The Assam keelback is endemic to lowland evergreen forests of upper Assam that were already fragmented into small patches, mainly from the expansion of tea plantations, habitation and agriculture.
Emerging threats of coal mining and oil exploration in these regions will only deteriorate the biodiversity values of these fragmented patches. In addition to new fieldwork, looking for the Assam keelback in other forest patches close to the Poba reserve forest is warranted, such as in the Pani Dihing Wildlife Sanctuary and the Dibru Saikhowa National Park in Assam, and the Daying Ering Wildlife Sanctuary in Arunachal Pradesh. (Abhijit Das is Scientist D, Wildlife Institute of India, Dehradun.)