The Assam keelback snake has been sighted by a team from the Wildlife Institute of India, Dehradun, for the first time since 1869. This snake was spotted in 2018 by zoologist Abhijit Das when he, along with a team, was retracing the Abor expedition – an iconic expedition that took place from 1911-1912 that had yielded a rich list of flora and fauna of the Assam region. After due identification, the find has been described in a paper published recently in the journal Vertebrate Zoology.
Rewarding expedition
The Abor expedition had covered a 130 km stretch along the Siang river from the base camp at Kobo Chapori (elevation approximately 121 metres above sea level) to the head quarter at Yembung ( about 3,500 metres above sea level) and beyond. “The staggering zoological result includes description of 244 species and 14 genera new to science,” says Dr Das. In the latest expedition which traced out the route of the earlier one, too, the researchers were not disappointed. As Dr. Das recounts, “We recorded 400 plants, 270 butterflies, 66 odonates, 25 amphibians and 44 reptiles, 239 birds and at least 20 mammals.”
The survey started from Poba reserved forest located at the interstate border of Assam and Arunachal Pradesh on September 30, 2018. “I spotted the snake as I was following a small muddy stream deep inside evergreen forest,” says Dr. Das. “Generally, in a forest you have a forest floor with leaf-litter, but here was a special habitat, consisting of stream and swamp within the forest, which attracted me.” Unlike other snakes, this one took shelter under water, below the fallen leaf-litter, a very special way to avoid attention.
Preserved specimens
First known as Hebius pealii this snake was named after Edward Peal, a British tea planter who first collected two specimens of this snake from upper Assam, 129 years ago. Of the two collected specimens, one was preserved in the Zoological Survey of India, Kolkata, and the other was kept in the Natural History Museum in London. Since the former specimen had disintegrated, the team had to compare the present specimen they found with the one kept in the Natural History Museum, London. Had that specimen gone bad, making the identification would have been that much more difficult.
The Assam keelback is so far known only to inhabit Sivasagar in Upper Assam and Poba in Assam-Arunachal border. So, as far as present knowledge goes, it is an endemic snake of Upper Assam. Through a molecular study, the team has shown that this snake belongs to the genus Herpetoreas, which has only three other known members, and not Hebius. This is also the first description of a live snake and its colouration. This is the first female Assam keelback to have been found. “So, we now know how male and female may differ in morphological characters,” says Dr Das.
