Guwahati: A team of researchers from Mizoram University and the biodiversity conservation group Help Earth has discovered a new species of rain snake from the tropical montane forests of Mizoram, further underscoring the state’s growing reputation as a biodiversity hotspot.
The study, published in the latest issue of Taprobanica: The Journal of Asian Biodiversity (August 5, 2025), describes the species as Smithophis leptofasciatus sp. nov.—commonly known as the narrow-banded rain snake. The discovery is based on detailed morphological and molecular analyses of two collected specimens, along with observations of several live individuals in the wild.
What sets Smithophis leptofasciatus apart is its striking appearance. With a shiny black body adorned with narrow, creamish-white or yellowish-lime transverse bands that form incomplete rings, the snake stands out from its closest relatives.
These distinctive markings inspired the species’ scientific name, derived from Greek and Latin, meaning “narrow-banded.” Locals in Mizoram have named it Ruahrul, reflecting its cultural significance.
“This species not only adds to the growing diversity within Smithophis, but also redefines the distribution of previously known species,” said Dr. Jayaditya Purkayastha, one of the corresponding authors. “Our study confirms that what was previously identified as Smithophis bicolor from Mizoram is, in fact, a genetically and morphologically distinct species.”
The narrow-banded rain snake inhabits humid, shaded microhabitats near small streams in Mizoram’s montane forests, at elevations ranging from 900 to 1,200 meters.
Field observations revealed its semi-aquatic and nocturnal lifestyle, with the snakes often found under leaf litter, beneath rocks, and around decaying logs during the monsoon season. Remarkably, the researchers noted the species’ gentle temperament, showing no inclination to bite when handled.
A gravid female kept in captivity laid six eggs, providing rare insights into the reproductive biology of this elusive group.
“This discovery emphasizes Mizoram’s central role in the evolution and diversification of the genus Smithophis,” said Dr. H.T. Lalremsanga, co-author and head of the Developmental Biology & Herpetology Lab at Mizoram University. “With three species now described from the state—S. atemporalis, S. mizoramensis, and S. leptofasciatus—it is clear that these forests hold exceptional ecological importance.”
Genetic analysis confirmed that S. leptofasciatus is deeply divergent from its closest relatives, including S. bicolor from Meghalaya, with which it had long been confused. The findings prompted researchers to formally restrict S. bicolor to Meghalaya and recognize the Mizoram population as a separate species.
However, the discovery comes with a note of caution. With a narrow range and dependence on pristine, streamside forests, Smithophis leptofasciatus may be vulnerable to habitat degradation. The study urges additional surveys and habitat assessments to better understand its ecology and conservation needs.
The research was supported by grants from the Department of Science and Technology (DST-SERB), The Habitats Trust, and international conservation funds. As Northeast India faces increasing environmental pressures, the discovery of Smithophis leptofasciatus serves as both a celebration of the region’s natural wealth and a reminder of the urgent need to protect it.
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