Guwahati: A small frog found along a stream on the Mizoram University campus in Aizawl has been formally recognised as a new species, adding to evidence that northeastern India’s amphibian diversity remains significantly under-recorded.
The new species, Ingerana aizawl, has been described by a team of researchers from Mizoram University, Cotton University and the conservation organisation Help Earth in a paper published on September 14 in the journal Zootaxa. The researchers associated with the study are Hmar Tlawngte Lalremsanga, Manmath Bharali, Malsawm Dawngliana, Mara Duasa Hlychho, Malsawmtluanga, Rupankar Bhattacharjee, Arup Kumar Hazarika, Nilutpal Das and Jayaditya Purkayastha.
The frog was discovered at Hratdawng Stream on the Mizoram University campus, about 15 km west of central Aizawl. The researchers found that populations in Mizoram, historically identified as Ingerana borealis, were in fact genetically and morphologically distinct from all other recognised members of the genus.
The finding was established using an integrative approach combining physical characteristics with mitochondrial 16S rRNA DNA data. Genetic analysis placed the Mizoram frogs in a strongly supported, distinct lineage within the genus Ingerana. The researchers found that the new species differed genetically from its closest relative, Ingerana occidens, by 4.8–6.6%, and showed a much larger divergence of 15.3–17.6% from I. borealis populations in Arunachal Pradesh.
The discovery also resolves a long-standing taxonomic confusion over the frog’s identity.
Mizoram populations had been reported as I. borealis since 2009. A 2026 reassessment subsequently established that populations in Meghalaya’s Garo and Khasi Hills represented another species, I. occidens, while true I. borealis was restricted to areas north of the Brahmaputra. The identity of the Mizoram population, however, remained unresolved because molecular evidence was lacking.
The new frog is small and stout-bodied. Adult males measure 22–25.5 mm in snout-to-vent length, while females measure 24.4–26 mm. It has a distinct circular tympanum, a prominent supratympanic fold, small rounded discs at the tips of its fingers and toes, and a notably wrinkled dorsal surface.
The frog is predominantly dark brown to reddish-brown, with darker lateral surfaces forming a diffuse band extending towards the groin. Its iris is dark brown to blackish with a faint coppery tint.
The species is closely associated with water and forest habitats. Researchers found it around streams, wetlands and marshes between 94 and 823 metres above sea level, with most individuals encountered at night on wet rocks in or beside trickling, fast-flowing and cascading streams. During the day, the frogs shelter in rock crevices, moist leaf litter and bushes.
Its breeding season appears to coincide with the monsoon. The researchers recorded breeding activity between May and July, with males calling from outside the water and mating pairs found along stream margins. No eggs or larvae were recorded in the field, while captive pairs also did not lay eggs during the study.
The frog’s call consists generally of 12 notes, with the analysed call lasting about 1.42 seconds and having a dominant frequency of 3,359 Hz.
The species name aizawl refers to Aizawl, the capital of Mizoram, and honours the region where the type series was discovered. The holotype is an adult male collected from Hratdawng Stream on April 18, 2024, while five female paratypes were collected at the same site in June 2026. Two additional males examined by the researchers came from Khaikhy in Mizoram.
The researchers said the discovery points to a broader pattern of hidden amphibian diversity in northeastern India. They noted that limited geographic sampling and the absence of molecular data had previously resulted in different populations being grouped under the same species.
They also warned that the genus Ingerana may contain further undescribed species, saying continued molecular and morphological surveys across northeastern India and adjoining regions will be needed to clarify species boundaries and the evolutionary history of the group.
The discovery also has conservation implications. Since Mizoram’s frogs had previously been included within the range of I. borealis, which was assessed as Least Concern by the International Union for Conservation of Nature (IUCN) in 2022, the newly recognised I. aizawl now requires a separate assessment of its conservation status.
The type locality itself is a reminder of the conservation value of urban and institutional green spaces. The university campus covers about 978 acres, with elevations ranging from 300 to 880 metres, and retains relatively undisturbed forest patches, particularly on its western side.