A small frog discovered along a stream on the Mizoram University campus in Aizawl has been formally recognised as a new species, highlighting the largely unexplored amphibian diversity of northeastern India.
The new species, Ingerana aizawl, has been described by researchers from Mizoram University, Cotton University and the conservation organisation Help Earth in a paper published on September 14 in the journal Zootaxa.
The research team comprises 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, around 15 km west of central Aizawl. For years, frogs from Mizoram had been identified as Ingerana borealis. However, detailed morphological and genetic studies showed that the Mizoram population was distinctly different from other known species in the genus Ingerana.
The researchers used an integrative taxonomic approach, combining physical characteristics with mitochondrial 16S rRNA DNA analysis. Genetic evidence placed the Mizoram frogs in a strongly supported and separate evolutionary lineage.
The new species differs genetically from its closest known relative, Ingerana occidens, by 4.8–6.6%. The genetic difference from I. borealis populations in Arunachal Pradesh is considerably higher, at 15.3–17.6%.
The discovery also helps resolve a long-standing taxonomic puzzle. Mizoram populations had been reported as I. borealis since 2009. A 2026 reassessment established that frogs from Meghalaya’s Garo and Khasi Hills belonged to another species, I. occidens, while true I. borealis was restricted to regions north of the Brahmaputra. The identity of the Mizoram population remained uncertain because molecular evidence was unavailable.
Ingerana aizawl is a small, stout-bodied frog. 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 on the fingertips and toes, and a distinctly wrinkled back.
The frog is generally dark brown to reddish-brown, with darker sides forming a diffuse band towards the groin. Its iris is dark brown to blackish, with a faint coppery tint.
The species is closely associated with streams and other wet forest habitats. Researchers recorded it around streams, wetlands and marshes at elevations ranging from 94 to 823 metres above sea level. Most individuals were found at night on wet rocks in or beside trickling, fast-flowing and cascading streams. During the daytime, the frogs were observed sheltering in rock crevices, moist leaf litter and bushes.
Breeding activity appears to coincide with the monsoon, with observations recorded between May and July. Males were heard calling from outside the water, while mating pairs were found along stream margins. The researchers did not record eggs or larvae in the field, and captive pairs also failed to lay eggs during the study.
The frog’s call generally consists of 12 notes. The analysed call lasted approximately 1.42 seconds and had a dominant frequency of about 3,359 Hz.
The species name aizawl refers to Aizawl, the capital of Mizoram, and recognises the region where the type series was discovered. The holotype is an adult male collected from Hratdawng Stream on April 18, 2024. Five female paratypes were collected from the same site in June 2026, while two additional males examined during the study came from Khaikhy in Mizoram.
The researchers said the discovery reflects a wider pattern of hidden amphibian diversity across northeastern India. Limited geographic sampling and the lack of molecular data may have previously led to distinct frog populations being grouped under the same species.
They also suggested that the genus Ingerana could contain additional undescribed species. Further molecular and morphological surveys across northeastern India and adjoining regions will therefore be important for understanding species boundaries and the evolutionary history of the group.
The discovery also carries conservation implications. 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. As a separate species, I. aizawl will now require an independent assessment of its conservation status.
The type locality also highlights the importance of protecting urban and institutional green spaces. Mizoram University campus covers around 978 acres, with elevations ranging from 300 to 880 metres, and still retains relatively undisturbed forest patches, particularly in its western section.
