IUCN threat status:

Vulnerable (VU)

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Khare’s frog, a ranid frog first described from Sanuoru and Rukhroma waterfalls in Kohima district in Nagaland, India, was originally placed into its own monotypic genus as Pterorana khare on the basis of its large, well-developed skin folds (dermal flaps) on the side of its body and upper legs, structures not shared by any of its Rana relatives (Kiyasetuo and Khare 1986).  The frog is also known as Khare’s gliding frog, Indian flying frog, gliding frog, and winged frog (Frost 2015).

Subsequent to its initial discovery, this poorly known frog was recorded from a number of mountain rivers and streams throughout northeast India (Chanda et al. 2000, 1994; Power and Birand 2001; Ao et al. 2003; Dey and Ramanujam 2004; Sen and Mathew 2003) and into Chin State, Myanmar (Ao et al. 2006), consistently at altitudes between 1050-1600 meters (3450-5250 feet).  In a comprehensive review of the types and multiple new specimens, including live observations, Ao et al. 2006 determined that in fact this frog and its tadpoles have a “normal” shape for the genus.  As did Dubois (1992), Ao et al. 2006 conclude that this stream frog belongs to genus Rana, subgenus Pterorana, though they call for molecular analysis to refine its precise relationship.

So what is the function of these fleshy dermal flaps, originally considered a feature so unique from other Rana?  Kiyasetuo and Khare (1986) interpreted them as “wing-like” structures, implying they had a gliding function (hence the genus name Pterorana and diversity of common names referring to wings/flying ability).  Comparisons of multiple R. khare specimens newly collected by Ao et al. (2006), revealed that the fleshy, baggy flaps of Khare’s frog do not resemble the single layered lateral skin fringes of gliding frogs; furthermore R. khare does not have complete hand webbing as do gliding frogs.  

Ao et al. 2006 found that the ventral flaps occur only on males (there was some confusion of sexes in the specimen collected earlier).  In field observations Ao et al. found that R. khare breed on the gravel surfaces of small, shallow low flow pools interspersed in surrounding high currents of the stream, sometimes in groups of 4-5 individuals in these crucial sites.  Interestingly, Ao et al.’s behavioral observations also reveal that while females leave the breeding site directly after laying, the males remain submerged at these sites, hidden in nearby debris for the whole season (October-November) to guard developing offspring.  The highly vascularized physiology of the skin flaps suggests these structures could play a respiratory role for males.  Capturing dissolved oxygen (which is in high levels in the turbulent stream waters) through capillaries in these folds of skin might allow males to stay and guard their territory and breeding sites without expending energy to frequently cross through strong, dangerous currents to access the scattered low-flow pools (Ao et al. 2006).

A rare species with fragmented distribution, R. khare is classified with “vulnerable” status by the IUCN.  It is threatened especially by exposure to poisons used in fishing in their habitat (Dutta et al. 2004).

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