Description

Ombrana sikimensis is a medium to large frog with a female snout-vent length of 60.5 - 88.0 mm. Males average about 63.0 mm (Shrestha et al. 2020). The head is slightly longer than it is wide and the snout and canthus rostralis are rounded. The loreal region is tilted and the interorbital distance is equal to the diameter of the upper eyelid. The tympanum is oval and indistinct, but the supratympanum fold is distinct. The dorsal skin is smooth and the dorsolateral fold is studded with tubercles that extend from the posterior corner of the eyes to the lumbar region. These tubercles are also found on the entire dorsal and lateral areas of the body, throat, sides of the head, upper eyelids, and the dorsal surface of the legs. The ventral skin is smooth and there is a circumanal skin fold present. The webbing on the fingers is rudimentary and the relative finger length is I = II < IV < III. The toes are completely webbed and have nearly straight margins. The tibio-tarsal joint reaches beyond the snout tip (Shah and Tiwari 2004). During the breeding season, males don’t have nuptial spines on their forearms, fingers, and pectoral regions, but they have spines above the cloaca (Shrestha et al. 2020).

Ombrana sikimensis is quite similar to Nanorana liebigii, but O. sikimensis has more fully webbed feet (Jerdon 1870). The two species also differ in terms of vocal sac, where O. sikimensis has a vocal sac and N. liebigii does not (Ohler and Dubois 2006; Shah and Tiwari 2004).

In life, the population in India is yellowish to blackish brown on their dorsum and the population in Nepal are reddish-brown to dark brown on their dorsum. They both are white to yellowish white on their ventral section (Mathew and Sen 2010; Shrestha et al. 2020). There’s a faint dark band between the eyes, and the lips and limbs have brownish cross-bars (Mathew and Sen 2010).

The females are typically larger than the males by about 20 mm, and during the breeding season the males have numerous spines above the cloaca (Shrestha et al. 2020).

The population in India has been noted with several distinct differences from the population in Nepal, although no genetic analyses have been conducted. The coloration leans more towards yellow in India and while it leans more towards red in Nepal (Mathew and Sen 2010; Shrestha et al. 2020). The Indian population also has a pointed snout, in contrast to a rounded snout in Nepal, and they have a distinct tympanum (Mathew and Sen 2010).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Bhutan, India, Nepal

View distribution map in BerkeleyMapper.

Ombrana sikimensis is found in Nepal and India, specifically in the Indian states of Assam, Meghalaya, Sikkim, and West Bengal (Mathew and Sen 2010). In Nepal, they are at altitudes of 1210 - 2500 m (Shah and Tiwari 2004). They are found in slow-moving shallow mountain streams that have rocky substrates, and they prefer high precipitation and moist areas such as forests (Mathew and Sen 2010). They have also been found in agricultural landscapes and secondary growth forests (Mathew and Sen 2010; Shah and Tiwari 2004).

Life History, Abundance, Activity, and Special Behaviors

They live in clusters underneath moderately sized rocks in their habitat of rocky mountain streams (Shrestha et al. 2020).

They are nocturnal (Shah and Tiwari 2004).

Trends and Threats

The most prominent cause of decline in O. sikimensis is hunting in Nepal and the lack of regulations surrounding it. They have been observed to be declining in the last decade and hunting regulations and educational campaigns have been suggested as conservation measures (Shrestha and Gurung 2019 - Ethnobiology). The population has also been declining because of their declining stream habitat that has been lost because of water diversion and deforestation (Shrestha and Gurung 2019 - Amphibian).

Relation to Humans

In Nepal, O. sikimensis along with Amolops formosus and Nanorana liebigii are called ‘Paha’ frogs and are hunted either as a delicacy or for their therapeutic benefits by the surrounding indigenous communities. Ombrana sikimensis in particular is highly sought after as a delicacy. The hunting takes place before or after monsoon season when the water flow is at a minimum and at night, and people collect as many as they can during each search (Shrestha and Gurung 2019 - Amphibian). During each hunting season, people catch between 51 - 100 frogs and they are sold locally at prices between NPR 50 - 250 (Shrestha and Gurung 2019 - Ethnobiology).

Possible reasons for amphibian decline

Habitat modification from deforestation, or logging related activities
Dams changing river flow and/or covering habitat
Intentional mortality (over-harvesting, pet trade or collecting)

Comments

Currently, no phylogenetic analysis has been performed for O. sikimensis, but it is recognized as its own genus (Frost 2005).

Ombrana sikimensis was named after where the holotype was found in Darjeeling, India, which at the time was a part of the state of Sikkim and now is a part of the state of West Bengal (Jerdon 1870).

References

Frost, D. (2005). “Ombrana Dubois, 1992.” Amphibian Species of the World 5.1, an Online Reference. American Museum and Natural History. Electronic database accessible at https://amphibiansoftheworld.amnh.org/Amphibia/Anura/Dicroglossidae/Dicroglossinae/Ombrana Downloaded on 16 November 2022

Mathew, R., Sen, N. (2010). Pictorial Guide to Amphibians of North East India. Zoological Survey of India, Kolkata, India.

Ohler, A. and Dubois, A. (2006). "Phylogenetic relationships and generic taxonomy of the tribe Paini (Amphibia, Anura, Ranidae, Dicroglossinae), with diagnoses of two new genera." Zoosystema, 28(3). [link]

Shah, K.B. and Tiwari, S. (2004). Herpetofauna of Nepal: A Conservation Companion. IUCN - The World Conservation Union, Nepal.

Shrestha, B. and Gurung, M.B. (2019). "Ethnoherpetological notes regarding the paha frogs and conservation implication in Manaslu Conservation Area, Gorkha District, Nepal." Journal of Ethnobiology and Ethnomedicine, 15(23). [link]

Shrestha, B. and Gurung, M.B. (2019). "Natural history notes on three sympatric frogs, Amolops formosus (Günther 1875), Nanorana liebigii (Günther 1860), and Ombrana sikimensis (Jerdon 1870), from Manaslu Conservation Area, Nepal." Amphibian and Reptile Conservation, 13(2), 152 - 159.

Shrestha, B., Pandey, B., and Gautam, B. (2020). "Conservation Guidelines for the Paha Frogs from Unchecked Harvest in the Northern Regions of Bhojpur district, Nepal." [link]

Species Account Citation: AmphibiaWeb 2023 Ombrana sikimensis: Sikkimese frog <https://amphibiaweb.org/species/8014> University of California, Berkeley, CA, USA. Accessed Mar 30, 2023.

Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 30 Mar 2023.

AmphibiaWeb's policy on data use.