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Order: Anura
Family: Microhylidae
The Microhylidae (the “narrow-mouthed frogs”) are one of the most recently evolved families of frogs and, totaling over 400 species, is also the largest with the greatest number of different genera (nearly 50). They are a very large and diverse family of frogs. They are widely distributed throughout the tropics, and include both burrowing / terrestrial (ground-dwelling) and arboreal (tree-dwelling) species.
The genus Microhyla (sometimes referred to as the “rice frogs”) are restricted to the Old World from Japan and China south through India to Sri Lanka and southeast through Asia to parts of Indonesia. They received the generic name “rice frogs” due to their habitat of spawning in shallow pools formed from activities such as rice farming. The temporary nature of these pools or puddles means that rice frogs have the ability to develop very quickly over the course of a few weeks, whilst some other groups of frogs and toads may remain in the tadpole phase for a year or more.
The Microhylidae diverged from all other amphibians 80 million years ago. The rice frogs are one of the oldest genera within this family, splitting away from their closest relatives about 50 million years ago, which is about the same time as the earliest known bat fossils started to form.
The genus Microhyla (sometimes referred to as the “rice frogs”) are restricted to the Old World from Japan and China south through India to Sri Lanka and southeast through Asia to parts of Indonesia. They received the generic name “rice frogs” due to their habitat of spawning in shallow pools formed from activities such as rice farming. The temporary nature of these pools or puddles means that rice frogs have the ability to develop very quickly over the course of a few weeks, whilst some other groups of frogs and toads may remain in the tadpole phase for a year or more.
The Microhylidae diverged from all other amphibians 80 million years ago. The rice frogs are one of the oldest genera within this family, splitting away from their closest relatives about 50 million years ago, which is about the same time as the earliest known bat fossils started to form.
The skin is smooth with a glandular fold extending from the outside edge of the eye to the forelimb. The stomach is white with black marbling, whilst the back is a pinkish grey-brown with a blackish stripe along the side of the body running from the eye to the groin. Dark brown band-like markings along the back generally start between the eyes, either ending at the shoulders or extending all the way down the back in variable patterns. The limbs, especially the back legs, have dark cross-bar patterning. They have white stomachs with black marbling.
The tips of the digits are disc-shaped and the toes are webbed. The digit disks are more developed on the toes than on the fingers, and clear notches are visible in the middle of each disc. Individuals are very small, measuring 15-20 mm in length.
Tadpoles are approximatley 30 mm long. They are transparent with a little pigmentation around the nostrils. They produce well developed hind limbs with completely webbed toes and notched digit-discs. The tail is about 1.7 times that of the body length.
The tips of the digits are disc-shaped and the toes are webbed. The digit disks are more developed on the toes than on the fingers, and clear notches are visible in the middle of each disc. Individuals are very small, measuring 15-20 mm in length.
Tadpoles are approximatley 30 mm long. They are transparent with a little pigmentation around the nostrils. They produce well developed hind limbs with completely webbed toes and notched digit-discs. The tail is about 1.7 times that of the body length.
Larvae are found in inland wetlands, including old abandoned gem mining pits surrounded by tropical forest.
Breeding has been observed in the clear water of disused gem pits, ranging in depth from about 0.5 to 2 metres. These pits are usually from 1-10 m across. Both calling males and tadpoles in all stages of development were observed during visits from 1992-1995 in the months of February, March, August, October and December. It appears therefore that breeding is not necessarily seasonal and probably occurs throughout the year. The tadpoles have been found to occur in pools with tadpoles of the Indian skipper frog (Euphlyctis cyanophlyctis). It has been noted that tadpoles of Karunaratne's narrow-mouthed frog were not present in pools with marginal shade from shrubs more than a few metres tall.
Tadpoles have been observed to go down to the mid-depths of the pool when disturbed, and remain stationary while rapidly beating the terminal filaments of their tails. Tadpole metamorphosis lasts approximately eight weeks in captivity.
Thought to feed on termites and / or other small invertebrates, which they may burrow to find. Microhyla or rice frogs have a call which is similar to the bleating of a goat.
Breeding has been observed in the clear water of disused gem pits, ranging in depth from about 0.5 to 2 metres. These pits are usually from 1-10 m across. Both calling males and tadpoles in all stages of development were observed during visits from 1992-1995 in the months of February, March, August, October and December. It appears therefore that breeding is not necessarily seasonal and probably occurs throughout the year. The tadpoles have been found to occur in pools with tadpoles of the Indian skipper frog (Euphlyctis cyanophlyctis). It has been noted that tadpoles of Karunaratne's narrow-mouthed frog were not present in pools with marginal shade from shrubs more than a few metres tall.
Tadpoles have been observed to go down to the mid-depths of the pool when disturbed, and remain stationary while rapidly beating the terminal filaments of their tails. Tadpole metamorphosis lasts approximately eight weeks in captivity.
Thought to feed on termites and / or other small invertebrates, which they may burrow to find. Microhyla or rice frogs have a call which is similar to the bleating of a goat.
This is a terrestrial species associated with shaded, wet leaf litter, in tropical moist forest. It has also been found in more disturbed areas of sub-montane scrub regrowth following deforestation. This species has been observed in and around the margins of fairly shallow small- to medium-sized pools of water (from 1-10 metres aross). Within Sinharaja World Heritage Site, adults are usually found in the tangled roots and stems of grass surround these small pools of water.
It is interesting to note that Karunaratne's narrow-mouthed frog has taken advantage of habitat use by humans, especially by using gem pits created by illegal mining activities.
It is interesting to note that Karunaratne's narrow-mouthed frog has taken advantage of habitat use by humans, especially by using gem pits created by illegal mining activities.
Known only from two sites in southern Sri Lanka: Morningside in eastern Sinharaja (06°24´N, 80°37´E), and Mahawalatenna in Balangoda (06°35'N, 80°45'E). The recorded elevation range is 515 - 1,110m above sea level.
An accurate population estimate is currently unavailable for the species, although it is considered to be generally uncommon.
Exact population data is currently unavailable although the population trend is assumed to be generally in decline in the IUCN Red List of Threatened Species. However, population numbers may actually be increasing in Sinharaja World Heritage Site as this species makes use of the pools of water that collect in disused pits created by illegal gem mining.
Listed as Critically Endangered in the IUCN Red List of Threatened Species because its extent of occurrence is less than 100 km sq., its distribution is severely fragmented, and there is continuing decline in the extent and quality of its habitat.
It is threatened by habitat loss through deforestation to establish cardamom plantations and also by agricultural pollution (both land and water). However, in a study of this species within Sinharaja World Heritage Site it was noted that it actually makes use of the habitat alteration for its breeding purposes. Even pit created by illegal gem mining in this area contained tadpoles of this species. It is therefore possible that this population has actually benefited from some of the habitat alteration inflicted upon its range in that the gem mining has created more breeding habitat for the species.
The species has been recorded from the Sinharaja World Heritage Site, which should afford it a certain degree of protection. Unregulated habitat alteration is clearly still occurring within this area of land, however the illegal gem mining seems to have actually benefited this species, creating additional pools for breeding habitat.
Continued active management of this area is required, and further survey work is needed to monitor the population status of the species.
In addition to conserving native habitat for this species, the IUCN Technical Guidelines for the Management of Ex situ Populations, part of the IUCN Red List of Threatened Species, recommend that all Critically Endangered species should have an ex situ population managed to guard against the extinction of the species. An ex situ population is ideally a breeding colony of a species maintained outside of its natural habitat, giving rise to individuals from that species that are sheltered from problems associated with their situation in the wild. This can be located within the species’ range or in a foreign country that has the facilities to support a captive breeding programme for that species. Since the Karunaratne's narrow-mouthed frog is characterized as Critically Endangered, the possibility of a captive breeding programme for this species should be investigated.
In addition to conserving native habitat for this species, the IUCN Technical Guidelines for the Management of Ex situ Populations, part of the IUCN Red List of Threatened Species, recommend that all Critically Endangered species should have an ex situ population managed to guard against the extinction of the species. An ex situ population is ideally a breeding colony of a species maintained outside of its natural habitat, giving rise to individuals from that species that are sheltered from problems associated with their situation in the wild. This can be located within the species’ range or in a foreign country that has the facilities to support a captive breeding programme for that species. Since the Karunaratne's narrow-mouthed frog is characterized as Critically Endangered, the possibility of a captive breeding programme for this species should be investigated.
AmphibiaWeb: Information on amphibian biology and conservation [web application]. 2006. Berkeley, California: AmphibiaWeb. Available: amphibiaweb. Accessed: 08 December 2006.
Dutta, S.K. 1997. Amphibians of India and Sri Lanka. Odyssey Publishing House, Bhubaneswar.
Dutta, S.K. and Manamendra-Arachchi, K. 1996. The amphibian fauna of Sri Lanka. Wildlife Heritage Trust of Sri Lanka, Colombo.
Fernando, P. and Siriwardhane, M. 1996. Microhyla karunaratnei (Anura: Microhylidae), a new species of frog endemic to Sri Lanka. Journal of South Asian Natural History 2(1): 135-142.
Frost, Darrel R. 2006. Amphibian Species of the World: an Online Reference. Version 4 (17 August 2006). Electronic Database accessible at:. American Museum of Natural History, New York, USA.
Frost, D. R., Grant, T., Faivovich, J., Bain, R.H., Haas, A., Haddad, C. F. B., De Sá, R.O., Channing, A., Wilkinson, M., Donnellan, S.C., Raxworthy, C.J., Campbell, J.A., Blotto, B.L., Moler, P., Drewes, R.C., Nussbaum, R.A., Lynch, J.D., Green, D.M., and Wheeler, W.C. 2006. The Amphibian Tree of Life. Bulletin of the American Museum of Natural History 297: 1-370.
Halliday, T. and Adler, C. (eds.). 2002. The new encyclopedia of reptiles and amphibians. Oxford University Press, Oxford.
IUCN, Conservation International and NatureServe. 2006. Global Amphibian Assessment. Global Amphibian Assessment. Accessed on 08 December 2006.
Kirtisinghe, P. 1957. The Amphibia of Ceylon. Published by Author. Colombo, “Ceylon”. 112 pp.
Manamendra-Arachchi, K. & de Silva, A. 2004. Microhyla karunaratnei. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. IUCN Red List of Threatened Species. Downloaded on 01 August 2007.
Obst, F.J., Richter, K. and Jacob, U. 1984. The Completely Illustrated Atlas of Reptiles and Amphibians for the Terrarium. T.F.H. Publication Inc., N.J., U.S.A.
Roelants, K., Gower, D. J., Wilkinson, M., Loader, S. P., Biju, S. D., Guillaume, K., Moiau, L. and Bossuyt, F. 2007. Global patterns of diversification in the history of modern amphibians. Proceedings of the National Academy of Sciences 104: 887-892.
Dutta, S.K. 1997. Amphibians of India and Sri Lanka. Odyssey Publishing House, Bhubaneswar.
Dutta, S.K. and Manamendra-Arachchi, K. 1996. The amphibian fauna of Sri Lanka. Wildlife Heritage Trust of Sri Lanka, Colombo.
Fernando, P. and Siriwardhane, M. 1996. Microhyla karunaratnei (Anura: Microhylidae), a new species of frog endemic to Sri Lanka. Journal of South Asian Natural History 2(1): 135-142.
Frost, Darrel R. 2006. Amphibian Species of the World: an Online Reference. Version 4 (17 August 2006). Electronic Database accessible at:
Frost, D. R., Grant, T., Faivovich, J., Bain, R.H., Haas, A., Haddad, C. F. B., De Sá, R.O., Channing, A., Wilkinson, M., Donnellan, S.C., Raxworthy, C.J., Campbell, J.A., Blotto, B.L., Moler, P., Drewes, R.C., Nussbaum, R.A., Lynch, J.D., Green, D.M., and Wheeler, W.C. 2006. The Amphibian Tree of Life. Bulletin of the American Museum of Natural History 297: 1-370.
Halliday, T. and Adler, C. (eds.). 2002. The new encyclopedia of reptiles and amphibians. Oxford University Press, Oxford.
IUCN, Conservation International and NatureServe. 2006. Global Amphibian Assessment. Global Amphibian Assessment. Accessed on 08 December 2006.
Kirtisinghe, P. 1957. The Amphibia of Ceylon. Published by Author. Colombo, “Ceylon”. 112 pp.
Manamendra-Arachchi, K. & de Silva, A. 2004. Microhyla karunaratnei. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. IUCN Red List of Threatened Species. Downloaded on 01 August 2007.
Obst, F.J., Richter, K. and Jacob, U. 1984. The Completely Illustrated Atlas of Reptiles and Amphibians for the Terrarium. T.F.H. Publication Inc., N.J., U.S.A.
Roelants, K., Gower, D. J., Wilkinson, M., Loader, S. P., Biju, S. D., Guillaume, K., Moiau, L. and Bossuyt, F. 2007. Global patterns of diversification in the history of modern amphibians. Proceedings of the National Academy of Sciences 104: 887-892.
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