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The purple frog used to be considered the only surviving member of an ancient amphibian family called the Nasikabatrachidae, but in 2006 this family was incorporated into the Sooglossidae. Up until around 120 million years ago in the early Cretaceous period, India was joined to the eastern part of the ancient southern supercontinent Gondwana, which subsequently split apart into Australia, Antarctica, India, Madagascar and the Seychelles over millenia of movement of the earth’s plates. The closest relatives of the purple frog are four tiny frog species found in the Seychelles in the Sooglossidae family. In their phylogenetic study of the purple frog in 2003, S. D. Biju and Franky Bossuyt (respectively of the Tropical Botanic Garden and Research Institute, Kerala and the Free University of Brussels) reported that the origin of the Sooglossidae/Nasikabatrachidae lineage occurred around 182 million years ago. It is thought that these two amphibian lineages diverged an estimated 134 million years ago form a common ancestor that inhabited Gondwana prior to the break up of this land mass. These frogs were therefore sharing the earth with the dinosaurs for 70 million years and started to evolve independently before the common ancestor of the elephant and the human.
The ancestors of the Seychelles frogs and the purple frog were present on the Indo-Madagascan land mass as it broke away from Gondwana and drifted through the movement of the earth’s plates for over 50 million years. Around 65 million years ago the Cretaceous/Tertiary boundary, the Seychelles split away from India and the ensuring plate movements separated the purple frogs from their closest relatives by around 2,500 km of Indian Ocean. The purple frog is therefore the only representative of a lineage that has been evolving independently for over 130 million years, has survived the break up of a continent and the extinction of the dinosaurs.
The diet of the purple frog predominantly consists of termites, and this species has a narrow mouth with a small gape, preventing it from catching and consuming larger prey items. Its strong head and pointed snout permits it to penetrate underground termite niches, and a fluted tongue may allow this species to suck up its prey from subterranean burrows. With its poor vision, this frog presumably depends on smell and tactile cues to detect and locate prey. It also consumes ants and small worms.
The burrowing and mound-building activities of termites increase the rate of percolation of rainwater and aeration of both the top and subsoil keeping the underground soil temperature low and the moisture content high. It may therefore benefit burrowing amphibians like the purple frog to live in close proximity to termite colonies, which improve the quality of their habitat as well as providing a food source. In India, the purple frog from the southern Western Ghats may be the only known amphibian species that is a fully underground forager. All other burrowing frogs are either open burrow feeders or diurnal burrow dwellers that are open ground feeders in the night.
Purple frogs require damp, loose soil to borrow into, and may dig themselves fully into appropriate soil within 3 to 5 minutes. When placed on hard ground, pebbled- or gravel-strewn soil, or areas with a thick mat of weeds, purple frogs are unable to borrow effectively and go in search of cover. The hind limbs have strong feet with wart-like structures that are primarily used for digging. This frog burrows downwards using its hind limbs like spades, throwing the soil over its back. They rest underground in a horizontal position with the limbs tucked under the body, although they do not remain idle underneath the soil, especially when foraging for their prey.
This project aims to discover more about the ecology of this elusive and recently described frog.
Developing an environmental education programme for the communities, farmers and plantation workers within the range of the purple frog would help increase local knowledge and pride in this species, especially if it can be made a symbol of local biodiversity. This could also enable local stakeholders to become involved in conserving through learning about more ecologically sensitive land uses and how to set aside some areas for this species.
Biju is a systematic biologist working on amphibians
Karthik is the coordinator and field scientist of a project which aims to find out more about the elisive purple frog.
Ashish Thomas is working on one of the most bizarre and fascinating frog – Nasikabatrachus sahyadrensis.
GWild will wear ONLY 12 outfits in 12 months for 12 threatened animals to fundraise for their conservation.
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Biju, S.D. 2004. Nasikabatrachus sahyadrensis. In: IUCN 2006. 2006 IUCN Red List of Threatened Species.
Duellman, W. E. and Trueb, L. 1986. Biology of Amphibians. McGraw-Hill, New York.
Dutta, S.K., Vasudevan, K., Chaitra, M.S., Shanker, K. and Aggarwal, R.K. 2004. Jurassic frogs and the evolution of amphibian endemism in the Western Ghats. Current Science 86(1): 211-216.
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Halliday, T. and Adler, C. (eds.). 2002. The new encyclopedia of reptiles and amphibians. Oxford University Press, Oxford.
Hedges, S.B. 2003. The coelacanth of frogs. Nature 425: 669-670.
IUCN, Conservation International and NatureServe. 2006. Global Amphibian Assessment.
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.
Radhakrishnan, C., Gopi, K.C. and Muhamed Jafer Palot. 2007. Extension of range of distribution of Nasikabatrachus sahyadrensis Biju & Bossuyt (Amphibia: Anura: Nasikabatrachidae) along Western Ghats, with some insights into its bionomics. Current Science 92(2): 213-216.
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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