Amphibians
Purple Frog
Nasikabatrachus sahyadrensis · also called purple frog, pignose frog, Indian purple frog
The purple frog looks like a deflated balloon with a pointed nose and beady eyes, and it lives a life to match its strangeness: buried metres underground for nearly the whole year, it surfaces for only a fortnight to breed in monsoon streams. It is also one of the most evolutionarily distinct amphibians alive, the sole survivor of a branch that split off before the dinosaurs died out.
Overview
The purple frog is found only in the Western Ghats of southwestern India, in and around evergreen forest with deep, workable soil and seasonal streams. For roughly 50 weeks of the year it lives underground — recorded as deep as 3.7 metres — in a self-dug chamber, feeding on termites and ants that it laps up through a small mouth and a specialised grooved tongue without ever coming to the surface.
Built to burrow
Its whole body is a digging machine. The rounded, bloated trunk stores water and energy; the small, hard, pointed head and spade-like projections on the hind feet cut into the soil; the short, powerful limbs shove earth aside. The skin is smooth and purple-grey and holds moisture in. None of this equipment is for jumping or swimming, which is why the frog looks so unlike the frogs people know.
Two weeks above ground
With the first monsoon storms, males move to the edges of fast-flowing seasonal streams, call from half-buried positions, and mate. Females lay eggs on wet rock beside the torrents. The tadpoles have sucker mouths and spend about 100 days clinging to rocks in the rushing water before transforming and, presumably, burrowing down to begin the adult life underground.
A 120-million-year-old branch
The purple frog’s family, Nasikabatrachidae, diverged from its closest relatives — frogs now restricted to the Seychelles — around 120 million years ago, when India and the Seychelles were still joined in Gondwana. It has ridden the Indian plate across the ocean ever since. In conservation terms it is evolutionarily distinct and globally endangered, meaning its loss would remove a disproportionate share of amphibian history.
Status
The purple frog is Endangered. Its tiny range is being eroded by plantation agriculture (coffee, cardamom, ginger), dams and stream modification, and forest loss, and it is still harvested for food and folk use in places. Parts of its habitat fall inside protected areas of the Western Ghats.
Purple Frog: common questions
Why does the purple frog look so strange?
Almost every odd feature is an adaptation to a life spent underground eating termites. The bloated body stores energy and water for the long dormant season; the tiny, hardened, pointed head and the shovel-like projections on the hind feet are digging tools; the short, muscular limbs push soil aside; and the small mouth with a specialised grooved tongue is a termite-and-ant vacuum, used without the frog ever needing to open wide or lunge. The purple-grey, glistening skin reduces water loss. It only looks bizarre because we almost never see a frog built for burrowing rather than for jumping and swimming.
How was the purple frog discovered so recently?
It was described as new to science in 2003, which is extraordinary for a vertebrate this large in a densely populated country. The reason is its lifestyle — it is underground for about 50 weeks of the year and only emerges for a week or two, at night, during the first heavy monsoon storms, so the window to find one is tiny and easily missed. Local communities in the Western Ghats had long known the frog and, in some areas, eaten it or used it in folk practices, but it had escaped formal zoology.
Why is the purple frog important to scientists?
It is a living link to the deep past. Its entire family, Nasikabatrachidae, split from its nearest living relatives — a group of frogs now found only in the Seychelles — around 120 million years ago, when the Indian landmass and the Seychelles were part of the same fragment of Gondwana. The purple frog therefore represents an ancient evolutionary branch that has survived India's 100-million-year journey across the ocean and its violent volcanic history. Losing it would erase a large, unique piece of the amphibian family tree.
Why is it endangered?
The purple frog is confined to a small strip of the Western Ghats and depends on undisturbed forest soil for its dormant life and on clean, seasonal, fast-flowing streams for breeding and for its rock-clinging tadpoles. Both are being lost to the expansion of coffee, cardamom, and ginger plantations, dams and check-dams that alter stream flow, and forest clearance. The frogs and their egg masses are also still collected for food and traditional use in some districts. Its range lies partly within protected areas, which offers some security.