This Exceptionally Rare Frog Species Only Emerges From Underground During Monsoon Season

It’s natural to assume all frog species spend their lives above ground, hopping along lily pads and rocky riversides. However, burrowing frogs are more common than you think. Known as fossorial species, frogs adapted to life underground are some of the most fascinating amphibians around.

There’s one such species you should know about. It is so elusive, unique, and rare that scientists only recently discovered it emerging from its underground home. This is everything you need to know about India’s purple frog and why it spends so much of its life beneath the soil.

“A Once in a Century Find”: Meet the Indian Purple Frog

Scientifically classified as Nasikabatrachus sahyadrensis, the Indian purple frog was discovered as recently as 2003. While locals were aware of this oddball long before the early 2000s (its tadpoles were first described in the 1900s), it is an elusive species. Also known as the pignosed frog and the Mahabali frog, this amphibian spends a shocking amount of its life underground.

Fossorial frogs aren’t rare. In fact, there are at least a dozen named species found around the world, including the giant burrowing frog in Australia and multiple shovelnose frogs located in Africa. However, the Indian purple frog remains one of two frogs in the Nasikabatrachus genus. Both of these frogs burrow and are directly affected by their regional monsoon seasons.

Pig-Nosed For a Purpose: Why Does the Purple Frog Look Like That!?

We need to address the elephant in the room… or, rather, the frog. The Indian purple frog is a unique-looking species, one that is optimally designed for life underground. However, it doesn’t necessarily look like a traditional frog by any means. This is largely due to its subterranean home, diet, and need to traverse swift streams on rare occasions.

The purple frog rarely grows over seven centimeters in length. Males are significantly smaller than females. It is small-headed compared to the average frog, with a pointed snout designed for sifting bugs out of soil. The body of the purple frog can best be described as bloated. However, it is capable of flattening against slick river rocks and clinging in the face of fast currents.

When it comes to the legs of the purple frog, its front limbs are significantly larger than its back ones. While it cannot leap like other frog species, its strong “spatula-shaped” front feet are designed for digging and burrowing. The palms of the purple frog are also tougher and more resilient compared to its hind limbs, allowing it to shove small rocks and debris aside with ease.

Endemic to India: Environment of the Purple Frog

It was once assumed that the purple frog only dwelled in a small portion of the Western Ghats Mountains in India. However, once scientists began studying this frog in earnest, its range actually extends to the Camel Hump Mountains and Cardamom Hill. There are roughly 130 breeding sites of the Indian purple frog, half of which are protected forest zones.

The purple frog’s preferred habitat consists of loosely packed and dampened soil near bodies of water, typically ponds or streams. They burrow deep enough to remain undetected by predators and scientists alike. In fact, the purple frog finishes its transformation from tadpole to adult underground, establishing its elusive lifestyle early on.

Welcome Home: the Purple Frog’s Underground Lifestyle

It’s unclear why the purple frog prefers life underground, but it’s certainly well-adapted to it. In fact, this amphibian spends nearly its entire life beneath humid soil. It emerges for only two weeks during India’s monsoon season. Why? Monsoon season makes an ideal breeding ground for the purple frog. Females lay their eggs in the swelling bodies of water near their subterranean homes.

Purple frog breeding times differ depending on location; monsoons occur either in April-August or October-December. Regardless of when monsoon season begins, purple frogs spend this roughly two-week period breeding and repopulating their endangered species.

These alternating storms are one of the only things separating the two species of purple frogs found in India. They emerge from their underground homes at different times, in different locations. However, the males of both species begin their mating calls a few inches below ground, a trait rarely exhibited by other fossorial frogs.

The Diet and Physiology of a Burrow-Dweller

While their narrow snouts assist in digging and shoving dirt aside, purple frogs also have an adept sense of smell. They feed primarily on insects they unearth in their underground homes, namely termites. The purple frog also relies on its sense of smell more than other senses because it is essentially earless.

Unlike other frog species, the purple frog lacks a tympanic middle ear, using scent and vibrations to find its way underground. This is one reason why scientists speculate that males of the species begin their mating calls underground, aside from a need for protection. The call of mating purple frogs sounds like a chicken clucking, its chest pulsating and puffing out as it does so.

How Rare is the Indian Purple Frog? Rarer Every Year

Given its limited region and threats to its habitats, the Indian purple frog is considered an endangered species. As few as 130 frogs have been recorded, with less than five females found in their preferred breeding sites. However, thanks to conservation efforts from the EDGE Project and others, the purple frog population is tentatively trending upward.

The secretive and shy personality of the purple frog hasn’t helped scientists determine a realistic population number. Regardless, this species faces many threats, including habitat loss, environmental pollution, and a long-held local belief in the healing abilities of their tadpoles.

The purple frog has survived thanks to millions of years of evolution. It is a testament to how unique and intricate nature can be, even if we rarely get to witness this underground frog firsthand.