Why the dancing frog may no longer be able to shake a leg

If you peer carefully at rocks in perennial streams in the Western Ghats in Karnataka, you might see a tiny frog tapping its feet and kicking its hind legs in the air in an attempt to attract a mate. At the width of three centimetres, the Kottigehar dancing frog (Micrixalus kottigeharensis) can fit into your palm and is an evolutionary distinct and globally endangered (EDGE) species.

Micrixalidae is one of the oldest families of frogs in the Western Ghats, and is known to have evolved  more than 60 million years ago and diversified five million years ago.

The genus, Micrixalus, commonly known as “dancing frogs”, represents an ancient lineage and certain studies have indicated that the lineage has no close living relatives.

Madhushri Mudke, a researcher who studies the Kottigehar dancing frog species at Ashoka Trust for Research in Ecology and Environment (ATREE), Bengaluru, said, “If they go extinct, there is no other species close to them, so they die with the evolutionary history of millions of years. They are also endangered because their distribution is limited in the world.” She notes that the species has a “unparalleled evolutionary history”.

While the Micrixalus lineage existed as a solitary branch without substantially diverging, it is likely that multiple offshoot lineages eventually went extinct, indicates a 2003 study of ancient frog lineages in the Indian subcontinent.

K.V. Gururaja, a behaviour ecologist at the Srishti Manipal Institute of Art, Design and Technology, Bengaluru, and other researchers, identified 24 species of “dancing frogs” in the Western Ghats, found over years of research, in 2014. Until then, only 11 species had been discovered. He said, “The key characteristic of this family is that they are active post or early monsoon, unlike other frogs that are active during the monsoon and are diurnal, meaning active during the day rather than the night. They inhabit perennial streams.”

He found that the foot flagging behaviour is exhibited during territorial fights between two male frogs, known as ‘male agonistic behaviour’ and during the mating season to attract female frogs. The female frogs also exhibit this behaviour when they lay eggs in shallow, flowing water. The females dance over the eggs as they cover them with pebbles so that they are not visible to predators.

Micrixalus kottigeharensis is threatened by invasive species like the mosquito fish, land use change, variation in temperature and humidity, extreme weather events such as floods and excess rainfall, infectious diseases, water pollution, light pollution, and infrastructure projects such as dams.

Despite this, the species is not listed under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix. In India, the species is not protected by the Wild Life Protection Act, 1972, as there isn’t adequate information about its distribution and numbers.

Studying the frog’s habitat and distribution

Mudke has been studying the habitat of the species since 2017 with support from the EDGE of Existence programme by the Zoological Society of London.

“Knowing what habitat supports what species is very important for conservation,” she said. She worked with local communities living close to perennial streams in the Western Ghats, the frog’s known habitat, to involve them in the sampling process. Through film posters displaying Kannada actor Uppendra to draw attention, she and her team began to create awareness about the Kottigehar dancing frog. If they found a frog near a particular stream, they would ask the local residents to introduce them to residents in nearby villages that hosted a similar habitat. Through this, the team aimed to map the range of the frog while involving the local villages in the exercise, increasing awareness.

Additionally, Mudke and her team conducted surveys and mapped perennial streams and Myristica swamps throughout the Western Ghats of Karnataka, and parts in Goa and Kerala. She discovered 18 new sites in the moist evergreen forests and Myristica swamps in Karnataka alone. Myristica swamps are freshwater swamp forest predominantly composed of Myristica plants that occur on either side of primary streams. She also found that the frog preferred habitats at elevations of 300 to 500 m. above sea level and in areas with thick canopy cover of at least 70-80%.

“Western Ghats are old forests. It’s important to consider the value of the place – cultural, traditional and ecosystem services provided,” said Mudke. “For example, local communities told us the importance of Myristica swamps – they hold water and slowly release it into streams and ponds.”

Malformations possibly influenced by anthropogenic stress

With the Western Ghats subjected to land use change, unchecked infrastructure projects and rapid conversion to agricultural lands, many of the swamps have lost their water retention ability. Streams are diverted and canopy cover is slashed, threatening the survival of the species.

While more studies and surveys are needed to understand the impact of these anthropogenic stresses on the frog population, in preliminary studies, Mudke and her team found that in one location where the stream flowed through the forest to an areca nut plantation, the number of frogs reduced from 4 to 1 due to reduced canopy cover in the plantation.

When infrastructure projects such as roads, bridges or dams are planned in such eco-sensitive areas, little attention is paid to the ecology of the landscape and how it may be altered, Mudke said.

“When one species is affected, it impacts the entire biodiversity of the place. The evolutionary history of the place is lost.” She emphasised that there has to be an integrated approach for conservation that is not limited to restoration alone. “Conserving the old forests is more important,” she added.

During her field surveys, she found skeletal deformities in many Kottigehar dancing frogs – such as disruption in the symmetry of the body, or a soft-tissue deformity that results in a missing eye or deformed limb. “Frogs tell us that the ecosystem is healthy. But when you have malformations in frogs, that means the population there is not doing well. It shows there is something wrong in the environment.”

Malformations in frogs were first seen in the U.S., in Minnesota and later in other parts of the country. Detailed surveys of the regions inhabited by the frogs showed this malformation was primarily due to infection with a parasite, Ribeiroia and pollution of the waters with fertilisers and cattle manure. The studies noted that was a clear correlation between habitat alteration by humans and presence of the parasite causing the malformation.

There have been many reports of malformed frogs in India too. While causes remain understudied, scientists believe that these deformities were owed to anthropogenic pressures. These could be water pollution, and pesticide run off entering streams from farms. More surveys are needed to determine the cause of these malformations.

To this end, Mudke has started a citizen science initiative called Malfrogs with India Biodiversity Portal, a first-of-its-kind effort to document the malformations – where they are found and in what species. “We don’t know why there are so many deformed frogs. We can use this data for future studies to understand these malformations and their impact on frog species and amphibian biodiversity.”

Read more: New frog species discovered in biodiversity-rich Western Ghats

Banner image:  Two male dancing frogs in the Western Ghats. Photo by Samyamee Srivathasa for the dancing frog project of India.