Last week the discovery was announced, in the Ceylon Journal of Science, of no less than fourteen new species belonging to a remarkable group of frogs, referred to as the ‘dancing frogs’ of India. The dancing part of their name points to their unusual behavior of foot-flagging that males use to attract the attention of the females. A combination of intensive survey efforts in the Western Ghats spanning more than a decade and the usage of modern molecular techniques enabled the Indian researchers to identify this incredible amount of new species, thereby more than doubling the known total of species in this amphibian taxon.
The Western Ghats in India is a mountain range covering approximately 1600 kilometers and spreads out from the Western state of Maharashtra to the tip of Southern India. This region is home to a spectacular array of wildlife and boosts a high amphibian diversity and a high degree of endemism. The reason so many species have evolved here has to do with the special geographic circumstances, isolating this region from its surroundings and a climate that has stayed (sub)tropical throughout history. Such a stable climate can lead to sympatric speciation, meaning that species inhabiting the same habitat, diversify because they occupy different niches. Especially in recent years the number of amphibian discoveries has been great, leading to almost a doubling of the known species in this region, now up to 181 different species.
The group of Micrixalidae, or dancing frogs, however hadn’t seen any new species coming into their group in almost 25 years. Partly this has to do with their small size, 13-35 mm, and their elusive nature, but also because no extensive surveys had been carried out. This despite the interest they had evoked in scientists, with their specific ecological and behavioral adaptations, due to their 85-million year separation from their closest relatives. The trademark of this group of frogs is their foot-flagging behavior that is thought to have arisen as an adaptation to the noisy environment of torrent streams in which they live. By waving and kicking their hind limbs to communicate they can bypass acoustic communication and use these visual cues for communication and in their mating behavior. This parallels the adaptation that we have seen in the Panamanian golden frog that uses semaphoring, or waving with the forelimbs, to communicate.
In an attempt to gain more knowledge on these frogs, the Indian researchers, led by Dr. Das Biju of the University of Delhi, have spent more than a decade in the field, from 2001 to 2012, studying them. They ended up with data from 87 populations from 70 localities and used the DNA barcoding approach to determine the diversity of the group. The results from the barcoding approach were validated by detailed morphological examination. It turned out that 14 new species could be added to the group of dancing frogs, raising the total number to 24. The barcoding approach seems like a very promising method to examine other understudied lineages in the Western Ghats as well. It would be no surprise if more species are awaiting discovery considering the already high biodiversity in this lush region of India. And indeed Dr. Das Biju expects there to be at least 100 more species of amphibians in the Western Ghats that we haven’t described yet. Finding them would mean a major contribution to conservation of amphibian biodiversity, as we would be able to prevent what Dr. Das Biju calls “nameless extinctions”, i.e. species that disappear without us knowing of their existence.
In these many years in the field, the scientist had been able to gather some more information on the remarkable foot-flagging as well: they found that at least 8 species of the genus exhibit the behavior and likely have independently evolved this adaptation to their noisy environment. In the original paper and in a lovely article on Mongabay you can view a depiction of the courtship behavior of male dancing frogs, which involves kicking, waving and whipping their hind legs out. In this way they want to convince the females they are the right man for the job. Convincing them won’t be easy as there are literally a 100 other males applying for the job, as the sex ratio is very skewed in this species. And to smack away their competitors males use these same kicks of their hind legs.
During the decade the scientists were surveying the area, they noticed an enormous decrease in numbers; in 2006 during breeding season they would spot up to 500 individuals. But each year they became scarcer until it became hard to even spot a 100 of them. Their decline might be related to climate change. These tiny creatures breed in rapid mountain streams and therefore run the risk of being swept away by the fast-flowing water. This means they can only reproduce during a certain period when stream levels drop and the water flows less rapidly. So stream levels need to be low, but not too low. Because here another discovery the scientists made, comes into play. After searching for clutches of eggs on land without any success they saw by chance a female bury her eggs in the stream floor. This peculiar behaviour, these are the only frogs to bury their eggs, leaves them very vulnerable to drying out of the streams. And unfortunately their habitats seem to dry out increasingly. Although the scientists admit that this latter observation is based on only anecdotal evidence, it is supported by a 2010 report by India’s Environment Ministry. The report said the Western Ghats were likely to see changing rainfall patterns due to climate change, and more recent scientific studies have also suggested monsoon patterns will grow increasingly erratic.
The future doesn’t promise to be easy for this group of frogs: even though the Western Ghats provide a relatively isolated home for them , the megapopulation of India exerts pressure on this region as well. Iron and bauxite mining, water pollution, unregulated farming and loss of habitat to human settlements are among the threats nature here faces. Dr. Das Bijou expresses his concern to the Guardian in the following way: “”It’s like a Hollywood movie, both joyful and sad. On the one hand, we have brought these beautiful frogs into public knowledge. But about 80% are outside protected areas, and in some places, it was as if nature itself was crying.” India’s government has been working to establish an environmental protection zone across the Western Ghats to limit polluting industrial activities and human encroachment, but it put the latest proposal on hold earlier this year. Meanwhile, at least 25% of the forests here have vanished and these newly discovered frogs could soon be joining them. Many of the 24 known Indian dancing frog species lives only in a single, small area. Seven live in highly degraded habitats where logging or new plantations are taking over, while another 12 species live in areas that appear in ecological decline.
Let’s hope the discovery of so many new and endemic species, might spur the Indian government to continue with the proposal for establishment of an environmental protection zone. I would like to conclude with the more hopeful words Dr. Das Biju spoke to Mongabay:“Documenting this biodiversity is the first step towards conservation,” Biju said. “First we have to know what we need to conserve. Discovering new species increases our knowledge of what we have and their status. People are now talking about frogs. I think the change is coming and hopefully it will affect conservation policies, too.”