Mountain Princes - Frog Tales From The Western Ghats

 

December 2007: I was on the top of the Chinnapul Mountain in the rainforests of the Kalakad Mundanthurai Tiger Reserve (KMTR) with two of my Kani friends on a cool Sunday morning. We were raking through the thick leaf litter and turning rocks when we came across a rotting log (the tree had probably died many years ago and all that was left now was a highly-weathered piece of wood). The always curious Sivakumar began excavating. The first creature to emerge was a huge tiger centipede belonging to the genus Scolopendra. Our interest aroused, all three of us dug with enthusiasm.

Then, suddenly Rajamani shouted, “Thawalai, Thawalai!" There, hidden in the crevices of the dead log, was something none of us had ever seen before - a lovely iridescent dark-bluish frog. It began to creep further into the crevice, but we were determined to identify this beauty and after a few gentle digs, we managed to get hold of the frog. I turned it upside down and saw lovely scarlet patches on its limbs that immediately confirmed our suspicion - what I held in my hand was the extremely rare black microhylid Melanobatrachus indicus, a frog that has been reported only thrice in India after Independence. I was overjoyed and the Chinnapul mountain, where I had already done much frog watching before, would now be forever etched in my mind.

I was in Chinnapul to complete the field work for my Master's dissertation in Wildlife Science from the Wildlife Institute of India. My mentor, Dr. Karthikeyan Vasudevan, had himself worked in KMTR on frogs for his PhD. My Master's thesis posed two simple questions: at what elevation would most species of frogs be found, and why does one see more species in particular mountain areas. I believed that the answers to these questions could help in advancing the conservation of frog species by helping to identify specific areas that hold more species in a larger landscape. Given the larger threat of global decline in amphibians and extinction of frogs from relatively-intact forests in different regions of the world, this could be the first step that may lead to specific conservation initiatives for frogs in India in the future.

The going was straightforward, yet tough, adventurous and even risky. But at the age of 21, you tend to relish the challenges and ignore the hardships! So the plan was simple, to search for frogs at sea level and continue right until the top of the mountain. We started in the 100 m. zones, starting from 0-100 m. and then 100-200 m. and so on till we reached the top of Chinnapul. We knew, though, that once we reached the peak, we would long to know what species of frogs all the other mountains harboured!

 

The famous Kalakad Mundanthurai Tiger Reserve is a very rewarding location for field work. KMTR and the other Protected Areas around it contain the largest continuous stretch of rainforests in the Western Ghats, the chain of mountains along India's west coast. Unfortunately, many other areas in the Western Ghats are now a matrix of rainforest patches interspersed with coffee, tea, cardamom, lemon grass, rubber or some other cash crop. The patchy and restricted distribution of many frog species makes them not only susceptible to extinction, but also has major implications in the context of habitat fragmentation.

KMTR provides an opportunity to look at floral and faunal groups from near sea level (40 m. ASL) to about 1,800 m. ASL. Also, the mountains of KMTR are primarily east facing, resulting in a diverse array of vegetation types. The lower reaches of KMTR receive only the northeast monsoon between November and January (with eight dry months) resulting in scrub to deciduous forests. The higher reaches, however, receive not only the northeast monsoon but also the full force of the southwest monsoons, and so have eight wet months in a year. This prolonged annual period of rain over centuries has resulted in the spectacular wet evergreen forests in the higher reaches of the KMTR. The Chinnapul, a tributary of the holy Thamirabarani river of Tirunelveli district in southern Tamil Nadu, is one of the many rivulets that rises from the mountains in the area. It originates in the montane forests of the Chinnapul peak at an elevation of around 1,300 m. ASL.

For the purpose of my study, I divided Chinnapul's gradient from 40-1,300 m. into 100 m. elevation zones and in each of these zones, we laid six fixed area (50 m. x 2 m.) belt transects parallel to the stream. In the riverine forests, we would search for terrestrial frogs during the day and also undertake three one-hour walks along the streams at night. The choice of areas around the stream was obvious because previous studies had revealed that the concentration of frog diversity was greater here.

As I initiated our frog study, I realised that the hydropower dam built by the Tamil Nadu Electricity Board in Servalar in central KMTR might have had an immense negative impact on the stream-dwelling frogs in particular. The dam reservoir drowned forests and the mountain current below the dam is but a mere shadow of its former prime. Above the dam, the river water is crystal clear and garrulous, while below it, the water is murky, stagnant and no longer potable. The dam has resulted in possible local extinctions of important groups of frogs like the Nyctibatrachus, which is endemic to the Western Ghats. Species belonging to this genus prefer to breed in flowing water. They are one of the rare groups of frogs that lay their eggs on rocks in streams in non-foamy nests. Nyctibatrachus vasanthi, currently known only in the forests of KMTR and adjoining areas, lays its eggs on rocks next to the small torrents. The water that splashes from the rocks keeps the frogs' eggs moist. As with any dam, however, the one built in KTMR caused flowing waters to stagnate. In addition, there are severe fluctuations in the water level depending on the releases from the dam. The dam has thus, eradicated the microhabitats needed by these frogs for breeding. Hydropower dams take a toll on frog species that typically depend on freely-flowing water for their survival. Walking through this magical land that was once riverine and moist deciduous forest, I wondered bitterly how anyone could term hydropower ‘eco-friendly'. Apart from frogs, heaven alone knows how many other species of vertebrates and invertebrates are being sacrificed for a few megawatts of power.

 

Because the dam at Servalar is built at 200 m., it has mercifully spared habitats of frogs above this elevation. Dams like Kodayar in southern KMTR, however, located at 1,200 m., would have devastated the downstream ecology and we do not even know which species vanished because no systematic studies have been conducted. Our studies reveal that the amphibian communities now found below Servalar are dominated by species like Fejervarya cf. limnocharis, Hoplobatrachus spp., and Microhyla spp., which prefer stagnant pools for breeding, while above the reservoir, species that evolved over eons to live in natural-flowing water systems still prosper. In addition to the dam, there is also considerable pollution caused by plastics and other wastes generated by pilgrims visiting the Agastiyar temple, Banathirtham falls and the Mundanthurai plateau in the lower reaches of KMTR. We currently have no clue of the long-term impacts of this on the amphibian communities.

But I tried to put such thoughts behind me when trekking the heavenly upper slopes of Servalar. The situation is very different in the 22 km. stretch from Servalar to the Chinnapul peak. There are no direct threats to wildlife in this area. It is not visited by tourists or pilgrims because of its remoteness and lack of facilities. No clear trail leads to the Chinnapul peak, and it was only because of the Kanis that I was able to explore the area. They have grown up playing and wandering in these forests and know where the elephant trails lead to and where to find suitable campsites. My field work would have been next to impossible without their knowledge of the area. The light-hearted Kanis virtually traipse through these pristine forests. They are excellent at spotting animals, leading you through the forests, camping in the wild and they even cook up some delicious food (a vital factor when you walk long distances uphill carrying a 15-20 kg. backpack!).

Above Servalar, Chinnapul is nothing short of majestic. It throbs with life. At times, I have counted more than 100 individuals of Micrixalus fuscus (an endemic genera), Sylvirana temporalis and Nyctibatrachus in a single hour of walking. All these frogs attract the attention of snakes like the Malabar pit viper Trimeresurus malabaricus and hump-nosed pit viper Hypnale hypnale, which come to the streamside to grab an easy meal. On numerous occasions, I have just about missed stepping on one of these poisonous snakes.

 

Walks along the streams, especially at nights, are fascinating because this is when you are able to see different species going about their daily chores - basically eating and searching for potential mates. However, each species has its own idiosyncratic manner and therein lies the magic. There are the Nyctibatrachus that sit in obscure positions on wet rocks. The sticky grooves on their toes and fingers help them to navigate with ease, sometimes giving the impression that they are virtually defying gravity. From steep angles on the rocks, they call out for females with their metallic notes. Then we have the bronzed frogs Sylvirana temporalis with their lovely golden upper lips that give them a positively regal look as they sit on the banks and rocks in the streams, observing ‘subordinates'. If disturbed, they dive instantly into the water and using their muscular legs, are able to swim against the swift-flowing current. Their diet includes snails, insects and even other small frogs. Watching them eat snails is an entertaining sight. The slimy snails always seem to slip out of their mouths and they must get at least half the snail inside, to be able to slurp it down (with much relief I imagine!). The Micrixalus are the acrobats of the streams, amazing jumpers and swimmers that leap over long distances about the forest floor when encountered. Ramanella triangularis are small, stout frogs with narrow heads that sit in small rock pools next to streams. In pools as small as 30 cm. in diameter, I have seen as many as 20 Ramanellas sitting and calling out for the females. Like many other species of frogs, the females of this species are much larger than the males. It is the female Ramanella that chooses her mate. For a long time I used to wonder where the Ramanellas vanish during the day. One morning, while checking out a dead log, I found a Ramanella pop out and their daytime hideout was revealed.

The most elegant and beautiful frogs found in the Western Ghats are those belonging to the genus Philautus, commonly known as ‘bush frogs'. These frogs are fascinating from an evolutionary standpoint - they no longer depend on water for breeding, and have circumvented the tadpole stage. Their eggs hatch directly into small frogs. This has allowed them to explore arboreal habitats.

As my field work led me up the mountain, I saw striking changes in species composition. I encountered many more species. Philautus was especially diverse in the higher reaches. Of the 10 species that I encountered throughout the study, I saw only two in the lower elevations while the rest were restricted to the higher reaches. The most significant addition that happens in the middle elevation is a species I nicknamed the “Don" - Nyctibatrachus major. Its characteristic large head and wrinkled skin gives it a distinctly ‘mafioso' personality. I also saw the stunning Rhacophorus calcadensis, a frog restricted to the mountains of the southern Western Ghats, the lovely Bufo beddomei with brilliant red on the hind side of the body, and the tiny Nyctibatrachus beddomei, one of the smallest in the region. Just measuring around one centimetre in length, they are most often missed.

 

By the time my six months of field work ended in mid-April, I had seen 37 species of frogs, each of which had left its own, distinct impression. After data analysis back in Dehradun, it turned out that the greatest diversity of frogs was found at elevations above 700 m. in the montane forests. This is because above these elevations, the temperature was cooler and the habitat more wet. Frogs, being amphibious, are sensitive to drier and hotter areas. Compared to stream-dwelling frogs, Philautus are more sensitive to temperature fluctuations and so eight of the 10 species of this genus were spotted in the montane forests above 700 m. Most of the species found in the montane forests in KMTR are endemic to the Western Ghats, possibly due to their isolation from closely-related kin in adjoining mountain ranges over hundreds of years, resulting in speciation. Such speciation events may have resulted in each mountain range bearing its own unique species of frogs.

One take home message of my study was the fact that though there are around 120 frog species in the Western Ghats, most of them have restricted ranges in terms of not only latitude but also altitude. Hence, there is a urgent need to protect representative rainforest habitats (mountain ranges) throughout the region. My subsequent study in the Kudremukh hills in central Karnataka threw up different patterns and results, making me realise that distribution of frogs is much more complex than I had originally believed. The factors governing their distributions across mountain ranges are varied. More such studies for better understanding of their geographic distribution are required so that sensible strategies for the long-term conservation of frogs in the landscape can be formulated.

The fate of the lovely frogs of Chinnapul, of KMTR, and of the Western Ghats is tied up with that of other frogs around the world. The preservation of their habitat, including wet montane forests, which harbour so many species is crucial. Biologists have been concerned for more than a decade about global declines in amphibian populations, including frogs missing from pristine, undisturbed areas with no anthropogenic influence whatsoever. Declining frog populations have been attributed to increased ultra-violet radiation caused by depletion of the ozone layer and fungal and parasite infections. There are also numerous human-induced threats to amphibian populations that must be equally addressed.

 

KMTR, spread over more than 898 sq. km., offers a unique opportunity for the conservation of frogs. This tiger reserve provides protection to a wide array of habitats across the entire elevation gradient, sheltering not only typically lowland species but also high elevation endemics with narrow geographic ranges. There are relatively few landscapes such as KMTR in the Western Ghats that have the dual advantage of a large geographic area over a wide elevation gradient. It is imperative that more representative mountain ranges with their own unique set of frog species be identified and conferred protection to ensure the future of these wonderful ‘princes of the mountains'.

By Rohit Naniwadekar, Sanctuary Asia, Vol XXVII No. 6, December 2007