The Wild

Leaps and Bounds: The Fascinating Frog World of Agumbe

A variety of amphibians reveal themselves on a night trail through the monsoon forests of Agumbe

By Dr. Seshadri KS

Growing up, the only connection I had to Agumbe was the sound bite that it is the wettest place in South India. Only many years later, when I stood there soaked to the bone, in the approximately 7,000 mm of annual rainfall it receives, did I realise what that meant. I was accompanying my PhD advisor Dr David Bickford and his colleagues to the Agumbe Rainforest Research Station (ARRS), established in 2005 by Rom Whitaker, fondly called the snake man of India.

Located in the central Western Ghats of India, the forests of Agumbe are known to be an exceptional repository of some of the most biodiverse  and unique plant and animal life in the world. Photo: Pradeep Hegde </br> The Malabar gliding frog has suckers at the end of its toes that allow it to get a firm grip around a twig. Photo: Saurabh Sawant

Located in the central Western Ghats of India, the forests of Agumbe are known to be an exceptional repository of some of the most biodiverse and unique plant and animal life in the world. Photo: Pradeep Hegde
The Malabar gliding frog has suckers at the end of its toes that allow it to get a firm grip around a twig. Photo: Saurabh Sawant

Located at the edge of Someshwara Wildlife Sanctuary, a mud road makes its way through the jungle. We were forced to stop and cover the last mile on foot as a small rivulet cut the road in two. Reaching the station, we were greeted with barking by a dog with an antipathy to people with bags, but who was otherwise very friendly. The all all-enveloping darkness welcomed us too; ARRS runs on solar power and electricity was a rare commodity during the monsoon. With the incessant rain and a chorus of frogs in the backdrop, we hit the bed, only to be woken up at daybreak by the song of the Malabar whistling thrush.

Found in the Western Ghats and parts of central India and the Eastern Ghats, the Malabar whistling thrush reveals its brilliant blue hue only under sunlight. Photo: N.A. Naseer - CC BY-SA 2.5

The rain lashed through the day and we spent the better part of it sipping sugary coffee. When it stopped for a short while we stepped out to explore the landscape and trekked to a nearby waterfall. In the evening we prepped our headlamps to go and look for frogs that were seemingly everywhere. One of the first frogs we encountered was the Rao’s intermediate golden-backed frog (Indosylvirana intermedius). These frogs are about the size of an adult thumb, have a golden back, and are abundant in waterlogged paddy fields.

Rao’s intermediate golden backed frog is very active during monsoon nights. Photo: Dr. Seshadri KS

They often congregate in groups over 20 individuals and emit a ‘chuck’ call. While we stood listening to the ‘chucks’ a loud ‘trroooonk…… trrooonk’ call was heard from across a ditch. Stepping carefully, I shone the light from where the loud call originated and it turned out to be a gorgeous Indian bullfrog (Hoplobatrachus tigerinus). These are the largest frogs we get in India, often larger than our palm. While the females are drab brown with black spots, the males change colour during the breeding season, turning into bright yellow, with a cobalt-blue vocal sack. We still do not know why they change colour, but it is presumably a signal to other individuals. These frogs congregate in groups of 20-50 frogs to breed and lay hundreds of eggs.

These are the same frogs that were once relentlessly persecuted for the infamous frog leg trade as well as for dissections in biology labs. Now, the frog leg trade banned and so are dissections and despite being listed in Schedule I of the Wildlife Protection Act 1972 (WPA), they continue to be caught and sold illegally as “jumping chicken” in several parts of India.

Preferring freshwater wetland and aquatic habitats, the Indian bullfrog (left) is the largest frog found in India. Photo: Shreeram MV
Tadpoles of the ornate narrow mouth frog breed in pools of rainwater and other still water bodies. Photo: Dr. Seshadri KS

Moving away from the waterlogged paddy field behind the ARRS dormitory, we stepped onto a narrow path which led to a stream. We saw something slither on the ground and assumed it to be yet another snake. But on closer observation, we were surprised to find it was a caecilian. Amphibians are of three kinds: frogs and toads belong to the group Anura, meaning those without a tail; salamanders and newts belonging to Caudata, meaning an obvious backbone; and Caecilians belonging to Gymnophiona, meaning naked snake-like amphibians. In India, there are only two kinds of salamanders, found only in the Himalayas. Caecilians, though common, are rarely encountered in the Western Ghats. They lead a mysterious life underground. On the rare occasions they do emerge they have been seen hit by speeding vehicles on roads. As we watched what looked like the Bombay caecilian (Icthyophis bombayensis), it slowly slithered away into the leaf litter.

Resembling large worms, caecilians are a group of limbless amphibians that spend a large part of their lives underground. These caecilians (left and right) belong to the genus Ichthyophis. Photo (left): Saurabh Sawant, Photo (right): Dr. Seshadri KS

As we got up to leave, we spotted a tiny frog, about half the size of our thumb making a sharp ‘zzzzrrrrr’ call. Crawling on all fours, I uncovered some leaves to see a frog with a brown body and ivory undersides. This turned out to be the Sahyadri cricket frog (Minervarya sahyadris) described only in 2001.

In the biologically rich Western Ghats, scientists are continuously discovering new species. The Sahyadri cricket frog, whose colour varies from brown to red, was identified on the basis of specimens collected from Karnataka and Kerala. Photo: Dr. Seshadri KS

After taking some pictures of this frog, I got up to leave and suddenly heard the calls of the water drop frog (Raorchestes nerostagona). This frog is the only completely canopy dwelling frog of the Western Ghats, which never gets to the ground. It belongs to the group of shrub frogs which lay eggs away from water, which undergo direct development into baby froglets, skipping the free-living tadpole stage. This unique adaptation has let these frogs move away from water and occupy hard environments like the forest canopy. Despite searching for this frog for over an hour, we could not see it and we moved on to the stream which was overflowing in full fury.

The water drop frog’s call resembles that of a drop falling into water. It is also known as the lichen bush frog, owing to the cryptic pattern (right) on its skin, which seems like lichen on a tree. Photos: L. Shyamal - CC BY-SA 3.0

The downpour ceased momentarily, and whilst we were looking for frogs in the stream we heard a loud ‘kkeeeeee’ call. We knew this was not a frog, but a slender loris. Looking up into a tall tree, we spotted two gleaming eyes. One thinks of them as slow-moving animals, but they are surprisingly quick and the one we spotted, quickly disappeared into the thick foliage.

Amidst the night-time orchestra of frog calls, one may hear the rare high-pitched screech of the slender loris in Agumbe. Photo: Kalyan Varma - CC BY-SA 4.0

Content with the sighting, we moved only a few steps when we heard a loud sound which made us stop on our tracks. As we looked up, a large tree began to tilt and came down right at us with a loud ‘krrrr-wooosh’. The adage, “If a tree falls in the forest, nobody knows” is an absolute lie. When a tree falls in the forest, it brings down a few other trees with it and the sound is heard over a kilometre away. We did not want to get caught under the falling trees and ran for our dear lives. When the commotion ended, we used our lights to tell each other where we were. Soon we realised that our group of four was split in two and one was hurt as he ran into a tree. After we managed to regroup, we realised that we were now lost. The trail on which we were supposed to go was nowhere to be found. The downpour had started too, making it all the worse. Trudging slowly but deliberately, we eventually found a road that would lead us to the field station after two hours of going around in circles.

The saving grace in all of this was that on our way back, we ran into another unique frog, the Malabar tree toad (Pedostibes tuberculosus). It is listed as critically endangered and included in the Schedule I of the Wildlife Protection Act of India. The frog gets its name from the fact that its back looks like a tuberculosed lung. Over several decades, the frog was never encountered. Recent observations indicate that the toad is arboreal in habit and is actively calling before the monsoon, starting from March. During heavy rains, they descend from the canopy and call in groups of 5-20 individuals.

The arboreal Malabar tree toad is seen only during the monsoon, after which it mysteriously disappears. Photo: Dr. Seshadri KS

Is all well in paradise?

Over the last two decades, our knowledge of amphibians has grown exponentially. Over 150 new species of frogs have been discovered, many of them from the Western Ghats. While such discoveries are absolutely necessary, there exists a large gap in the knowledge about the species ecology. We don’t have an answer to a simple question: What is the lifespan of a frog? While such information sounds trivial, it is important when we are attempting to conserve them.

For example, we know about 30 species of amphibians are found in the Agumbe landscape, but we know the ecology of only 5-6 species. For the rest of them, we do not know where they breed, what they feed on, or what habitats they need to survive. An ever-increasing human population, has destroyed natural habitats, and fragmented our landscapes. Roads, for example, are a huge threat to the amphibians of Agumbe.

With the introduction of more roads and vehicular traffic cutting through the landscape in Agumbe, frogs like this Malabar gliding frog, and other wildlife are at severe risk and often end up as roadkill. Photo: Dr. Seshadri KS

We have repeatedly shown that roads cause mortality among smaller organisms like frogs, and studies in Agumbe have shown road mortality of frogs going up to thousands of individuals every monsoon. Yet recently, the road from Thirthalli to Agumbe has been doubled, causing large-scale destruction of habitat. Coupled with this is the mindless abuse of pesticides. While pesticides do kill pests, they often have catastrophic effects on other organisms like frogs which naturally consume pests.

There are many ways in which we could conserve the wonderful world of amphibians. It would need to start with learning about them and acknowledging their presence; for we will not conserve what we do not care for. It is time that we let amphibians one leap closer to our hearts. It would a sad world to live in without the night-long symphony of the wonderful creatures we call amphibians.

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