It is unbelievable but true that there exists an interesting group of frogs that spend their entire life on leaves, small branches of shrubs, or on trees. They are commonly known as Tree Frogs and Bush Frogs. However, other species like Nyctibatrachus petraeus (Castlerock Night Frog), Uperodon mormoratus and Indirana semipalmata can also be called arboreal, as during the breeding season, they try to climb trees, shrubs or walls.

Though the southernmost areas of the Western Ghats (Kerala and bordering Karnataka) are richer in terms of amphibian diversity, Castlerock holds its own. Castlerock is a small village in North Karnataka, in the Western Ghats of the Dandeli-Anshi (now named Kali) Tiger Reserve. It owes its importance to the railway line connecting Karnataka to Goa, and the famous Dudhsagar Falls that fall majestically near the railway track. Amongst snake and frog enthusiasts too, it is a favorite destination, holding the promise of more species waiting to be discovered.

Arboreal frogs have some peculiar adaptations in their feet, suited for living on trees. Their fingers and toe-tips have dilated adhesive disks (not suction pads) that are used to climb on trees, bushes and rocks. These disks are lined by columnar cells with flat tops and small gaps lubricated by mucous. On pressure, the cells get a grip on the irregularities of a surface and are thought to be maintained by surface tension. The frogs’ hind legs are thin, long, and less muscular than those that are needed to jump about on land or swim in water.

Pseudophilautus wynaadensis (Wayanad Bush Frog / Dark-eared Bush Frog), one of the arboreal frogs found in Castlerock.

Pseudophilautus wynaadensis (Wayanad Bush Frog / Dark-eared Bush Frog), one of the arboreal frogs found in Castlerock.

It is indeed thrilling and tedious to search for these arboreal frogs. It is easiest to find them during the monsoon (their mating season), soon after dusk, when they descend to low heights and are vocal. However, tracing them by their calls is quite tricky due to ventriloquism-like effect (since they have a circular, inflated vocal sac, their sound appears to come from all directions, making it difficult to find them). Also, they become silent on detecting strong light.  With practice, they may be detected by their eye gleam, using a thin-beam torch. Knowing their habitat and life-cycle is helpful in finding them and photographing them at their best.

In the Western Ghats, we find one family each of arboreal frogs (which include several genera) and arboreal toads. Six species of these frogs and one species of toad are known in and around the Castlerock region:

Family Rhacophoridae

Bush Frogs

Pseudophilautus wynaadensis

Pseudophilautus amboli

Raorchestes  bombayensis

Raorchestes tuberohumerus

Tree Frogs

Polypedates maculatus

Rhacophorus malabaricus

Family Bufonidae

Tree Toads

Pedostibes tuberculosus

Family Rhacophoridae includes five genera in India, of which some species of four genera (Pseudophilautus, Polypedates, Rhacophorus, Raorchestes) are found in the Castlerock region. The fifth genus, Ghatixalus, is only found in the moist, wet high altitude forests of southern Western Ghats of Kerala.

Genus Pseudophilautus (Bush Frogs):

These are small (2.8 cm – 3.3 cm) bush frogs endemic to the Western Ghats. They are found calling from lower tree trunks and leaves early in evenings, after which they start moving upwards. Two species are known from Castlerock, easily recognised by the dark brown colour of the upper 2/3rd of their tympanum (eardrum). They may be coloured greyish, yellow, or brown. Differentiation between them by external morphology and calls is difficult. They are locally quite common, though classified as endangered due to their restricted distribution. They often enter houses, clinging to walls at night, attracted by insects coming to light sources. They lay eggs in wet moss on tree branches. An interesting fact is that their eggs develop into juvenile, fully-metamorphosed frog-lets by directly bypassing the water-living tadpole stage.

Pseudophilautus wynaadensis (Wayanad Bush Frog / Dark-eared Bush Frog) is found southwards from Castlerock to Kerala.

Pseudophilautus wynaadensis (Wayanad Bush Frog / Dark-eared Bush Frog) is found southwards from Castlerock to Kerala.

Pseudophilautus amboli (Amboli Bush Frog) is known from a few localities from Amboli (Maharashtra) to the Anshi region in the northern Western Ghats (Karnataka).

Pseudophilautus amboli (Amboli Bush Frog) is known from a few localities from Amboli (Maharashtra) to the Anshi region in the northern Western Ghats (Karnataka).

Genus Raorchestes (Bush Frogs):

These are the smallest of our bush frogs. Of the 59 species in this genus, 51 are found in the Western Ghats, 1 in the Eastern Ghats, 4 in NE India and 4 in Vietnam, China and Myanmar.

These frogs lay eggs on the ground, under small stones. Like in Pseudophilautus species, the eggs directly develop into adult-like frogs. One of the species noted in the Castlerock region is Raorchestes bombayensis (Maharashtra Bush Frog), 2 cms in size, greyish brown, with a granular skin. Its typewriter-like “tik-tik-tik” call common emerges from shrubs, hedges throughout the forests, and house gardens, earning it the colloquial nickname ‘typewriter frog’.

Raorchestes bombayensis (Maharashtra Bush Frog)

Raorchestes bombayensis (Maharashtra Bush Frog)

Genus Polypedates (Tree Frogs):

One of the species in this genus is Polypedates maculatus (Common Indian Tree Frog / Chunam Tree Frog). A larger arboreal frog (size 7–8 cm) found in forests, grasslands, and agricultural areas, it often enters human habitations and is seen clinging to walls. They are found in many parts of India and are not endemic to the Western Ghats. These descend to ground near small water-bodies, during their mating season in the monsoon.

Polypedates maculatus (Common Indian Tree Frog / Chunam Tree Frog)

Polypedates maculatus (Common Indian Tree Frog / Chunam Tree Frog)

Genus Rhacophorus (Tree Frogs):

The Rhacophorus malabaricus (Malabar Gliding Frog) is a beautiful, large (8 cm) arboreal frog, and a Western Ghats endemic. The term ‘gliding’ refers to its ability to glide in a parachute-like fashion by stretching the webbing between its fingers and toes, while leaping down from tree-tops. Gliding jumps can be an astonishing 9 – 12 meters, up to 115 times its length! 

Rhacophorus malabaricus (Malabar Gliding Frog)

Rhacophorus malabaricus (Malabar Gliding Frog)

In the breeding season (monsoon), pairs mate on low branches or on walls above stagnant pools. The female deposits the fertilized eggs in a foam-like nest made from her secretions. Tadpoles, upon hatching, fall into the water and complete a part of their development in the water before climbing onto trees.

Foam nest being created by a female Rhacophorus malabaricus

Foam nest being created by a female Rhacophorus malabaricus

 

Genus Pedostibes (Tree Toads):

There are marked differences between tree frogs and tree toads (parotid glands, granular skin and differences in their toes and fingertips, to name a few). In tree toads, tips are wedge shaped and not dilated discs.

Pedostibes tuberculosus (Malabar Tree Toad) is a species of tree toad found in the Castlerock region. Small (3.5 – 3.7 cm) and uncommon, it is an endangered Western Ghats endemic. The skin on its back is rough with tubercles and its toes are fully webbed. The best – and perhaps the only – time to see them is during early monsoons in June, near shallow forest streams. This is the only time when they descend from tree canopies for breeding.

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Pedostibes tuberculosus (Malabar Tree Toad)

 

Getting there and Accommodation: Castlerock Railway Station is easily accessible by train or bus from Belgaum and Dandeli. The nearest airports are at Panaji and Belgaum.

Castlerock Adventure Camp and the PWD Guest House are possible accommodations at Castlerock. Whistling Thrush Homestay, a few kilometres away from Castlerock, is another stay option.