The Bicoloured Frog's Wedding Suit

The polka dots had thinned into the skin. The blacks had greyed into sallower shades. But the red-rimmed eyes still gleamed like rubies. Here was the Bicoloured Frog again, dressed for its wedding party

Bi-coloured Frog (Clinotarsus curtipes).

In early June this year, just as Agumbe awaited the deluge of the southwest monsoon, we visited the Agumbe Rainforest Research Station there. You might remember that we had posted an encounter with the polka-dotted Bicoloured Frog (Clinotarsus curtipes).

In his Book of Indian Reptiles and Amphibians, J C Daniel mentions that the species begins to breed with the onset of the southwest monsoon and tadpoles can be sighted in plenty in April, May and June. However, in Agumbe, none of the frogs we encountered displayed any hint of breeding colours.

The Kulgi Nature Camp abutting the Dandeli-Anshi Tiger Reserve (15°16'01"N 74°37'01"E), with its broad-leafed north Western Ghats moist deciduous forests, is drier than Agumbe (13°30'30"N 75°5'45"E) and the monsoon had receded by early October, though thundershowers staged a mock-charge in the evenings.

Agumbe, June: Bi-coloured Frog in non-breeding colours

The forest floor was not just a lot drier, the leaf litter was much less than at Agumbe

It was mid-morning and we were out birding along the Birder's Trail near Kulgi Nature Camp, having just enjoyed watching a mixed hunting party -- Velvet-fronted Nuthatch, Paradise Flycatcher, Scarlet Minivets, Brown-capped Pygmy Woodpecker, Greater Flameback and Common Iora -- and a much-relieved Sandy commented on the uncharacteristic lethargy of the leeches (there was to be no nightmare-induced macabre storytelling tonight). And then a casual glance at the forest floor revealed this treasure.

Creamy yellow upper body with prominent black dots

The upper body is bright golden-yellow and the dots have almost faded off

The transformation was remarkable. The dots on the upper body had almost faded off and the yellow was much brighter -- almost golden. The sharp division between the coloration of the upper and lower parts of the body remained but the glistening black limbs were now brown.

The black limbs have turned brown

The white patch that ran from the snout towards the eye was now yellow and a small black band separated it from the greenish-yellow (almost olive) skin of the sides, which now displayed a dual coloration -- a change from the uniform black of the non-breeding form. The most remarkable change, however, was the white-blotched grey of the frog's underside and the lower half of the belly between the fore and hind-limbs. It gave the frog's underbelly and sides a rather lichen-patched texture (less on the underbelly than the sides of the lower belly), perhaps a useful camouflage from slithering predators on the forest floor.

The large red-rimmed eye still glowed like a ruby.

Notice the lichen-patched texture of the underbelly that was uniform black before breeding commenced

Behaviourally the frog did not seem to have changed much. It was solitary, did not call, and was not jumpy or nervous. While we photographed, it stayed put, only taking a single jump if we stepped too close. 

It did seem a bit late in the season, but the forest had several wet patches and we hoped that somewhere, not too far away, was another individual of the species. Of the opposite sex.

Text and photographs by Sahastrarashmi

Encounter: Bicoloured Frog

It's tiny and blends in completely with the leaf litter but once you spot it, the Bicoloured Frog is unmistakable

The southwest monsoon has just set in and the entire forest is dripping wet. The dimly lit floor is an abstract mosaic of rust, maroon, brown, beige, green and black – leaves in all stages of decomposition, slowly turning into soggy mulch. An occasional vein of green moss on a tree buttress glows iridescent under a rare shaft of sunlight. Fungi sprout everywhere feasting on death and decay. Every tentative footstep encounters leeches – tiny cold-blooded filaments swaying in the stagnant and humid air, relentlessly in the hunt for the iota of warmth that our feet radiate, setting them off on a determined somersaulting advance. Rotting twigs and branches give way at the slightest footfall and the soft murmur of rain on the dense closed canopy is a permanent hum in a forest which is otherwise silent, at least until nightfall provides the cue to lovesick frogs and crickets.

We are on the lookout for the Hump-nosed Pit Viper but instead we sight the Bicoloured Frog. It, too, is wet and soaked, motionless until it notices us with its large, round, red eyes, which are well adapted to sight in the semi-darkness of the rainforest. 


True to its name, the predominant impression of the Bicoloured Frog (Clinotarsus curtipes), is the neat division of the colouration of the upper and the lower halves of its body. The upper half (which has been described as grey or brown) is cream-coloured, tinged with yellow resulting in a very light shade of brown that matches the surrounding leaf litter. The lower half of the body is glistening black with no banding on the limbs. Seen in dimmer light the glistening back gives the impression of deep beige. 


The nostrils are very close to the mouth and the tympanum, present on the black half of the body and hence not very easily seen, is as large as the eye. The size is approximately 7 cm and the snout is pointed. The backs of all the four or five frogs that we encountered bore randomly distributed black spots, providing excellent camouflage in the leaf litter. The spotting on the back may or may not be present on individual frogs though all the frogs that we encountered had them.

While we photographed the frog – almost lying on the ground for an eye-level view (an act of extreme gallantry considering the omnipresent, ever-flipping thirsty-for-blood leeches) the frog was moderately alarmed and tried to move away, on one occasion walking up using its limbs, but was not unduly shy, never taking more than one hop. Clinotarsus curtipes seemed to be fairly common but none happened to be in breeding colors yet.

The IUCN status is Near Threatened, primarily on account of habitat loss. Clinotarsus curtipes is a terrestrial leaf-litter frog but has webbed toes and enters the water only during the breeding season. It adapts well and is found in different forest types -- evergreen, semi-evergreen and deciduous. In the breeding season the frog acquires a ruddy disposition with the black receding out from the sides and the underside becoming very dark, almost black. The vocal sac is internal. As in a lot of frog species the female is larger than the male. J C Daniel notes that the dispersal of young frogs is very orderly and almost battalion-like. 

The spots, like the stripes of the tiger, can be distinctive and are used to identify individual frogs during density surveys. The spots are also a good aid to locate the frog since an uncannily well synchronised set of polka dots hopping on the forest floor give away an otherwise excellent camouflage.

Read more Agumbe Diaries
Text and photographs by Sahastrarashmi 
Photograph of the breeding male by L Shyamal (Wikipedia Commons)