Frogs and Toads Recorded in Karanji Lake Premises
Dr. Pranjalendu Ray, Scientist-in-charge, RMNH, Mysore
(An article that appeared in SPOTBILL, an occasional publication of the Mysore Amateur Naturalists, May 1999 is reproduced here. Courtesy: Sri Manu K, MAN)
Warty dry skinned toads and smooth slimy frogs are well known creatures which show their presence around aquatic habitats during the monsoon. Their chorus call in the evening forecasts rain and is specific to the humidity and temperature of their surroundings. The exact role played by these creatures in relation to natural history is not well studied in India, despite the fact that they are an extremely important animal in laboratory work, in the spheres of anatomy, physiology, developmental biology and more recently the study of ozone depletion. We are still in our infancy as far as understanding amphibians goes. Several specialists have contributed tones of information regarding identification, osteology and developmental studies of amphibians, yet an amateur finds it difficult to identify the common species around his neighbourhood. Without proper identification, it is difficult even to start any impact assessment or conservation strategy for any living component on this earth. Animals of this phylum spend part of their developmental stages in water and the rest on land. They are often confused with amphibious animals which can live on land and water. To be clear, amphibians are the first vertebrates which evolved from fish-like ancestors, about 350 million years ago in the Palaeozoic era. Prehistoric studies based on fossil records reveal that to avoid competition with large fish in a shrinking water habitat, a group of lobe-finned fish evolved into four-limbed lung breathing vertebrates. The abundance of insect life on land also prompted these coldblooded creatures to become the forerunners of present day amphibians. The environment brought about several adaptive modifications to survive on land. It is well established how over the course of millions of years the paired fins were modified into pentadactyle limbs; gills to lungs and so on.
Most of the species are restricted to selective microhabitats of the North-eastern region and the Western Ghats of India. Noting much has been done except the naming of most species. The need and scope to study their biology is still wide open.
Amphibians depend on glandular permeable moist skin for cutaneous respiration. So lack of moisture may lead to instantaneous death. There is a remarkable difference between the tadpole and the adult. The tadpoles breathe with the help of gills whereas the adults respire through lungs, bucophoryngeal and skin. All Anurans have a species-specific call to attract females of their kind. Once he finds a receptive female, the male rides paddy-back on her towards water to mate. The female produces spawn, which is externally fertilised by the mate. Water acts as a nurturing ground for the developing embryo. While developing through larval stages they more-or less look like fish. Their feeding habit is also entirely different from that of adults. Tadpoles feed on various water-borne organisms by rasping with the help of their oral structures. The long digestive canal gives them a continuous supply of food for their growth. The tail helps their movement in water while the spiracle helps to expel water from the gill chamber. Each species has a different adaptation and preferred micro-habitats which never overlap. Hence tadpoles clearly give the telltale signs of their adults, if studied properly. As adults, they have better locomotion with the help of two pairs of limbs. However, their laborious mode of locomotion and their very selective environmental preference limit their migratory power. The reduction of aquatic habitats and pollution are a major threat to these creatures. The wheels of progress are causing a tangible loss of several thousands in 16th July 1997, 62 pairs of toads were counted, squashed to death in a span of less than 100 mtrs on Vinayaka Road, Siddartha layout. These slow-moving, rather crawling bufo species usually come out of their burrows or crevices on rainy nights to elect water-bodies for mating. They move about to find a wider choice of mates and often have to cross the roads to find new habitats. The motorable roads when wet appear like canals which tempt the mature toads as an ideal breeding place with disastrous consequences.
Each adult female lays 15-20 thousand eggs per season. Their survival rate to larval stage is 70-90% and the tadpoles swarm in thousands in their water-bodies. They feed on vast quantities of insects controlling a teeming population which would otherwise cause severe damage to the green cover. Their capacity to regenerate lost tails and limbs during this stage is unique to amphibians.
The study of amphibians touches every sphere of ecology as their lifecycle encompasses both water and land habitats. The present-day man-induced problems like pollution, salinity, and the indiscriminate use of pesticides and fertilizers are threatening mankind and natural history as well. The acid rain allows the aluminum present in the soil to dissolve in waster and kill the embryos of fish and frog. Hopefully much can be alleviated if we carefully study the effect of changes in the environment on these helpless animals. A brief guideline based on first-hand knowledge is incorporated for the benefit of readers to understand the usefulness of Anurans.
In July 1993 I began a study of frogs & toads on the campus of the Regional Museum of Natural History. This institute has an ideal setup amidst natural surroundings with the backdrop of Chamundi hills. Apart from its realistic indoor environmental exhibits, it nurtures a wide variety of flora and fauna on the campus.
During the four-year study a total of eleven species were recorded within a 4.5 acre plot of land on the Campus. From 93 to 95, I used to see all eleven species between May-September each season. Since then there has been a change of landscape, in order to keep the campus aesthetically appealing. As a result, only six species are seen now. It is a sad irony that a number of species fell victim to the process of establishing an institution intended to create awareness about the environment. Nevertheless, despite the development of museum, its surroundings continue to offer a beautiful intricately-balanced natural network of different soil, water, plants and animals.
The living amphibians are grouped under Urodela (Latin cauda=tail) which consists of newts and salamanders: Anura or Salientia (Greek anura=tailless) (Latin salieus=leaping) consists of toads and frogs; lastly Apadons or Caecilians which are worm like animals and are restricted only to the moist soil in the tropics. Of the 206 species of amphibians in India, there is only a single salamander, found exclusively in the North Eastern states of Sikkim and Arunachal Pradesh. There are 14 species of Caecilians of which 12 are from the Western Ghats and 2 from the North East. The remaining 191 species are Anurans.
The general term Anuran is applicable to all tree frogs, burrowing frogs and toads, which can be classified as follows: (Family-wise breakup of Indian Toads and Frogs only)
- Pelobatidae - 6 species
- Bufonidae - 21 species
- Hylidae - 1 species
- Microhylidae - 15 species
- Ranidae - 98 species
- Rhacophoridae - 45 species
RMNH campus amphibian diversity comprises four families under seven general and eleven species as below;
- Bufonidae – Bufo fergusonil, Bufo melanostictus
- Microhylidae – Microhyla ornate, Kaloula pulchra, Ramanella variegate, Uperodon systoma
- Ranidae – Rana cyanophlyctis, Rana crassa, Rana limnocharis, Rana tigerina
- Rhacophoridae – Polypedates maculates
Snout rounded or truncated; limbs rather short; teeth none. Tongue elongate-ovate, entire and free behind. Parotoids very distinct, swollen; skin more or less warty. Openings of the eustachian tubes of moderate width. Fingers quite free; toes generally half webbed, sometimes entirely webbed. Males generally have a single vocal sac, which is not visible externally. Warty skin with parotoid glands on back, Tympanum distinct. Skin on skull strongly adheres with bone. Two species were seen in the campus. Both are very common and many juveniles were seen from May to September on moist grassy patches. At night under illuminated lamp posts, they feed on insects which are attracted to light.
Common Toad Bufo melanostictus:
Adult size varies from 6- 12 cm. Males are smaller than females and more colorful. Though all look dirty, yet they control maximum terrestrial insects and preferably ants during juvenile stages. Black-headed egg strings are a common occurrence in any water pool during June-August. It takes 32- 35 days from eggs to miniature toads. Black tadpoles in stagnant water bodies cleanse the dirt, algae-infested bottom, and sometimes they consume all dead animals, even dead frogs and toagds, Millions of them collectively purify the stagnant water pool.
Toads have skull with black cranial ridges near eyelid and nostril with broad tympanum which is more than two thirds of eye diameter. Parotoids are longer than wide and two parallel rows of warts or dosomedial aspect is distinct from all other species. During breeding season 1st finder or thumb bears nuptial pad.
Furguson’s Toad Bufo fergusonii
Difficult to differentiate from Bufo melanostictus but with experience and close observation, it is possible to recognize them. First of all tympanum half the diameter of the eye and marbled bands on thigh are distinct. Juveniles are colorful with red and brown patches on dorsal side. The tadpoles are similar – but oral structures are different and need magnification to distinguish them from others. Regular observation and study of the egg-laying pattern and calling pattern may help field biologists to distinguish better than available information.
Head small, with rather pointed snout; mouth narrow; body thick; upper arm and thigh rather short. Teeth none, in jaws or on the palate. Tongue elongate, ovate, entire behind. Tympanum hidden; openings of the Eustachian tubes very small. Skin smooth; fingers free, toes one-third webbed; metatarsus with two obtuse tubercles. Male with a single subgular vocal sac.
Small Indian Ornate Frog Microhyla ornata:
Colorful in appearance, size varies from 2 – 3 cm. Dorsally smooth, earthy brown colouration with a typical darker pattern continues to the leg. Only come out from hiding places at night during breeding season. Termites are favorite diet. Very agile. Advertising call of male in comparable to violin rubbing the card.
Indian Painted Frog Kaloula pulchra:
Size 5-7 cm, pink to red with speckled brown patches on dorsolateral side. The tip of fingers with disc and four fingers directed towards climbing surface. Basically burrowing in nature but expert climber also. One was collected from tree-hole at a height of 6 ft.
Marbled Balloon Frog Uperodon systoma:
Distinctly different from all other species by the presence of chocolate to dark brown network on dorsal side. Hind foot has got spade-like burrowing metatarsal tubercle. These frogs are backward burrowing in habit, always conceal themselves in loose soil.
Marbled narrow-mouted frog Ramanella variegate:
Attain 3 – 4 cm in length, look similar to Uperodon systoma in respect of color pattern but smaller in size without spade like structure. Finger tips dilated like that of Kaloula pulchra, but differs in smaller size without color patch. With a little experience, one can differentiate them from two other allied species and these frogs breed first during first monsoon shower.
Fingers quite free, none of them opposed to the others; toes webbed; head covered with skin. Vomerine teeth in two series of groups; tongue large, oblong, free and deeply notched behind. Metatarsus with one or two blunt tubercles.
These frogs vary in size from 4 – 9 cm. and always float on water and catch insects on the surface of water. Sometimes they jump instantaneously and catch the prey with the help of wide sticky tongue. This is the only frog which can tolerate extremely polluted water near human habitation. Most probably due to their food preference they devour many water-loving insects including the mosquito which is abundant in sewage/ stagnant water. Tadpoles also feed on various insect larvae including mosquito larvae.
Common Bull Frog Rana tigerina
This is the largest and heaviest frog in India. IT can consume whatever it can overpower. E., small rats, nestlings of bird, small grass snakes, crabs, etc., apart from usual diet of slugs and insects. Large size with green and light golden yellow dorsal colouration makes its identification easier. Only confusion arises with neighboring species Rana crassa which can be differentiated only by smaller hind leg with a spade like inner metatarsal tubercle for doffing. Both share similar habitat near banks of waterlogged area. Due to their muscular hind leg being perceived as a delicacy by Europeans, these frogs were indiscriminately collected, slaughtered and exported to fetch foreign currency. In 1973, Indian exported 26, 97,601 Kgs of processed frog legs to the USA. After its ecological importance was understood collection and export was officially banned in 1980. Since then the population has not been assesses. But due to overuse of pesticides and fertilizers in and around cultivated land, these delicate frogs are dwindling in numbers near agricultural fields.
Jerdon’s Bull Frog Rana crassa
Overall appearance similar to Rana tigerina and to some extent R. hexadactyla but differs by its stouter and shorter hindleg. A spade-like metatarsal tubercle on hind foot helps in digging loose soil near water. Toes interconnected with broad complete webbing. Males during breeding season show thickened thumb. Food mainly larger grasshoppers, beetles, snails etc.,
Paddyfield Frog Rana limnocharis
Very common. With or without broad yellow vertebral line can be located in grassy patches near water pools. Males of these grogs usually start calling at a time of day when humidity is 74% and above with temperature ranging from 21 -24 ° C. Shrill Trr – Trr – Trr is usually heard but it is hard to locate them due to their cryptic colouration and inconspicuous nature. When disturbed they immediately jump into the water and stay at the bottom for at least 3 – 4 minutes. Nevertheless most common and easily seen frog in water is the skittering frog of India.
All tree frogs in India grouped under this family. The frogs depict green, grey, brown, yellow colouration in life. Shows change to colouration according to the surrounding habitat. Sometimes can be seen in moist corner of damp toilet or bathroom in dry season. All the fingers and toes bear a disc like pad which helps in sticking on any surface. Pads on end of toes act like suction cups to help tree frogs climbing on vertical or horizontal surfaces. Egg laying habit is arboreal; a frothy mass adhered to ventral surface of leaves, over hanging on waterlogged area and tadpole continues to grow in water rich in organic substance. Only one species recorded from study area.
Common Tree Frog Polypedates maculates
Usually 4-7 cm long. Brown to cream-colored with yellow marbling on hind thigh and waist area. Long hind leg helps in jumping from one tree to another. Male advertising call Tok, Tok, Tok-Tok Tok.
There are many more known facts interwoven around frogs and toads and many more to be discovered. However, I am confident that the readers would find out relevant information on these amphibians and take up observations to explore the vital ecological role played by these coldblooded amphibians in and around any neighborhood.