Scared to leap

Amphibians in India are besieged by numerous threats

Published: Thursday 31 May 2001

-- The Himalayan newt, also called the Indian salamander, takes shelter among bamboo stumps in and around the hills of Darjeeling. It lives close to calm and still waters. During the monsoons, it feeds on algae, water beetles and bugs. After the showers, it leaps down on insect larvae, snails, slugs and earthworms. During the dry period of the year, it manages just as well by eating termites, wood lice and insects infesting rotting bamboo stumps. Its voracious appetite helps keep a check on the bugs in the area. But the newt, the only one of its kind in India , is itself threatened with extinction.

Ritwik Dasgupta, professor at the department of zoology, Darjeeling Government College, lists numerous threats to the newt. An increasing number of cattle graze in its habitat. Grazing loosens the soil, causing siltation in the water ponds. The Indian salamander, exists only in stagnant water, finds its haunt destroyed. Then, freshwater fish introduced in the ponds eat the newt's eggs. If that isn't enough to annihilate the species, the area is drained for supply of water and agriculture. Rock-blasting and quarrying takes place close to their habitat while roads criss-cross through the region. The newts scramble around, only to be crushed to death under the vehicles rushing by. For a species that is on the snack list of snakes, lizards, small animals, fish, diving birds, and even other hungry frogs that eat the eggs, it is truly besieged.

So are more than half of the 217 species of frogs, toads, salamanders (amphibians with tails) and caecilians (amphibians without legs) found in India.
Biomarkers Amphibian means 'double life' in Greek, a reference to the fact that they dwell as merrily on land as in water. But, that also makes them twice as vulnerable. Any change in land or soil conditions or the quality of water affects them. The 5,000 odd species of frogs, newts, toads and caecilians worldwide act as biomarkers -- creatures whose condition indicate the health of the environment -- because of their unique physiology and habits. Living in moist regions, they breathe through their skin as well as absorb water through it. The amphibian skin does not have a shell to protect it from the vagaries of nature. In fact, the skin layers become weaker and more vulnerable during winters and spring, seasons that overlap with the egg-laying period of most species. Any pesticide or fertiliser residue that seep into waterbodies in the amphibian habitat can easily permeate through the sensitive skin of the inhabitants. Heavy metal residues and effluent from industry, untreated sewage and other pollutants, all easily make it into the frog's defenceless body, killing it or leading to mutated offspring.

Even salty water is harmful for the amphibians. One per cent salt by weight in water can kill the eggs and larvae of frogs. The amphibian eggs, laid in large numbers and usually covered by a gelatinous layer, are just as sensitive to the conditions around them.

The acidic level of the soil and water in the habitat is crucial. A slight change in the p h level (which is a measure of acidity) can be fatal. Marc Brodkin, researcher at the Widener University, usa, and Martin P Simon, researcher at the Benedictine College, usa, have shown that alteration in p h levels of water in which frogs dwell makes them susceptible to bacterial attacks and ultimately kills them. The bacteria colonise the spleen, reducing the white blood cell efficiency.

The toads' croak tells us more than the myths attribute to it. Their nocturnal low-frequency cacophony, a part of the mating ritual, not only announces monsoon's arrival, it also assures that all is hunky-dory in our backyard; there isn't an overdose of pesticides, acidic or malaria-infested water ponds anywhere near.
In India But, all is not well in our backyards. In fact, the picture for the entire country is a grim one. The way things stand, many amphibians may not survive for long. A survey carried out during the Conservation Assessment and Management Plan Workshop for Amphibians of India in 1998, using techniques developed by the Conservation Breeding Specialist Group of iucn (World Conservation Union), has shown that 48 per cent of all species in India and 59 per cent of endemic species in India are threatened.

The greatest threat to the amphibians in India is from the destruction and alteration of their habitat. Frogs and toads inhabit relatively smaller areas, what scientists call microhabitats. A minor change in the niche and the beleaguered frog or toad can end up on the threatened species list. The effect on the amphibian population, at times though, is not immediate and takes several years before one becomes aware of the ill consequences.

Western Ghats, which are home to about 60 per cent of Indian species, are a perfect place to study the threats faced by amphibians. Numerous species enjoy the dense canopy cover that keeps the temperatures down in the forest under-story, allowing frogs, such as the narrow-mouthed Microhyla ornate, to take advantage of the shade and rummage through the litter for food during the day. But when people move in and remove the thick layer of dry leaves and fallen twigs, much of the amphibian life is inadvertently destroyed. Logging and illegal felling is catastrophic for these species. To compound the danger, chemical fertilisers, pesticides and factory waste from tea and rubber estates find their way into the clear perennial streams, turning the streams into turbid seasonal ones and making them uninhabitable for the amphibians. A known example is that of the bronzed frog ( Rana temporalis ). It used to be widely seen in the clean perrenial streams of the Keeriparai and Mararmalai, in Tamil Nadu, but is now hard to come by in the waters of the region which are putrified by the waste from rubber plantations.

"One can find many mutated frogs and toads across the country," says Sanjay Molur, co-chairperson for the Declining Amphibian Population Task Force for South Asia. With a limb less or a limb more, these mutated progenies of pesticide-infected frogs tell the sad tale of their ancestors, who gobbled bugs by squeezing and pushing their eyeballs down while gulping but couldn't digest the chemical soup dished out by humans.

Toad killers
Unlike the frog, which jumps, leaps and hops with freedom, wherever man treads, he builds a road. The number of frogs killed on roads close to their habitats is astounding. In a single study, conducted by Karthikeyan Vasudevan, herpetologist at the Dehradun-based Wildlife Institute of India ( wii) , in 170.7 kilometre-days (kilometres multiplied by days of observation during the study) 311 amphibians were found killed on one particluar road running through the Western Ghats. The study projected that for each kilometre of the road, a toad is killed every 28 hours, and a frog every 31 hours.

Roads, pesticides, fertilisers, pollutants and habitat fragmentation are the visible threats to amphibians. There are threats that may not be so evident but are as lethal, such as Chytridiomycosis, a recently discovered disease known to cause mass deaths in amphibian species in different parts of the world. It has yet not been detected in India. Molur says, that doesn't mean that the pathogen isn't present in India. Other diseases, like ranaviral, also pose a threat. Ranaviral is caused by a few closely related species of viruses of the genus ranavirus. It causes skin ulceration in tadpoles, metamorphs and adults and can be fatal. Other threats to the amphibian populations that are yet to be studied in India include the increase in the uv (ultraviolet) radiation due to the depletion of ozone. Studies show that frogs and toads cannot survive increased exposure to uv light. Bivash Pandav, herpetologist at wii, says increased uv radiations could be the cause of the huge fall in amphibian population in the Kargil area of Jammu and Kashmir. Sanjay Molur concurs, though both point out that studies are yet to be conducted to confirm this.

The study of amphibians in India is, relatively, still in infancy. Efforts like those by the South Asian chapter of the Declining Amphibian Population Task Force are helpful to piece together a larger picture. Individuals do carry out research across the country, finding nuggets of information here and there. A prudent combination of studies, inventories and systematic surveys, says Molur, is the need of the hour. There is a lot that needs to be done or the toads will no more be recalled in the myths of tomorrow as the harbingers of monsoon.

Subscribe to Daily Newsletter :

Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.