Introduction
Silent Valley will probably remain one of the last important repositories of snakes of the Western Ghats.  Kerala’s rain forests are mere fragments of what they were and India is losing valuable genetic resources as species endemic to this once rich area race towards extinction.
Silent Valley’s size (89 km2), elevation zones (880-2300 m), topography (hills, valleys, streams and rivers), vegetation (grasslands, evergreen and moist deciduous forests) and climate (tropical and sub tropical with heavy rainfall) offer the widest possible scope for reptiles like snakes to exist.  While relatively a few species of snakes have actually been recorded from Silent Valley because so little herpetological survey and collection have been carries out there, there is no doubt that the list of snakes of Silent Valley will grow as more survey work is done by experienced herpetologists.  Aside from the scarcity of herpetological work carried out in the Valley, the fact is that even the most experienced herpetologists find it difficult to locate and capture snakes for identification while working in intact rain forests.  The wealth of habitats that Silent Valley offers its snakes makes it incredibly easy for them to find convenient hideaways when approached.  Hence, snakes remain mere glimpses even for people who are looking specifically for them.
The answer to this problem is to conduct years of continuous survey through all the season, especially the monsoons when snakes are most active and easier to find.  Monsoon in Silent Valley is intense and leeches are plentiful and very few researchers stay there during the rains thereby losing out on valuable information.

The senior author’s personal experience with Silent Valley goes back to 1970 when he first started visiting the area on general wildlife survey work.  He collected the first Shieldtail snake (Uropeltid) to be recorded from the Valley, confirmed the presence of the King cobra (Ophiophagus Hannah) and its main prey, the Rat snake (Coluber mucosus).  Later, in 1990, he found an unidentified water snake in the river Kunthi, but since he did not have a collection permit, the snake was allowed to escape.  It is likely that this and several other new species of snakes will be described from Silent Valley in the coming years when proper surveys are conducted.

Common snakes of Silent Valley

In one of the herpetological surveys of Silent Valley, Murthy (1981, 1986) reported 16 species of snakes.  In addition to these, we confirm the presence of nine more species.  There are only a few species of snakes that could be considered commonly visible in Silent Valley.  The most frequently seen snake is the Rat snake (Coluber (Ptyas) Mucosus).  Growing to 2.7 metre (9 ft.) in length, the Rat snakes in the Silent Valley area – indeed in many parts of the forested Western Ghats – are shiny jet black or grayish black if they are sun and they are common and active by day along streams and in open patches in the Forest.  Rat snakes eat mice, rats, frogs, toads, lizards, snakes, birds and birds’ eggs.

Micro-habitats like the buttresses of large trees, thick layers of leaf litter, rock crevices and bamboo clumps offer perfect refuge for many small snakes.  Among these are the Wolf snakes (Lycodon sp.) and the Pit vipers (Trimeresurus and Hypnale sp.)  A thick layer of leaf litter and loose soil – both typical of pristine forests – afford ideal habitats for small terrestrial and burrowing species like the Kukri snakes (Oligodon sp.), the Shieldtail snakes (Uropeltidae) and the Keelbacks (amphiesma, Macropisthodon and Xenochropis sp.).  Along streams and in cool mossy areas you may see a small Brown snake with black dots and an attractive white or yellow stripe on either side of the face.  This is  Beddome’s keelback (Amphiesma beddomei), a harmless frog and toad eater that may grow to 80 cm.  This snake is easily startled and is incredibly adept at disappearing in the leaf litter.  The Uropeltids or Shieldtail snakes are a fascinating group of small burrowers which are mainly found under rocks and logs.  About 40 species are found in the Western Ghats and each hill range seems to have evolved one or more distinct species.  Shield tails are generally black or brown but often have brilliantly marked yellow or red undersides.  Their skulls are very strong and tightly sutured and their muscular necks can efficiently propel their pointed heads deep into fairly hard soil.  Uropeltids are harmless and feed on earthworms and insect larvae.

The continuous and multi-layered canopy houses a variety of tree snakes which feed on the abundant lizard and bird life attracted there by the seemingly endless supply of insects.  Tree snakes in Silent Valley belong to four genera: Boiga, Dendrelaphis, Ahaetulla and Chrysopelea.  Although most of these species are fairy common, they blend in with the foliage and usually remain motionless to avoid being detected.  The Vine snake (Ahaetulla sp.) is another frequently seen snake, either crossing the path or motionless in a bush along streams, roads or trails.  All the species of this genus have very distinctive, long thin snouts and usually a strikingly camouflaged green body.  Vine snakes have a mild venom with which they subdue lizards and frogs but they are absolutely harmless to humans.
The Cat snakes are nocturnal and are amazingly difficult to spot even with a powerful flashlight.  They are usually seen crossing paths at dusk or inside houses at night.  They often hide in rafters in the roofs of houses searching for geckos and mice.  In 1996, an American visitor in Silent Valley was startled by a snake coiled on the window of her room in the Forest Rest House at Sairandhri.  After the excitement abated, the authors identified the snake as an exceptionally large Ceylon cat snake (Boiga ceylonensis).  This snake grows to 1.5 metre and though it does slightly resemble a Pit viper with its thin neck and triangular head, its very long thin body, tapering tail and protruding eyes quickly identify it as a harmless Cat snake.  Cat snakes, if seen during the day, will be coiled up asleep on a branch or root.  The Large-eyed bronzeback tree snake (Dendrelaphis grandoculis) is another well camouflaged olive brown snake.  We have seen them perched on branches overlooking the path, absolutely motionless. They do indeed have large and eyes and these harmless diurnal snakes are long and tapering like all other tree snakes.

If you walk slowly along stream edges, looking carefully amongst the tangles of roots or bamboo stems bent over the water, lyou may be lucky enough to spot a Malabar pit viper (Trimeresurus Malabaricus).  These area small to medium sized snakes (upto 90 cm long and about 3 cm wide), which are sometimes quite brightly marked.  The over all colour is green with brown and yellow markings, which means that they blend in beautifully with the coloured lichen and  moss covering roots and rocks.  The head of this Pit viper is typically triangular with a thin neck.  Being nocturnal, they are sluggish by day and we have seen one Pit viper remains on the same rock in a stream bed for seven days – perhaps very patiently waiting for a frog to come by.  Pit viper bites in India are rarely serious but can be very painful.
The King cobra (Ophiophagus Hannah) is a rare snake and you have to be very lucky to see one in the wild.  Silent Valley is a good habitat for this largest of all venomous snakes.  Dense rain forests and stands of bamboo make ideal nesting areas for the king cobra.  This is the only snake that actually constructs a nest.  The Valley has a plentiful supply of Rat snakes which from the main diet of the snake-eating King cobra.  King cobras are diurnal, they reach five metre in length and in the Silent Valley area they are deep olive green with jet black tails.  The distinctive yellowish chevron on the neck and crossbars down the body become quite faint in bigger snakes and can only be seen if the snake raises its hood.  King cobras have the reputation of being aggressive but in our experience they will avoid humans and invariably try to get away when approached.  If cornered, caught or injured, however, this is a formidable animal and there is no antivenom serum for its bite in India.

The Spectacled cobra (Naja naja) is largely nocturnal in the plains but in Silent Valley (and in other hill forests) we have seen cobras out during the day hunting through leaf litters for frogs, toads and perhaps a mouse or rat.  One particularly beautiful dark cobra, the senior author remembers, was crossing the road when his brother and he stopped to photograph it.  After getting a few shots it suddenly darted straight towards the senior author, went right between his legs into a thick bush.  Since we are used to snakes we could see that all that the cobra wanted was to get into that bush.  Another less experienced person might have run away and the story would be related that he was ‘charged’ by a cobra.