Snakes have been both revered and persecuted throughout history for various reasons. Vipers are a group of venomous snakes that typically gets most of us shuddering. In fact, two of the vipers found in Karnataka are so venomous that they are listed among the big four venomous snakes that cause the most number of human deaths. Globally, there are 347 species of snakes in the family Viperidae. In India, 32 species have been reported so far and 7 of them are found in South India.
Typically, snakes belonging to this family are nocturnal in habit and are characterised by a triangular-shaped head, a pair of fangs on the upper jaw located behind the eye and, a stocky body with a short tail. They are ambush predators who sit motionless for days at end to bite and inject venom into an unsuspecting prey. Although they appear sluggish, they are quite aggressive if needed and can strike a quick bite. Once envenomated, the venom works by denaturing proteins and causing a swelling and drop in blood pressure.
Within the larger Viperidae family are a group of snakes that have evolved a unique adaptation of having heat-sensing pits between their eyes and nostrils and are assigned to a sub-family Crotalinae. The heat-sensing pits are connected to an infrared-sensing organ that enables them to find prey and perhaps even avoid predators, but the prey or predator needs to be warm-blooded. Most members are ovoviviparous, meaning they have eggs which develop inside the body of the female snakes, who give birth to live young ones.
Exploring the multitude of habitats in the state of Karnataka, one can encounter the following five species of vipers. In fact, two species can be found right in the city of Bangalore and the rest can be found if one moved a mere 100-150 km away towards the undulating forest hills of the Western Ghats.
Russell’s Viper (Daboia russelii)
The Russell’s Viper is the largest of the five vipers found in Karnataka and is known as ‘kolaku mandala’ in Kannada. They are widespread throughout the Indian subcontinent and parts of SE Asia. The snake is named in honour of Patrick Russell, a herpetologist. It is nocturnal in habit and has a stocky built with keeled scales, giving it a rough appearance. The head is triangular and distinct from the neck. Nostrils are large and as big as the eye, which has a vertical pupil. The upper body colouration is a varying shade of brownish yellow with regular black/brown oval spots with a white margin, sometimes connected like a chain.
On an average, they grow up to four feet in length and are found in a variety of habitats ranging from empty housing plots in rapidly urbanizing cities to agriculture fields across the state. Typical habitats include open grassland, scrub forest, rocky areas, and thorny shrubs. They are known to eat rodents, crustaceans and other reptiles. During the months of May–July, they give birth to about 60 live young ones. Once they coil up and sit under shrubs or grasses, it is difficult to spot them and but when threatened, they hiss loudly. Unfortunately, this species is responsible for the highest number of deaths from snake bites in India.
Saw Scaled Viper (Echis carinatus)
The Saw Scaled Viper is a small viper found throughout India. This nocturnal snake is known locally as ‘garagasa mandala’ and as the English name suggests, they have saw-like keeled scales. It is a slender bodied snake with rough, keeled scales. The head is distinctly wider than the body, having large eyes with vertical pupils; the nostrils are smaller in comparison to the Russell’s Viper. The upper surface of the body is of varying shades of reddish brown but with characteristic dark brown blotches amidst a zigzag pattern. An arrow head mark on the head is distinct. The pale white underside is speckled with brown.
They grow to a maximum length of 80 cm. They coil up and rest under rocks, shrubs or tree barks. On cold nights, they can be spotted on the warm surface of roads. They eat small lizards, mice, frogs and a variety of arthropods. Breeding season is between April-August where they produce up to 8 live young ones. They move quickly by side-winding but when agitated, rub their scales against each other to create a rasping sound. When provoked, they bite quickly. The venom is fatal and this snake is rightly listed among the big four snakes in India.
Bamboo Pit Viper (Trimeresurus gramineus)
The Bamboo Pit Viper is an endemic snake, found in parts of the Western and Eastern Ghats. They are nocturnal and arboreal in habit. It is the largest of the three pit vipers found in south India. As the name suggests, they are often found in areas dominated by bamboo clumps. Their body profile is stout, having rather smooth scales and a short prehensile tail helps them climb. The triangular head is distinct and a pair of heat-sensing pits is predominant between the eyes and nostrils. Like other vipers, the pupil is vertical and eyes are larger than the pits. Upper body colouration is usually varying shades of green. Underside is yellow or pale green.
Individuals are known to reach about 130 cm in length. They are commonly found on bushes near the edges of streams. They feed actively during the monsoon when they eat frogs, lizards, birds and occasionally rodents. Breeding season is between June-July where they give birth to about 15 young ones. Their movement is rather sluggish but they can bite readily. They are known to vibrate their tail tips when disturbed. Human bites are uncommon but the venom causes severe pain and localized swelling, lasting a few days.
Malabar Pit Viper (Trimeresurus malabaricus)
Malabar Pit Vipers are arboreal and endemic to the Western Ghats of India. They are found in forests and around human habitation and often known as ‘hapatte haavu’. They are active at night but are seen perched on branches even during the day. They can be seen coiled up on twigs or branches for many days. The triangular head is distinct from the moderately sized body. Tail is short and prehensile. The eyes are large, as big as the heat-sensing pits which are located between the eyes and nostrils. Scales on the head are small and smooth as compared to the upper body scales with are weakly keeled.
Colouration is variable ranging from a predominant green to a predominantly brown/orange morph with prominent markings on the upper and underside of the body comprising brown, yellow or grayish colours. Adults grow up to 100 cm in length. They feed on lizards and frogs. Although venomous, bites do not appear to be fatal to humans. Moderate pain coupled with local swelling over a few days has been observed in persons bitten by it. This species is a significant component in the diet of the King Cobra (Ophiophagus hannah).
Hump-nosed Pit Viper (Hypnale hypnale)
The Hump-nosed Pit Viper is the smallest of the three pit vipers found in Karnataka. This terrestrial snake is commonly found in forests and plantations of the Western Ghats of India and parts of Sri Lanka. It is nocturnal in habit and known locally as ‘tagadu happatte haavu’ or ‘kudrala’. Its head is flat, broad and broader than the neck. The eye is large and has a vertical pupil. The pit is not all that obvious. The upper body is predominantly reddish-brown coloured with brown specks or with large spots. Two dark brown stripes along the neck and a thin pale line from snout to mid body are present.
They are often encountered on the forest floor or under fallen logs – body in tight coil and head pointed upwards. The tip of the snout has a small protrusion, giving it the name hump-nosed. They feed on skinks, lizards and small rodents and occasionally eat reptile eggs and frogs. Juveniles are known to wriggle their tails to lure prey. When agitated, they flatten their body and can strike defensively. Humans, when bitten, develop pain and swelling. However, no fatalities have been recorded from India.
Threats to vipers
The most common threats to these snakes are fear and road mortality. A lot of people still fear these snakes, perceive them as dangerous and whack them to death. Indeed, Russell’s and Saw Scaled Vipers cause significant human casualties. Not walking barefoot, having a torch at night are some of the steps to prevent snake bites. With increasing density of roads, wildlife mortalities are bound to increase and as new roads are being recklessly built or widened. Snakes suffer because they cannot quickly get out of a speeding vehicle’s way. Putting up speed barriers, stopping night traffic through wildlife reserves and, educating drivers would be the way forward to mitigate the impacts.
Our collective knowledge about these beautiful snakes has only increased incrementally over the years. Several basic questions remain unanswered. For example, how large are the populations of vipers? What are the kinds of habitats they use to move around and feed? Does reduction of forests affect them negatively? Studying snakes is a challenge but it is sure to give great results and we need to take up this opportunity and get a peek into their wonderful world.