After the long drive to Agumbe, I step out at the Agumbe Rainforest Research Station and immediately start scanning nearby branches for the tell-tale texture of scales, pressed against mossy- and lichen-riddled wood. Even before I’ve put my bags down, I spot the first one. It’s a Malabar pit viper (Trimerusurus malabaricus), a male, settled on the rafters of the veranda.
Of the five species of pit viper found in south India, this one is definitely the most commonly seen and yet, at each sighting I’m left captivated by this enigmatic species. One possible reason for this is that despite the abundance of this species, there is still very little known about its natural history, ecology, and even taxonomy. To date, all we know about the species has come from anecdotal observations and next to no concerted work has been done on it.
(Top) Agumbe Rainforest Research Centre and the environment around it is a hotbed of snake activity. (Above) The Malabar pit viper is an ambush predator. Its hunting strategy is to wait at one place for prey to come to it instead of actively chasing it down. Photos: Anirudh Nair (top), Shreeram MV (above) Cover photo: Endemic to the Western Ghats of India, the Malabar pit viper, also called the rock viper, is partial to dense rainforest habitats with streams and rivers. Photo: Bhavya Joshi/Shutterstock
What we do know is that Malabar pit vipers can stay in the same place for months on end, waiting for prey to come by. We know that they are exceedingly common in some locations and that they prefer moist habitats with thick vegetation and high humidity. They also seem to vanish to a large extent during the dry parts of the year. But nobody quite knows where they go. It’s possible that they shift to a higher elevation in their habitat or they might congregate closer to streams and other cool, damp microhabitats.
A king cobra that was being followed and studied using a radio transmitter once ate over two dozen pit vipers over a period of three months. It did this by climbing high up into the canopy and chasing the pit vipers down (they most often jumped off branches) on to the forest floor, where the king cobra proceeded to catch and eat them. This was during the torrential Agumbe monsoon. Repeated observations like this indicate that the Malabar pit viper may actually spend a lot more time in the high forest canopy than previously thought.
This species of pit viper has highly developed heat sensory pits between its eyes and nostrils, which allow it to sense the smallest variation in temperature and accurately attack prey even in darkness. Photo: Rohit Varma – CC BY-SA 4.0
They’re found from the southern tip of the Western Ghats to the northern extent of the mountain range in Maharashtra, and from just above mean sea level to altitudes of 2,000 metres. This is the most widespread of pit vipers in south India and it is synonymous with the forests and plantations that cover the Ghats.
Of late, Malabar pit vipers have captured the attention of many a nature photographer. The colours, textures, and poise of the snake make it an ideal candidate for some spectacular images. Many people are keen on finding the (not so normal) yellow morph of the species, while others are compiling various collections of different colour phases of this stunning snake. In truth, we don’t really know if these phases are permanent or if they simply change colour over the span of their lives, a phenomenon called ontogenic variation.
(Left) The various colours of the Malabar pit viper, its mottled appearance, and calm demeanour have made it a favourite among wildlife photographers. (Right) Juvenile Malabar pit vipers are usually brown in colour and are mostly seen close to the ground. Photos: Rushikesh Lohar – CC BY-SA 4.0 (left), Gerry Martin (right)
On this note, all the neonate (newborn) individuals that I have seen have been brown in colour and invariably very close to the ground. There does seem to be some sexual dimorphism with males being more mottled and brownish. Females not only grow a lot bigger, but also seem to have a more green-based colour to their patterning. Whatever the reason, all this variation in the species’ colour and patterning make each time I find one an exciting experience.
Although a relatively high number of bites are known from this species, very little is known about its venom except that it does cause tissue damage and some coagulopathy (impairment of the blood’s ability to coagulate). Coffee and tea plantation workers seem to be the ones most at risk of bites from this species. However, they too don’t take it particularly seriously. There have been a few instances of people losing tissue, a digit, or a limb after Malabar pit viper bites, but we can’t be sure if this is in fact a consequence of the venom itself or poor and damaging first-aid.
Malabar pit vipers target tree frogs such as western tree frogs, when they congregate near ponds to mate. Photo: Saurabh Sawant
The diet of this species seems to be quite broad. Individuals have been seen eating frogs, lizards, rodents, and birds. Individuals have been observed to gorge themselves on tree frogs when the latter congregate near ponds to mate. Young Malabar pit vipers have been reported to feed on small frogs, lizards, and even soft-bodied insects.
Not much is known about the breeding biology of the species either. Young are usually seen in late April and May. One dead female was dissected to find nineteen embryos. Like most other vipers, the Malabar pit viper carries its eggs inside its body until the young are ready to ‘hatch’. The young, like all other snakes are on their own from the beginning. We know nothing of the survival rates of this species, but I would imagine that it is very low. This is only natural.
Like with other snakes found in India, few scientific studies have been done on the Malabar pit viper. As a result very little is known about the significance of its colour variations, or its habitat, diet, behaviour, and threats. Photo: Amal U S – CC BY-SA 4.0
However, the species is suffering from habitat loss, pesticide use, and general intolerance. Coffee plantations used to be a hotspot for this species. But with the onset of more intensive spraying of pesticides and fertilizers, I don’t see as many of them in places that I used to. Nothing is being done specifically to conserve this species and it is still very low on the list of species that need urgent conservation. But at least we know that there will always be a lot of them hanging around Agumbe!
