Russell's viper is a venomous snake found in Asia. The species is named for Patrick Russell, a Scottish herpetologist who first described many of India's snakes. In Bengali, this snake is called Chandroborha since it carries lenticular or more precisely lunar marks all over its body. Apart from being a member of the big four snakes in India, Russell's viper is also responsible for causing the most snakebite incidents and deaths among all venomous snakes. These snakes are deep yellow, tan, or brown in color, with three series of dark brown spots that run the length of the body. Each of these spots has a black ring around it, the outer border of which is intensified with a rim of white or yellow. The head has a pair of distinct dark patches, one on each temple, together with a pinkish, salmon, or brownish V or X marking that forms an apex towards the snout. Behind the eye is a dark streak, outlined in white, pink, or buff. The venter is white, whitish, yellowish, or pinkish, often with an irregular scattering of dark spots.
Russell's vipers are found in India, Sri Lanka, Bangladesh, Nepal, Myanmar, Thailand, Pakistan, Cambodia, Tibet, China (Guangxi, Guangdong), Taiwan and Indonesia (Endeh, Flores, east Java, Komodo, and Lomblen Islands). These snakes are not restricted to any particular habitat but do tend to avoid dense forests. They are mostly found in open, grassy or bushy areas, but may also be found in second-growth forests (scrub jungles), on forested plantations and farmland. Russell's vipers are most common in plains, coastal lowlands, and hills of suitable habitat. Humid environments, such as marshes, swamps, and rain forests, are avoided. They are also often found in highly urbanized areas and settlements in the countryside because of the abundance of rodents.
Russell's vipers are solitary terrestrial creatures. They are primarily a nocturnal forager. However, during cool weather, they become more active during the day. These snakes like to bask in the sun during the day. The rest time is spent hiding in the caves, cracks in the soil or under the leaf litter. Adults move slowly and sluggish unless they are threatened; after that, they can become very aggressive. Juveniles are generally more nervous in nature. When threatened, Russell's vipers form a series of S-loops, raise the first third of the body, and produce a hiss that is supposedly louder than that of any other snake. When striking from this position, they can exert so much force that even a large individual can lift most of its body off the ground in the process. These snakes are strong and may react violently to being picked up. The bite may be a snap, or they may hang on for many seconds.
Russell's vipers are carnivores. They feed primarily on rodents but will also eat small reptiles, land crabs, scorpions, and other arthropods. Juveniles hunt lizards. As they grow and become adults, they begin to specialize in rodents.
Russell's vipers are ovoviviparous which means that females give birth to live young. Mating usually occurs early in the year, although pregnant females may be found at any time. The gestation period lasts more than six months. Young are produced from May to November, but mostly in June and July. Litters consist of 20-40 young, although fewer offspring may also occur. At birth, snakelets are 215-260 mm (8.5-10.2 in) in total length. They are independent at birth and reach reproductive maturity at around 2-3 years of age.
Main threats to Russell's vipers include illegal collection and trade for food and skins. They are also often killed because of fear.
Russell's vipers are often found in settlements in the countryside attracted by the rodents, thus playing a useful role in controlling their populations.