Russell's Viper

**Russell's viper** (*Daboia russelii*) is a species of venomous snake in the family Viperidae. ***Daboia*** is a monotypic genus of venomous Old World vipers. The single member species, *D. russelii*, is found in Asia throughout the Indian subcontinent, much of Southeast Asia, southern China and Taiwan. The species was named in honor of Patrick Russell (1726–1805), a Scottish herpetologist who first described many of India's snakes, and the name of the genus is from the Hindi word meaning "that lies hid", or "the lurker". Apart from being a member of the big four snakes in India, *Daboia* is also one of the genera responsible for causing the most snakebiteincidents and deaths among all venomous snakes on account of many factors, such as their wide distribution, generally aggressive demeanor, and frequent occurrence in highly populated areas.

*Daboia russelli* is commonly known as **Russell's viper** and **chain viper**, among other names.

## Description

*D. russelii* can grow to a maximum total length (body + tail) of 166 cm (5.5 ft) and averages about 120 cm (4 ft) on mainland Asian populations, although island populations may be slightly smaller on average. It is more slenderly built than most other vipers.

The head is flattened, triangular, and distinct from the neck. The snout is blunt, rounded, and raised. The nostrils are large, each in the middle of a large, single nasal scale. The lower edge of the nasal touches the nasorostral. The supranasal has a strong crescent shape and separates the nasal from the nasorostral anteriorly. The rostral is as broad as it is high.

The crown of the head is covered with irregular, strongly fragmented scales. The supraocular scales are narrow, single, and separated by six to nine scales across the head. The eyes are large, flecked with yellow or gold, and surrounded by 10–15 circumorbital scales. The snake has 10–12 supralabials, the fourth and fifth of which are significantly larger. The eye is separated from the supralabials by three or four rows of suboculars. Of the two pairs of chin shields, the front pair is notably enlarged. The two maxillary bones support at least two and at the most five or six pairs of fangs at a time: the first are active and the rest replacements. The fangs attain a length of 16.5 mm (0.65 in) in the average specimen.

The body is stout, the cross-section of which is rounded to circular. The dorsal scales are strongly keeled; only the lowest row is smooth. Mid-body, the dorsal scales number 27–33. The ventral scales number 153–180. The anal plate is not divided. The tail is short — about 14% of the total length — with the paired subcaudalsnumbering 41–68.

Dorsally, the color pattern consists of a deep yellow, tan, or brown ground 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 dorsal spots, which usually number 23–30, may grow together, while the side spots may break apart. 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.

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