Friday, September 18, 2015

Russell's Viper

Russel's viper (Daboia russelli) is a large species of viper found throughout the Indian subcontinent and other parts of south-east Asia.  Most of the snakebites (about 50%) in the Indian subcontinent are caused by the Russell's viper.

Physical Features
The russell's viper is a large and bulky viper, normally growing about 1 to 1.2 meters long.  However, specimens over 1.5 m have been recorded.  The color of their dorsal side is generally brown of varying shades, tan or deep yellow.  Their are a series of dark ovals running along their back which are outlined successively by black and white.  Another series of similar ovals runs down each flank alternating with those on the back.  They have a triangular head with a blunt snout.  Their head is very distinct from the body and they have very short tails.  Their belly is white, yellowish or sometimes pinkish.  The coat of the russell's viper very closely resembles that of the rough scaled boa, a harmless snake.

Distribution and Habitat
The russell's viper is widespread in the Indian subcontinent and is also found in Thailand and the Indo-Australian archipelago.  It is most common in India, Sri Lanka, Pakistan and Myanmar.  It inhabits plains, grasslands and plantations.  However, it has been recorded at heights of 2,100 m in south India and 2,000 m in the Himalayas.  It is common along the west coast of India.  It is abundant in Punjab but quite rare in the Ganga Valley.

Their diet mainly consists of rodents like mice, rats, squirrels, etc.  However, they will eat anything like lizards, frogs and small birds.  Juveniles are known to be cannibalistic.

The russell's viper is largely nocturnal.  Adults are known to be sluggish while juveniles are more excited and alert.  When aggravated, they stand their ground and produce a loud hiss that is distinctly louder than other snakes.  They are slow movers.  However, when they strike, they hurtle themselves with such force that they may even leave the ground.  Adults normally just prefer to just hiss when disturbed while juveniles may be more aggressive and bite.

Reproduction Cycle
Russell's vipers are ovoviviparous.  This is a mode of reproduction where the embryo's develop inside eggs which remains in the mother's stomach till they are ready to hatch.  The embryo's are nourished by the egg yolk. After they hatch, the mother gives birth to them.  A russell's viper generally gives birth to litters of 20 to 40 young.  However they have been known to give birth to litters of 63 individual as well as to a single young.  The gestation period exceeds six months.  Gravid females have been recorded in all months of the year. Females give birth between the months of May and November.  They sexually mature at the age of 2-3 years. 

A dose of 50-70 mg is lethal to an adult human.  The bite results in immediate pain and swelling in that region.  Post 20 minutes, bleeding occurs in the gums, urine and sometimes sputum.  Necrosis (the premature death of cells due to injuries) is a common symptoms.  Heart rate falls and blood pressure drops.  The victim may die of kidney failure, septicemia or cardiac arrest.  Death from any of these may occur in a period of 1 to 10 days.  Russell's viper used to cause about 300,000 deaths per year in the Indian Subcontinent before the introduction of its antivenin.  This has reduced the deaths by russell's viper considerably. 

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