World Snake Day: Identifying the 'Big Four'

India recorded 1.2 million snakebite deaths in 20 years, an average of 58,000 deaths annually

According to a paper titled ‘Trends in snakebite deaths in India from 2000 to 2019 in a nationally representative mortality study', India recorded 1.2 million snakebite deaths in 20 years. It reveals that an average of 58,000 deaths are recorded annually.

“Snakebite deaths of human beings, as well as the killing of these serpents by humans, arise due to one major problem, the lack of identification between venomous and non-venomous snakes,” says Surya Keerthi, a snake rescuer.

Russell’s viper, Common Krait, Indian Cobra and Saw-scaled viper are the four deadliest snakes in India and are referred to as ‘Big four’.

People commonly misidentify snakes and tend to kill them as many non-venomous snakes mimic venomous snakes in appearance. In some cases, people mistake venomous snakes for non-venomous snakes and get bitten by them.

Identifying venomous and non-venomous snakes:

Around 3,000 species of the snake are present across the globe out of which about 600 species are venomous and only 200 species can kill human beings. In India, more than 270 snake species are present out of which around 60 species are venomous.

Venomous snakes can be identified by carefully observing their tail and the nature of their ventral scales, head scales, jaw scales and vertebral scales.

Tail: -The tail of a sea snake is usually flat and laterally compressed. Sea snakes are venomous, with several species capable of severe envenomation. Eg: Coral reef snakes

-Most non-venomous snakes have short and blunt tails. Eg: Rat Snake

-Some non-venomous and most venomous snakes have cylindrical and tapering tail ends. Eg: Spectacled Cobra

Ventral scales: -If the tail is cylindrical with tapering tail ends observe the ventral scales:

-If the scales are small on the ventral side of the snake, it is considered to be a non-venomous snake. Eg: Garter snake

-If the ventral scales are large but do not cover the belly region completely with small scales arranged at the end of broader scales, it is considered to be a non-venomous snake such as Python.

-If the ventral scales are broad and cover the entire width of the belly region it might be either venomous or non-venomous.

Head scales: -If the tail is cylindrical, tapering and the ventral shield is broad covering the entire belly region, the snake could either be venomous or non-venomous. It is then best to observe the head scales:

-If the head scales are small, it is usually venomous such as a Viper but if there is a large shield in the head region it could either be venomous or non-venomous.

Vertebral scales and jaw scales: -If the tail is tapering with large ventral scales and the head covered with a large shield, the snake could be either venomous or non-venomous. It is then advised to observe the jaw and vertebral scales.

-If the vertebral scales (scales along the top of the back of the snake) are not large but the third supra-labial scale (upper jaw) is large and touches the nostril and eye it could be venomous.

-If the vertebral scales are large and hexagonal having four infra-labial scales (lower jaws) with the fourth one being the largest it could be a venomous snake such as a Krait.

Identifying the big four:

1. Russell's viper (Daboia russelii): Russell's viper is considered to be one of the most dangerous snakes in India. The Russell's viper has a triangular head marked with a V-shaped white line, which meets at the tip of the snout. It has three longitudinal rows of circular or oval-shaped dark markings on the dorsal surface of its brown body. Each spot has an inner black area and an outer white margin.

2. Common krait (Bungarus caeruleus): The Common krait is a nocturnal snake. It can be recognized by its triangular body in cross-section. Kraits are jet-black or bluish-black and have a series of narrow white paired dorsal bands. These bands are more prominent on the posterior end of the body.

3. Spectacled cobra (Naja naja): The Indian cobra or the spectacled cobra varies in colour and pattern throughout its range. The colouration of its ventral scales can be grey, brown, reddish, yellow, tan or black. The dorsal scales of this species may have a hood mark. The hood mark is two circular ocelli patterns connected by a curved line.

4. Saw-scaled viper (Echis carinatus): Saw-scaled vipers are characterized by a stout body with a pear-shaped head that is distinct from the neck. They have rough and strongly keeled scales. Several rows of obliquely arranged serrated scales are present on both sides of the body. Their colouration includes various shades of brown, orange or grey with darker dorsal blotches and lateral spots. Saw-scaled vipers are small, but their irritability, aggressive nature, and lethal venom make them very dangerous.