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Cobra (gokhra) venomous snakes belonging to the genus Naja under family Elapidae. The family also includes the equally poisonous King Cobra, and kraits. Two species of cobra, the spectacled/binocellate cobra (khoia or khodom paia gokhra), Naja naja and monocled/monocellate cobra (gokhra), Naja kaouthia occur in Bangladesh. When excited, a cobra can inflate its elongated neck ribs, thereby showing its spectacular hood. The hood of a spectacled cobra has a prominent black U-mark bordered by a light-brown line. The monocled cobra has a large black blotch or an O-ring encircled by another yellow or orange ring on the hood.

Cobras measure about 1.5 m in length. They are nocturnal and live near human habitations, cultivated fields and in forests. They feed mainly on rodents, small birds and amphibians, but rarely on fish. The female guards a clutch of 10-25 eggs for about 2 months but do not incubate them. Eggs hatch within 60-70 days. These snakes have a pair of fixed poison fangs at the front end of the upper jaw. Each fang is connected to a venom gland. Certain specialized muscles work to open the mouth and pressurize the glands to send a jet of venom through a groove over the fang. Its venom is neurotoxic that attacks the nerves, leading to paralysis of the lungs and heart failure.

The King Cobra in the Sundarbans [Courtesy: Ali Reza Khan]

King Cobra (raj gokhra) The longest poisonous snake of the world, Ophiophagus hannah. Its length may extend up to 5.5 m. The hood is smaller than the cobra (Naja species) but it can be raised to the height of a man. Adults are blackish to pale brown with faint bands over their heads and necks while the juveniles are colourfully banded. It is common in the sundarbans but rare in the forests of Sylhet and Chittagong.

The King Cobra or Hamadryad is mostly diurnal and adept in climbing, swimming and rapid movement over the ground. Its generic name Ophiophagus is related to its habit of eating both poisonous and non-poisonous snakes. It provides the best egg-care amongst snakes.

Mates form a pair bond. After mating, a female builds a two-storey nest by gathering debris and leaves from the forest floor by making a loop of her body around a bunch of leaves and heaping these by repeated leaf-gathering sessions. She also makes a depression at the centre of the nest. This is followed by laying of up to 3 dozen eggs. The nest is then covered by additional supply of debris. Afterwards, she sits tight over the roof of the nest up to the time the babies hatch in 70 days or so. During this period she does not go for hunting. Although there is no 'incubation' by her, the temperature released by the debris warms up the eggs. In each strike a Hamadryad is known to release over 200 mg (dry weight) neurotoxic venom. Only 16 mg of this venom is enough to kill an average person of 60 kg in weight.

Cobras are now a threatened species in Bangladesh. The moncellate cobra is particularly vulnerable, and the binocellate cobra and the king cobra are endangered snakes. It is estimated that about 1600 people die every year of snakebite in the country. Cobra bites are associated with neuromuscular paralysis; necrosis of soft tissues has also been reported. In the past no effective treatment was available in the country, except the traditional healing given by ojha, who used to chant mantras and make incisions on the site of the bite to suck the venom. Now antivenoms are available in almost all hospitals.

The Hindu goddess Manasa or Visahari is worshipped for curing snakebite. In Hindu mythology Ananta is regarded as the king of nagas, a race of serpentes. He is described as having a thousand hooded-heads. He bears the universe on his head and produces earthquakes whenever he yawns.

Snake charmers, locally known as bedeys, always keep cobras in their collection of snakes as these snakes can raise their head to an appreciable height and inflate their hoods. As the charmer plays his flute and keeps chanting mantras while moving either his head, elbows, or knees the cobra sways its raised hood and body to fix its vision towards the moving object and not to the music. Sometimes a snake charmer maneuvers the lid of the basket or pot that is used as storage for the snake itself instead of the charmer's own knees or elbows. The cobra is teased into attacking the snake charmer. Once the snake fixes its attention on the object, it dares attack it either with its open mouth or amidst production of loud hissing noise. [Ali Reza Khan]

See also snake; snake charmer.