Cobra snake
To many people, the cobra is the quintessential venomous snake. Cobras discussed in this article include species in the genus Naja and other similar venomous snakes, such as Ophiophagus hannah (king cobra), Hemachatus haemachatus (ringhals), Walterinnesia aegyptia (desert black snake), Boulengerina species (water cobras), and Pseudohaje species (tree cobras).
Most cobras are large snakes, 1.2-2.5 m in length. The king cobra, which may reach 5.2 m, is the largest venomous snake in the world. Cobras live throughout most of Africa and southern Asia. Their habitats vary, and some species adapt readily to life in cultivated areas and around villages.
When encountered, cobras usually try to escape but occasionally defend themselves boldly and may appear aggressive. Most of these snakes elevate the head and spread the neck as a threat gesture. However, a number of other snakes, venomous and nonvenomous, use this defense as well.
Most snakebites are inflicted on body extremities. Because cobras are popular as show snakes, bites on the hands and fingers are common.
By far, rural agricultural workers and other people in Asia and Africa receive most bites while working outdoors without protective footwear or when cutting tall grass with a hand blade. In North America and Europe, captive snakes usually cause bites, zookeepers and amateur collectors being at greatest risk.
Not all snakebites result in envenomation. In the case of cobras, the percentage of blank bites may be quite high, 45% in one series of 47 cases from Malaysia. In another series, 1 of 3 snake charmers bitten by large king cobras showed no signs of envenomation.
In addition to biting, some cobra species have a unique defense; they eject or spit jets of venom toward an enemy, usually at the eyes. The fangs of these species are specially modified with the discharge orifice on the anterior face rather than at the tip. The effective discharge range of a large snake is at least 3 m. The ringhals and certain African species of Naja are the most effective spitters, but the spitting behavior also is observed among some Asian Naja species.
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