The image of a cobra spitting toxic venom across great distances is rather arresting, and unfortunately untrue. The cobra actually sprays its venom, using muscular contractions and the process of respiration. While this might be viewed as semantic hairsplitting, spitting is actually an entirely separate biological action, involving the muscles of the mouth in a series of motions which propel substances from the interior of the mouth. The idea that cobras spit venom is widespread around the world, much to the frustration of herpetologists. For our purposes in this article, we will call it “spitting,” since “spraying” venom does not really do justice to the activity.
All of the snakes thought of as spitting cobras are in the genus Naja. These cobras spit venom, or at least appear to, when they are threatened or trying to disable an attacker. As with the venom of other poisonous snakes, the substance is irritating to mucus membranes and can poison someone if it penetrates the skin. When cobras spit at bare skin, the victim will not suffer as long as there are no open wounds on the skin for the venom to penetrate.
The process through which it appears that cobras spit venom starts with muscular contractions above the fangs, which force the venom into a hollow area in the fangs. The same muscles are used in non-spitting cobras to pump venom into their prey after they have bitten down. As the venom starts to exit the fangs, it forms a small droplet. When the droplet forms, the cobra exhales, creating a sudden gust of air which propels the venom outwards, sometimes at a distance as much as three feet (one meter). Given all appearances, people can be forgiven for thinking that cobras spit their venom, but the venom never actually enters the mouth of the cobra before it is propelled outwards.
In addition to being able to spray attackers with their venom, spitting cobras are also perfectly capable of using their fangs. In some cases, cobras spit venom into the eyes of prey to disable the prey animal so that the cobra can move in closer with its formidable teeth. In others, cobras spit as a defensive mechanism, to warn a potential predator that the cobra is dangerous, or to distract the predator with searing eye pain, should the venom land in its eyes.
Should you encounter a spitting cobra in the wild, the best course of action is to stay calm. Remember that the venom can only hurt you if it penetrates your skin or makes contact with your mucus membranes. Use an arm to shield your eyes as you slowly move away from the snake, and once you are out of range, feel free to move more quickly. Cobras spit venom if they feel threatened or attacked, but they will not engage in an unprovoked attack; the snake will probably be as unhappy to see you as you are to see it.