I can remember the first time I saw one, at the St. Louis Zoo, and the feeling that certain death was just on the other side of the glass. I could not get over the snake’s size  this one was about 12 feet long. I was used to looking at giant snakes in zoos (I always made a beeline for the reptile house), but pythons did not seem so scary to me because they rarely moved. This sleek, agile and very alert snake was a king cobra, the largest venomous snake in the world and an icon to all snake enthusiasts, including this writer.

The king cobra’s venom is not, ounce for ounce (or milligram for milligram, as the professionals would measure it), the most potent. Among land snakes, that honor appears to belong to the inland taipan of Australia. But what the king cobra lacks in potency, it makes up for in volume. Its half-inch fangs deliver a huge dose, up to seven milliliters of venom, or about one-quarter of a whiskey shot glass. The lethality of venom depends on a combination of its potency, the volume delivered and the size of the victim. A king cobra bite can kill a human in 15 minutes and a full-grown elephant in a few hours.

What makes these cobras kings is not just their size, or their deadliness  after all, they don’t eat humans or elephants  it is that they eat other snakes. Even deadly snakes like kraits or other cobras are prey. These snakes bite when attacked, of course, which raises the question: How does the king cobra maintain such an apparently high-risk lifestyle?

Krait and cobra venoms, including that of the king cobra, act very quickly by crippling the nervous system. Among the arsenal of weapons in the snakes’ venom is one especially potent neurotoxin that works by binding to receptors on muscle cells. The toxin blocks the ability of acetylcholine, one of the body’s chemical neurotransmitters, to control muscle contraction. The blocking of these receptors causes paralysis, respiratory failure and death.