What makes [king] cobras kings is not just their size, or their deadliness . . . 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. . . . [causing] paralysis, respiratory failure and death.

But the king cobra is not fazed by bites from its victims. . . . Mutations have altered the snake’s [nervous system] in such a way that [it is unharmed by the bites from its victims]. The king cobra can subdue its dinner without suffering from any venomous counterattack.

This large snake, resistant to the very potent venoms of its prey, would appear then to be impervious. But we all know the story of the mongoose— if not from wildlife programs, then from Rudyard Kipling’s “Rikki-Tikki-Tavi.” How does the mongoose defeat the king cobra?

The mongoose’s quick reflexes help it dodge the cobra’s defensive bite, and its powerful jaws can dispatch a snake in one blow. But there are also genetic grounds for the mongoose’s courage. Sometimes an attacking mongoose is bitten, but it has another line of defense against the venom—its [nervous system] has also evolved so that the cobra toxin cannot [harm] it. A set of changes in the mongoose’s nervous system makes it resemble the cobra’s own resistant [nervous system].