The mongoose’s evolutionary adaptation is not unique Other small, humble creatures have evolved ways to endure what for most animals would be lethal snakebites. . . .

Sea snakes generally possess very toxic venoms. . . . Sea snakes prey on small marine animals, and the powerful toxins in the venom quickly immobilize the prey before it can swim off. Eels are some of the favorite foods of the banded sea krait. Some eels, however, have been observed to be remarkably resistant to the sea krait’s venom.

A similar situation has evolved among California ground squirrels with respect to the venom of northern Pacific rattlesnakes. This species and most other rattlesnakes kill their prey with a battery of toxins that is different from those of sea snakes and cobras. Rattlesnake venom toxins work by breaking down tissues and causing internal bleeding.

A good-size rattlesnake can deliver a hefty dose of venom that is sufficient to kill a human if the bite is left untreated. But ground squirrels in some parts of California, despite being one hundredth the size of humans, exhibit fairly mild effects from the venom. This resistance is not the result of [an] altered [nervous systems], but comes from the ability of . . . their blood . . . to neutralize the . . . venom.