Snake Island: The Forbidden Shore Where the Vipers Outnumber You

Off the coast of Brazil there is an island so dangerous that the government forbids you to land on it, and the reason is not radiation or a military secret. It is snakes. On this one small patch of forest live thousands of venomous vipers found nowhere else on Earth, packed so densely that old sailors' lore claims you are never more than a step or two from one. The Brazilian navy keeps people off. The snakes keep it that way.

Ilha da Queimada Grande, better known as Snake Island, is a real place, and the truth about it is unnerving enough without the exaggerations that have grown up around it.

The island and its only residents

Queimada Grande is a rocky, forested island of modest size, cut off from the mainland when sea levels rose after the last ice age. That isolation trapped a population of pit vipers and set them on their own evolutionary path. The result is the golden lancehead, Bothrops insularis, a slender, pale-gold snake that exists on this island and nowhere else in the world. With no ground prey to hunt, it adapted to catch migrating birds that stop to rest, and evolved unusually potent, fast-acting venom to make sure a bitten bird does not fly off to die out of reach.

Population estimates vary widely and the popular "one snake per square meter" figure is an exaggeration, but the density is genuinely high, and the species is critically endangered, threatened by poaching for the exotic-pet and biomedical trade. Brazil bans access both to protect people from the snakes and to protect the snakes from people; only occasional sanctioned researchers and navy personnel, who maintain an automated lighthouse, are allowed to set foot there.

The legends the closed door invites

An island you cannot visit breeds stories, and Snake Island has a full crop. Tales tell of a lighthouse keeper and his family killed by snakes that came through the windows, of fishermen who drifted ashore and were found dead, of pirates who seeded the island with vipers to guard buried treasure. These are folklore, unverified and mostly untraceable, the kind of legend that always attaches to a forbidden place. The pirate-treasure story in particular has no basis; the snakes are a product of geology and evolution, not a booby trap.

It is worth being plain that the real danger is straightforward biology: a lot of well-armed snakes on a small island with no medical help. The mythology of curses and murdered keepers is the human mind doing what it does with a place it is not allowed to enter.

The residue beyond the ban

The facts explain the island entirely, isolation, a unique viper, a sensible prohibition. What the facts do not quite dissolve is the pull of the place in the imagination: a green shore off a populous coast that people are forbidden to walk, guarded by something that was there long before us. Rational fear covers most of it. A residue, the unease of a closed door with living teeth behind it, does not tidy away, and that is what our readers weigh.

Below, readers have filed their own encounters with forbidden places and the creatures that hold them, each voted True, Fake or Not sure by the jury. Read them and cast your verdict.