Brazil's Snake Island, home to thousands of venomous snakes, is closed to the public

In the Atlantic Ocean off Brazil's Sao Paulo coast lies an island whose name makes people shudder. It is called Ilha da Queimada Grande, and the world knows it as Snake Island. The island spreads over 43 hectares, or just 106 acres. The fear it inspires is such that the Brazilian government has banned the general public from entering it altogether.

An island usually brings to mind pristine sand, coconut palms and blue sea. The story of Snake Island is the opposite. According to researchers, around 2,000 to 4,000 highly venomous snakes live on it. At least one to five snakes can easily be found in every square metre, so anyone setting foot there could face mortal danger at every step. Anyone who goes without proper preparation and antivenom could lose their life in just an hour.

The biggest danger on the island is a snake called Bothrops insularis, commonly known as the golden lancehead viper. It is golden-yellow in colour. The snake is found nowhere else in the world; the island is its only natural habitat.

The venom of the golden lancehead is said to be five times more lethal than that of ordinary snakes. After a bite, human cells and flesh begin to rot. The venom attacks the nervous system and blood flow directly, and death can follow within minutes. About 10,000 years ago, sea levels rose and the island was cut off from mainland Brazil. The snakes stranded there had to hunt migratory birds to survive. Over thousands of years of evolution, their venom became faster-acting and deadlier so that the birds die immediately.

Many frightening and intriguing stories about the island circulate in Brazil and among local fishermen. The best known concerns a secret pirate treasure. It is said that pirates once hid their loot on the island and released highly venomous snakes there so that nobody would dare go near and steal it. Whether the tale is true or not, it is said that no one who went to the island in search of treasure, or to test their courage, has returned alive.

The only sign of human settlement on the island is an old lighthouse. In the early twentieth century, a lighthouse keeper lived there with his family to maintain it. According to local folklore, one night snakes entered through a window and attacked the whole family, who all died a painful death. The Brazilian Navy later made the lighthouse automatic. Today, armed forces personnel visit it only once a year for maintenance, under special protection.

Given the grave danger and the growing risk to life, the Brazilian government has declared Ilha da Queimada Grande a fully protected forbidden area. Tourists and ordinary citizens are strictly prohibited from going there. Only the Brazilian Navy, accredited snake researchers and biomedical scientists get special permission, and even then only with a medical team.

Scientists say that despite its danger, the golden lancehead viper is extremely valuable for medical research. Certain proteins in its venom are being used to make medicines for heart disease, high blood pressure and clot-dissolving drugs. For this reason the snake is smuggled and sold on the international black market, where its price is reported to run into lakhs of rupees. The snake is now on the International Union for Conservation of Nature (IUCN) list of threatened species. Snake Island is one of nature's secrets that reminds humans of their limits. Even humankind, which rules the world through technology, thinks a hundred times before setting foot on this 106-acre island.