Off the coast of Sao Paolo, Brazil, sits Ilha de Quimada Grande or, as it's known colloquially in English, "Snake Island." The island, roughly 110 acres of trees, is uninhabited. Travel to the island is expressly forbidden by the Brazilian navy. Why? Because Queimada Grande is home to hundreds of thousands of golden lanceheads, the snake pictured at left.
Golden lanceheads are unique to Queimada Grande. The snake typically grows to be about two feet long, but in some cases can be nearly double that length. And its venom is poisonous. Very, very poisonous.
Lanceheads (that is, the more common cousins of the golden lancehead) are responsible for 90% of snake bite-related fatalities in Brazil. The mortality rate from a lancehead bite is 7% if the wound goes untreated, and can be as high as 3% even if treatment is given. The venom causes a grab bag of symptoms, including kidney failure, necrosis of muscular tissue, brain hemorrhaging, and intestinal bleeding.
For Snake Island, the picture is even scarier. The data above does not include bites from the golden lancehead, as there are no official records of a golden lancehead-caused fatality due to the de facto quarantine on their island. A chemical analysis of golden lancehead venom, though, suggests that the snake is much, much more dangerous than its continental cousins: Golden lancehead venom is faster acting and more powerful — perhaps five times more powerful.
Getting close to a two-foot snake with such powerful venom carries with it a high risk of death. And getting close to one is all but certain on Snake Island. Even the most conservative estimate suggests that the golden lancehead population density on Queimada Grande is one per square meter; others suggest a population as high as five per square meter. Regardless, as Atlas Obscura points out, even at the lower estimate, "you're never more than three feet away from death."