Ilha da Queimada Grande, nicknamed Snake Island, is a 430,000-square-meter island located about 33 km off the coast of the state of São Paulo, Brazil. The island is home to a variety of snakes including an endemic species called the Golden Lancehead Viper (Bothrops insularis), which is one of the most venomous snakes in the world. According to a 2015 estimate, there are between two and four thousand snakes on the island, which equates to an average of one snake per 75 square meters over the entire island. Exaggerated claims suggest there are as many as five snakes per square km. Local folklore is also filled with stories of horrible deaths suffered by those who wandered onto the shores including that of a fisherman who landed onto the island in search of bananas, and the family of a lighthouse keeper who lived there.
Officially, there never has been any report of a human being bitten by the golden lancehead viper, so the toxicity of its venom on humans couldn’t be tested, but other lanceheads are responsible for more human morbidity and deaths than any other group of snakes in either North or South America. A bite from a lancehead carries a seven percent chance of death, and even with treatment, victims still have a three percent chance of dying. Death usually results from intestinal bleeding, kidney failure, hemorrhage in the brain and severe necrosis of muscular tissue. The venom actually melts flesh and tissue making it easier for the snake to digest. Tests have found that the venom of the golden lancehead viper is the fastest acting in the genus Bothrops.
The snakes on Queimada Grande were originally the same species as those on the mainland, when the island and the mainland were a connected landmass. Between 10,000 and 12,000 years ago when the sea level rose, Queimada Grande was isolated from mainland Brazil and the snake population was marooned. With no small mammals to hunt, the snakes adapted to life to the trees because their main source of food were the birds that passed over the island on their migration. The islanders learned to hold it high in the trees by the tail, and pluck birds who rested on the branches. Their venom also evolved to become five times more potent as that of their brethren on mainland. This was required to kill the birds faster, otherwise they would fly away. When there are no passing birds, they filled themselves with lizards, centipedes, slugs and frogs.
The island is currently off-limits to human, and the Brazilian government strictly controls who visits the island and when. Visitors are mostly biologists and researchers, who are granted special permission to visit the island in order to study the golden lanceheads. The Brazilian navy does make an annual stop on the island for maintenance of the lighthouse, which, since the 1920s, has been automated.
Despite the dangers, wildlife smugglers sneak into the island to trap the golden lanceheads which fetch a high price in the black market.
Also see: Narcisse Snake Pits in Manitoba, Canada
Subscribe to our Newsletter and get articles like this delieverd straight to your inbox