To protect both the safety of humans and of its slithering residents, access to the island is controlled by the Brazilian Navy. Protecting the island’s inhabitants is particularly crucial as, despite carrying incredibly toxic venom, the most populous snake species living there is, in fact, critically endangered.

The golden lancehead (Bothrops insularis) is a species of pit viper in the Viperidae family, to which cottonmouths and rattlesnakes also belong. A bite from a golden lancehead contains hemotoxic venom that is fast-acting and can take down small prey like birds in a matter of minutes. Unlike the neurotoxic venom of cobras and taipans, which disrupts the nervous system, causing paralysis, hemotoxic venom targets the circulatory system, causing blood clots, hemorrhaging, and other circulatory-related complications.

However, despite the deadliness of hemotoxic venoms, they are actually a vital and life-saving component used in cardiovascular drugs, anticoagulant therapies, and in diagnostics – with the particular potency found in the golden lanceheads of Ilha da Queimada Grande making their venom especially valuable.

While other lancehead species are found in mainland Central and South America, the golden lancehead is only found on Snake Island. The evolution of this distinct species is thought to have occurred as a result of Ilha da Queimada Grande breaking away from mainland Brazil at the end of the last ice age, isolating these snakes without an abundance of land predators or prey.

Over the course of 11,000 years, the snakes adapted to their environment, becoming the only semi-arboreal lancehead species and developing a venom that is three to five times more toxic than mainland species, making them better adapted to catch fast-moving birds.

Of the 41 bird species found on the island, the lancehead’s diet consists predominantly of just two migratory bird species – the Chilean elaenia (Elaenia chilensis), which arrives in late summer, and the yellow-legged thrush (Turdus flavipes), which arrives in the winter. 

How many snakes are on Snake Island?

Of the 430,000 square meters (106 acres) available to the golden lanceheads of Snake Island, they live in just 255,000 square meters (63 acres) of dense forest. However, with a population between 2,000 and 4,000, it’s claimed there are roughly five snakes per square meter of the island.

While the golden lancehead is the most populous and deadly species of snake on the island, there are a number of other species of snake that inhabit it in smaller populations. There are few records of the other species living on Snake Island, but it’s thought several arboreal, non-venomous mainland snakes, like the Sauvage’s Snail-Eater (Dipsas albifrons), may be living alongside the golden lanceheads.

Has anyone died on Snake Island?

While Snake Island has no current permanent human inhabitants, a lighthouse can be found perched atop the island’s mountainous central ridge. This lighthouse was once home to a lighthouse keeper and his family between 1909 and the 1920s; however, some reports suggest the family met a rather expected fate.

As the lanceheads made their way into the lighthouse through the windows, it’s thought the family met their end on Snake Island as a result of their venomous neighbors.

However, while a handful of researchers are granted access to the island each year, there aren’t yet any confirmed recorded deaths on the island, due in no small part to Brazil’s strict protection protocols and the efforts of locals to warn visitors of the island’s deadly reputation.