A Herpetologist Explores ‘Snake Island' — Home To The World's Largest Concentration Of Venomous Snakes

Forbes

27-03-2025

Few places in the world are more dangerous than Ilha da Queimada Grande — the Brazilian island where ... More venomous vipers rule the land and only a few researchers are ever allowed.
Despite their fearsome reputation, snakes and their lives are always a hot topic for humans. From keeping them as pets to watching them in action every chance we get, we've always found a way to keep snakes close.
In Manitoba, families crowd wooden platforms to watch tens of thousands of red-sided garter snakes mate en masse at the Narcisse Snake Dens. In Colorado, a rattlesnake 'mega den' livestreams newborns slithering between their mothers' coils, gaining fans and nicknames in the chatroom like 'Woodstock' and 'Agent 008.'
But not every serpent spectacle comes with a picnic table and a selfie spot. There is one island in Brazil where snakes reign supreme. A place so densely packed with venomous vipers that even the Brazilian government has barred civilians from setting foot on its shores.
Ilha da Queimada Grande, commonly known as Snake Island, lies off the coast of São Paulo and harbors an estimated 2,000 to 4,000 critically endangered golden lancehead pit vipers — though 2.0.CO;2.short">some studies suggest numbers are closer to the lower end. These snakes possess venom potent enough to rapidly immobilize prey and cause severe tissue destruction in humans.
Only a handful of researchers are granted access each year — and even they tread lightly.
Ilha da Queimada Grande wasn't always an island. Around 11,000 years ago, it was just a ridge along Brazil's southeastern coastline — until rising seas carved it off from the mainland, leaving whatever lived there to fend for itself.
And for one species of pit viper, life would never be the same again.
That snake was the Bothrops jararaca, a notorious mainland species responsible for many of Brazil's venomous snakebites. On the continent, it preyed on rodents and reptiles, but once isolated, its options changed rapidly.
Stranded without mammals and under constant pressure to catch fast-moving birds, a population of Bothrops jararaca slowly became something else entirely. Today, its descendant — the golden lancehead pit viper (Bothrops insularis) — is longer and deadlier. Found nowhere else but this forested rock, it has evolved venom so potent it can take down its prey with terrifying speed, ensuring that even a glancing bite can bag a meal before escape is possible.
This isolation rewrote the rules of survival for Bothrops insularis. On this island with no large predators, venom became this viper's greatest competitive advantage.
While 41 bird species have been recorded on Snake Island, the golden lancehead relies almost entirely on just two — the Chilean elaenia (Elaenia chilensis) and the yellow-legged thrush (Turdus flavipes). Both are migratory songbirds that arrive in seasonal waves. Elaenias arrive in late summer, and thrushes arrive in the winter.
Perhaps more importantly, both are just the right size and slow enough to catch.
Interestingly, the study noted that the southern house wren (Troglodytes musculus) — despite being the island's most abundant resident species — was able to avoid the viper's deadly fangs. And while the golden lancehead has been observed preying on other creatures like centipedes and lizards, it appears to make up an insignificant part of its diet.
The golden lancehead's preference for perching migratory birds has been forged by necessity. With no mammals and few reptiles to hunt, adult lanceheads have evolved to target these transient flocks with surgical precision. Their venom, the fastest-acting of any lancehead snake, ensures birds drop quickly — often before they have time to take flight.
Snakes even adjust their behavior to match their prey. While usually found coiled on the forest floor, lanceheads have been observed climbing trees during elaenia season, waiting motionless on branches to ambush birds mid-forage.
The golden lancehead's venom evolved for one job — to kill quickly. In fact, as mentioned in the video, the venom is almost 5 times more toxic than its mainland relatives, capable of killing human tissue, hemorrhaging the brain and triggering massive intestinal bleeding.
That biochemical brutality has made the snake a target for scientists and smugglers alike. On the black market, a single golden lancehead can fetch anywhere between $10,000 to $30,000.
And there's real promise of scientific breakthroughs. The venom of other Bothrops species have already shown pharmacological potential in the development of antitumoral compounds that could help in the treatment of certain cancers, according to a February 2024 study published in Toxicon. Another striking example of Bothrops venom's medical value is captopril — a groundbreaking blood pressure medication developed from Bothrops jararaca venom, which revolutionized the treatment of hypertension and paved the way for modern ACE inhibitors.
In that razor-thin space between danger and discovery, Ilha da Queimada Grande may yet hold the key to something greater. On an island where no human lives and few dare to walk, a critically endangered snake could one day save lives — demonstrating that even in the most hostile environments, nature continues to shape science in unexpected ways
While the golden lancehead may not make for a great pet, a lot of non-venomous snakes do. How well do you connect with your pet snake? Take the science-backed Pet Personality Test to find out now.