Snake Island: Why Brazil Banned Visitors from This Deadly Paradise

Ilha da Queimada Grande, also informally called Snake Island, is a small island located 33 kilometres off the coast of São Paulo state, Brazil, in the Atlantic Ocean. The island covers an area of approximately 43 hectares (106 acres) and is covered with low Atlantic rainforest, rocky outcrops and coastal grasses. It’s known for accommodating an extensive amount of venomous snakes. Let’s look at its history and mystery in detail.

About 11,000 years ago, during the ice age, the island was connected to the mainland of Brazil. However, at the end of the last Ice Age, when the sea levels rose, the island was cut off from the mainland, isolating its flora and fauna. This isolation allowed a unique evolutionary path for species like the golden lancehead viper, which diverged from its mainland relative, the Bothrops jararaca.

Over time, the golden lancehead viper learnt to adapt to the island environment. It became 5 times more venomous than mainland relatives to quickly subdue migratory birds like doves and thrushes, which are its main prey. It lost its camouflage ability and behaviour needed for a forest floor and instead adapted to rocky outcrops and trees. With no natural predators and an abundant number of birds whom they ambushed once they landed briefly on the island, the viper population thrived, and this unique ecological niche is one reason for the snake’s evolutionary divergence and toxic specialization. Additionally, despite being physically smaller than mainland vipers, it became one of the most venomous snakes in the world, so it’s an example of insular gigantism/toxicity.

Many centuries later, between the 16th to 19th centuries, there are no records of Indigenous people inhabiting or frequently visiting the island. Even Portuguese colonizers and explorers mostly ignored this island due to its inaccessibility and reputation for danger. However, there were attempts to clear the land with fire to make it habitable or for agriculture, but for some reason, these efforts were abandoned but the name of the island Queimada Granda was derived after this incident as Quimada means burned, referring to the attempt.

In 1909, Brazil sent in engineers and labourers were sent in to build a lighthouse on this island to guide ships along the treacherous southeastern coast. These were likely the first documented group to set foot on the island for a prolonged period. The island was known for its dense snake populations, but regardless of its reputation, the lighthouse keeper and his family lived there for some time in the early 20th century, probably between 1910 to 1925. There are stories of the entire family being killed by snakes, but there are no exact records, and they might just be exaggerated or folklore.

Between the 1920s to 1930s, Early scientific interest began in Brazilian herpetology (study of reptiles and amphibians), though visits to the island remain rare due to its inaccessibility and danger. During this time, the golden lancehead viper was officially recognized as a distinct species, Bothrops insularis and it was confirmed to be critically venomous. Its venom is incredibly potent and is capable of melting human flesh and causing death within an hour if untreated. It contains unique enzymes and proteins that cause rapid haemorrhaging and necrosis. Also, this snake is endemic, meaning it is only seen on this island and nowhere else in the world. Apart from snakes, some insects, spiders, birds and small amphibians exist in limited numbers, but in reality, very few species thrive here due to the snake population. Even though people were curious; only Brazilian navy servicemen were allowed to occasionally patrol nearby.

Then, between the 30s and 50s, the local communities near the island started believing the island was cursed or haunted due to the number of people who allegedly died there. Locals also talk about people who set foot on the island and never returned. There are also legends of treasure hunters and pirates dying there, but they are likely fictional. The government also recognised the dangers and began restricting access to the island first for safety reasons but later also for conservation. Even the lighthouse became automated in the late 20s, thus ending permanent human habitation.

Between the 50s to 80s, early scientific interest in this island was seen, and likely herpetologists and biologists from Brazilian institutions like Instituto Butantan might have visited the place, but Visits were infrequent and poorly documented due to logistics and danger

The 1980s to 90s was the era where scientific interests largely increased. The earliest formally documented research visit was in 1981 by Dr. Vital Brazil Filho, son of the famous Brazilian immunologist Vital Brazil. He was affiliated with Instituto Butantan, and his purpose of the research was venom research and species sampling and. He contributed to early venom analysis of Bothrops insularis. They found there might be about 2000 to 4000 snakes on this island, with a density of 1 to 5 snakes per square meter. However, they were all interested in one specific species of snake. Researchers begin detailed ecological and genetic studies of the golden lancehead. Studies reveal the species’ venom contains potent hemotoxins and other compounds with possible medical applications, as it can be used in developing anti-coagulants, tumour inhibitors and hypertension drugs. Another key Herpetology expedition was in the 1990s, where Research teams from Instituto Butantan and USP (University of São Paulo) entered. The key researchers were Dr. Otavio Marques and Dr. Marco Antonio de Freitas. The purpose of their visit was Population density, ecology, and venom potency studies.

On the other hand, it’s hard to do these studies because there are logistical challenges. Researchers must bring all supplies, including antivenom, GPS equipment, food, and shelter. There are no freshwater sources, and the terrain is rugged and difficult to navigate. They Must conduct work quickly (often within 1–3 days) due to limited permissions. There are also many safety protocols they have to follow. Every member of the Team must wear full snake-proof gear. Must establish radio communication with the mainland in case of emergency evacuation. Despite the measures, there are a few documented envenomation incidents, all treated successfully due to strict safety protocols.

In the 2000s, conservation concerns arose because habitats were limited and fragile. Criminals started to bribe and pose as researchers to enter the island without governmental permission, kidnapped the golden lanceheads and sold them for tens of thousands of dollars on the black market. Illegal wildlife trade increased rapidly due to the snake’s rarity and venom value. In fact, a single specimen can be worth $10,000–$30,000 USD or more in the illegal exotic animal market. Thus, the species is listed as Critically Endangered on the IUCN Red List. Also, the government took this issue seriously and enforced stricter restrictions on island access. They also only started to permit authorised scientists with armed navy escorts into the island. Also, from 2002 onwards, patroling and drone monitoring were done by the Brazilian navy to prevent poaching and environmental degradation. Violating the rules can result in heavy fines or imprisonment, as the island is now a protected ecological reserve under Brazilian law.

During the 2010s, research continued by institutions like Instituto Butantan and international universities with researchers from America, Canada and Brazil. Dr Bryan Fry (University of Queensland, Australia) was possibly among them, and their purpose was to study venom for pharmaceutical applications. Sequencing of the snake’s genome was done. Also, there was a detailed analysis of venom for use in blood pressure, clotting and cancer research.

In 2017, a scientific study was done on “Ecology of the golden lancehead Bothrops insularis” by Pontes et al. Researchers were Danilo Pontes, Eliana Moura-da-Silva and others from Instituto Butantan. Their purpose of the visit was to do long-term monitoring of snake behaviour and habitat threats. Studies also show declining snake populations, likely due to inbreeding, habitat loss, and climate change. It is important to note that there are challenges when researching these snakes on the island. Scientists have faced near-fatal encounters. Some scientists report being struck at close range or stepping within inches of a snake — near-misses are common. The island’s camouflaged terrain makes spotting snakes especially difficult in leaf litter or shaded rocks. It was during this era when the media was extremely interested in the island. Hence, in 2012, the national geographic visited along with a Brazilian navy escort. Their purpose was to Document golden lanceheads and raise awareness of conservation. However, due to the dangers, they did Snakebite risk protocols, drone photography, and short on-foot expeditions.

Even in the 2020s, Instituto Butantan continued their research, but this time along with the Federal University of São Carlos (UFSCar) and International genetic research groups, but Access is tightly controlled by ICMBio (Brazil’s environmental agency). The surveys show the population density has declined to 1 snake per square meter in many areas. This reduction in population size is a concern, so researchers have proposed possible captive breathing programs to preserve the species against extinction. They also suggest DNA banking to preserve genetic material. However, there’s a constant ongoing tension between conservation and scientific interest because some suggest Controlled ecotourism to fund conservation, but it is widely opposed by scientists.

Currently, in 2025, access to the island is still strictly prohibited. No one can enter without federal approval from Brazil’s environmental agency (ICMBio). They only approve scientists, medical researchers and Brazilian Navy personnel. Additionally, some documentary filmmakers might be allowed to visit, but this is very rare. Additionally, due to the latest technology, some modern research teams are using AI-assisted models to Predict snake movement and behaviour, Map venom gene evolution, and Monitor populations using automated drone imagery analysis.

Overall, this island is a place of fascination for many. Thus, it has earned a spot in pop culture and has been featured in documentaries by National Geographic, Discovery Channel, and Brazilian TV. It has also been featured in video games and fiction novels. To conclude, this island for us is a unique natural laboratory for evolution, adaptation and venom study, but for the snakes, it’s their home; hence it’s better to let them be.