Snake Island, officially Ilha da Queimada Grande, is a small, rocky island off the coast of São Paulo state in Brazil. It is often called the island of snakes because it is the only place on Earth where the golden lancehead, a critically endangered and highly venomous pit viper, lives in the wild. The Brazilian Navy keeps the island closed to the public, and only vetted researchers are allowed to land.
Snake Island key facts
- Official name: Ilha da Queimada Grande, part of the municipality of Itanhaém, São Paulo, Brazil
- Distance from the coast: about 33 km (21 miles) off the mainland, in the Atlantic Ocean
- Size: 43 hectares (106 acres), rising to 206 metres (676 ft) above sea level
- Famous resident: the golden lancehead (Bothrops insularis), found nowhere else and listed as Critically Endangered by the IUCN
- How many snakes: the first systematic survey counted roughly 2,000 to 4,000 golden lanceheads, far fewer than older popular claims
- Other snake: a smaller population of Dipsas albifrons, a non-venomous species
- Access: closed to the public; only the Brazilian Navy and researchers vetted by the Chico Mendes Institute for Biodiversity Conservation (ICMBio) may visit
- Protected since: 1985, as an Area of Relevant Ecological Interest together with neighbouring Queimada Pequena
Facts and figures on this page come from the Wikipedia entry on Ilha da Queimada Grande and its article on the golden lancehead.
Snake Island overview
Snake Island is one of the most secluded natural spots in the world, and one of the most studied by herpetologists. Its fame rests on the golden lancehead, a viper that exists only here, which makes the island a critical habitat for the species’ survival. Because of the danger to visitors and the risk to the snakes, Brazil strictly controls who may land. The isolation also raises curious questions about how these reptiles sense the world, such as whether snakes can hear without external ears.
Where is Snake Island?
Ilha da Queimada Grande lies about 33 kilometres (21 miles) off the coast of São Paulo state, Brazil, in the Atlantic Ocean. The island covers 43 hectares (106 acres). Rainforest covers about a quarter of a square kilometre, and the rest is bare rock and open grassland. The climate is temperate, with average temperatures from about 18 °C in August to about 27 °C in March.
How the snakes got there
The snakes were not brought to the island. Their ancestors were stranded thousands of years ago, after the last ice age, when rising sea levels cut the island off from the mainland. Cut off from mainland prey and competitors, the population adapted to life in a closed ecosystem. That isolation has made the island a focal point for scientists studying evolution on islands.
Why it is called Queimada Grande
In Portuguese, queimada refers to burning land to clear it. Part of the island is barren rock because locals once tried to burn the forest to make room for a banana plantation, and the name stuck.
The golden lancehead viper
The golden lancehead (Bothrops insularis) is a pit viper that evolved from mainland lancehead snakes. Its common name comes from the pale yellowish brown colour of its underside and its lance-shaped head. It is regarded as one of the most venomous snakes in Latin America, and like other lanceheads its venom is hemotoxic, attacking blood and tissue.
With no ground-dwelling mammals to eat, the golden lancehead feeds on birds. Although 41 bird species have been recorded on the island, studies found the snake preys on just two: the southern house wren and the Chilean elaenia, a migrant that stops over on the island. The snakes are concentrated almost entirely in the small patch of rainforest.
Researchers at Brazil’s Butantan Institute study the venom for its potential in medicine. Because the whole species lives on one small island with limited genetic diversity, inbreeding is a concern for its long-term survival.
Conservation and threats
The golden lancehead is listed as Critically Endangered on the IUCN Red List. Older popular accounts claimed the island held around 430,000 snakes, but the first systematic population study put the number at roughly 2,000 to 4,000.
Since 1985 the island and neighbouring Ilha da Queimada Pequena have been protected as an Area of Relevant Ecological Interest. Unauthorised visits can lead to heavy penalties, but the island still attracts wildlife smugglers seeking snakes for the black market.
People on Snake Island
A lighthouse was built on the island in 1909 to warn ships away. Keepers lived there until the light was automated in the 1920s, and nobody has lived on the island since. Today the Brazilian Navy maintains the lighthouse, and research visits are limited to teams with permits. Researchers such as Marcelo Duarte have worked to understand the island’s ecology. As with the new species still being found in the Amazon, scientists hope the island may hold more surprises.
Frequently asked questions
Where is Snake Island in Brazil?
Snake Island (Ilha da Queimada Grande) is in the Atlantic Ocean about 33 km (21 miles) off the coast of São Paulo state, and belongs to the municipality of Itanhaém.
How many snakes are on Snake Island?
The first systematic study estimated about 2,000 to 4,000 golden lanceheads. The often repeated figure of hundreds of thousands of snakes is an outdated overestimate. A smaller population of a harmless snake, Dipsas albifrons, also lives there.
Can you visit Snake Island?
No. The island is closed to the public to protect both people and snakes. Only the Brazilian Navy and researchers approved by the Chico Mendes Institute for Biodiversity Conservation are allowed to land.
Why are there so many snakes on the island?
Rising seas after the last ice age cut the island off from the mainland and trapped the snakes there. With no ground predators and a steady supply of birds, the population adapted and became dense within the island’s small rainforest.
Is the golden lancehead dangerous?
Yes. It is considered one of the most venomous snakes in Latin America, with hemotoxic venom typical of lanceheads. That danger is one of the reasons the island is off limits.