Where is Snake Island?

Ilha da Queimada Grande, better known as Snake Island, is part of Brazil.

It is a rocky outcrop in the South Atlantic about 90 miles (145 km) off the coast of São Paulo. It is infamous for its population of deadly vipers. The island is small, covering only about 43 hectares (106 acres).

How Did the Snakes Get There?

Snake Island separated from mainland Brazil about 11,000 years ago when the land bridge was cut off due to rising sea levels at the end of the last ice age. Due to its extreme isolation, it is one of the most unique natural laboratories in the world.

When the island was first isolated, it is likely that ancestral snake species and populations were similar to those found on the mainland. Over time, the golden lancehead outcompeted other snake species and dominated the limited resources available.

How Many Snakes are on Snake Island?

Roughly 3,000 snakes inhabit Snake Island, all of which are golden lancheheads.

The golden lancehead (Bothrops insularis) is a highly venomous pit viper species native to Brazil. It is one of the most venomous snakes in Latin America. They have a pale yellowish-brown base color overlaid with dorsal blotches. Their name refers to the cream colored underbelly and lance-like head shape. They typically grow to an average length of about 27 to 35 inches (70 to 90 cm), although some individuals can reach up to 46 inches (118 cm).

The golden lancehead is critically endangered and found only on Snake Island. The vipers found on Snake Island differ markedly from their mainland relatives. Isolated for thousands of years, they developed highly specialized traits that gave them a competitive edge.

Food resources on the island are scarce. The vipers feed almost entirely on migratory birds. When birds land to rest, the snakes strike quickly and deliver potent, hemotoxic venom. Their venom is up to five times more potent than other pit vipers, adapted for quickly immobilizing the birds. It can cause severe symptoms in humans, including brain hemorrhaging, kidney failure, and tissue death. Scientists estimate that an untreated bite carries a 7% human fatality rate.

Snake Island’s golden lanceheads also exhibit subtle changes in size and coloration, reflecting genetic bottlenecks from isolation. This specialization occurred because the island’s environment offered no alternative predators or competitors, forcing the vipers to refine traits that enhance survival in a constrained, resource-scarce habitat.

Estimates of snake density suggest there may be as many as one snake per 1,506 square feet (140 square meters) in areas where conditions allow. Earlier exaggerated claims of one snake per square meter have been debunked. Nonetheless, their numbers remain remarkably high given the island’s small area.

What Animals Live on Snake Island?

Apart from the vipers, a few bird species nest on the island’s rocky outcrops. Migratory songbirds like the Chilean elaenia and the yellow-legged thrush are common visitors. Two resident bird species—the southern house wren and the bananaquit—manage to coexist with the vipers. A limited number of lizards and invertebrates also inhabit the island, though overall animal diversity is extremely low due to the harsh conditions.

Can I Visit Snake Island?

Human activity on Snake Island is minimal and highly controlled.

Due to the extreme venomous risk, the Brazilian government has imposed strict regulations against visitation. Public access is forbidden.

The island features an old lighthouse that has been automated since the 1920s. The Brazilian navy maintains it with infrequent visits. There are no permanent residents. Only select researchers are granted access. Their work focuses on the golden lancehead. Studies examine venom composition, evolutionary adaptation, and population dynamics. Strict protocols minimize human disturbance. These measures protect the island’s fragile ecosystem and ensure that its natural processes remain undisturbed.

Illegal collection is a serious threat. Biopirates target the golden lancehead for the pet trade, with prices ranging from $10,000 to $30,000 per snake. Habitat degradation and reduced bird migrations have already caused the population to decline by nearly 50 percent in recent years. The island’s dense snake population, combined with its inaccessibility, makes it one of the most perilous places on Earth.