Brazil's Ilha de Queimada Grande is infested with highly venomous snakes. So many golden lancehead vipers live on "Snake Island" that the government banned visitors. Most people wouldn't dare set foot on it, but occasionally, researchers or the military visit, and they take along a doctor in case of bites. Incredibly, Smithsonian.com reports, wildlife smugglers take their lives into their hands and ignore the ban. There's a demand for these specialized snakes in the exotic pet trade and on the scientific black market.

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Brazil mainland separated from the deadly island

About 12,000 years ago, "Snake Island," as it's come to be known, formed part of the mainland. However, between 10 and 11 thousand years ago, the seas levels rose.

Those snakes trapped on the island adapted and their evolution mainly involved developing a deadlier venom. Their close cousins, the original lancehead snakes still live on the mainland, and despite them not being so toxic, they account for 90 percent of snake bites in Brazil. Scientists hope to study the golden version to see if their much stronger venom could be used to counter snake bites in Brazil.

The golden lancehead didn't have anything to catch and eat at ground level, so they climbed up trees to catch birds. Allthatsintersting.com noted that "since the island vipers had no prey but birds, they evolved to have extra-potent venom so that they could almost immediately kill any bird."

Venomous snakes' potent bite

When a human gets bitten they can die within the hour. Even with a doctor and medical treatment [VIDEO], three percent of victims pass away.

The snake's bite can "cause kidney failure, necrosis of muscular tissue, brain hemorrhaging and intestinal bleeding," according to Smithsonian.com. Reports of deadly encounters with the snakes include that of a fisherman who allegedly visited the island to harvest bananas. Later, his boat was found and revealed the dead man bore snake bites and he was surrounded by a pool of blood.

The military visit the island every year. They need to take precautions as they inspect the lighthouse. Local stories point to the last lighthouse keeper and his family all being killed by snakes in their home. It is estimated that about 4,000 golden lancehead vipers live on the 430,000 square meters (110 acres) sized island.

Endangered status of Brazil's venomous snakes

While the island's snakes seem numerous enough, they actually face longterm survival issues and are listed as endangered. It seems that human development in the past [VIDEO] and predation by biopirates helped to drop their numbers by 50 percent in the last 19 years. While humans may feel the deadly island off Brazil might be better off without the snakes, research shows their venom may provide treatment for various heart conditions.