This African Island Was Once Used As A Prison – But Now It’s Overrun With Giant Creatures

In the Indian Ocean a few miles off the coast of Zanzibar, there lies an idyllic-looking island with an extraordinary secret. Despite being just 800 meters in length, this tiny slice of land was adapted to provide a rather unsettling service. Now, though, it’s been taken over by enormous creatures.

The beautiful land mass is officially known as Changuu in the Kiswahili language, which is the common tongue of Zanzibar’s inhabitants. And the name is derived from a species of fish that’s plentiful in the seas that surround it.

Changuu is situated about 15 miles from the African mainland and is just a half an hour motorboat ride from Zanzibar City, which is the semi-independent African island’s capital. The islet is often referred to as Kibandiko, or by two other nicknames that reference its chilling past.

Yes, the tiny, oblong-shaped island has a fascinating yet somewhat disturbing history. But for many years it was just a desolate atoll out in the Indian Ocean. Not until deep into the 19th century was the site populated by humans, you see.

That’s according to what’s been recorded in the history books, anyway. It seems, then, that the first time humans populated Changuu Island was back in the 1860s. It was then that Zanzibar’s ruler Sultan Seyyid Majid personally handed it over to a pair of Arabs.

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While those Arabs’ names appear to be lost to history, what we do know is that they’d selected the island for a sinister purpose. Yes, Changuu would become an incarceration center for slaves who were deemed to be particularly unruly. And this would inform the island’s later uses as well, which were prompted when a fearsome world power began to flex its muscles in the area.

That formidable force would, of course, be Great Britain. The European nation had held sway with those who ruled the principal island of Zanzibar for a considerable time. The reigning sultans there had originally come from Oman and had seized control of the territory from the Portuguese explorers who’d settled there at the end of the 15th century.

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Nearly 360 years later, the then-ruling Sultan, Majid bin Said, broke with Oman and made Zanzibar a state in its own right. Great Britain was pleased with that decision, but several years later it began to exert even more influence over the country. And in 1873 the British gave a warning that they’d lay siege to the island if the trafficking of slaves continued on Zanzibar.

Then, in 1890 – after negotiations between Germany and Great Britain – Zanzibar was classified as a protectorate under British control. A military officer named Sir Lloyd William Mathews was duly selected as the first minister. And the Madeira-born Briton would serve the authorities there until his death in 1901.

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Before his passing, Mathews certainly made his mark on that area of the world. After serving in the Third Anglo-Ashanti War, he moved to East Africa to assist the abolition of slavery. And from 1877 he helped Zanzibar’s rulers to create a modern armed force, training thousands of men to quell local uprisings and fight against slavers in the area.

Three years after the main island had been turned into a British protectorate, Changuu itself was acquired by Great Britain. The powerful empire purchased it on behalf of the Zanzibar government. Mathews stumped up the necessary cash in 1893 to buy it off its Arab proprietors.

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But when it came down to deciding how the island was to be used, both Matthews and the ruling authorities of Zanzibar had a clear objective in mind. They wanted to construct a brand new penitentiary there, you see. And the intention was to incarcerate the region’s most feared criminals in the purpose-built jail.

It didn’t take long to build – they weren’t aiming for five star luxury, after all – and was ready to house prisoners just a year after the island was purchased. Changuu was widely referred to as “Prison Island” during this period and may well have had a fearsome reputation.

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But as it turned out, local criminals needn’t have worried about the development at all. That’s because, in reality, the purpose-built penitentiary on Changuu would never be used to house prisoners. And the region’s hardened crooks could all breathe a sigh of relief.

It’s no doubt that a lot of work would have gone into constructing the jail. So why, then, did it end up being unoccupied? Well, the answer seems to be down to a lack of foresight and planning. In the end there simply wasn’t enough fresh water on Changuu to be able to run the complex effectively.

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“Prison Island,” therefore, turned out to be something of a misleading name. And its planners were certainly guilty of such a huge and embarrassing oversight. All was not lost, though, as the Zanzibar authorities still found another use for the tiny islet.

That new purpose was informed by Zanzibar’s ever-increasing status and its strategic positioning on the world map. Yes, those two factors led to the island becoming the most significant port on Africa’s East coast by the start of the 20th century.

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As a result of its increased status as a major port, the authorities of Great Britain, Zanzibar and the nearby African countries Kenya and Uganda began to grow anxious. Becoming East Africa’s main port obviously meant more ships and people were arriving. And, naturally, this influx greatly increased the likelihood that illnesses would spread.

Authorities didn’t want epidemics to be transmitted to Zanzibar. So at the close of the 19th century, the British-led authorities in the country – supported by Uganda, Kenya, and Tanganyika – decided to do something about the threat. And they’d need Changuu Island for their plan.

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That’s right: a quarantine station was set up on the tiny islet in the Indian Ocean. Infected passengers would be brought here to recover from illnesses that likely included malaria and flu. But the most significant of the conditions treated on the island was yellow fever.

Yellow fever was a particularly problematic illness for the British to contend with and is widespread in areas of Africa with a tropical climate. Like malaria, it’s transmitted to humans via mosquitoes, and in this case, infected adult females. The virus causes head pains, muscle aches, sickness and jaundice among other symptoms. And if untreated, it can be fatal.

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The quarantine station on Changuu would serve all of the territories controlled by the British Empire at that time in East Africa. And the unused penitentiary that the Brits had built was transformed into a medical center. Those who’d fallen ill were brought down from the vessels and supervised for a week or two, at which point they were allowed to go on their way.

Due to its new use as an isolation station, then, the islet became known as “Quarantine Island.” And that’s regardless of the fact that it only really served this purpose from April until November, which is when most of the ships were arriving.

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It made sense, then, that the owners of the island wanted to put it to yet another use during these quieter seasons. And that’s how the idyllic islet in the Indian Ocean turned into a bustling vacation spot. It’s got a lot to offer, after all, what with its attractive beaches, plentiful flora and the stunning waters that surround it.

The picturesque island soon attracted a cluster of holidaymakers from both Zanzibar and further afield. This prompted the authorities to construct a new building – which they called the European Bungalow – near the end of the 19th century. Pits created by earlier coral-mining projects were transformed into swimming pools, too.

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The number of sun-seekers who could stay on Quarantine Island was strictly capped, though. The issue was essentially the same as with the aborted prison – the rainwater captured and stored in underground tanks was the only fresh water that was available. But in 1919 a small group of unusual visitors arrived to permanently put down roots on the island paradise.

Those new settlers were four Aldabra giant tortoises, an ancient and endangered species of aquatic reptile. The enormous creatures were donated by the British governor of the nearby Seychelles to Zanzibar’s government. And the awesome foursome would happily make Changuu their home.

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You see, the four Aldabra giant tortoises would in time essentially take over the whole island. The reptiles – which often weigh more than 500 pounds – began to thrive in their new environment, cut-off from the world with no potential predators. There was also ample foliage on Changuu for them to eat and plenty of shelter among the trees.

Before long, the Aldabra giant tortoises began to reproduce. And without the threat of any species that might fancy taking a nibble out of them, their numbers progressively swelled. In 1955 – less than 40 years since they first settled on Changuu – the population of the huge reptiles had grown to approximately 200.

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The herbivorous giants evidently spend much of their waking hours searching for food. And as we suggested, they thankfully didn’t have to look too far on Changuu. They were able to munch their way through over 20 different types of grass and herb there – sometimes referred to as “tortoise turf” – with the odd fruit or insect thrown in for a treat.

The adorable reptiles have even been observed standing on their back legs in order to reach desirable food placed on branches higher up. So, Changuu had evidently been an ideal home for them since their introduction in 1919. But in subsequent years, the giant tortoises would suffer a succession of cruel blows.

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One such setback for the endangered reptiles was the other animals being brought to live on the island by humans. These additions included both domesticated creatures such as dogs and livestock including goats. And it meant that the numerous Aldabra giant tortoises roaming across Changuu now had an unwanted contest for food.

But in reality, it wasn’t much of a competition, as the goats that were introduced to Changuu were able to graze much more quickly than the slow-moving tortoises. They could chomp through much of the islet’s flora before the reptiles even had the chance to reach it. As you can imagine, then, it wasn’t an ideal situation for a species that was already endangered.

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On top of that, the giant tortoises had to endure the increasingly destructive impact of humans. As is the case for a lot of animals, unscrupulous visitors began to poach the creatures to eat or to peddle as exotic pets.

These issues saw the giant tortoise population suffer an alarming drop in numbers. Three decades after their clan reached the high-point of 200 individuals, the reptiles’ presence had been cut in half. Just a couple of years later, it had been halved again to 50. And even more shockingly, in 1996 their numbers had plummeted to only seven.

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Clearly, something had to be done before these magnificent creatures were lost from the island altogether. And attempts were then made to address the worrying drop in numbers. Later in 1996 concerned conservationists brought 80 young tortoises to Changuu to increase the population. But half of these newcomers disappeared, perhaps falling victim to more illegal poaching.

The now-independent government of Zanzibar needed to take serious action. Helped by a global conservation agency, it set to work on constructing a huge compound to safeguard the endangered tortoises. And, thankfully, by the year 2000, the population had started to rise – with 90 hatchlings, 50 juveniles and 17 adults recorded.

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Since then, these efforts have borne even more fruit. The population slide has been successfully addressed, and further tortoises are periodically relocated to Changuu from elsewhere in the world for the species’ safeguarding. It certainly helps as well that an organization is currently based on Changuu that’s devoted to the Aldabra giant tortoises’ survival.

In recent years the island has become something of a tourist trap, in fact. People from far and wide travel to Changuu via Zanzibar, primarily to get up close and personal with the giant tortoises. The curious creatures often unwittingly pose for photographs with an adoring public who’ve voyaged across the ocean to pet and feed them.

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With regard to the island’s former uses, work has continued since 2002 on restoring Changuu’s many historical buildings and expanding its amenities. The old quarantining area, for example, has been turned into luxury accommodation with incredible views. The prison has been converted into living quarters, and numerous new facilities such as shops, a tennis court and even a library have been added. But despite all the fancy new structures and facilities, there’s little doubt the giant tortoises remain the island’s star attraction.

And residents are probably glad that it was one of the friendlier reptiles that went on to roam their island. The same can’t be said for Brazil’s Ilha da Queimada Grande, though, as what’s taken over there is arguably much deadlier. In fact, the situation has got so bad that the navy forbids visitors from setting foot on its shores.

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If you sail from the coastal city of Itanhaém in Brazil and head south, you’ll come across a small island. It’s unassuming and measures just over 100 acres – and no one lives there. That’s because Ilha da Queimada Grande hides a deadly secret. And only a handful of intrepid travelers and scientists have made the journey to the atoll to report back on its treasures.

If you view Ilha da Queimada Grande from a boat, it may look inviting. Its rainforest probably gives the impression of a jungle paradise to onlookers, and its sandy beaches look like the perfect places to spend a lazy hour or two. The climate is ideal for barefoot strolls, too, getting to a balmy 66 degrees Fahrenheit in winter and rising to 82 degrees when summer kicks in. But don’t be fooled by this air of idyll.

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Once you land on Ilha da Queimada Grande, it becomes even more deceiving. Think thick foliage and outcrops of rock wherever you look – and the sound of waves landing on the shores never being too far away. But this spectacular landscape hides one of the natural world’s deadliest predators.

In fact, danger lurks around practically every corner: this seemingly peaceful paradise is actually known as “Snake Island.” In the past, people have said that the islet was home to hundreds of thousands of snakes. And although estimates are far lower than that today, there are still plenty of serpents living on the island. The reason for this drop in numbers, however, may stem from the actions of an even more ruthless predator.

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Among the snakes on the island is Dipsas albifrons, which is no danger to humans. It is a lethal enemy of snails, though, which it happily consumes. But alongside this snail-eater are at least a couple of thousand golden lancehead vipers. And they pose a much greater threat to people. In fact, they are among the deadliest snakes on Earth.

The golden lancehead viper is a member of the Bothrops genus – a group of snakes named for the shape of their heads. But the ones on Ilha da Queimada Grande are distinguished by the color of their bellies. And although 36 sister species are found across South America, the golden lancehead viper is only found on this specific island.

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While golden lanceheads usually grow to a little over 2 feet long, some, terrifyingly, have been observed at nearly double that. And if that’s not worrying enough, these snakes have evolved a long tail so that they can travel through trees. However, the creatures are doomed to stay on their island home.

That’s because the golden lancehead viper cannot swim. Some snakes are perfectly at home in water; for instance, some coral reef snakes live their whole lives in the sea. But these serpents don’t like to get their snouts wet. And so, they’ve lived in isolation on this island for thousands of years.

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But how did the golden lancehead come to live on Ilha da Queimada Grande in the first place? One story goes that pirates brought the serpents ashore and used them to guard their buried treasure from other bandits. Mind you, it’s not clear how these gold-loving buccaneers might have managed to convince the snakes not to attack them, too.

In fact, the truth about the snakes is that they became stranded on Ilha da Quiemada Grande about 11,000 years ago. It’s believed that the level of the sea rose so much that the island was cut off from mainland Brazil. Then, isolated on their new home, the serpents evolved over the following millennia into their own distinct species.

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Thanks to this remote island habitat, the golden lancehead viper has no known predators. It’s possible that youngsters may fall prey to various creeping, crawling and flying beasts. But once grown, it is believed that the snakes live in complete safety. And this has meant that the creatures have been able to reproduce to the point that the atoll is now swarming with them.

But just as Ilha da Quiemada Grande seemingly has nothing that can challenge the viper, it in turn provides little for it to tuck into. Indeed, the main source of food comes in the form of birds that have landed on the island during their seasonal migration. And to get at the prey, the serpents have to wriggle skyward, climbing up tall rainforest trees.

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That said, the golden lancehead only really chows down on two species of birds. This is despite the fact that 41 species have been spotted on the island. The viper eats the southern house wren – if it can catch it. And the snake also enjoys the occasional meal of white-crested elaenia, which is a flycatcher that feeds in the same places as the snake.

Meanwhile, a curious outcome of preying on birds is that the golden lancehead viper has evolved powerful, fast-acting venom. Snakes usually pursue their victims after biting them, you see, waiting for them to succumb. But this isn’t as easy once it comes to birds, and so the species has adapted to possess a far more deadly weapon.

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So potent is the golden lancehead’s poison, in fact, that if one of these snakes bites you then you have a seven percent chance of dying. And even if you’re treated, the likelihood of death is three percent. The other consequences of a bite aren’t pretty, either, mind you. For instance, the venom can cause a person’s kidneys to fail or their brain to bleed.

What’s more, the venom is so toxic that it can also melt skin. When chemists have studied the poison, they’ve observed that it may be five times stronger than that of other Bothrops snakes. Altogether, the powerful punch of the snake’s bite means that the golden lancehead viper ranks among the world’s most dangerous serpents. And yet not even this unsettling revelation has kept some individuals away from Ilha da Quiemada Grande.

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Indeed, locals on the Brazilian coast have their fair share of stories about the snakes’ deadliness. One terrifying tale is that about a fisherman who visited the isle for bananas, not knowing that it was home to the vipers. Assailed by the serpents, it’s said that he struggled back to his boat, where he was allegedly found lying stone dead. But he wouldn’t be the last explorer to be tempted by the island’s riches.

Perhaps unsurprisingly there is a lighthouse on the island to warn mariners of the rocky shoreline. And it’s believed that a plucky handful of people actually lived there for some years, although this was a long time ago. They tended to the lighthouse between 1909 and the 1920s – until tragedy struck.

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You see, one dark night, a bunch of vipers allegedly slipped into the lighthouse keeper’s home. And there were gruesome consequences: it’s said that he and his family were killed by the vicious reptiles while they were sleeping. Worse still, when rescuers arrived to search for the family, they too apparently fell prey to the deadly creatures.

And while this story may be more myth than fact, there’s no doubt that the location still poses a threat today. Indeed, when staff from Vice magazine accompanied the Brazilian navy to the lighthouse, they were in for a nasty surprise. The magazine’s Editor in Chief had been sitting on a box in the lighthouse, out from which a snake slithered just moments later. Clearly, the journalist had had a lucky escape.

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Given this danger, no one lives on Ilha da Quiemada Grande today, and the lighthouse now works automatically. The Brazilian navy, meanwhile, forbids anyone from even visiting the isle apart from a few specific exceptions. So, since the 1920s, very few individuals have ever stepped foot on Snake Island. But there are still some who are daring enough to make the eight-hour trip.

Among them are Brazilian servicemen, since the navy has the responsibility of keeping the lighthouse in good condition. Some researchers are also permitted to study the snakes, with the island and its serpentine inhabitants proving important to science. And as we’ve already noted, journalists accompany these visitors on rare occasions, too.

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When it comes to scientists, they spend their time on the island monitoring the serpents and keeping the species going. This care is needed because Snake Island is not a natural habitat for the vipers – despite its moniker. Researchers hence look at where the snakes move and what parts of the island they inhabit. And they also work to restore the atoll’s vegetation, which has been damaged over time.

The work in tracking the serpents is done by small groups of experts who visit the island regularly. These brave souls actually set out to capture individual vipers. And once they get their hands on one, they measure the animal’s weight and length before injecting a tag into it and letting it go.

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Of course, the scientists must take precautions when they visit. They have to dress appropriately and be on the lookout for slithering serpents. Plus ,they handle the snakes with specialized equipment designed to keep themselves safe. And understandably, the authorities won’t let anyone onto the island unless a doctor goes, too.

One person who hasn’t been put off by the risks posed by the vipers is photographer João Marcos Rosa. He has visited the island three times in order to snap images of the snakes and their spectacular habitat. And some of the daredevil’s stunning images can be seen right here in this article.

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Rosa traveled to Ilha da Queimada Grande with a group of researchers who were taking a census of the island’s snakes. During the four-day trip, Rosa saw the deadly serpents first hand and at terrifyingly close proximity. As he told Scribol, “It is easy to find the snakes. As soon as you leave the rocks and start walking in the middle of the trees, you will always find them.”

Indeed, Rosa and the team happend across hundreds of snakes during the course of their four-day visit; it seems as though the creatures were wherever they turned. During a trek to the uppermost part of the island, Rosa and the scientists reported that they had “48 encounters with [individual snakes].” And while this may give us the shudders, it was a risk that the photographer was willing to take.

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In order to get the best photographs, Rosa had to get very close to the snakes at times. In fact, he would position himself just a few inches from the serpents. It’s a situation that would make most people extremely nervous – and rightly so. But for Rosa, it was all worth it for the perfect shot.

That said, Rosa and the researchers did take a number of precautionary steps on their visits to Ilha da Queimada Grande. It was important to make the possibility of a bite as unlikely as possible, after all. Rosa explained, “We had to use protections for our legs and be very careful where we put our hands [in order to] not grab a snake.”

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And it would seem that said measures were effective – for Rosa and for others – as there’s no official record of a viper biting a human on the island. But other lancehead snakes have been known to be deadly, too. In fact, they cause more deaths than any other serpent in the Americas. In Brazil alone, for instance, they are actually responsible for nine out of ten snakebites. One can only wonder if this information is known to those who would visit the island illegally.

That’s right: the snakes’ dangerous reputation has not put off travelers from illicitly making their way to the island’s shores. These wildlife “bio pirates” land with the aim of capturing the vipers in order to sell them on the black market. Just one serpent can go for as much as $30,000. So it’s no wonder that even security cameras cannot deter the poachers. There are reportedly even temptations for those in law enforcement who are tasked with capturing the bio pirates.

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Yes, there are in fact claims that corruption has crept into the police’s crackdown on the poachers. A smuggler using the pseudonym “Juan” told Vice that criminals could pay inspectors a bribe. And this would subsequently help get them out of prison. He went even further, though, suggesting that some authorities were actually involved in smuggling themselves.

This illicit activity has perhaps played a part in landing the golden lancehead viper on the Brazilian endangered species list. Meanwhile, competition for food seems to have suppressed the population of the snakes. A 2008 survey in fact suggested that there were no more than 4,000 of these serpents on the island – and it identified illegal capture of the serpents as a critical threat to their survival.

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Another reason for the snakes’ endangered status is revealed by the island’s name. In Portuguese, Ilha da Queimada Grande means “Island of the Great Burn.” This moniker stems from the fact that people once tried to create a plantation for bananas there. And to clear the land, they had to burn the rainforest – likely killing vast numbers of the serpents and destroying much of their habitat.

Mind you, biologist Marcelo Duarte says that there is still probably one snake for every 11 square feet on the island. And Duarte should know, as he’s been to the island on no fewer than 20 occasions. Frighteningly, the prevalence of the serpents means that you are, on average, within about three feet of one at any given time. It may be a good thing that there are so many of the creatures, though, as they could hold a very important purpose.

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Duarte told Smithsonian in 2014 that the golden lancehead viper may yield significant medicinal value. Indeed, he explained that the snake’s venom has the potential to assist with blood circulation, clotting and heart disease. Speaking to the magazine, he said, “We are just scratching this universe of possibilities of venoms.”

More wrongly, though, this medical potential may actually be what is fuelling the smuggling trade. The poachers’ clients may be willing to shell out thousands for a single snake in order to get hold of the venom, which they could then patent. And individuals have apparently been known to offer cash to scientists on their return from the island in exchange for live specimens.

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All in all, though, Ilha da Queimada Grande will probably never be much of a tourist destination. Indeed, during their trip, the journalists from Vice magazine found that the snakes were just one of the alarming animal species to be found on the island: they shared their camp with locusts and giant cockroaches, too. Suffice to say that they did not make a return booking.

So while it’s not impossible to break the law to sneak onto the island, it’s a very bad idea indeed. Instead, visitors can safely see the snakes at Duarte’s Butantã Institute in São Paulo, or they can visit that city’s zoo. There, five of the venomous reptiles can be found, safely contained behind a fence: all hiss and no bite.

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