Paradise for pit vipers
Copyright 2000, Environmental News Network
October 3, 2000
By Robin Eveleigh
A deserted island where the forest floor writhes with the world's most venomous vipers. A fisherman found dead on his boat, its deck awash with his blood. A lighthouse keeper and his family massacred in a nocturnal snake invasion of their isolated cottage home.
What sounds like the script from some tacky, low-budget horror flick may be as much fact as fiction. What's more, these tales have a purpose that goes beyond fireside entertainment. Chilling by design and passed down from fisherman, father to son, the stories perpetuate myths surrounding the forbidden shores of Brazil's Snake Island.
That's the name locals have given to Ilha de Queimada Grande, a speck of land off Brazil's southeastern coast. There, a unique species of the fer-de-lance pit viper, armed with a super-potent venom and found only on the island's 430,000 square meters, is jungle king.
Legend has it that the snake guards its forest realm with brutal ferocity. Real life has responded with a Brazilian navy ban forbidding anyone to set foot on the island.
In Brazil, snakes don't elicit the same hysterics as they do in, say, the UK, where your chances of seeing one are pretty much limited to glass cases in reptile houses and photographers on Blackpool beachfronts with bored pythons draped around their shoulders. In Brazil, particularly in the countryside where they are abundant, snakes get healthy respect and the kind of ignorant fear born of hearsay and hand-me-down fiction.
But of the country's four venomous serpents, the infamous fer-de-lance of the genus Bothrops is undoubtedly the most feared. This genus, with more than 30 different varieties, is responsible for nearly 90 percent of all snake bite accidents in Brazil, where around 20,000 people fall foul of snakes — and 100 die as a result — each year.
Named by French settlers after its characteristic lance-shaped head, the fer-de-lance is found all over Latin America, from Mexico to Argentina. Although it prefers forest regions, it is noted for being highly adaptable and is able to survive in a variety of environments. It prefers to hunt under the cover of darkness and sometimes lies on paths and trails at sundown, possibly attracted by the warmth retained by stonework, one of the reasons it counts so many humans among its victims.
But it is not just this snake's prevalence that makes it an animal to be feared. The fer-de-lance also comes equipped with a particularly nasty venom. A necrotising element causes living tissue literally to rot, which can lead to the loss of limbs, and anti-coagulants mean some victims simply bleed to death, especially if they attempt that old "remedy" of cutting the bite to suck out the poison. One embarrassed bite victim I met, 24-year-old woodcutter Jisto Dutra do Sousa, was caught out by a fer-de-lance coiled in his woodstacks and spent almost two weeks recovering in hospital. "It's the first time I've been bitten, and what I remember most about it is the incredible pain. It was immediate," he recalled from his hospital bed.
After 11 days Jisto still bore the first symptoms of the hemorrhaging and necrosis that fer-de-lance venom can cause: crusted, fading blood blisters surrounding the site of the bite on his left arm.
Jisto's story was worrying enough, but in the coastal town of Itanhaém, the nearest mainland port to Queimada Grande, the fer-de-lance has a fearsome reputation among the town's fishing community, who recognize the island as a place you simply do not go to. Few, if any, would be willing to break the navy ban for a nosy paying passenger, but they are happy to explain just why they steer so clear.
The island is home to the world's most poisonous snake, some locals told me, and there are five to every square meter. You have to hop, skip and jump over their snapping heads to avoid being bitten.
I heard the story of the fisherman who went ashore to pick bananas, got bitten and somehow managed to struggle back to his boat. There, he bled to death and was found sprawled on the blood-soaked deck of his boat. And then there's the one about the island's last lighthouse keeper (it's now automated), killed along with his daughter, two sons and wife. The family ran in panic one night after snakes crawled in through their windows, so the story goes, and were bitten as they fled through the forest by vipers dangling from tree branches. Their bodies were found spread across the island when a navy vessel stopped to make a routine supply drop.
Such stories might be enough to keep the locals at bay, but they only served to make me more curious. To reach the place myself, I turned to the Butantan Institute in Brazil's sprawling economic capital of Sao Paulo, a snake research center unrivaled in Latin America that produces nearly all of Brazil's bite serum. There, a tiny band of scientists has been working on a 10-year study of Queimada Grande's fer-de-lance — the golden lancehead (Bothrops Insularis) — and it was there that I began to learn the facts behind the Snake Island fiction.
Though it's plain the tales have been embellished with the aim of discouraging the curious, they do have some basis in fact. The venom of the golden lancehead has the same anti-coagulant properties as that of the regular fer-de-lance and there is an unusually large number on the island. The population is unchecked by humankind and the snake has no natural predators.
What's more, probably through natural selection, the beast has developed a highly potent venom. While not the world's most deadly, its venom is thought to be the fastest-acting of all fer-de-lance species.
The golden lancehead feeds almost exclusively on small birds, so rather than biting and then tracking a struggling rodent to it's place of death, it must kill fast, before dinner literally flies away and drops dead in the sea. No mammals have been found on the island and, consequently, the golden lancehead displays some unusual tree-climbing behavior, nestling in high branches as it waits for an unwary meal-to-be to flit down through the forest canopy. This is perhaps one of the reasons the snake has caught so many human visitors such as the lighthouse keeper and his family unawares.
Marcelo Duarte, a biologist who, with the permission of the Brazilian navy, has become a Queimada veteran with 21 field trips under his belt, invited me to join one of them. Our first bid to reach the island was hampered by torrential rain,and it was another month before we finally chugged out of Itanhaém, tossed by waves that rear up over the sand bar stretching across its harbor.
Three hours of tummy torment later, we reached the relatively calm and sheltered waters surrounding Snake Island, its sheer rocky sides rising up from the ocean's deep blue. A lone penguin, lost on its way north from Argentina, pondered its misfortune as it bobbed on gentle waves.
Queimada is beautiful, with steeply rising and sparsely vegetated flanks capped by dense forest where we would spend the bulk of our time. Gulls wheel about its shoreline, waiting for the fishing boats who trawl the waters around the island and guarantee a healthy feed for opportunist sea birds.
After a difficult time with a tiny dinghy, sloppy waves and slippery rocks, we were able to scramble ashore under the curious gazes of nesting brown booby (Sula Leucogaster). At this low level, researchers have only ever found one golden lancehead, so I figured the brown booby chicks and my ankles were safe for the time being.
Even so, I was handed a pair of leather leg guards — similar to knee-length, wrap-around shin pads — before we set off on the short, steep scramble through the bush to Queimada's lighthouse. From there, the study trail stretches just a mile through dense forest, along the island ridge to its highest point.
Bending low, wary of the viper's tree-climbing abilities and wishing I had eyes in the back of my head, I followed the team into the forest, happy that we were accompanied by a doctor carrying a black bag stuffed with serum. Vines tugged at my feet and thorns snagged at my clothes. Serpent fangs, happily, did not.
"We don't know what happens if a human gets bitten," explained Marcelo. Serums are specific to species, so the antidote for a rattlesnake bite is different than that for a fer-de-lance. "We know the serum for the normal fer-de-lance will work, but we don't know how much we need to use, or exactly how it would affect the victim."
Given the thickness of Queimada's undergrowth and that it's totally impossible to keep an eye on every one of your limbs, I imagine it's only a matter of time before they find out.
The unique venom is one of the reasons Marcelo and his team are so interested in the golden lancehead. "Who knows what secrets it holds? The snake's not found anywhere else in the world, just here," he said, shrugging. "Maybe the venom contains some new protein that will lead to a medical breakthrough — a new treatment or medicine?"
We made our first find literally meters from the start of the trail. Coiled on top of the earth accumulated in an old stone water tank was an adult golden lancehead, a surprisingly light yellow compared to its browner continental cousin, but still well camouflaged against the leaf litter.
It made no attempt to move at first as we peered over the stone shelf, but there was little time to appreciate the beast in this natural setting before the team burst into hurried activity, coaxing the viper into a plastic tube so it can be handled safely, measured, weighed and sexed. A tiny radio transmitter was inserted under its skin, giving the snake a unique numeric identity. If it turns up on future field trips, the biologists can follow its development.
While the scientists fussed over the delicate procedure, our accompanying sharp-eyed doctor made a startling find of two more vipers coiled less than a meter from the spot where the first was found. The snakes soon received the same treatment before being sent on their way.
Thankfully, the rumors about a writhing forest floor are somewhat exaggerated. Our eyes swept the area as we walked, scanning above our heads as well as below for more snakes. The true population of the golden lancehead is a mystery, but it's low enough for the species to be considered at "extreme risk of extinction" even though it thrives on Queimada. "A single fire could wipe the species out," said Marcelo. "It would be lost forever."
In the past, that was the aim of some mainland locals who dreamed of cultivating Queimada as an offshore banana plantation and tried to exterminate the golden lancehead with a series of bush blazes. The fires took their toll on the snake population, as did previous field trips, most notably in the 11940s and '50s when hundreds of specimens were removed for lab study. Earlier in the century, one lighthouse keeper emerged as the Island Jararaca's most feared predator, killing more than 500 in the 10 years between 1914 and 1924.
"It's too early to estimate the current population," said Marcelo, "but we've logged 400 individuals so far, on our trail alone. By the end of the study, we'll have a better idea. What we usually say is that if you're looking, along the trail, you'll see a snake about every 10 minutes. Having said that, we've discovered that where there's one, there are usually more. That compares to finding one or two snakes a day if you're searching on an island comparable to Queimada."
Marcelo's 10-minute rule proved surprisingly accurate over the next day and a half, as we found another 30 or so vipers. Toward the end of the trip I grew increasingly disappointed that I didn't see any in trees.
But then we reached a sunlit clearing at the end of the trail. There I found two golden lanceheads on the forest floor and three more coiled in sparse, spindly branches high in tree tops, where they waited for dinner. They were the last I saw before we hurried back along the trail to make it safely off Snake Island before sundown.