Tropical rain forests hold a special, almost romantic allure for those who live far enough away from the equator to experience that yearly, cold, often uncomfortable event we call winter. They are particularly appealing for those looking to add another exotic adventure to their bucket-list. Hiking, rafting, and generally exploring outside the boundaries of a comfy all-inclusive resort and into a mysterious, steamy jungle is high on many travelers’ agendas. And that approaching cold season in the northern hemisphere is a call to thousands of travel junkies and adventurers to escape the ice and snow – at least for a week or two – and head south to a warmer clime where palms replace pines and where the dollar goes a long way. Southern Mexico, Costa Rica, Belize, Panama, and Brazil are a few favorite destinations for the adventurous traveler. In general, those countries are safe, tourist-friendly, and chalk full of ample eco-touristic and off-the-beaten-path exploration opportunities for a first-hand jungle expedition.
Getting schooled on natural hazards
However, there’s a fair amount of education involved before trekking into a tropical rainforest for the first time and most resorts and eco-outfitters offer expertly guided tours and work with local professional guides who provide that education. The main message that any guide worth his weight in bug-spray will tell a guest is: Safety first! Like scuba diving or bungee jumping, there is a list of safety precaution boxes to check before entering the jungle. A good guide will make sure visitors are well informed about local hazards and to take only pictures and leave only footprints (and as little of the latter as possible). A very wise guide will also make it perfectly clear to quell that all-too human urge to touch things. That urge is perfectly normal and encouraged at petting zoos; in a tropical rain forest, that same urge can land the novice explorer in the hospital for days, result in nasty rashes and months of antibiotics, or even the relinquishing of a digit or limb. The prettiest butterfly, tree frog, caterpillar, or even flower should be eyed from a distance with caution before approaching for that macro shot or selfie. The basic rule of thumb when exploring a jungle is not to touch anything at all (except your own face and arms when smacking mosquitos) and if it’s brightly colored, it’s probably toxic. If in doubt, simply ask your guide. His safety speech may take the romance out of a jungle excursion, but it’ll save tourists from a whole lot of discomfort. Because while half of his job is to point out the beautiful, interesting and photo-worthy jungle denizens, the other half of his job is to make sure tourists make it back to the resort in one piece, literally.
Of course, every forest around the world possesses its own characteristic groups of hazardous indigenous life forms, but New World tropical rainforests are particularly noteworthy for their assemblages of dangerous species. The most notorious images that materialize tend to include large predatory animals with big, sharp teeth such as jaguars, crocodiles and the world’s largest constrictor, the anaconda, a snake that can reach almost 7 meters in length (22 feet) and weigh over 113 kilograms (250 pounds). For others, it’s the horrific mental picture of a swarm of voracious piranhas quickly turning an unfortunate cow that happened to wade into the wrong stream into an unfortunate cow that has become a fleshless skeleton. In fact, most of the jungle’s large predators tend be shy and will sooner flee and hide from humans than attack, let alone let themselves even be seen at all. They are generally much more cautious than the tourists seeking them. Even piranhas will avoid a large animal in the water unless that animal is already injured and very clearly does not offer much of a fight. Wild animals’ deadliest threats to people are usually acts of defense and self-preservation, not because they have evolved as man-hunters specifically. And although many South American animals truly are dangerous and do claim the lives of hapless tourists on rare occasions, waves of B-movies featuring giant scientist-hunting anacondas and hordes of genetically mutated piranhas out for bikini-clad flesh on spring break, of course, make real life encounters with predatory animals seem much more common and forbidding than they really are.
Toxic things come in small packages
Most of the biological hazards of Central and South American jungles, in fact, have less to do with large predators and aquatic terrors and more to do with the smaller critters that often go unnoticed. Sometimes the nastiest threats are completely unseen altogether and those are the ones about which an expert guide will offer the most caution – as well as being the ones he usually sees before you do. For example, the term fer-de-lance refers to members of a group of mainly small, inconspicuous pit vipers in the genus Bothrops. They are usually less than a meter in length and quite slim, but their relatively small size is more than made up for by their highly toxic venom, ferociously defensive behavior, and apparent lack of fear of anything. Their heads form the distinctive triangular shape of a viper (much like their rattlesnake cousins of North America) and their coloration consists of alternating dark and light diamond-shaped bands of brown to grey running the length of their slender bodies; a pattern that gives them the innocuous appearance of tree bark or dried leaves on a forest floor, a perfect disguise when hunting small birds and rodents. Their camouflage is so effective that they usually go unseen by passers-by. If, however, they are disturbed by being accidentally brushed or stepped on – or sometimes, simply stepped near – or if they are grabbed by an unwitting hiker reaching for a branch, they strike defensively and with such lightning swiftness that their victims may never see them, even after being bit. Their larger and much more reticent cousin, the bushmaster (genus Lachesis), grows up to more than two meters long and will often wait motionless on forest floors for unaware rodents, doing an equally good imitation of a tranquil pile of dried leaves. That is, unless stepped on. Envenomation by a fer-de-lance or bushmaster, if left untreated, is typically fatal.
The other generally hard to see but noteworthy hazards of South American tropical jungles comprise even smaller critters, such as invertebrates that deliver venom or microscopic parasites, or both. Those include, among other things, mosquitos, wasps, fire ants and bullet ants (named on account of how their bites feel), giant centipedes, beetles, spiders and on occasion, even venomous caterpillars. As for mosquitos, malaria still claims hundreds of lives throughout South America every year. Among spiders, the Brazilian wandering spiders of the genus Phoneutria are the most notorious and most aggressive of South American spiders; far surpassing the infamous tarantulas, which are relatively tame by comparison and not nearly as venomous. Brazilian wandering spiders are highly defensive when protecting their webs and are reported as having bitten more people than any other spider on record. They range from two to 15 centimeters (six inches) across (quite unsettling to an arachnophobe), and have been documented in the Guinness Book of Records as the world’s most poisonous spiders. Their bites can cause severe allergic reactions, but their venom is lethal enough on its own even to those with no spider allergies.
However, microbial parasites delivered by mosquito bites, or those found in poorly filtered water or improperly cleaned food, result in more medically compromised visitors to the New World tropics than all other groups of organisms combined. Those microscopic parasites responsible for dysentery, for example, can and do lead to extreme cases of dehydration to hikers and backpackers who are unlucky or unwise enough to get to a hospital in time for treatment. While it most often leads to an amusing (in retrospect) if disgusting dinner-party story after an eco-tour of Ecuador turned rough and raw, or a romantic trip on a dinner cruise up the Amazon River gone very sour, extreme cases of Montezuma’s Revenge (aka, traveler’s diarrhea), if left untreated, can lead to death by dehydration.
Charles Darwin, the father of modern evolutionary biology, is thought to have contracted a microbial infection during his travels through South America known as Chagas disease (aka, trypanosomiasis), caused by the parasitic protozoan Trypanosoma cruzi. The main vector for Chagas are small bugs in the triatomine family, which are often called assassin bugs for their practice of ambushing other small insects, or kissing bugs, referring to their habit of biting humans on the face around the mouth, sucking blood and leaving small bite marks or “kisses.” Kissing bugs in particular have been found to be mainly responsible for the spread of Chagas throughout tropical America. The symptoms include an acute initial phase of various combinations of fever, diarrhea, head and body aches, severe fatigue and loss of appetite, which can clear up abruptly within a few weeks to a couple months. However, the infection typically persists as a chronic phase over the lifetime of the host, with intermittent symptoms appearing and disappearing arbitrarily. Over time, the protozoan will cause a very slow breakdown of cells in certain vital organs. Often, the host will experience nerve damage, cardio abnormalities and digestive disturbances, leading to heart arrhythmia and malnutrition as the years advance; symptoms that Darwin experienced from his middle years on, until his death.
In his 1839 publication, The Voyage of the Beagle, about kissing bugs, Darwins wrote:
“At night I experienced an attack (for it deserves no less a name) of the Benchuca (a species of Reduvius) the great black bug of the Pampas. It is most disgusting to feel soft wingless insects, about an inch long, crawling over one’s body. Before sucking they are quite thin, but afterwards they become round and bloated with blood, and in this state are easily crushed. They are also found in the northern parts of Chile and in Peru. One which I caught at Iquique, was very empty. When placed on the table, and though surrounded by people, if a finger was presented, the bold insect would immediately draw its sucker, make a charge, and if allowed, draw blood. No pain was caused by the wound. It was curious to watch its body during the act of sucking, as it changed in less than ten minutes, from being as flat as a wafer to a globular form. This one feast, for which the benchuca was indebted to one of the officers, kept it fat during four whole months; but, after the first fortnight, the insect was quite ready to have another suck.”
Darwin did, in fact, suffer from a distressing infection while traveling through Peru not too long after he was ‘attacked’ by kissing bugs, where in he was confined to a bed for more than a month. And due to Darwin’s celebrity status and because of his widely known declining health during his mature years, in some circles Chagas disease is called ‘Darwin’s disease.’
Do not stop and smell these roses
If venomous animals and parasitic microbes aren’t enough, there is yet a whole other category of living liabilities of hiking in a tropical forest; much of the peril can come, quite literally, from the forest itself. Many tropical plants present formidable barriers to travelers. Various palm species and trees and shrubs of the pea-bean family, particularly acacias, are thorny or prickly enough to poke, scrape, and stab the un-mindful hiker, causing serious wounds despite protective clothing. There is also an array of tropical, vine-like species of cactuses with spines that can pierce leather boots and gloves – and by extension, feet and hands. Additionally, anyone who has hiked the uplands and tropical dry forests of Mexico and northern South America can testify to the effective sheering capabilities of the sharp, saw-toothed edges of members of the agave family. And any qualified climber from southern Mexico to South America will attest that the dagger-like leaves of the otherwise mostly not-so-tasty members of the pineapple family, the bromeliads, are the wrong things to grab onto when scaling a rocky cliff face.
But the fun doesn’t stop there. There are also countless plants in the American tropics with chemicals that can cause skin rashes and allergic reactions ranging from mildly irritating to maddeningly painful. There’s the stinging Neotropical spurges of the genus Cnidoscolus, locally known as ‘mala mujer’ (evil woman), notorious for their spiteful, tiny hair-like spines that inject a bothersome toxin and also work their way into their victim’s skin, causing an itchy rash that can last weeks [Author’s note: Mala mujer makes stinging nettles feel pleasant by comparison. Trust me on that one.]. Then there’s the burning sap of Sapium trees, which can cause skin to blister, bubble, and fall off like hot wax if left untreated. At the extreme end, some plants contain toxins that rival the venom of any spider or snake. Chief among those is the furari vine, Strychnos toxifera, commonly known to westerners as curare. This climbing liana produces small, attractive red berries that should, under no circumstances, be eaten. Even a small amount of raw curare sap, found throughout its bark, leaves and fruit, contains enough powerful alkaloids to cause extreme muscle spasms that will stop lungs from functioning within minutes upon passing into the blood stream; causing the victim to quickly suffocate, turn blue, pass out and die. Curare sap is the most common poison used by South American tribes to coat the tips of arrows and darts for hunting and warfare. It is also one of the sources of strychnine, a chemical used in pesticides for killing rodents (basically, rat-poison).
Perhaps trekking through tropical rainforests has been summed up most accurately, if somewhat unglamorously, by Dr. Mark E. Olson, professor of evolutionary botany at the Universidad Nacional Autónoma de México, and veteran explorer and plant collector of tropical forests all around the world. About exploring New World tropical rainforests specifically, Dr. Olson says:
“It’s hot and humid and the air never moves under the gloomy canopy. I sweat a lot, uncontrollably and without dignity. My undergrad took to calling me ‘the shower.’ The mosquitoes and no see-ums bite more ferociously when your clothes are wet. There are chiggers. Chiggers!!! They are what make you look like hamburger after a day in the woods. And tiny, tiny ticks and fleas that are invariably in places where peccaries root or wallow. Just when it dawns on your slow brain that you’re in one of those spots, it’s too late and you are covered in fleas and millions of mini ticks. You get a caterpillar down your collar and they sting your hot, sweaty neck. And don’t forget the common and surprisingly annoying stingless melipona bees that burrow into your hair to your scalp and bite you… You have to look out for snakes on the ground, especially fer-de-lances, which are not afraid of people, often don’t slink away, and can inject a huge amount of a powerful hemo-/neuro-toxin cocktail. But you’re sweating, remember, so your glasses, if you wear them, get drops of sweat on them and now and then fog up completely. You’re looking intently at the ground for snakes so you walk into spider web after spider web. Many are a lovely golden color and are like fine steel, made by the largest orb weaver in the Americas; a giant mother with a body (not including legs) more than two inches long. You can’t get all the webs out of your hair, off your wet, foggy glasses, or off of your arms, and you get bitten by spiders. I was finally able to bend my left middle finger a week after a bite on the knuckle. It’s muddy, so you slip. Foolishly, you grab a palm trunk, but they’re covered with vindictive spines that manage to stay cruelly rigid even after decades in the rain. You stand up horrified to examine the throbbing wounds on your hand and you bump your head into the spiny leaves of the same palm, now digging spines into your scalp. You jump back, shaking what looks like a nudibranch onto your face from the palm leaves. It looks soft and yellow and made out of little elongate oval packets. Maybe an insect egg case? You will never know for fear of it biting too, or maybe leaking some nasty poison onto your skin. Anyway, it’s too dark to see anything under such a closed and tall canopy. Try finding a tree when you can’t even see the leaves. I could go on and on, but I swear I don’t believe the [authors] who wax eloquent about the primeval majesty of the rainforest.”
For the most part, a first time trek into a rain forest is fun and pleasant and will usually yield more good memories and photos than ailments. Mosquito bites are expected, but they go away quickly and aren’t fatal. Being self aware, listening to the guide and generally having a healthy dose of respect for the natural surroundings of a tropical rain forest (or any nature area, for that matter) are good things to keep in mind. Don’t forget the bug-spray.