There’s a lot to excite the imagination when navigating rivers, but what’s really dangerous about them, apart from the swirl and the dirt, of course? Fear has big eyes, they say, and when it does, a sinister reputation does not escape, whether one deserves it or not. Were the natives of the Amazon right when, in their day, they dared not even walk along it, let alone jump in? And which is more likely to end up in the mouth of a hippopotamus or killed by a sea whip, if we are not first smothered in its embrace by a green anaconda, another of the fearsome inhabitants of the world’s rivers? Or will we be eaten by piranhas after all?
“They are the most terrifying fish in the world,” wrote Theodore Roosevelt, the 26th US President, in his book Through the Brazilian Wilderness. Even sharks attack animals smaller than themselves, he continued, and “piranhas as a rule attack those much larger than themselves. They bite the finger of a hand thrust carelessly into the water and disfigure swimmers – in every seaside town in Paraguay there are people who have been disfigured by them. They will tear apart and swallow alive any wounded man or beast, because the blood in the water excites them to infinity.”
The book was published in 1913, four years after he left the White House. It became a bestseller, and piranhas, which live mostly in South American rivers, became a fear and a tremor in people’s hearts.
But quite unfairly, says Richard Conniff, because most piranhas live like humans, “in quiet hopelessness. Instead of showering their prey with a display of gleaming teeth, piranhas mostly lie in wait for their prey, stalking it and even pretending to be other species of fish in order to cunningly catch their prey.”
Stories of piranhas tearing humans apart are a myth, although it is true that they are attracted by the splashing, the sounds and the blood. It is possible, say researchers, that they have become accustomed to recognising the sounds of fruit and nuts falling from trees into the river, so they may mistake children playing in it for food.
Blood may not upset them as much as Theodore Roosevelt wrote, but it is true that they can smell a single drop of blood in 200 litres of water. But even if we were injured in the water, the likelihood of being bitten by a piranha is small, unless perhaps a starved member of the most aggressive species, the red piranha, were nearby.
But it wouldn’t just attack a human, either. Most likely, it would bite into the flesh if it was really hungry or threatened, for example when the water level is low and it was defending itself. Fishermen have to be a little more careful when they throw piranhas back into the sea from their nets, or perhaps harvest them for sale, as they are a sought-after speciality in some parts of the world.
They are mostly used to make soup, although it’s not supposed to be good, or grilled and served on a banana leaf with tomatoes and limes. Elsewhere, people would not touch a piranha even if they were starving, because it is unthinkable to eat an aggressive fish, while others eat piranhas because they are supposedly an aphrodisiac.
The average person would not touch a piranha, but the average piranha would not touch him either. Not only because many piranhas eat fruit and greens along with meat, and some species are even completely vegetarian, but also because they are fundamentally uninterested in human flesh.
They mostly eat insects, fish, insects, crustaceans, carrion, grass and other aquatic plants, but little else. A red piranha, for example, eats an eighth of its weight a day, or 2.46 grams of food, but it’s true that in times of trouble, it can also help itself to a bit of its siblings, dead or alive.
If a human corpse has ever been found with piranha bites, they usually occurred after the person was dead, so they were not killed by piranhas. For a man weighing 80 kilograms to be gnawed to the bone in five minutes, as seen in the movies, he would have to have been gnawed by 300 to 500 piranhas at once.
There could be that many in a pile, because piranhas are not solitary, although they do not form large groups to control their prey, but because they are scared. Researchers have noticed that the core of the group is always made up of older members of their species, with younger members at the edges, and that they tend to group more consistently in shallow waters where they are more at risk.
The fact that piranhas are essentially cowardly is shown by the fact that they prefer to bite their prey in the tail, although they will sometimes attack it in the eyes, but it is true that they do not retreat before a fight.
When they see a rival, they first make a few short sounds to warn the opponent to think again before they decide to fight. If this does not work, they lower their tone and “growl”. If the opponent does not understand even this open threat, they gnash their teeth to indicate that they are ready to fight.
They can bite quite hard then, but still not very hard. The bite force of the largest of its kind is three times its weight, when it has teeth of course. Every now and then they fall out, but not one by one, but four together, so that a partially stubby piranha is not an unusual phenomenon.
The word piranha means ‘toothed fish’ in the Tupi language, and the description is quite apt, as piranha’s teeth are as sharp as a blade. They have to be, given that piranhas are carnivorous, not only in South America, but also in the UK and Texas in the USA.
Not that they are native there either, but they are very adaptable and invasive, so they survived when the reliable exotic fish lovers got fed up with them and poured them from the aquarium into the local river. And even there, although they don’t like picking abundantly coated bones, such as human bones, people are still scared to death of them, despite the best efforts of researchers to wash away their sinister reputation.
Anaconda
But the fear of the green anaconda, which is what we usually refer to when we say anaconda, is well-founded, even though that name encompasses four different species of anaconda. It swallows its prey whole and can also put a 54 kg white-tailed deer through its extremely flexible jaws.
If it can swallow him, could it swallow a man? It could, researchers say, if it was similarly heavy, but so far they have never heard of such a thing. All that is known is that two anacondas have attacked two researchers, and that because they were provoked. They had been in their vicinity for so long that the snakes simply had to move away, even though they failed to feed.
But the average person will find it very difficult to cross the path of the green anaconda, which is the heaviest snake in the world, one of the longest, and, like its three smaller cousins, lives in South Africa’s tropical rivers and swamps east of the Andes.
But even if you walked there, it would be hard to see it on land, because it spends most of its time in the river. She is an excellent swimmer and can hold her breath for up to 10 minutes underwater. She doesn’t usually need to do this, but because her eyes and nose are on top of her head, she can swim, hidden beneath the mantle of the river, and only a fraction of her head can emerge from the water.
It swims steadily and also quickly, but is slow and clumsy on land. It does not like to wade on it, even though it is not in any danger, because it has no natural enemies apart from man.
When she wants to warm up and dry off, she hangs herself on a tree and hangs from it, which is an unusual scene considering how heavy and long she is. Well, nobody knows exactly how heavy and long it is, because researchers can’t ask it to step on the scales or stretch out to measure it.
Thus, its length is estimated by eye, but because fear has large eyes, anacondas are usually longer than they are, according to those who have encountered them. Theoretically, researchers could measure their skin after someone has skinned them and brought it to them after death, but it can be stretched, so even this measurement would not be reliable.
In principle, an anaconda is thought to weigh between 45 and 68 kilograms on average, although the heaviest is thought to weigh around 250 kilograms. The average male is 2.7 metres long and the average female 4.5 metres long. The sex differences between the sexes are extremely large in anacondas, which means that, among other things, the female is much larger than the male, which also means that she eats him easily.
Sometimes you really do, because these snakes, which have a reputation for devouring people and changing shape, and which people also believe are magical and spiritual creatures that have a healing effect on humans, are not very picky when it comes to food. They eat all kinds of meat, from the males and young of their own species onwards, although they prefer caiman and rodents, and will also eat, for example, jaguar. When they decide to attack such large prey, they risk being at least injured in the fight, if not falling and becoming dead.
As a rule, they are the ones who bring the prey to the other world, but not in the way we used to believe, when it was believed that the victim was crushed or broken bones were broken, or the chest was squeezed so hard that the victim breathed out. When the researchers looked a little more closely at what was happening during their meal, they saw that they were not crushing their victims, but rather straining their circulation so that the blood could no longer reach the brain. The prey thus dies within seconds from ischaemia or lack of oxygen.
Sometimes they even drown their victims, but only after they have grabbed them with their powerful teeth. They may not have poison in them, but with the body they have, they don’t need it either.
They hunt in the cover of darkness, so they look for prey mainly at night and in the evening, usually close to the shore or in murky waters, where they blend in beautifully with their surroundings.
Once they have control of their prey, they can easily stuff it into their mouths because they can open their jaws 180 degrees and stretch the ligaments so that the prey slides easily into the body, which is also stretchable. They will not touch food for several weeks, or, if the meal has been large and abundant, not for several months.
An anaconda that is “pregnant” does not eat a live pup until it is born, for fear of losing it during the hunt. It carries its eggs – which can be 20 or even 80 – and when they are ripe for hatching, it gives birth to live chicks. Nothing is taken from them, so it is no wonder that it is the adult green anaconda that can be fatal to the young green anaconda, who crave a modest but tasty starter.
Kandiru
The opposite of the giant anacondas are the tiny candiru fish, which have sometimes been shown to hide poison in tiny bottles. 19th- and 20th-century explorers gathered a whole series of accounts of attacks by these slender fish, barely 5 centimetres long, which were said to be more feared by locals along the Amazon than a school of piranhas.
Why? Because they supposedly crawl into a man’s penis or a woman’s vagina, although they also feel quite at home in the rectum of either. When they reach their destination, they wedge themselves in tightly and then drink blood, and they also serve themselves tissue.
The pain is reportedly immense, but the solutions are few. Kandiru cannot just leave its host, so herbal teas were once tried to decompose the fish, but did not work, and warm baths were equally unsuccessful. Experts of the time thus suggested only one:
“The only way to prevent it from reaching the bladder, where it would cause inflammation and ultimately death, is to amputate the penis immediately.” A doctor reported that on a trip along the Amazon he met a man and his three sons who had been deprived of their manhood by a fish.
They did not explain how the problem was solved with women or when the fish jumped into the rectum, probably because the writers were all men and more concerned about their masculinity than the fairer sex, although they never failed to mention that they were also at risk.
The threat was particularly great, they wrote, if the individual not only swam or walked in the water, but also urinated. The fish was said to be so attracted to the urine that it was willing to jump out of the water to get it.
Thus, stories circulated of men urinating into the river from land. When the fish detected the urine, it is said to have rushed to the surface, swam up the stream of urine to the penis and buried itself inside it.
Researchers in those days also reported how they jumped out of the water, probably terrified, made a hole in the victim’s skin and sucked out some of the blood, because they are parasitic.
But it was the genitals that were the worst hit, so locals reportedly tied them up to protect themselves, and also fenced off public water points to prevent them from even daring to step into the water.
Reports of this kind have appeared regularly for 200 years, but no one has ever seen a single attack of this fish with their own eyes. Modern scientists don’t bother with it much, but when they did try to see how many of them really smell of ammonia, they showed no interest in it.
They put a goldfish in the water and added an ammonia source, but it only had eyes for the goldfish. In reality, it was supposed to feed on the blood of fish. The parasite that it is, it supposedly crawls into the fish through its gills, but leaves after just two and a half minutes, when it vomits up a dose of its blood.
But while it could indeed enter a man and his urinary tract, it probably wouldn’t survive more than a few minutes, say modern researchers, because it would be too cramped in the penis and, above all, it would have no oxygen.
There are also purely technical doubts that it can swim up a stream of urine. It would have to be extremely strong to jump out of the river and, despite gravity, swim faster than the flow of the urine stream to reach the penis and finally enter it.
And no, no one in modern times has seen an attack by this fish, “very small but inimitably skilled at causing mischief”, as it has been described for two long centuries, apart of course from the 1997 event in Manaus, Brazil.
At the time, Dr Anoar Samad claimed that he had operated on a patient at the local hospital, and that the fish had entered the patient by swimming up the stream of his urine and getting stuck in his urinary tract. After several hours of painstaking surgery, it supposedly left by the same route it had come in, through the penis, the only problem is that he could not credibly prove it.
The fish was preserved, but there are no visible signs of surgery and the photographs are so blurry that they cannot be considered conclusive evidence. So far, it seems that the tiny candiru fish is only spooky in the records of explorers of yesteryear, who may have misunderstood the scary stories about it because they were told to them by locals.
Nevertheless, it seems a bit strange that a misunderstanding could have dragged on for two whole decades. It is more likely that the locals have passed on legends that have been circulating among them for decades.
And the man who claims his penis has become the new home of the tiny candiru fish? He has never heard of it, and apparently not even the stories about it. So how could he have made up the experience?
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Sea whip
Who knows, man is as complex a creature as nature is mysterious, although the sea whip is not exactly hiding from humans. Even if he is one of those freshwater animals we are scared to death of, he is actually supposedly very friendly and downright curious.
Not that he’s exactly looking for the company of divers, but if he meets one, he doesn’t run away from it. It does nothing for him, and the only time a diver gets into trouble is if he swims so far that his sensors are blocked and the whale feels he has nowhere to go.
A threatened person can really attack. Its whip is as strong as a dagger, and it is laced with venom, but the attack is only fatal when it hits the chest or abdominal cavity. If it does not, the stab is only extremely painful and unpleasant.
The whip cannot just pull out its “dagger” because the barbs are pointing in the other direction. They are coated with a thin membrane and contain a poison that causes swelling and desperate pain, and also causes the wound to fester.
The easiest way to relieve the pain is to pour hot water over the wound immediately, as this supposedly partially breaks it down. The ancient Greeks preferred to use it for their own benefit, as an anaesthetic.
And for a long time, however, it is not at all reassuring for anyone who steps on this mat-like fish, which happens easily because it likes to burrow into the river bed. First he hides his head in it, then his torso, and then he takes a day’s rest. He also uses the same technique when he wants to retreat from his attackers, and can easily substitute a human leg on top of his own.
It kills then, but usually does not bite, although its jaw is so strong that it can easily break a hard shell. Divers usually comb the bottom in front of them when entering the water to warn them of these large but invisible inhabitants of the river bottom.
How expensive or cheap it will be to take depends on which of the 200 different species of whale shark the one that crossed its path belongs to. It would be a bit of a problem, for example, if you were to hike up a giant Asian freshwater whale, which can be up to 6 metres long and weigh around 590 kilograms.
Its whip is 38 centimetres long and, of course, poisonous, but not many of these giants have been seen because they hide, especially in the Mekong River. The locals do not hunt them because it would be too expensive.
Giant sea whips are simply too heavy and too strong to be handled with normal fishing gear. If the rod doesn’t break, the boat could be damaged, because these ‘fish’ are so strong that they can drag the boat behind them or sink it without much effort.
Because they are so strong, whales usually have no problems with their prey. When they detect it with their sensors, they cover it with their body and kill it. Shrimps are their favourite. They don’t like humans.
Vampire fish
Vampire fish also don’t like humans, even though they could easily sink their big, sharp teeth into them. The bottom two teeth are even so long that they have to have holes in the upper jaw to pass through and close their mouths.
The teeth are between 10 and 15 centimetres long, so it’s no wonder the dogfish, or Dracula as it is also called, is so scary, given that it can grow up to 1.18 metres and weigh a whopping 18 kilogrammes.
It is also voracious, and swallows its prey whole, although it doesn’t mind having to scavenge a little. She is particularly keen on piranhas. Yes, those piranhas that we humans are so afraid of, but for a vampire fish they are the best food, although it will not refuse any other smaller fish if it is offered.
In the wild, of course, trapped in an aquarium, it is very strenuous and may even refuse food altogether. Instead of two years in captivity, it usually dies after six months, if it lasts that long at all, because there are no clean, oxygen-rich waters, which are also tarry.
While younger vampire fish may not mind so much if the water is a bit calmer, older “vampires” really need the rapids and falling water of waterfalls. They are not exactly loners, but they don’t form large groups either, and in aquaria they are unspeakably willful anyway: if they are alone they are nervous, and if they have company they are just as nervous.
They are not suitable as pets, but they are an ideal challenge for fishermen. Sharp-toothed vampire fish are extremely strong and hardy, and are especially loved by sport fishermen because they always promise a fair fight.
Water spider
Those who are afraid of spiders will especially have to fight their fears when they learn that one of them spends its entire life underwater and can sting very painfully and painfully.
But to do heartburn, it must first build a home out of its web. He starts by wrapping it around underwater vegetation, then reinforces the bottom part so that his home ends up looking like a bell. He drags silky lines from the top of the bell to the bottom, so that it descends and ascends like a ladder.
And then it lives here, even though it has no gills. So how does it breathe? By floating to the surface and pushing its buttocks above the water. When it sinks again, the air is trapped in special hairs in a balloon on its abdominal cavity. She holds this balloon firmly with her hind legs as she returns home to the deep and finally deposits it in her living room.
Then it breathes normally. Researchers once believed that it brought home enough air to live for 20 minutes, but then realised that it could spend a whole day in its bell without rising to the surface, but only if it was completely inactive. If he has a lot going on and is using too much oxygen, of course he has to go and get it.
But it breathes in not only the water that comes up from the surface, but also the water that is carried into its bell. This allows him to hide from predators for quite a long time, although he is no coward himself.
A hunter at heart, he can handle everything from small fish to shrimps and marine insects without getting too tired. He squats in his bell, waiting for lunch to swim by. When his home is shaken, he rushes out, grabs his prey and kills it.
But he doesn’t immediately come to the guesthouse. First, he surfaces a few times to refill his balloon with new air. Only when it has enough does it drag the victim into its home and eat it.
Males eat more often than females, but this is normal because they are also much larger than females, which is quite unusual for spiders. But survival in the water is harder than on land, and aquatic spiders have also adapted so that the babies stick to their mother for at least a few weeks after birth before leaving her oxygen-rich bell to build their tiny new home.
Nile crocodile
The hippopotamus, or common crocodile, is another matter altogether, and more or less rightly holds the reputation of being one of the most fearsome and deadly animals in the world. The males, which average around 5 metres in length, although they can grow up to 6, are frightening in their own right, weighing around 225 kilogrammes, and apart from the record-breaking 730 kilogrammes, they can attack almost anything they see.
For example, people who wash along the Nile, where they more or less live. And all the animals, from zebras to birds, no matter how big or small. They are really not picky when it comes to food, and will swallow anything from carrion to man. They are said to be responsible for around 200 deaths a year, although some people count them in the thousands.
They usually attack alone, but when they join a crocodile pack, a larger animal, such as a hippopotamus or a rhinoceros, has to say goodbye.
Considering how aggressive and scary they are, it is amazing how loving parents are. While most reptiles hatch their eggs and move on, a crocodile’s mum and dad protectively watch over their 16 to 80 eggs until the babies hatch. When they emerge, mum gently digs them out of the hole she dug for them and carries them in her mouth into the water. She then looks after them for about 6 to 8 weeks until they slowly leave her.
In Egypt, crocodiles have always been prominent, either for their lethality or for their worship. The Egyptians revered them by mummifying them and their eggs, and then placing them in ancient graves.
Wealthy Egyptians also tried to domesticate them. They were said to roam around freely in the houses of the rich, adorned with jewels.
The poor feared them, but prayed to the god Sobek, who was depicted with a crocodile’s head, for protection against their attacks. How well he protected them is unknown, but he was probably not very successful, at least not when they went harpooning, even though the Nile crocodile is the largest of all crocodile species in Africa.
