Narrator: They're the Mike Tyson's of the serpent world.
Short and stocky, they move at lightning speed, packing mighty punches laced with hardcore venom.
From the American Wild West to the steamy African jungles, vipers are notorious for their bad attitudes, diamond-shaped heads and the longest snake fangs on earth.
But these super-snakes aren't just a family of coldblooded killers.
The females have a softer side when it comes to family.
Thelma, Velvet and Nala are three species of Viper with one thing in common a basic maternal instinct.
But is this what makes them so successful in the game of survival?
Enter the lab to experiment with snakebites and venom, dissect specimens, and study anatomy as we explore the lives of these Viper Queens.
Scavengers with a taste for flesh have picked up the scent of new life in the air.
Born into the wilds of New Mexico, these western diamond-back rattlesnake babies are instantly at the mercy of the elements, and other creatures they share their home with.
Only minutes old, their survival instincts are already firing up even if they don't achieve the desired effect just yet.
With no way to defend themselves, newborns are easy targets for predators...
like this king snake.
But they've got back up.
This is Thelma, and she is one mean mama.
Unusually for most snake species, but characteristic for vipers, their mother's still around.
Thelma and her offspring will only remain together for a few weeks, until they're strong enough to head off into the wilderness on their own.
In the meantime, the family's keeping a low profile, and her presence alone does a good job of discouraging would-be predators.
Eastern King snakes hunt other snakes and baby rattlesnakes make for easy prey.
Thelma's not shy to let her enemies know she's around.
A rattled warning is a rattlesnake's first line of defense.
It's the signature sound of the desert.
Synonymous with danger, it's the reason for Thelma and her family's infamous status as symbols of the American Southwest.
Young snakes shed their entire skin every few months.
But rattlesnakes are born with a tiny button at the end of their tails, and this becomes the matrix for their rattles.
Each time they shed, a modified scale remains behind and adds another segment to the rattle.
Operating at up to 2000 cycles per second, the shaker muscles used to vibrate the segments are some of the fastest known to man and they have an all-or-nothing function the muscles work only at full capacity and they don't get tired.
It's a similar level of muscle control that links Thelma to her African cousin, but in quite the opposite way.
Velvet is a West African Gaboon viper, or adder.
She's silent, solitary, and is rarely seen.
Her beautifully tapestried scales render her invisible on the forest floor.
But her quiet demeanor and incredible loveliness belies her deadly nature.
Velvet's like a highly trained assassin, capable of infinite patience and extreme muscle control.
She can wait motionless for days, weeks, or even months, and then unleash a sudden, powerful attack.
Armed with fangs up to 2 inches long, Gaboon vipers not only have the longest snake fangs, they're also the largest and heaviest viper species in existence.
But Velvet's not aggressive, and prefers to stay hidden.
She rarely attacks and then only to predate or defend herself.
Most of the time, no one even knows she's around until it's too late.
Velvet, and Thelma the rattlesnake, live worlds apart, but they share a simple mission in life to stay alive, and grow their families.
It's a game of survival, but what happens if you don't have Thelma's early warning system, her badass attitude and legendary status?
Or Velvet's size, stealth, lethal patience, and immense weaponry?
She's not as showy as Thelma, nor as beautiful as Velvet, but she belongs to a group of tough little vipers the puff adders.
They're small, but formidable killers, and they're going about the survival game a little differently.
They've built a fearsome name for themselves, through sheer numbers and tenacity.
Spread throughout Africa and southern Arabia, puff adders occupy one of the widest distributions of all viper species.
They're adaptable, and hardy, and can survive in a wide range of habitats in the wild, and alongside humans.
Puff adders are masters of disguise.
Their skins come in a range of color variations, sometimes making them hard to identify.
But for one distinguishable feature the chevron markings on their backs.
Displaying such blatant warning signs on their own bodies, and living so close to humans, puff adders have had to learn to operate under the radar.
Velvet has few, if any natural predators as an adult and rarely comes into contact with humans.
While Thelma does, she plays fair, giving her enemies a chance, warning them before they get too close.
But puff adders don't run from fights.
When faced with danger, they hunker down, a classic viper ambush tactic.
Nala has attitude, she fights dirty and it's earning her a bad reputation.
Narrator: For Nala the puff adder, life in an African village is fraught with danger.
Dogs don't like her, and neither do people.
When she senses a potential threat nearby, like most vipers, fleeing isn't her first reaction.
While Thelma the rattlesnake warns off her enemies, Nala prefers to draw as little attention to herself as possible.
She freezes, her camouflage allowing her to blend into her surroundings.
She waits for the threat to pass.
In this way, Nala conserves her energy and venom for when it's really needed.
It's a good strategy, if discovered she could be hurt or even killed by the villagers.
But sometimes she's so well camouflaged, perceived threats unknowingly get too close, and are often bitten when they accidentally step too near sometimes even on top of a puff adder.
This shoot first ask questions later attitude has earned puff adders a bad reputation.
But it's not entirely undeserved, because puff adders kill humans every year.
Death from a Western diamond-back rattlesnake bite is virtually unheard of, and no fatalities from a Gaboon viper bite have ever been recorded.
So in comparison, Nala the puff adder is deadly.
Yet her motives are usually misunderstood.
Puff adders often live in close proximity to human settlements.
Because their prey do.
But venomous snakes lurking about are a hazard to humans.
In most cases, puff adders bite in defense or when they've mistaken a limb for prey!
The results of such an error can be horrific.
Puff adder venom is predominantly cytotoxic.
It destroys cell tissue with devastating efficiency.
But it's not only humans that fall victim to these feisty little vipers.
In the wild, animals create pathways through the bush known as game trails.
For creatures like tiny rodents, to the world's largest land mammals, these trails provide easier movement and often lead to waterholes or good feeding grounds.
And it's along paths like these that puff adders will position themselves, to wait for prey.
But when unsuspecting victims weighing thousands of pounds tread too close for comfort, a little 13-pounder puff adder can defend itself in a mighty way.
It doesn't seem possible that a bite from a tiny snake could pierce the skin of a rhino, let alone do any serious damage.
But here's evidence to the contrary.
A bite caused such severe necrosis on the leg of this black rhino, that her entire foot rotted off, leaving behind just bone fragments and flaps of decaying flesh.
Trauma like this would render most animals immobile, ensuring a slow and painful death due to starvation and septicemia.
It's an extreme example of what happens when a puff adder bite is left untreated.
With cases like these and human deaths on their hands, surely puff adders must be more dangerous than their cousins?
They are, but for reasons other than we think.
When tested Thelma the rattlesnake's venom proves to be primarily haemotoxic, which attacks the blood.
It can be rapidly lethal to natural prey, but it's not nearly as dangerous to the average healthy adult human, which is why fatalities are virtually unheard of.
In contrast to hers, Nala the puff adder and Velvet the Gaboon viper each produce their own individual mix of tissue-destroying venom containing cytotoxins, and when compared, puff adder venom proves to be more potent - than a Gaboon vipers' - drop for drop.
But Gaboon vipers have a much more complex array of toxins which makes it more deadly due to the devastating effects it has on cells of the body.
A puff adder bite will cause immense pain, inflammation, bleeding that can't be stopped, and skin cells to self-destruct.
Venom left to run its course could cause death.
A Gaboon viper's venom will do something similar, but in extreme, because it works faster, and comes with extras.
Tiny blood clots form throughout the body and can cause organ failure.
A powerful array of neurotoxins to attack the nervous system, myotoxins the muscular tissue, and cardiotoxins the heart these are just some of the extras to be found in the Gaboon's venom cocktail.
But that's not all.
Because Gaboon fangs are so long, and their venom glands so large, they dispense much more venom, much deeper into the bodies of their victims.
A bite from a Gaboon would be considered an urgent, life-threatening medical emergency for a human and certain death for prey.
Yet puff adders are considered more dangerous to humans than Gaboon vipers for a very simple reason.
Gaboons favor forest habitat, so it's not often they come into contact with people, and as adults, they don't have many, if any, predators, so they're not naturally aggressive because they usually have no need to be.
But life for a puff adder like Nala is totally different.
With a number of natural predators, and living in a range of habitats, including human settlements, puff adders have learnt to stand their ground, with fight before flight.
But meeting an enemy head-on is risky, so Nala sticks to the shadows.
It's just safer that way.
Lucky for Thelma, her rocky outcrop home is far from humans on the ranches in the valley below.
It's a peaceful place to live... usually.
Trouble in the shape of a strapping young green-colored male rattlesnake is brewing down in the valley and he's slowly heading her way.
In these circumstances, the sound of her rattle alone isn't going to keep the peace.
Narrator: Far below Thelma the rattlesnake's rocky outcrop home, trouble's brewing.
Living in this American Southwest valley isn't for the faint-hearted.
A rattled warning means nothing here; the sound is lost in the mayhem.
The only way to survive this place is to keep a low profile.
But it's not that easy.
Everyone's watching, everyone's on constant alert for danger.
His reputation alone makes Cody the male rattlesnake an unpopular guy round these parts!
But hanging around the ranch has its rewards.
All Cody's favorite treats are readily available, whenever he wants them.
So what if he's got to duck and dive and keep things low-key?
It's well worth the effort.
And he's really good at it.
But Cody's real party trick is something else.
He doesn't need to worry about humans catching him because he can operate under the cover of darkness.
To the naked eye, the inside of the barn is pitch black.
But Cody and his rattler group members are equipped with a particular skill that many of their cousins like Velvet and Nala don't have.
It's like having the coolest super power on earth.
Cody has thermal imaging abilities.
Snake species sharing this skill are also known as pit vipers.
On either side of their snouts right at the very end between their eyes and nostrils, are tiny little pits.
These house their heat-sensing organs, which are always 2 to 3 degrees cooler than the rest of their body, keeping their sensitivity maxed at all times.
A small membrane lines these pits, hanging in a bony chamber, which allows it to heat and cool rapidly, in doing so making it hyper sensitive to changes in temperature in the snake's immediate vicinity -- at any time of day or night.
The nerve cells of the membrane produce a protein that is only activated when temperatures of around 82 degrees Fahrenheit or higher are detected.
Which is roughly the measure of body heat of a warm-blooded animal within a meter of the snake.
When this happens, nerve impulses based on the temperature readings sent to the brain create thermal images of the prey item on offer.
Cody can single out living creatures in the darkness.
Without them even realizing he's there.
But something's up.
He has complete advantage of the situation, but he's not taking the opportunity for a meal.
Is it possible for a rattlesnake to turn vegan?
While Cody ignores his dinner, on the other side of the world, in her African village home, Nala the puff adder has no such dietary inhibition.
Like Cody, she's weighed up the pros and cons of hanging around humans and their snarly watchdogs.
But even that's not enough to put her off.
Not when the place is crawling with ready-made meals at all hours.
She's still got to be careful though.
Once she's in position, it's easy pickings.
A quick stab of her fangs injects enough venom to ensure the rat doesn't get far, making it easy to follow, find and eat.
But one isn't enough.
Nala is going to make the most of her visit to this village.
It may look like Nala's being a glutton, but she's preparing for a big event one that's going to put her out of action for a while.
So she's taking full advantage of this opportunity.
Deep in the forest, Velvet the Gaboon viper is also hungry.
But she's got a whole different way of doing things.
It might not look like she's doing much but that's all part of the plan.
When the time is right, all hell will break loose.
Velvet settles in to wait.
As predators, snakes aren't exactly armed with the best hunting equipment.
They don't have legs to chase down prey, claws to grip, nor teeth for tearing flesh.
So they've had to come up with a different strategy to find their niche as sophisticated predators.
Velvet and her Gaboon viper relatives have outdone themselves.
They aren't particularly graceful when climbing trees so they stick to the ground.
The forest floor is their domain, and they've made it their own.
Intricate patterns and colors on Velvet's back allow her to disappear into the leaf litter.
Once settled, she doesn't move.
Just the slightest motion can betray her position.
It may look like Velvet's just chilling out, but to keep this still actually takes an extreme amount of muscle control.
While waiting in ambush, Velvet keeps firm responsive muscles, practicing what's called active stillness.
While she needs to remain absolutely motionless, her muscles need to be ready for a sudden burst of activity at any given moment.
To do this, alternate muscle bundles are either active or relaxed, continually rotating to maintain muscle tone and prevent one group from getting tired.
In this way, Velvet conserves her energy and muscle power, so she's always ready to launch an attack.
She only gets one chance.
If she loses the element of surprise, it could be weeks before another potential prey animal comes along.
She's got to get it right the first time and if she gets the strike right, the rest is easy.
Narrator: Velvet the Gaboon viper is lying in wait for prey.
She's kept still for days.
Her muscles are like a hair-trigger, ready to strike in a split second.
But that's not all she's relying on to make a successful kill.
Velvet may not have any limbs, but she's equipped with one of the most advanced hunting and defense systems in the animal kingdom:
It's Velvet's ultimate weapon, allowing her to kill or at least immobilize prey before they have any chance to escape.
But to dispense this modified, toxic saliva, she needs a specialized injection system.
And Velvet's just happens to be the deadliest in the world.
She's capable of injecting up to 600mg of venom in a single bite.
It takes only 100 to kill an adult human.
Like all vipers, her fangs lie flat against the roof of her closed mouth.
When hunting, as she opens her mouth, they unhinge and swing down, ready to stab into a victim.
But it's not easy to bite and then release when you have rows of long, backward-pointing teeth.
To get them in, and back out of a victim's body, it sometimes looks as if they're chewing.
This lethal combination of hardware and chemicals make her a deadly predator, but she's got one more trick up her sleeve to guarantee success:
Any number of potential prey could venture past.
Velvet isn't picky -- she'll eat anything from rodents and birds to small antelope and monkeys.
A slight miscalculation makes no difference.
Once she's set her sights on a target, there's no chance for escape.
Her strike isn't the fastest in the snake world, but at over 20 feet per second, it does the job.
The shock of the attack stuns the bird, while the complex venom cocktail rapidly floods its body.
As she waits for her prey to die, Velvet adjusts her fangs.
They can really get in the way sometimes.
Within 10 minutes, it's all over, and lunch is ready.
Eating is a specialized process.
Velvet unhinges her jaw to allow her to open her mouth wide enough.
Using rows of teeth to latch on, she drags her prey to a safe place where she can eat in peace.
Back at the ranch, it turns out that Cody the male rattlesnake hasn't turned vegan after all.
But he's clearly not hungry either.
Snakes are able to control the volume of venom they inject even withholding it completely when dishing out a warning to stay away.
This rat has had a lucky escape with only a dry bite from Cody.
There's only one reason he would decline the opportunity of a meal once again.
With a very slow metabolism, it could take him days, if not weeks, to digest a meal as big as that rat.
Cody can't afford to be out of action that long
'cause he's on a mission.
It's not a meal he's after
he's looking for a mate.
And he's heading straight for Thelma's rocky outcrop.
But someone's beat him to it.
Cody's arrival on the rocky outcrop has thrown him headlong into a love triangle, with a huge, pink-colored male as the competition.
Cody has no idea of who Thelma is, nor that this is her home, but the fact that another male, with a really bad attitude is hanging around, tells Cody all he needs to know.
He's found a female worth fighting for.
Like boxers meeting in the ring, Cody sizes up his pink opponent.
It's all about moves, making the first and dominating with each.
With no limbs to make things awkward, they fight with their whole bodies.
But it's not about throwing punches.
Neither intends to hurt or maim his rival.
It's merely a ritual,
a dance of domination.
The twists and turns and thrusts are a show of strength.
A power struggle meant to single out the stronger male.
But he needs to leave the fight unharmed and ready to claim his prize of mating with the female.
The other male may be pink in color, but he doesn't fight like a girl.
Pinned to the ground by the weight of his rival, Cody knows he's out of the game.
Defeat means eating dirt and a humiliating exit.
It's a devastating blow for Cody.
He's foregone food, traveled long distances, and risked injury through fighting, but it's all been for nothing.
He didn't get the girl.
But Thelma's not just not into him, she's not into anyone at the moment.
Narrator: Cody the male rattlesnake has just lost his fight for Thelma.
But while the other has male won the battle, it doesn't mean he's won Thelma's heart.
She's just had her babies and isn't interested in mating right now.
It will take time for Thelma's body to recover from giving birth.
While the youngsters are around, she gets no alone time to stage an ambush for food.
But once they leave home, she'll rebuild her strength, and maybe consider mating again in the spring.
For now, no amount of nudging and rubbing from the pink male is going to turn her on.
Coiling against him, her flicking tail dismisses him.
He has no choice but to leave reluctantly.
He'll have to try his moves elsewhere.
Snakes mate in a ritual of gently rubbing bodies.
The male nudges the female with his snout, bumping her lightly as if to cajole her.
Their bodies caress, and tongues flicker as the male tastes the female's pheromones, testing if she's ready to mate.
When the female is aroused, she'll lift the base of her tail and they'll mate.
Like these puff adders are doing.
The males tend to do most of the work.
Perhaps the females pace themselves during mating because just one session can sometimes carry on for up to 3 hours.
Yet it's the coming months they'll most need their energy for, as they have big decisions to make.
Females hold all the cards when it comes to making babies.
They can store sperm from one mating session for up to 5 years before it starts to deteriorate.
When the female feels the time is right and conditions are good enough to bring offspring into the world, she'll dip into her sperm-bank and impregnate herself, or 'become gravid.'
Fertilization will occur and eggs will form, but a female vipers' job doesn't end with laying the eggs and leaving them to fate like most snakes.
Instead, their bodies become living incubators!
When the young are ready to hatch, mothers give birth to live snakelings.
Vipers are ovoviviparous so they produce eggs, but the eggs have a soft membrane instead of a shell,
It's not clear whether mothers share nutrients with the developing embryos, so it may seem like a waste of time for Nala's to have lugged over 20 eggs around for months.
It's a great sacrifice on a mother's part to carry the growing embryos.
As she gets heavier, it gets harder to hunt and her own body loses condition, just as Thelma's did.
But by carrying their embryos as they develop, instead of laying eggs, Nala, and Thelma, like most viper moms, have given their offspring the best possible chance at life.
And hardships aside, viper moms have the best of both worlds in the animal kingdom.
Now that Nala has given birth, her maternal duties are done.
She doesn't provide any postnatal care like suckling, grooming, baby-sitting, training.
Imagine doing that for over 20 babies?
But it could have been worse, the record number of offspring born to a puff adder, and any snake species, is 156!
Within two weeks of birth, usually once they've shed for the first time, Nala's youngsters will go their own way.
Equipped with fangs and venom, they're fully independent and perfectly capable of surviving on their own.
Life in the wild is a continuous battle for survival, and vipers take it seriously.
They're a super family of snakes, each equipped with a different set of skills and sophisticated weapons born ready to lead lives as proficient killers.
But it's these traits combined with the females' basic maternal instincts, their softer sides, when it comes to family that ultimately gives the Viper Queens their edge for success over many other snake species.