This is a programme about the most successful of all predators.
Watch and wonder.
This giant snake could squeeze me till I'm unconscious
and then it could unhinge its lower jaw and eat me.
So it's not surprising that I treat it with some respect
and that people have a proper fear of some snakes.
But the fact is that snakes are wonderful creatures,
superbly adapted to their particular lives.
And to appreciate that,
you have to see the world through the snake's eyes.
That's what this programme is going to try to do,
to allow you to become, in your imagination, a snake.
To enter into their world, we've used miniature cameras on many snakes,
but, in particular, a giant African python.
Snakes are far and away the most successful of all predators.
There are 2,700 species of snake in the world.
They come in all colours and sizes.
They live at ground level and in trees.
They live underground.
They even live in the sea.
There are snakes that live 16,000 feet up in the Himalayas.
And snakes that live in scorching waterless deserts.
Some live as far north as the Arctic Circle.
But most inhabit tropical forests.
There are few places that don't have snakes.
Antarctica and Ireland are among them.
There are few hiding places for the animals that snakes feed on.
Some snakes hunt by day. And most of them have huge round pupils.
Some snakes hunt at night. They have vertical slit pupils.
All snakes can kill from the moment they are born.
Snakes are masters of camouflage...
... and ambush.
They can climb.
They can even fly.
They're killing machines.
But they are also truly beautiful,
with a range of behaviours that are intricate and fascinating,
from the vast gatherings of garter snakes newly emerged from hibernation
to the coiling behaviour of sea snakes,
which use the technique for rubbing barnacles off their skins.
The smallest snake in the world lives here,
and here, and here.
In fact, any town or city anywhere in the tropics.
This snake is so small it's been exported in the soil of tropical plants
to garden centres all over the world.
Like this one in Sao Paulo.
It looks like a worm.
In fact, it's difficult to see which is its head and which its tail...
... until it tongue-flicks.
This is a typhlops, five or six centimetres long,
practically blind, and feeding on tiny invertebrates.
So the world's smallest snake is also the world's most widespread snake.
At the other end of the scale, possibly the world's largest snake -
certainly the heaviest - is the anaconda.
It can reach nearly nine metres in length...
... have a bodily girth as big as a pig,
and weigh as much as 200 kilograms.
Animals without legs. They seem so ridiculous.
So unversatile, so inefficient.
Yet we know this isn't so.
Otherwise snakes wouldn't be the most successful predators on the planet.
But if we go back in time a few million years,
we discover that snakes then did, in fact, have legs.
The ancestor of modern snakes might have looked like this, a kind of marine lizard.
But when this animal came out of the water
and tried to run beneath undergrowth or chase its prey underground,
it would have found its legs an encumbrance,
so over generations it lost them.
And that's the point about snakes.
It was actually an advantage for them to lose their limbs.
Now snakes could move equally well
on the ground, under the ground, in undergrowth, in trees or in water.
And different snakes solve the problem of legless movement in different ways.
Our giant python moves by contracting and relaxing the muscles
along the underside of its body.
The muscular movement ripples down the body in waves from nose to tail,
the scales gripping the ground and pushing the snake forward.
So the python moves ahead in a straight line.
This kind of snake movement isn't particularly fast,
but it uses very little energy - just 20 calories a day.
A python only eats occasionally
and doesn't have that many enemies it needs to escape from.
But how does such a slow animal ever catch anything?
Well, we'll be returning to our giant python to discover if its hunt is successful or not.
Most snakes, like this Cape cobra, move in a serpentine way.
The snake pushes at the point where its body bends,
and that propels it sideways.
But if two opposite coils push at the same time,
the sideways forces cancel each other out and the snake is propelled forwards.
Some snakes can move really fast using this method.
From the marks the cobra leaves,
it's clear that it's only pushing at the points where its body bends.
This sidewinder racing over the Sahara at night
has perfected a way of moving that works well on slippery and very hot surfaces.
As its name implies, it goes sideways, or, rather, diagonally.
It doesn't slide. Muscular waves move along its body,
lifting and twisting sections and then setting them down a short distance away.
Thus the body sort of rolls along from neck to tail,
leaving a characteristic track behind it in the sand
which could only be from a sidewinder.
But, at the end of the day, snakes don't travel all that fast, do they?
Well, that's where you're wrong.
There is a snake in Africa that's been called the most dangerous in the world
because of its speed.
0ver long distances, the black mamba can travel at bursts of seven miles an hour.
But over short sprints it can move at 14 miles an hour.
Some observers claim to have seen mambas going at 18, even 20, miles an hour,
faster than most people can sprint.
It can even travel with a third of its body raised off the ground.
Certainly, the black mamba is the most feared snake in Africa.
It's highly strung, twitchy, aggressive.
A black mamba can move fast in trees, on open ground or in water.
In thick undergrowth it would overtake you.
Mambas can kill a human with two drops of venom
and they can inject formidable amounts of it.
No wonder we fear them.
More, it seems, than they fear us.
But the snake's speed on land can be transformed when it takes to water.
In this medium, a cobra can triple its speed.
All snakes are at home in water, especially this anaconda.
It makes them even more versatile, adaptable hunters.
In fact, so successful were snakes
that four and a half million years ago they spread into the sea.
Now you can find 55 species of sea snake
in the tropical waters of the Indian and Pacific 0ceans.
Sea snakes are all highly venomous.
Having conquered the land and the sea, snakes have even taken to the air.
In the high jungles of Malaysia, a lizard glides to safety from a pursuing snake -
or so it thinks, because this is a hunting snake that can follow it.
It can contour its body to ride on the air like the wing of an aeroplane.
It can even steer itself towards a particular landing spot.
This time, however, the lizard escapes.
All snakes kill.
They do so in basically two different ways. They either ambush or they hunt.
In the deserts of the Kalahari, the Cape cobra is a hunter par excellence.
It's found its way towards a colony of nesting weaver birds.
As yet, they are still 100 metres away.
The snake detects their presence not simply with its inefficient sight,
but by using its tongue.
All kinds of particles drift around in the air - odours, water droplets, pollen.
In the little copse, trees, grass, adult birds and chicks all give off scents.
This kaleidoscope of particles stream back to the snake
which plucks them off the air with its tongue.
The cobra's tongue retracts, transferring the particles
to a processing unit in the roof of its mouth, its Jacobson's organ.
All snakes have forked tongues. Why?
They're tasting in stereo.
establishing the direction of the weaver bird chicks at long range.
The Cape cobra is a superb tree climber.
A miniature camera attached to its back
gives a remarkable snake's-eye view of its arboreal journey.
The adult weaver birds escape from their nests, streaming downwards.
The nest entrances are underneath, making them hard for predators to enter.
The snake anchors itself by its tail, letting its body hang free.
Then it works its way systematically from nest to nest.
Eventually, the Cape cobra will strike lucky.
Hunting snakes will go wherever there is prey.
Climbing trees. Climbing rock faces.
At the entrance to these caves in Queensland, Australia,
two species of python have learned that the hunting is easy.
Bats - millions of them.
Revealed by night-vision cameras, the snakes anchor themselves to the ceiling of the cave
and try to pluck the bats out of the air.
Pythons are not venomous.
They squeeze their victims to death.
Another snake hunter is found on a tiny uninhabited island off Tasmania.
Vast numbers of mutton birds come to Chapel Island once a year
to nest underground in burrows.
They won't stay long.
But it's now that tiger snakes will get their annual feast.
They're after the chicks.
But to get at them, they'll first have to get past the adult nesting bird.
Unlike other killers at the top of the food chain, such as big cats,
snakes are comparatively small, robust and adaptable.
These tiger snakes can actually survive for 11 months without food.
In fact, not having to eat very often has been one of the keys to the success of all snakes.
Back in the African bush, our giant python is making its way back to the hole
This snake, too, hasn't had a meal for months,
but, as we've seen, that's no big deal for a large snake.
Once underground, its metabolism simply slows down.
It's one of the great advantages of being a cold-blooded predator.
Snakes don't have to eat so often or so much,
so they only need a 20th of the food of a warm-blooded mammal of the same size.
There's another way of catching prey.
Instead of chasing after it, you can wait for it to come to you. You can ambush it.
South Africa. Table Mountain rises out of a thin spit of land
that bisects two mighty oceans.
To the south is an area strewn with rocky heathlands.
This is the Fynbos.
One of Africa's most notorious and feared snakes, a puff adder,
is warming up in the morning sun.
Once the puff adder has reached ideal operating temperature,
it comes down off the rocks in search of food.
Labelled ugly, bad-tempered, fat, sluggish, vicious,
in reality, the puff adder is simply efficient.
It's a viper, and vipers are the most highly evolved, sophisticated killers of all snakes.
Today it's after striped mice.
Like any professional assassin, the puff adder is equipped with an arsenal of high-tech weaponry
and extremely sensitive detection equipment.
But it will not hunt. Its technique is to wait for food to come to it.
So the puff adder takes up its ambush position near to a scent trail.
Its eyes are particularly good at detecting movement.
But now the snake's other senses come into play.
It has special sound detectors.
Rather than hearing sounds, like we do,
it picks up vibrations through the skin around its jaw bone.
This doesn't work too well with airborne noises,
but if the puff adder rests its jaw on the ground, vibrations are amplified enormously.
Even the miniscule impact of this mouse's feet on sand
can be detected by the snake.
Now the snake tongue-flicks.
It's targeting its prey using its acute sense of taste and smell.
But when the mouse moves within 15 centimetres of the snake's head,
cells in the adder's lips become stimulated by the mouse's body heat
and let the snake finally know that it's within strike range.
The information from sight,
hearing, smell and taste and thermo-detection
is processed by the snake's computer - its brain.
The target is confirmed.
The puff adder bites, venom is injected deep into the mouse's tissues
by its super-long fangs, and releases.
It's anxious not to be hurt during the strike,
so it uses its venom as a hunting aid to immobilise or to slow down
rather than to kill.
The puff adder is now content for its prey to escape.
It probably won't go far before the venom takes effect.
The snake yawns to reset its jaw, dislocated during the strike.
It's in no hurry.
The escaping mouse has left a trail behind it.
Not a trail that you or I could detect, but the snake can.
The invisible paw prints of the mouse release odour particles
which waft towards the puff adder.
It captures them with its forked tongue.
The mouse has also left invisible drops of urine behind it.
The snake uses specialised cells on its retina
to "see" ultraviolet reflectance from this urine trail.
As it sets out in pursuit, it also feels the residual heat left on the ground
by the paws of the unfortunate mouse.
The puff adder follows this invisible trail
back to its inevitable meal.
Except that this time, it is not to be.
Enter a secretary bird.
A bird of prey that hunts not on the wing, but on foot.
And it uses its feet to kill.
The secretary bird has a partiality for snakes.
The puff adder has no chance. Its strike is easily avoided by the secretary bird.
(BIRD STAMPS)
(THUD)
And with two stamps of its foot, the snake is dead.
Africa's most feared ambusher has itself been ambushed.
Another technique used by ambushers is camouflage.
The ultimate camouflage expert is the gaboon viper.
Down there, on the forest floor, is a gaboon viper.
Can you see it?
Let's go a bit closer.
Got it yet?
Now?
Yes, that leaf there isn't a leaf at all.
It's the back of the head of a gaboon viper.
But you don't have to be camouflaged
to deceive your prey into thinking you're not there.
Deep in the rainforests of Costa Rica,
another ambusher, an eyelash viper, has climbed a ginger flower
and is waiting for its food to come to it.
Humming birds.
It's hardly camouflaged. We can see it easily.
But its lack of movement doesn't draw it to the humming bird's attention.
To the bird, it's just another brightly coloured bit of flower.
The snake scents with its tongue.
It'll have to be fast and accurate with its strike.
The humming bird is possibly the fastest of all small birds,
so the snake uses a sense which we sophisticated humans don't have.
The eyelash viper can "see" heat.
When the bird comes to within 75 centimetres of the snake,
the heat it gives off fires up two sensors on the snake's face,
small pits of supersensitive nerve endings.
They're sensitive to changes of temperature as small as 1,000th of a degree.
They work in stereo, giving the snake precise information
on the range as well as the bearing of the humming bird.
The eyelash viper can even predict where the bird will be
in a split-second's time.
The eyelash viper hits the bird in mid-air, holding on to it.
So fast-acting are the neurotoxins in the venom
that the bird is unconscious within seconds, dead inside a minute.
The strike of a poisonous snake is a minor miracle of engineering.
It first has to recoil and flex its body.
Then it strikes, aiming phenomenally accurately.
Then, using its mouth and fangs like a hypodermic syringe with two needles,
it has to inject its venom without damaging its delicate fangs.
Then it has to retreat out of harm's way.
Just look at the fastest snake in the world striking, the saw-scale viper.
From coiled up to launching its strike to unhinging its fangs,
injecting venom, releasing its victim and returning.
Just look at it in real time.
It all happens in one third of a second.
But all that is nothing compared to the complexity of the venom itself.
Venom from the spitting cobra is simply modified saliva.
But it contains all kinds of toxic chemical compounds.
Its purpose is not to kill but to immobilise the prey.
And then to start digesting it.
So the faster the victim, the more potent the poison.
The fastest acting of all venoms are the neurotoxins
which stop birds and fish in their tracks before they can get away.
Back in Africa, one of the largest of ambush experts, our giant python.
The same one that hasn't eaten for four months.
But now it's desperate for food.
It's detected the many scents of the animals coming to drink at a waterhole.
It takes up its ambush position underwater.
For an animal so ponderous on land,
it's transformed in water, moving speedily with ease
in this different medium.
The snake selects its ambush position,
sinks gently just below the surface and waits.
We talk about the patience of a saint, but it ought to be the patience of a python.
The snake has to breathe - it has lungs -
but the python can shut down its body at will.
It only rises quietly to the surface to take a breath every 15 minutes or so.
The hours pass.
Animals come and go to the waterhole.
Night comes.
Day comes. And still the python waits.
Days pass.
The vibrations of feet and the silhouettes of animals are detected by the python.
its senses working almost as well beneath the water as above it.
How long will it continue to wait? Well, we'll see.
To any naturalist, snakes are wonderful creatures.
But there's no escaping the fact that snakes kill a lot of people.
A recent study revealed that five million people worldwide
are bitten each year by snakes.
Of those, 40,000 die.
In India alone there are 12,000 deaths every year.
The culprits? Cobras.
And kraits.
In South America, it's one of the fer-de-lances that's most likely to kill you.
In North America, rattlesnakes.
Many is the snake that, in the search for water, has found its way into a shower.
This Egyptian cobra needed a place of high humidity
to soften its skin prior to sloughing it.
There have even been authenticated stories
of people waking up to find snakes in bed with them.
But our understandable fears can turn into irrational paranoia.
That's led to millions of snakes being killed worldwide needlessly.
The simple fact is that snakes do not go out in search of people.
They only bite defensively. They only bite out of fear of us.
The evil image of the snake is doubly unfair
when you realise just how often they're victims rather than aggressors.
Even the most venomous of snakes falls prey to other animals,
like this white-bellied sea eagle taking a sea snake,
officially the most venomous snake in the world.
The bird's rugged talons are impervious to the snake's fangs.
And snakes are routinely killed by other snakes.
The much feared fer-de-lance of Central and South America
is merely a meal for the larger, to us less frightening, mussurana.
The fer-de-lance speeds off like a bullet, but in vain.
The mussurana kills it by constricting, much like a boa or a python.
This gold cobra in the Kalahari Desert is also in dire peril.
It's encountered a troupe of meerkats.
The snake expands its hood and strikes defensively,
but the meerkats are too many and too quick.
The evolutionary arms race between snake and meerkat
dictates that at this particular moment in history, the snake will almost never win.
The meerkats' reaction times are a millisecond faster than the snake's.
But an eagle going overhead disturbs the meerkats
and, in the confusion, the snake manages to get away.
It would seem that snakes are hunted and reviled everywhere.
But there is one wild haven where they live in perfect safety.
20 miles off the Atlantic coast of South America
is a place where even snake lovers fear to tread.
Ilha Queimada Grande is "Snake Island".
It has the densest population of snakes on earth.
It's paradise for snakes, but for man one of the most dangerous places on the planet.
No one, apart from scientists, is allowed to land here.
This lovely subtropical island has, in places,
one snake for every pace you dare to walk.
They're all one species, a type of fer-de-lance called a golden lancehead.
The snakes are on the ground,
...they're in the trees,
... they're at the summit of the island and they're on the sea shore.
They're even at home in the old lighthouse, now long since abandoned.
They're after millipedes and cockroaches most of the year, and butterflies and lizards,
but, come September, they feast on migrating birds,
taking them on the wing.
The golden lancehead is highly venomous.
Untreated, a person unlucky enough to be bitten would almost certainly die.
The story goes that of the last 11 fishermen who chose to ignore the warnings
and explore what seemed a paradise all died within hours of landing.
But what's a snake hell for us is snake paradise for them.
This is one of the few places on earth where snakes are not persecuted.
They're protected by the Brazilian government.
They have plenty of food and there are no other animals which predate on the snakes,
so the snakes rule.
The golden lanceheads, however, are nocturnal.
What seems dangerous enough in the daylight
gets far worse as the sun goes down.
Then the snakes come out of the forests and down from the trees
to take possession of their kingdom.
Back at the African waterhole, after four long days,
the giant python has selected its prey.
Now it changes position in the water, going into the reeds close to the bank.
Its heat-sensitive pits tell it the exact range and direction of a springbok.
The snake's long, curved teeth anchor into the springbok's flesh and hold fast.
The springbok is pulled to the ground by the python's weight.
There's just time for the python to throw a single coil over its prey.
One coil becomes two coils and the constriction begins.
People imagine that a giant snake kills by crushing its victim,
breaking its bones.
But that isn't true. The python goes for the torso,
wrapping its coils around the rib cage that contains the lungs.
It waits for the animal to breathe out, and then tightens its grip a little.
Here, inside the very coils of the python,
the animal discovers that every time it breathes out,
the snake simply tightens its grip again.
Eventually, the springbok can't expand its lungs at all and it asphyxiates.
But, also, senses on the python's underside can detect the heartbeat of its victim
and it may continue constricting so long as it feels that heartbeat.
Once its prey is dead or just unconscious, the python releases its grip
and, using the grain of the animal's fur to guide it,
moves round to the head of the springbok to start eating.
Everybody knows that the snake can somehow unhinge its lower jaw.
But that's only a part of the solution
to eating an animal that is three times the width of your head, with horns on top.
The head of the snake is divided into four main sections,
the two halves of the lower jaw
and the two halves of the upper jaw.
All four sections are connected by elastic ligaments
that allow each to move independently of the others.
The python's brain is sealed in a nice, little solid compartment
on top of the skull behind the eyes.
So, as the head splits into four, the brain case rides over the top.
In effect, the snake moves over the top of the prey
and the jaws just expand around it.
But the prey is not necessarily dead.
Horror of horrors, it might still be alive, albeit unconscious.
If you were swallowed by a giant snake, this is what it might be like.
The snake's peristaltic muscles, used for swallowing,
push you deeper and deeper into its throat.
Your head is inside,
but the rest of your body is still outside the snake.
The outside world disappears
as the peristalsis relentlessly pushes you deeper and deeper.
Is it possible that the victim could actually recover consciousness during this process?
Who can tell?
Eventually, the powerful acids in the python's digestive juices do their job.
They dissolve flesh and bone
and convert the victim into nutrition.
This python will not need to feed again this year.
Snakes - animals that can go on the ground,
under the ground, in the trees, or in water.
Animals that can, at will, shut down their bodies,
and then bring them up to speed again.
Hunters equipped with a multitude of detection devices and sophisticated weaponry.
But hunters that can also go for weeks between meals.
Lightning fast in the strike, snakes have conquered the planet.
They are the most successful predators on earth.