Original subtitles

The snakes of Australia are as diverse and striking

as the landscape they inhabit.

While some are largely harmless to humans,

others have a decidedly dark side.

The taipan, whose bite can kill a hundred men.

The death adder,

whose strike is almost quicker than the human eye.

And the scrub python,

equipped to track down its prey...

..wherever it may be.

These snakes set spines chilling more than most.

And they know how to survive in this inhospitable land.

Living in the deserts, forests

and human suburbs of this vast ancient continent.

Home to some of the planet's

most unusual and fascinating animals.

These are the secret lives of Australia's snakes.

For around 50,000 years,

Australia's only humans were the indigenous Aborigines.

They lived side by side

with the country's most dangerous animals.

They even adopted a rainbow serpent

as an important part of their legends.

The later European settlers, though,

didn't have such a philosophical attitude

to the resident reptiles.

They found an entire country, full of dangerous creatures

that lurk, slither and scurry.

In water.

On land.

Even in the trees.

There are over 800 different species

of reptiles in Australia.

While some are just likely to give a human a firm nip,

others are the stuff of nightmares.

They may be terrifying to humans,

but they have their own challenges to overcome.

The sheer size of Australia means it spans desert,

tropical and temperate zones.

(Roll of thunder)

The weather can be extreme and change in an instant.

Sudden floods.

Bush fires.

Drought.

Anything that lives here has to be as tough and adaptable

as the climate and terrain.

They must each have a strategy for survival.

The amethystine or scrub python

lives in the far northeast of the country.

In Queensland's wet rainforests

and dry woodlands.

In these wild lands, it eats brush-turkeys...

..and even small kangaroos.

But this clever snake has found another world...

full of promise...and prey.

Suburbia.

Far north Queensland is tropical and largely untamed.

Humans tend to cluster together

in pockets of habitation, mostly along the coastline.

This female scrub python feels right at home.

She's used to their buildings and noise.

And when she visits, she likes nothing better

than a chicken dinner.

So she's employing a snaky secret weapon,

to sniff out a potential meal, chemoreception.

She's using her tongue

to pick up chemical traces of odor.

Inside her mouth, a structure called the Jacobson's organ

analyses these scent molecules.

It can determine whether the smell is prey,

a rival, a potential mate, or a predator.

It's been suggested their tongues are forked

for directional guidance,

because the snakes may be able to detect

which of the tips pick up the strongest scent.

Snakes have evolved to fit all their organs

into a long, narrow body.

Their lungs, kidneys and sex organs are greatly elongated.

They have two of each of these organs,

but instead of lying alongside each other

in a pair, one is moved down towards the tail.

They don't have a collar bone,

but have more ribs and vertebrae than most animals.

While humans have 33 vertebrae,

most snakes have between 150 and 400.

This makes them extremely flexible

and along with their powerful musculature,

gives them their mesmerizing, sinuous locomotion.

The scrub python is Australia's largest snake,

capable of reaching 28 feet long.

So for her, suburban fences are a piece of cake.

Her sense of smell leads her faithfully

to the chicken coop.

She begins her stakeout.

(Clucking)

She enters the chicken coop in the daylight.

Then settles down and waits for nightfall.

She's delaying her attack.

The python's eyesight isn't as good as a human's

and she can't afford to make a mistake with a strike.

If she misses, the chicken would not only escape,

but could injure her.

And the smell of chicken is now all around her,

so her chemoreception equipment is of less use.

As the light levels reduce,

she switches to another of her prey-detecting weapons.

Infrared.

Like many pythons,

she has in-built heat-seeking equipment.

These hollows in the snakes' jaw are called labial pits,

thermoreceptors that enable them to see heat.

As the temperature drops, towards the cool of night,

the heat signatures of prey show up in greater contrast.

Once locked onto a living heat source,

the snake can time her strike.

She can stay in the same ambush site for many days,

waiting for prey to get close.

The python doesn't intend to wait that long.

She selects her victim.

(Frantic squawking)

As she constricts her coils ever tighter,

she cuts off the prey's blood supply.

Compressed blood vessels prevent circulation

to the brain and heart and the victim quickly dies.

Now she displays another snake survival adaptation.

Even though she's a large snake,

the chicken, by comparison with the size of her head,

is massive.

Comparable to a human eating a watermelon in one mouthful.

Snakes don't have any way to dismember their prey

into more manageable chunks.

They have to swallow it whole.

So snakes' skulls are heavily modified.

Although the bones around the braincase

are solid like humans',

the rest of the bones in the head

are held together by very flexible joints.

So it's capable of a vast degree of distortion.

Their lower jaws are in two halves,

connected at the front by just muscle and ligament.

Each side of the jaw can stretch very far apart,

independently of the other.

The snake walks the prey in over its teeth,

drenching it with saliva to ease swallowing.

Then, the snake's powerful muscles contract in waves,

to move the prey downwards.

Afterwards, she needs to coil up and rest to aid digestion

which can take a number of days.

This is another snake that's so highly adaptable,

it happily lives side by side with mankind.

The eastern brown.

As well as frogs and birds,

it especially likes the rats and mice

that always live close to human populations.

It's found all along the eastern coast,

from northern Queensland to South Australia,

the areas most densely populated by humans.

It'll happily take shelter in man-made cover

like building sites

This snake is fast...

- (Dog barks) - ..nervous...

(Children's voices)

..and deadly.

It's responsible for around

half the snakebite fatalities every year.

This is the snake most likely to bite and kill a human

in the whole country.

The eastern brown is highly venomous.

Venom is modified saliva,

containing proteins and peptides.

Within the mixture, there's a deadly cocktail of toxins.

In Australia, around 500 people a year

are hospitalized with snake bites.

The eastern brown's venom is neurotoxic,

causing muscle weakness and paralysis.

While there is an anti-venom,

an eastern brown bite needs fast treatment.

Victims who don't get it in time

can die of cardiac arrest

within 30 minutes of being bitten.

If they don't have a heart attack,

the neurotoxin traveling around their body

will eventually lead to respiratory failure.

It's one of the most powerful snake poisons in Australia.

But there's another snake species

whose venom leaves all others in the dust.

The legendary taipan.

Of its two main species,

the inland taipan

is the undisputed champion of lethality.

Although it almost exclusively

eats rats and mice, one bite from this snake

is capable of killing a hundred men.

But as it lives in the arid center of the country,

away from most human settlement,

bites to people are very rare.

Its cousin, the coastal taipan,

is not only more aggressive than the shyer inland,

it also lives much closer to humans

along the northern and eastern coasts.

The python uses sharp, backwards-pointing teeth

to secure its prey, before constricting it.

But the venomous snake has an ingenious way

of delivering its deadly poison

as quickly as possible.

Fangs.

These curved, hollowed teeth connect to venom glands.

Large muscles squeeze the venom from the gland,

along into the fang.

There are many different ways of measuring venom,

but the taipans come out at the top of almost every list.

Many live in the sugar cane crop fields

of the northern and eastern coasts,

which are usually infested with rats.

So they're actually the farmers' friends.

Absolutely nothing is as effective as the taipan

in keeping rodent numbers down.

An active hunter, the taipan uses its chemoreceptors

to trail rodents back to their underground burrows,

enter their homes

and envenomate everything it finds.

Half-inch fangs

pump a deadly cocktail into the prey.

Like the eastern brown, the taipans' venom

is based on a neurotoxin

that causes paralysis and respiratory failure.

It also contains an enzyme that maximizes absorption,

and an agent that interferes

with the body's clotting ability,

causing massive internal bleeding.

The victim's urine may turn reddish-brown

as the venom dissolves their muscles,

which then pass through their kidneys.

It's a murderous mixture.

Until an anti-venom was developed in the 1950s,

pretty much every bite to a human was fatal.

But science is discovering that venom

may also have the potential to save human lives.

Venom is an incredibly active and complex substance,

full of peptides and enzymes

that are a treasure trove for medical researchers.

Scientists are investigating the potential

of venom-derived medicines to treat diabetes,

high blood pressure, auto-immune diseases

and even cancer.

These potential benefits aside,

snake venom remains one of the most noxious

natural substances on the planet.

Naturalists have long pondered

why the deadliest snakes

need their venom to be quite so toxic.

One bite from a death adder or taipan

is enough to kill their usual prey

tens of thousands of times over.

One theory on why their venom is so potent

is that as the early Australian snakes

were evolving millions of years ago,

some of their prey began

to develop a resistance to venom.

As they evolved alongside each other,

predator and prey may have become bound together

in a biological arms race.

Snake venom needed to become more and more powerful

to overcome the growing immunity of their prey,

leaving today's venomous snakes

with hugely toxic venom.

Perhaps supporting this theory,

some animals like this skink

do have a measure of resistance to snake venom.

In energy terms, making venom is expensive.

But the advantages of having it are huge.

In Australia's harsh climate,

where nutrients are hard to come by,

having excessively deadly venom

may make the difference between life and death.

Being able to overpower prey so quickly

means there's less chance of injury to the snake

from its panicking victim.

Snakes, especially juveniles,

can also bring down a much larger animal

than they could without venom.

Larger meals mean they can go for longer without food,

essential in areas where prey is scarce.

Venom is just one specialization snakes have.

As reptiles, they share some amazing adaptations

to their extreme environment.

This golden tree snake is sunbathing.

Reptiles are ectotherms.

They use external means

to regulate their internal body temperature.

Basking in the sun, like this monitor lizard,

collects heat.

When they get warm enough,

their internal systems activate.

Sunbathing on conductive, heat-absorbing

and reflecting material, like stone,

intensifies the effect and makes basking more efficient.

Different levels of energy

are needed for different tasks.

For the meat-eaters like this mulga snake,

sunbathing can even be urgent.

He's on the prowl for some lunch.

His survival strategy is to be a generalist eater.

Frogs, lizards, eggs, small mammals and birds,

they're all on the menu.

He'll also eat carrion, as well as other snakes

and even members of his own species.

When he's recently eaten,

it's vital he basks in the sun.

He needs to reach a body temperature

high enough for him to digest his meal.

If food is left long enough inside him

without being digested, it can turn putrid and kill him.

Before he can even think about going hunting,

he has to warm up.

Some snakes have found a way to attract more heat

by turning themselves into solar panels.

This venomous red-bellied snake flattens out its body,

so there's more surface area to absorb the sun's rays.

The non-venomous black-headed python

has a different technique,

because it's vulnerable to predators.

It lives in crevices or rock piles

and waits for the last hour of sunlight.

Then, the python pokes just its head

above the safety of its home,

minimizing the risk of being attacked.

Its black scales absorb the day's last heat rays

and solar-charge the snake,

ready for its evening's hunting.

The black-headed python hunts by actively searching for

its lizard, bird and mammal prey.

Like the mulga, it too will eat other snakes.

It lives throughout the top third of the country,

which encompasses arid desert-like terrain,

as well as tropical rainforests.

Because it lives in so many different environments,

each with different prey,

the black-headed python is a highly adaptable hunter.

Although moving around so much expends precious energy,

the active hunting method is a successful strategy

and common among snakes.

Many venomous snakes also spend time

actively tracking down their dinner,

rather than waiting in ambush.

Using their tongues to pick up smells,

they don't just stick to ground level.

By lifting themselves up,

they collect scent samples carried on the breeze.

This gives them a different level of chemical input

and more information.

It all combines to make the snakes

who actively search out their prey

highly effective hunters.

But not all snakes choose this method.

This one is an ambush specialist.

The green tree python is a non-venomous arboreal snake.

It lives in the rainforests

of the very far north of Queensland.

Tropical country... and full of prey.

As a juvenile, it spends a lot of time on the ground,

hunting small lizards and frogs.

So its coloring is mottled yellow

to blend in with the leaves on the rainforest floor.

As it becomes adult, it turns a stunning green,

the perfect camouflage in the tree canopy.

It catches rodents on the ground at night.

By day it takes to the trees

in search of canopy-dwelling animals.

After getting into a good position,

the green tree python sits and waits

for prey to come within strike range.

Many of its prey are well adapted to see movement.

So this snake has come up with a means to exploit that.

It doesn't just passively wait for its victims.

It tries to actively attract them.

It wriggles the very end of its tail.

This is called caudal luring.

By doing this, it's trying to convince

any passing reptile or bird that the tip of its tail

is actually a juicy snack like a small lizard.

It's a classic ambush... with a twist.

The venomous death adder also lies in wait for prey.

This mouse has good senses of its own.

But the death adder's coloring

means that once it digs itself into the leaf litter,

it's almost invisible.

It lurks there... deathly still.

The unsuspecting mouse walks right over the top of it.

Although the death adder doesn't have heat pits

like most of the pythons,

it picks up the vibrations of the rodent.

And when the mouse is close,

the snake can use its eyesight

to zero in on its target.

The death adder has one of the fastest strikes of all snakes.

It can attack, inject its venom

and be back into its original position

in a quarter of a second.

The kill is often swallowed head first.

If the snake is low on venom, its prey may still be alive

for a while after being bitten.

Eating headfirst reduces the risk

of the snake being bitten itself.

All snakes are very vulnerable

whilst they're eating.

Their main weapons are now out of play.

So they need to get every meal down

as quickly as possible.

And head first is the fastest.

Powerful enzymes and gastric juices

break down the food and the nutrients are absorbed.

This process can take days or even weeks.

But some prey parts get left behind.

This black-headed python has no use

for the fur of the rat it's just eaten.

The waste material passes through the cloaca,

an opening near the tail that functions

as both a reproductive and digestive opening.

The paler substance is the reptilian equivalent

of urine, though it's far more concentrated.

For many snakes, lizards are a staple part of their diet.

They're both reptiles. It's thought that snakes

actually evolved from lizards,

slowly losing their legs.

In Australia, the lizards outnumber the snakes,

with more than 500 lizard species

versus over 300 of snakes.

The lizards have evolved many different adaptations

in their attempts to stay off the menu.

One is just to be very big.

The lace monitor,

one of the lizard family known as goannas in Australia

can reach six and a half feet in length

and 33 pounds in weight.

This is a true carnivore in its own right.

When fully grown, the goanna is capable

of killing koalas and small kangaroos.

It can even take on a snake.

Like a snake,

it can unhinge its jaws to envelop large prey.

Also like a snake, it has a deeply forked tongue

that it flicks in and out,

sending the chemical messages it picks up

to the Jacobson's organ in its mouth.

The goanna's teeth are sharp and curved backwards,

like a python's, making it hard for prey to escape.

It likes to climb trees,

where it can keep an eye on its surroundings.

The trees are also a good place

for the smaller monitors to escape

ground-based venomous snakes, called elapids.

Although some elapids are good climbers,

most are uncomfortable going too high.

Up here, the goanna can investigate

any likely hollows where it might find food,

insects, mammals, nesting birds and even carrion.

Most of Australia's lizards

don't have the luxury of the monitor's enormous size.

They must find other ways to deter potential predators.

At between 18 and 24 inches,

the blue-tongued skink is a fairly hefty species,

but nowhere near the size of the monitor.

Like other smaller lizards, it can fall prey

not only to snakes, but to animals

which hunt using visual cues,

like cats, wild dogs and carnivorous birds.

It's also a very slow-moving lizard,

so it relies on bluff when confronted by a predator

by opening its mouth wide

to show its brightly colored blue tongue.

It tries to look bigger

and more aggressive than it really is,

in an attempt to deter an attack.

Discombobulating your foe

is also a good way to avoid being a snake's dinner.

Like the brightly colored tongue of the skink,

this frill-necked lizard

has a built-in anatomical shock factor.

(Hisses)

When threatened, he opens his mouth wide

and erects a huge scaly membrane

that frames his head.

While some snakes like the taipan

and eastern brown are ready biters,

many are actually cautious about attacking.

They don't want to risk an injury

that might compromise their ability to feed,

so they select their prey carefully.

Looking big and aggressive

might just be enough to put off an attacker.

Both males and females have the neck frills.

This one is keeping an eye out for predators

on a cycad plant.

Known as living fossils,

DNA studies have found the cycad species living now

to be around ten million years old,

a long time for any one species to remain on earth.

Their earliest ancestors were around

long before dinosaurs ruled the planet,

and fossil records suggest

they probably dominated the ancient forests.

Most are long-lived and slow-growing.

For the frill-necked lizard,

the plant makes a handy perch...

and a good vantage point.

Some, like this shingleback lizard,

try to confuse their enemies.

Its tail is pretty much identical to its head,

which it hopes will befuddle a predator

long enough for it to make its getaway.

A truly cunning disguise

could also help one avoid becoming lunch.

There is a lizard on this tree.

This is a leaf-tailed gecko.

His markings look like patchy tree bark and lichen.

This disruptive patterning is the same principle

that military camouflage gear is based on.

His base coloring is specialized

to the area he lives in.

If a gecko lives in a grove with paler trees,

it will have paler coloring to match.

In the next patch of forest, which may have darker trees,

it'll have corresponding dark skin.

His spiny flanks diffuse any tell-tale shadows.

Bird-like, clawed feet

help him climb over the rough bark.

Motionless, the leaf tail waits for spiders

and insects like crickets and moths to come within range.

Because he spends all night in position,

he needs large eyes to let in as much light as possible.

The downside to this is that he has a reflective retina.

So at night, the gecko's tell-tale eye shine

is a dead giveaway to his nocturnal predators,

owls, rats and snakes.

But, even when he may be staring

into the scaly jaws of certain death,

he has a last-ditch trick up his sleeve.

If things are looking desperate,

the leaf-tailed gecko wriggles his tail

to draw attention to it.

Should the snake take the bait and attack the tail,

the gecko can actually disengage it

from his body and drop it.

This gives the snake a temporary mouthful,

while the gecko makes a getaway.

Its tail regrows in just six to eight weeks.

Lizards and snakes

are built to survive their tough environment.

But while snakes may seem terrifying and indomitable,

many of them are themselves

under threat from other species.

There is one animal that easily kills

even the most deadly snake.

The cane toad.

Imported into Australia from South America in the 1930s,

the cane toad was introduced specifically

to prey on pest beetles in the sugar cane fields.

It was entirely ineffective against the beetles,

but much worse was to come.

The cane toad is itself highly poisonous,

with glands on its back and sides

that excrete potent toxins.

Almost anything that tries to eat it dies.

Many snakes eat amphibians

and unwittingly take cane toads.

They don't get a chance to have

any sort of learning curve about avoiding this prey.

The toads are so toxic,

snakes will die with the toad still in their mouths.

Many native species

are only too happy to get a snake snack.

Especially if it's a vulnerable juvenile.

The jabiru or black-necked stork

is a whopping four feet tall

and easily capable of taking a snake.

As are many of the big birds of prey

that live all over the country.

Predatory birds and foreign toads

aren't the only threats to snakes.

Bush fires are the terror of the outback.

There are apocryphal stories of bush fires

spreading faster than a galloping horse.

It's certainly true they're devastating for animal life.

A fire like this can start from a lightning strike,

and last for days, taking out the animals' cover and food.

Most try to flee, many die.

But while many snakes will be killed by fire,

the black-headed python is able

to use a bush fire to its own advantage.

It's a capable climber,

but just as happy to stay safe from the flames

by going underground or into small, cramped rock crevices.

This all-terrain beast has the largest array of options

to survive a bush fire.

Regrowth starts again after around six weeks,

and small mammals and reptiles

move back in as soon as they can.

They form a veritable feast for the black-headed python,

who's been able to wait it out.

The snakes of Australia

all have their part to play in the ecosystem,

and many perform vital roles in pest control.

From the rodent-eating of the taipan,

and hunting prowess of the scrub python,

to the cunning caudal lure

of the green tree python,

and the death adder's lightning strike...

..Australia's snakes have found ways

of flourishing in this severe terrain.

Beautiful...

..bizarre...

..and often deadly...

..the snakes of Australia continue to inhabit

a prominent place in our imaginations,

as well as our nightmares.

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