Wild Down Under Wild Down Under

Modern Australia - it seems a familiar sort of place...

..but step outside these cities

and you could almost be on another planet,

because Australia is the strangest continent on Earth.

It's wildlife is so weird that, at first, some people thought that the animals were a hoax,

or the work of the devil.

It's a paradox, a place of extremes -

its centre a burning desert,

but also with rugged mountains covered in deep, winter snow.

It has endless horizons of magical, timeworn landscapes.

And in them, an amazing variety of wildlife.

More species of animals than Europe and America combined.

Almost all of them unique - they live nowhere else on Earth.

It's a place that likes to do things differently,

and, somehow, this remarkable mix of wildlife

manages to survive on the harshest, driest inhabited continent on Earth.

So how did Australia come to be so special?

To answer that, you need to travel back in time

to when this was a very different type of place, covered in trees.

One hundred million years ago,

massive forces shattered the supercontinent of Gondwana,

and gradually a giant fragment floated off northwards

with a unique cargo of wildlife.

Australia was born.

This was an extraordinary world, lush, green and dripping with life.

Today, there are still a few places in Australia where you can get a feel for that past.

These are the rainforests of Tasmania.

They're ancient, mysterious places,

and some of Australia's oddest animals live here, like the Tasmanian devil.

They're scavengers, sort of antipodean hyenas,

and they use their powerful jaws to crush up every bit of a carcass.

You may get a dozen or so around a dead wallaby.

They find it hard to share, let alone be sociable.

With such lethal teeth, manners like these can be very dangerous.

Screaming at each other is safer, but, better still,

is bum-barging your neighbour with a few powerful blows from behind.

This competitive spirit starts early in life.

Devils are marsupials - their babies develop inside a pouch -

and while this mother is jostling for a meal, the young are tucked away inside,

doing much the same thing.

Mothers produce about twenty embryos and they have to fight for just six teats, so competition is fierce.

Even the ones that survive still have to fight for a drink.

Only three or four usually make it out of the pouch.

By then, the competitive spirit is well-established and will stay with them for the rest of their lives.

Dense forests are not just confined to Tasmania.

They spread right up the eastern coast of the continent,

because soon after Australia became an island, its eastern side was buckled into mountains.

These trapped rain, blowing in from the ocean.

So their lowest slopes are covered in thick forest.

Higher up, there are rugged peaks.

And in the south,

in winter, the rain falls as snow.

These are the Australian Alps, snow-covered for months of the year.

In places, it drifts up to 30m deep.

It's not something you'd expect to see in a land which is mostly dusty and hot,

but this weather can be ferocious and unpredictable.

Sometimes there are blizzards.

But even here, there are marsupials determined to make a living.

A wombat doubles up as a snowplough in an attempt to find food.

Wombats are world-class diggers and use strong front legs and snout

to bulldoze through the snow in search of grass beneath.

They're normally nocturnal, but now it's too cold to come out at night,

so they forage during the day, even in the worst of the weather.

It's a tough place, but there are other marsupials up here as well -

dainty little wallabies.

Surprisingly, the wallaby AND the wombat

have young families in these conditions.

But there's a good reason for this.

These joeys will emerge in spring,

just in time to feed on the new green shoots.

Meantime, a centrally-heated pouch is the warmest place to be.

Even the world's weirdest mammal, the platypus,

makes a living in the icy waters of these mountains.

Uniquely Australian, it has a duck's bill,

an otter's tail and webbed feet with claws.

Males have poisonous spurs, and females lay eggs, like birds.

It's no surprise that early reports of them were treated as hoaxes.

It's a monotreme, a typically Australian group of mammals.

That weird-looking bill is highly specialised,

with tiny sensors to detect electrical signals from the muscles of its prey.

It's so sophisticated, it can swim with its eyes and ears closed.

Swinging its head, it builds up a radar-like map of the stream,

pinpointing the shrimp and worms it wants.

It's a very adaptable animal, making its home in forest streams like these,

all the way up the east coast of Australia.

From the snowy mountains of the south right up to these tropical rainforests in the north.

Like the Tasmanian forests,

these are also ancient and have been here before Australia was born.

The land they cover today is relatively small, just 1/1000 of the continent.

They have just about the richest mixture of wildlife of any of Australia's environments.

It's here, of all places,

you can see what a truly strange place Australia is.

Here more than anywhere, you see how its original cargo of wildlife

has evolved into such a variety of unique species.

Improbable giants, like this flightless cassowary.

And marsupials in every shape and form, including the possums.

One of the most striking is the striped possum,

which scampers over tree trunks, looking for grubs and nectar.

There is no better source of nectar than the bumpy satin ash,

covered in tiny blossoms, growing straight from the trunk.

The possum gets a sticky meal

and it picks up pollen on its fur, transferring it from tree to tree.

There are 26 species of possum in Australia and almost half of them live in these rainforests.

Some have found ingenious ways to move around.

This is a sugar glider.

Flying through the air, or perhaps just falling with style,

they use their built-in skydiving suits to glide from tree to tree

for up to 50m.

They can steer, even change direction, by 90 degrees,

by adjusting their flaps of skin and using their tails as a rudder.

When it's time to land,

they just lower their flaps and put out their landing gear.

Although touchdown could be better!

But why did some possums evolve to glide?

When Australia became an island, its climate started to dry out.

The thick, tangled forest that had covered most of Australia long began to thin out into open woodland.

It was a change that stamped the character of today's bush.

The lush rainforest was replaced by eucalypts or gum trees.

With trees now further apart, some possums evolved to glide across gaps.

And there was now space for other types of travel, too.

Kangaroos evolved in woodlands just like these.

You need room to bounce like this - a uniquely Australian solution to budget travel.

At certain speeds, a hopping kangaroo is more efficient than any horse or antelope.

They live in family groups called mobs, and females can be impressive breeding machines.

There are 50 million kangaroos in Australia, more than twice the human population.

Having a successful design is all very well,

but you need to know how to use it.

Days out of the pouch, this joey has more than just a spring in his step.

Learning to get about on two super-charged pogo sticks is no mean feat.

That was exhausting! Time for a nap.

But as you grow older, fitting those legs inside isn't easy.

In two months, he'll be out for good.

Up in the gum trees is another marsupial, with a less energetic approach to life.

It has the laid-back Aussie love for leisure.

This koala is putting his back into taking it easy.

Koalas eat gum leaves, which are full of toxins and hard to digest.

To survive on this diet, they turned napping into a national sport.

It looks like dozing, but they are working hard to digest their meal.

Bu at one time of the year, this all changes. It's spring, and the males want to mate.

GROWLS AND SNORTS

To start the season, they begin calling.

But if your date is almost comatose,

that may not be enough.

For some older males, this is already too much hard work. They can't keep the mood going for long.

For those who CAN gather enough energy, the chase is on.

But this female, with a baby on her back, is not ready to mate.

For a koala, this is really getting a move on.

MALE CALLS

But males can be very determined.

Gentlemanly courtship is not his style.

SHE GROWLS Nor is she willing to give in.

His only skill is the ability to turn a drama into a crisis.

THEY GROWL AND GRUNT

The baby is now in serious danger and gets separated from its mother.

But it gets even worse.

In the confusion, the youngster ends up dangling from the male.

This farce could easily turn into tragedy.

SQUEALING

The male has bungled the whole episode. It's time to exit,

but as he slams into reverse, he takes the baby with him.

Escape at last, but the baby isn't out of danger yet.

Koalas depend on their mothers until a year old,

and this one is too small to survive on its own.

MOTHER CALLS

Encouraged by her calls, though, he manages to sprint the last metres

back into her arms.

Now he's safe.

Raising babies, with or without rampaging males, is not easy in these eucalypt woodlands.

They're tough places - dusty and dry, without a lot of food.

Especially with mouths like these to feed.

This is a kookaburra, and these chicks are demanding customers.

They want round-the-clock room service.

It's a problem for parents to provide this on their own,

so last year's brood helps. It's a sort of kookaburra catering corps,

with work experience thrown in. They learn all about bringing up chicks.

Kookaburras are the largest kingfishers in the world.

Being Australian, they don't always catch fish and don't always live near rivers.

To keep the brood well fed, they catch everything they can find.

Spiders, snakes, sometimes small mammals.

Anything to keep the noise down.

With the entire family working together on constant dinner duty,

they can deliver food round the clock.

But it seems the faster they shovel it in, the louder the babies cry.

Now and then, though, a big mouthful of lizard seems to do the trick.

These parched woodlands aren't just tough places to live in and bring up a family,

they're dangerous as well.

They're tinder-dry and easily ignite.

When a spark hits the volatile oils in their leaves and bark,

gum trees burst into flame. In minutes, the woodland is a fireball.

Animals that can move fast get out quick.

If the wind gets up, it can fan the blaze, causing crown fires that race through the tree tops.

And afterwards...Armageddon.

The morning after, there may be some dead insects around, the odd shoot,

but any animals that survived will have to move on.

And they may have a long way to go.

Hundreds of kilometres of woodland can disappear in days.

Three million hectares a year are incinerated by fires like this.

But then something extraordinary happens.

Many gum trees have evolved to survive bush fires.

And some have energy stores beneath their bark, so they burst back into life.

Within a week or two, their trunks are covered in dazzling green foliage.

The drying out of Australia's climate over millions of years

not only had a major effect on its forests, but also on its rivers.

Long ago, Australia had a network of mighty rivers, stretching right into the heart of the continent.

But when the climate dried, they dried up, too.

Today, the largest river system left is the Murray-Darling.

And here it is - barely wider than the average road.

It's extraordinary that a 2,500km river should be so narrow.

And this is in full flood.

Even in a year, less water flows down the Murray-Darling than down the Amazon in a single day.

Most of Australia's rivers are even smaller.

Many are streams that dry out for part of the year. Others are creeks that haven't seen water for years.

But in many river beds, water remains in pools called billabongs.

In a parched landscape, these stand out as irresistible lures, drawing in wildlife from every direction.

Many animals live or die by their skills at finding vital billabongs.

None arrive in greater numbers than corella parrots.

BIRDS SCREECH

These turn up in their thousands.

In flocks so huge that early explorers in search of water learnt to look for them on the horizon.

In this early-evening rush hour, they're joined by budgies -

tough little nomads, who will travel a long way for water.

By the end of the day, thousands of birds have gathered here,

and every available tree seems packed with budgies and corellas.

Most animals in the outback get at least some water from their food,

but corellas and budgies eat seeds, which are very dry,

so they need to drink every day.

Kangaroos can survive longer without water,

but rarely stray far from it.

On the other hand,

emus may have followed a trail for over 100km.

They use cues like distant clouds

or thunder to help them find water.

And it's not just vital for daily life.

Animals need it for breeding, too.

Because rain is so unpredictable, kangaroos breed when they can.

When there's water, females move into mass production.

She may be suckling an older joey, with another in the pouch, and an embryo inside her as well.

Budgies, too, make the most of it.

When they find water, they set up home and raise a family instantly.

But they have some rather annoying neighbours.

All the activity at this budgie household seems too much for the corellas.

They are intelligent birds,

but they also enjoy sticking their beaks into other people's business.

For the budgies, they're the neighbours from hell.

The corellas are just being nosy, but it is best for the budgie chicks to stay in their hole.

These are playful birds, and after a few drinks at the billabong, they like a bit of fun.

Fooling around helps strengthen their relationships.

But some of it's just showing off.

While the water lasts,

they make the most of this time off in the cooler evening light.

Although much of Australia has very little water, there's one area that's awash with it.

Since becoming an island, Australia has drifted north at 5cm a year,

so its top end's now in the tropics,

right in the path of the tropical monsoon.

This is one of the most powerful weather systems on the planet.

It lasts for only a few months each year.

While it does, Northern Australia becomes a very different place.

It has a dramatic wet season.

For a short time,

rain falls so hard that rivers turn into raging torrents.

When they burst out of their gorges, they flood out onto open plains,

creating some of the world's largest tropical wetlands.

The most famous of these is called Kakadu.

Every year, huge numbers of birds arrive to feed and breed.

Two million magpie geese alone jostle for space

with ducks, herons, ibis and other water birds,

some feeding on the flooded grass, others on shrimps and small fish.

But birds aren't the only animals here.

In the quiet streams on the edge of the swamp,

are residents who live here all year round.

This prehistoric-looking reptile is an amphibious lizard called Merton's Water Monitor.

They're graceful swimmers, spending some time completely submerged,

propelled by a long, powerful tail, which doubles up as a rudder.

They're scavengers and, even under water, they can taste the scent of rotting food.

Finally, it finds the meal it's been looking for - a dead fish.

There are other reptiles here, too.

Freshwater crocodiles, also uniquely Australian.

These daintier cousins of the giant saltwater crocs feed on small prey,

like fish and crustaceans.

This is boom time, but it won't be long before the monsoon ends and the blazing sun takes over again.

As the water evaporates, the swamp congeals

into an ocean of sticky mud.

On the margins of Kakadu, streams dwindle into pools of sludge.

The monitors can move back on land

but these freshies rely on water to keep cool.

Their situation is beginning to look increasingly sticky.

Before they get stuck fast, these crocs must do something - quickly.

As the evening heat dies down,

they slide to the edge of the pool.

Their only chance of surviving is to travel overland in search of water.

They'll need to find it before sunrise.

Instead of the normal crocodile belly crawl,

they march overland with this unusual high walk.

It's the fastest way to travel if they're going to find water by dawn.

When the sun comes up, they're in real danger of overheating.

But freshies have one last trick.

With a unique gallop,

they make an Olympic dash

and become the fastest crocodiles in the world.

With any luck, a deep pool like this will survive

until the monsoon returns.

But most of the streams and pools

will have all water sucked out of them by the burning tropical sun.

Throughout its long history, Australia has dried out so much

that half the continent is desert -

in places, so arid and alien,

it looks more like the surface of Mars.

In the harshest areas,

there are vast lakes of dry salt.

With almost no vegetation, the bones of the continent are laid bare.

Like a gigantic ribcage,

these parallel sand dunes stretch for hundreds of kilometres.

At the heart of the desert - Uluru, one of the world's largest rocks.

And THIS is just the tip -

the rest extends 6km below ground.

In such a dry landscape,

it seems bizarre that Uluru was actually weathered into shape

by millions of years of rain.

At first glance, there's not much sign of life in the desert.

But during the day,

sensible Australians stay out of the sun - including the planigale.

It's one of Australia's smallest marsupials and one of the toughest.

It needs to be. Most of its meals are larger than it.

Dwarfed even by this moth, the planigale doesn't give in.

With true outback grit,

it tries to wrestle this oversize meal to the ground - and fails.

In these underground cracks, it's almost 15 degrees cooler

than in the sun. The planigale can hunt for a smaller meal in comfort.

Or so he thinks.

This is no time to relax

when above you is the world's deadliest snake - the inland taipan.

This snake scares even Australians.

It's loaded with venom -

enough to kill thousands of planigales and you or me in minutes.

NOW being small has its advantages.

With a specially flattened head,

it can squeeze into tiny crevices.

Even the world's most venomous snake can't always get a meal.

The Australian desert is full of deadly snakes.

In fact, all sorts of reptiles flourish here - especially lizards.

Australia has more than any other continent.

A single sand dune can support 40 species.

This really is the land of the lizard.

The largest are more than a metre long.

This is a sand goanna, also known as a racehorse goanna -

for obvious reasons.

Lizards are much more successful here than mammals

because they need less food.

Meals can be scarce and goannas will eat almost anything they can catch -

even scorpions.

Goannas do get stung but they seem to be immune to the poison.

It may not be much but this could be its last meal for weeks.

Animals don't come much tougher than the adult goanna

but their eggs are more vulnerable.

They need protection from the harsh climate

and termite mounds make perfect incubators.

These eggs were laid about nine months ago

and now they're ready to hatch.

Fully formed, miniature adults emerge.

The termite mounds gave perfect protection

but now they're a barrier to the outside world

and these babies need to get out.

The walls can be rock-hard.

But the youngsters are already as determined as adults.

One by one, they clamber out to one of the toughest habitats on earth.

Over its long history, Australia has dried out so much

that, in places, its desert heart has expanded right up to the coast.

Millions of years of drying

has had an enormous impact on the character of Australia.

But one further event put the finishing touches to its shape.

Just 10,000 years ago,

at the end of the Ice Age, sea levels around the world rose,

Australia's coastline was flooded,

creating thousands of beautiful islands.

This flooding also helped shape the world's largest living structure -

the Great Barrier Reef.

This reef was once dry land.

Aborigines might even have hunted kangaroos here.

Now, at over 2,000km long,

it's the greatest coral complex to have ever existed.

It's hard to imagine a more colourful contrast

to the dry, crusty old continent.

Over 400 different corals, in every shape and size,

support more than 2,000 species of fish.

And just for a few days in spring,

the reef bursts into a special frenzy of activity.

With precision timing, using cues from the moon and the tides,

many fish begin to breed.

Thousands of them condense their courtship and spawning

into just a few minutes of frantic fertilisation.

But on just a few nights each year,

an even more remarkable event takes place.

On certain tides, just after the full moon,

the reef itself begins to erupt.

2,000km of coral takes part

in a synchronised release of eggs and sperm

in vast quantities.

No-one knows quite how so many billions of eggs

are timed to release on the same night, so precisely.

It's the biggest synchronised breeding event on the planet.

It seems extraordinary that Australia -

the harshest, driest inhabited continent on earth -

has also produced such a colossal, vibrant, growing structure.

But from the moment Australia became an island,

its isolation and history have made it into this continent of extremes.

It is a land of fantastic diversity,

the weirdest mix of animals and plants

living in some of the toughest, most beautiful, landscapes imaginable.

This really is the strangest continent on earth.

Next week, Wild Down Under takes you to Australia's desert heart,

a place where only the hardiest animals survive.

But this extraordinary landscape is full of natural secrets.

From ancient mountains to disappearing inland seas,

this is a journey across the most surprising desert in the world.