All language subtitles for 2Nature of Australia. D2.Eng

50 million years ago,

all of Australia was covered
by a mantle of dense rain forest.

This green luxuriance
was the cradle of evolution

for the unique plants and animals

that now give Australia
such a distinctive character.

Today, three-quarters of the continent
is arid.

But some fragments
of that primeval jungle remain,

mostly here in the tropical north-east.

It's a living museum, where
the very beginnings of the bush survive.

The canopy is so dense here

that in the cooler winter
pythons emerge from the trees

to warm themselves in the sun.

Today, this is one of the few places
on the arid continent

where the struggle for life
is not for water but for light.

On the forest floor, where it's dark,
the young plants have reddish foliage,

all the better to absorb the light.

Ingenious solutions

have been evolved by the plants
in their race to the sky.

Vines send out tendrils or barbed hooks
to claw their way swiftly to the top,

using existing trees for support.

Some figs get a head start

by germinating their seed
high up in the canopy

then sending down roots
which eventually strangle their host.

The fig itself grows on,

and pushes its massive crown
high above the forest roof.

There's a constant jostle
for light and space in the canopy,

and the crowns weave together
in a dense and billowing layer.

Were they simply to drop,
seeds might not grow in the gloom.

So they're packed in fruit

to entice birds into eating them
and carrying the vital contents away.

Where there are birds,
there are nests and eggs,

food for the green tree snakes
that patrol the upper storey.

Only the flesh of the fruit is digested.
The seeds simply pass through the gut.

The more birds eat, the more seeds
get scattered around the forest.

Even the fruit that does fall to the ground
may be picked up by cassowaries,

a flightless bird unique to Australasia.

They too void the seeds.

And because the birds
tend to do so in clearings,

where there's more light,

the seeds have a better chance
of developing.

Such a wealth of food within easy reach

gives certain birds
more time to devote to breeding.

Male bowerbirds have become
skilled artists and builders

in their quest for sex.

On the dim forest floor,

the decorated structures
are marvels of arf and architecture,

designed solely
to attract and impress females.

Among the golden bowerbirds,

these courtship theatres
are passed down the generations

and freshly embellished
with mosses and lichens.

The more brilliant the plumage,
the less elaborate the bower.

This regent bowerbird
has a fairly modest arena,

but he still can't afford
to leave it for long,

because other males
may try to take it over.

Male satin bowerbirds make an avenue -

twin rows of twigs are glued in place
with a mixture of charcoal and saliva

and later painted with crushed plants.

It's impressive enough to lure a hen.

The sight of her excites the artist
into a brilliant song and dance.

In a season's wooing, many will be won.

The male role ends with copulation

and the hen's left to build a nest
and raise their chicks alone.

As well as disperse seeds,

birds play another imporfant part
in the forest's procreation,

as pollinators.

Up in the canopy,

there's much competition
for animals to carry pollen.

Perhaps that's why this bumpy satin ash
grows its flowers directly from the trunk

to catch the passing traffic
of honey eaters.

A rich flow of nectar rewards them
for taking pollen between trees

and fertilising the flowers.

When nightfalls, the mammals emerge.

Among them are tree kangaroos.

Despite their name, they spend
as much time on the ground as aloft.

Lemuroid possums prefer the canopy,

where they find
some of their favourite foliage.

But it's flowers that are especially prized.

And their scent brings
yet more visitors to the satin ash,

to harvest the nectar
and collect the pollen.

Like the honey eaters,

the blossom bats have long tongues
tipped with tiny brushes

to soak up the sweet liquid.

Flowers provide
their only source of food.

And enough pollen
sticks to their whiskers and fur

to make these tiny bats
gentle and reliable go-betweens.

The trees derive no benefit
from this possum.

The Herbert River ring tail
relishes the flowers

as a welcome break
from its usual fare of leaves.

Possums first evolved in the rain forests.

And overtime, they diversified
into many specialised kinds.

For arboreal animals, lemuroid
possums aren't all that agile.

While most of the larger species
feed on leaves and other plant food,

this small and elusive striped possum
prefers insects.

Searching along
the rotting and dying trees,

it tears at the bark with sharp teeth
and digs out wood-boring grubs.

Its hands tap along the wood

for the hollow sounds
that betray the presence of borers.

The fourth finger on each hand
is much longer than the others

and it's tipped with a sharp claw

to skewer fat and juicy grubs
from deep inside the rotting timber.

Today, this pretty striped possum
is hard to find.

Although the rot and decay that's so
much part of this dense and wet forest

gives it a good living here,

its special way of life
left it no match for a dramatic change

which began to gather pace
15 million years ago.

Australia star fed to dry out.

And most of the rain forests
and their inhabitants vanished.

But among the plants
were some that adapted -

plants that already had evolved features

to survive in places
where the soil was poor.

And it was these
marginal, hardier plants that took over

while the ancestral forests
retreated to a few pockets.

From among the new plants

rose a group that spread around
Australia in splendid variety-

the eucalypts, the gums.

They reach their most majestic form
in the mountain ash.

Growing to 100 metres, it's
the tallest flowering plant in the world.

And with its light and airy crown,
it's the king of the eucalypts.

The open canopy

lets through much more light
than the rain forest it replaced.

And in these higher, wetter areas,

it allows an understorey of tree ferns
to flourish -

a backdrop of green lace for what
sounds like a great chorus of birds.

In fact, all the songs
have but one singer, the lyrebird,

a uniquely Australian master
of both mimicry and display.

The aim is to persuade females nearby

that the cock bird
is a fine and healthy specimen,

well worthy of fathering their chicks.

This hen seems to have
heard it all before.

And she's more interested
in the insects hiding in the litter.

But in time, the display will work its spell.

Eucalypt forests
are spacious and uncluttered.

And that gave some of the possums
added impetus

to turn leaping into gliding
as a means of getting around.

Folds of skin

that stretch between the fore-
and hindlimbs of the leaping possums

evolved into
strong and supple membranes

to carry sugar gliders and their kin
on long flights through the open forests.

Gliding doesn't use as much energy
as climbing.

And it's an economical way
for possums to harvest a special food

provided by some kinds
of widely scattered gums.

In these uncommon trees,

a sugary sap flows
so close to the outer skin

that a slash of sharp teeth
has it oozing out

to become a rich and sustaining food.

The sap trees are few and far between.

And so sugar gliders band together
to defend this precious resource.

As a result, they've become
the most social of the possums.

It's a society where the chief language
is not sound but smell,

and a complex idiom it is.

Whenever gliders meet,

they stop to sniff
and refresh their communal scent.

The glands
are in the most unlikely places -

under the chin, on the forehead,
even under the feet.

As well as the tribal odour,

there are subtle blends that tell
who's who in the social order

and details of sex-

for instance,
whether this female is ready to mate.

The unfamiliar odour all around

warns this stranger
that he's in the wrong place.

To warn all comers
that this is occupied territory,

the resident males smear pungent
trails around the tribal range.

A strong scent from glands around
the vent is mixed with drops of urine.

Again, it's scent,
or rather the lack of a familiar one,

that marks out an intruder.

His body odour
declares him to be a male,

but a very young one
and so no real threat.

Before dawn breaks,

the gliders make their way
to the communal den.

Such a tight squeeze
keeps out larger possums

and gives protection against whatever
enemies might come prowling by.

Inside the eucalypt hollow,
it's also a fairly snug fit.

Some colonies have as many as
eight gliders bedding down together.

Sharing body warmth saves energy

and helps to pass around
the all-important tribal scent.

The eucalypts' distinctive
dull green foliage is much more open

than that of the rain forest trees
from which they evolved,

with smaller, hardier leaves
to withstand the climate.

The leaves hang angled away
from the sun to keep water loss down.

And to make them unpalatable,

they're loaded with potent cocktails
of toxins and oils.

Despite this,

some animals have found ways
of breaching the eucalypts' defences.

And they form a web of life

that extends even to the streams
flowing through the forest.

The leaves fall all year round.

And almost the moment
they hit the water,

the first of a long line
of insect shredders gets to work.

Caddie-fly larvae,

armoured in a suit
of sand grains and plant fragments,

reduce the leaf to a skeleton,

carefully munching their way
around the poisonous oil glands.

The bits of leaf
get broken down further

and are swept downstream,

some to fetch up in a tiny net
spun by another kind of caddis larva.

Instead of having
a portable suit of armour,

this one builds a fortress
out of tiny pebbles.

It's such a good spot

that another larva mounts an assault
on the miniature castle and takes over.

The usurper's first task is to
improve and strengthen the structure.

One side of the keep
serves to anchor the net.

And with all the rebuilding,
it's become rather tattered and torn.

When the last pebble
is securely in place,

the caddie sets about reweaving
its gossamer snare,

producing sticky threads
much like a spider's.

The net is delicate but tough -
only 5mm across,

yet sturdy enough to catch and hold

the bits of broken-down leaf
swept into it by the strong current.

The creatures that inhabit these streams
belong to very ancient families.

It's only the nature of the leaves
on which all their lives depend

that's changed -

from rain forest to eucalypt.

The leaf-shredders and net-spinners

become food for larger insects
and crustaceans.

And there are enough of those
to help feed the platypus,

which lives much as it did

when these streams were still fed
not by eucalypts but by rain forest.

Change becomes more apparent
further downstream,

in the drier woodland
of the lower rainfall country.

The soils are poorer here,
and the gum trees don't grow as tall.

They're more gaunt and spare
than the eucalypts of the higher ranges.

This is the characteristic bush.

Unlike their rain forest ancestors,
gums don't make fleshy fruit.

Instead, seeds are packed
in woody cases to stop them drying out.

A colourful company of cockatoos,
parakeets and Iorikeets

feeds on gum nuts and berries,

deftly peeling them
with tongue and beak.

The open canopy allows
a lot of sun to reach the ground.

There's plenty of light and space
for seeds to germinate and grow.

And the eucalypts have no need
to bribe birds to carry the seeds away.

Though many are eaten by parrots,
many more survive.

But sun also dries the litter
as it builds up,

accumulating fuel

for another powerful force that moulded
the nature of Australia -fire.

Astonishingly,
the eucalypts came to thrive on fire.

Features that developed first to cope
with poor soils and then with drought

now stand them in good stead
in dealing with flames.

In the aftermath,
the bush looks black and lifeless.

But it's far from dead.

Already, the wombats which hid from
the flames in their burrows are out,

squabbling over
bits of plant food left unburnt.

The eucalypts live on.

The reserve shoots and buds
under the bark and the main branches

begin to sprout.

And within weeks,
the gums are veiled in green again.

The fresh growth
attracts armies of insects,

for leaves are best eaten
when they're young and tender,

even though they're already loaded
with defensive toxins.

A vast array of suckers, cutters,
nibblers and munchers goes to work.

They're mostly the larvae
of moths and butterflies.

And they consume
great quantities of leaves.

Some simply nibble their way
around the chemical defences.

Others are immune.

Because the eucalypts
can put out new growth repeatedly,

they seem to suffer more insect attack
than many other trees.

Fire, insects, and still the trees survive.

Indeed, they do attract some allies
in the insect wars,

though even a legion
of praying mantises

wouldn't take much of a bite
out of the hosts of leaf eaters.

The intervention of this bell-miner
actually works against the trees.

The reason forth at is its fondness
of these small sugary domes

that form on the leaves
of some eucalypts.

They're called lerps,

and they're made by
the larvae of psyllid insects

to protect their soft bodies from the sun
while they suck the sap from the leaves.

The psyllids
digest what they need from the sap

and use the waste
to build their sunshades.

At first, the material is soft and pliable,
and the larva can work it into shape.

Eventually, the fruit
of two hours patient labour

sets into a tiny house of sweet glass.

Bell-miners relish the stuff,
and carefully remove the domes,

leaving the insects to manufacture more.

They chase other birds away-

birds that eat the insects
as well as their shelters.

And that's a problem for the eucalypts,

for with the bell-miners protecting
the psyllids and taking their domes,

the insects' appetite for leaf sap
is constantly being stimulated

to become ever more voracious.

The eucalypts can't count this bird
among their friends either.

It's gone into parfnership with
a parasitic plant-the mistletoe.

The mistletoe taps into the eucalypts
for its own growth

and it employs the mistletoe bird
to spread its seeds and gain a root hold.

The bird and its chicks
have the gut specially designed

so that the berries go directly into
the intestine and bypass the stomach.

That way, they go through very quickly,

and when the partly digested berries
emerge, they're still sticky.

The seeds are dropped
high in another tree, and sprout.

One eucalypt may carry
several mistletoes

and struggle to survive itself.

The mistletoe is at the centre of another
even more remarkable relationship.

At the base of some host trees,

the caterpillars of azure butterflies
are tended by sugar ants,

which give them shelter
in their own nest.

Every night, the grubs go on a long
and dangerous trek to the top of the tree

to feed on the mistletoe leaves.

The ants go with them,

and their presence guards against
spiders and other enemies.

In return, the grubs supply the ants
with a rich, sugary liquid

from their body glands.

In their rise to dominance
over the last two million years,

the eucalypts formed a range
of extraordinary associations,

but most involve birds and insects,

which either avoid
or cope with the toxic leaves.

By contrast, only a few leaf-eating
marsupials have been able to adapt.

Of all the rain forest ring tail possums,

only the common ring tail
thrives in these drier woodlands.

It's successful because its digestion
can cope with the oils and toxins

in the eucalypt foliage,
which is the most abundant food here.

As soon as they're out of the pouch,

the baby possums start weaning
on the tough plant food

that'll be their adult fare.

That grasping tail helps them reach
the fragile outer branches

bearing the fresh new leaf growth

and it also makes a handy carrier
for nesting material.

The leaves that pose the marsupials
with such a digestive challenge

make a dry, hard litter which takes
a long time to break down,

but enough insects and other
invertebrates live amongst it

to provide a good living
forth is an tech in us.

Its hunting skill is extraordinary.

Speed and a single-minded ferocity

enable it to tackle
almost any kind of prey.

But it's the antechinus's sex life
that's even more remarkable.

There too, ferocity is the hallmark.

With the advent of the mating season,

males competing for females
fight each other to a standstill.

The male sex drive
is especially urgent with an tech in us -

as well it might be, for they have
only one season to reproduce.

It makes their couplings fairly brutal -
more like a rape -

and lengthy they are too.

All this frantic breeding is lethal.

It takes tremendous energy
and produces great tension,

and males hardly eat, their teeth
fall out, they get gastric ulcers,

and their stress hormones
rise to levels so high

that their immune system fails,
like AIDS.

By the end of the season
they're all dead,

leaving only the pregnant females.

It's a high price to pay
for breeding success,

but there is sense in it.

Small mammals don't live long anyway,

and among the an tech in us,
evolution has favoured males,

which put all their reproductive effort
into their first and only mating season.

Success lies not in personal survival
but in how many young are fathered,

to ensure that the line is carried on.

The challenge of procreation
in these wood lands

has fashioned other,
equally intriguing, strategies.

Many of the birds here
form extended families

to share the task of rearing young.

Several generations of kookaburras -

older brothers, sisters,
unattached uncles and aunts -

pitch in with feeding
and even help to incubate the eggs.

Communal breeding is away
of giving chicks a better chance

in an environment where
food supplies aren't always reliable.

But animals don't usually
do anything for nothing.

Perhaps the return comes later,

when the helpers get help
with their own young.

The galah's strategy is to form
a lifelong bond with one mate.

Pairs come back to nest
in the same tree hollow year after year.

Hollows are fairly safe places

but no bond is strong enough to guard
against lace monitors on the prowl.

Though they're only active
for a short time each day,

their acutely sensitive taste and smell

make them the most feared predator
in these parts.

It's just another meal
for the lace monitor,

but for the galahs,
it's the end of their chance

to rear a family this season.

Beneath the eucalypts live banksias -

ancient plants going back
to the primeval rain forest.

They are inhabited by pygmy possums.

Vacant bird nests often provide a home,

and some of their food
comes from insects.

Insects are relished,
but the banksias themselves

provide their small guests
with even more important nourishment.

The pygmy possums feed on the nectar

and in so doing
help pollinate the flowers.

The possum babies soon get the hang
of clambering around.

After all, the pygmy possums
and banksias evolved together

over an immensely long time.

The shape of the flowers
suits these nocturnal pollinators -

each spike has hundreds of tiny flowers,

densely packed together
to provide support,

and plenty of nectar and pollen.

Banksias and their relatives

come splendidly into their own
in the heathlands,

especially here in Western Australia.

In these ancient leached soils,
so poor they're almost pure sand,

climatic hardships created
an evolutionary nursery without parallel.

So many flowers
eager to attract pollinators

have fostered
a matching diversify of insects.

Many, like these jewel beetles,
are rewarded with nectar,

but some plants show
even greater entrepreneurial flair.

Honeyeaters make good go-betweens,
and many plants employ them.

Even more recruit insects,

and the result is
a wonderful assortment of shapes

designed to suit the various visitors.

Certain plants even resort to fraud
to seduce insects.

One group of orchids

cunningly exploits
the sexual habits of this wasp -

habits remarkable enough in themselves.

The female has no wings,
and when she's ready to mate,

she rubs off chemical signals
for a male to come and fly off with her.

The wasps mate on the wing,
and, still coupled end to end,

he takes her
to some nectar-rich flowers.

Now he feeds,
dragging his partner behind him.

She can't feed herself,

but when he's had his fill,
he rubs her abdomen,

which prompts her to curl forward
and receive a few drops from his mouth.

Feeding her is his investment
in the eggs now forming in her body.

The whole method hangs on
the chemical signals she sends out,

and the orchids have evolved
almost identical signals

to trick the male wasps
into trying to copulate with them

and so become their pollen carriers.

This flower looks as well as smells
like a sexy female wasp,

and he keeps on trying to mate

even when the orchid flips him
onto its pollen-bearing part.

Such mimicry is an economic way
of seducing pollinators

without having to supply nectar-

a great advantage in these poor soils.

The plants that use birds
do give a reward,

but the flowers are shaped

so that the visitor has to collect
a dab of pollen as well.

The honey eaters
are also matched to the task.

Inside the long bill
there's a long tongue

tipped with a brush
to soak up the nectar.

Rather than opt
for one particular kind of pollinator,

banksias play the field.

Their dense blooms are arranged
to tempt various honey eaters,

reward them with nectar
and ensure they carry away pollen.

But those same blooms also support
a much more ancient partnership

with this extraordinary animal.

Much smaller than a mouse,

the marsupial honey possum is one
of the very few mammals in the world

designed to feed exclusively
on nectar and pollen.

Like the honey eating birds,

it has a long tongue
fitted with a brush at the end.

The partnership began
in the ancestral rain forests,

and while many other
plants and animals vanished,

the honey possums
stayed with the banksias

as they became transformed
into these hardy plants of the bush.

In the eucalypts
that fringe the heathlands

lives another very specialised
marsupial -the numb at.

Its survival is linked closely
to the termites

that became abundant as
the Australian landscape dried out.

Uniquely among marsupials,
they become active only by day,

because that's when the termites
upon which they feed

move near the surface
and into the fallen timber.

The stripes are good camouflage,

but having to step out in broad daylight
still makes the numbats very cautious.

This kind of eucalypt woodland
provides a plentiful supply

of the wood-eating termites
that the numbats prefer.

And they're well-equipped
to harvest them,

with a tongue that unrolls
to half their body length.

It's a specialised way of life,
and it's enabled the numb at

to live through the ever-drying climate
that made the bush.

The rise of the eucalypts
offered a secure place

for any marsupial
that could stomach their foliage.

Some possums managed it,

but it's the koala that's come to typify
the supreme gum specialist.

Its gut has special bacteria
to extract all it needs

from just a few types
of eucalypt leaves.

It means koala life revolves around
a small range of gums -

that's where they fight, feed and mate.

Mating is what's on the mind
of this old dominant bull right now.

The female is still carrying
last year's young,

and she sees the approach
as a threat to herself and her joey.

She's much lighter

and she can move out to the thinner
branches where he daren't follow.

The awkward way they clamber around

suggests that they haven't been
tree dwellers all that long.

In fact,
their closest relatives are wombats.

The old bull
is about to suffer more frustration.

A young rival has come into his range
with designs on a virgin female.

The commotion sends the king koala
hurrying to protect his mating rights.

If this intruder manages
to impregnate one of his consorts,

there's one less chance
off a the ring a royal cub.

The old male
is an experienced campaigner.

His tactic is to drive the young rival
far out on a slender limb.

Now the choice is to fall
or risk an escape past the royal rage.

Peace returns, but the tension remains.

Sooner or later,
the young male will try his luck again -

he may even displace the old bull
and become the new ruler.

It'll make no difference to the females.

They'll continue to care for their young

and when the time is right, receive
the seed for the next generation.

It's important for joey
to stay close to mother,

not only for milk, but also to be fed
with some of her faeces.

It's a pap that will prime the young

with the special bacteria
to process gum leaves -

its sole food in adult life.

Of all the marsupials,

the koalas have tied their fortunes
most closely to the eucalypts.

It's the quintessential partnership
in the bush,

a partnership that could only
have evolved in Australia.

Inland from the wooded margins,

the drying centre of the continent

posed animals and plants
with an even greater challenge,

and that's the theme
of our next program.

In the back of beyond
lies a shimmering wilderness

where even the stones seem to burn.

It's been called the never-never,
the dead heart of Australia.

Three quarters of the continent
is arid now,

but once, this vast interior
was a place of plentiful rain

with rivers flowing into great lakes.

Even today, huge rains occasionally
transform the arid lands

into a semblance of that wetter past.

In these deep valleys,

run-off from the infrequent rains
filters through the rock

long after the surrounding country
has dried out again,

and the water preserves
stands of ancient palms.

Permanent pools teem with fish.

They are now able to cope

with wild swings
in water temperature and salinity,

and they breed into vast shoals

when the heavy rains flush them out
into the desert rivers.

That happens perhaps only a few times
each century now.

Most of the time the rivers are dry.

And yet they're far from dead.

For deep within their sandy beds,

there's moisture left behind
by the last rains.

It's these hidden waters
which support a rich mosaic of life

through even the driest times.

Millions of years of erosion

carved deep and wide
through the shields of rock.

Pillars of harder stone remain,

while the rest of the plateau
wore away

to form the deserts
of Central Australia.

Ancient floods scattered the
eroded rock into plains of stone -

the gibber deserts,

their bright sheen
a film of iron oxide

left by evaporated moisture.

It seems that nothing could grow
here amid this wilderness of rock.

Yet amazingly there's life.

The shingleback lizard seems
a pattern of stone, until it moves.

There aren't many places to hide,
and camouflage is a good defence.

Reptiles manage well here,

for they can do without
regular food or water.

While there isn't enough to support
many mammals or birds,

the gibber bird does thrive here.

There are sufficient insects
to supply all its needs,

including the little moisture
it requires.

It escapes the worst
of the blistering heat

in what shade there is,

holding the wings out to keep air
circulating close to its body.

The fierce winds that came

with the last great drying
of Australia 20,000 years ago

sifted the sand from the gibber
and swept it into vast dunes.

Row upon row of dunes
arc halfway around the continent,

some running without a break
for 300 kilometres.

The sand seems a meagre
basis for life.

Yet life there is.

Its presence is written in the sand.

A moving ripple announces a most
intriguing and secretive creature -

the marsupial mole.

The mole spends much of its life
swimming through sand.

Its sturdy little claws
are shaped like shovels.

Eyes would be useless
beneath the surface,

and they've all but disappeared.

Instead, it relies on touch and smell

to find its subterranean meals
of grubs.

But not all that ripples is a mole.

Some lizards
have also become sand swimmers.

Several skinks
have gradually lost their legs,

the easier to slip
through the shifting granules

and sneak up on insects.

But this grasshopper's
come up with a defence.

Already patterned like sand,

it completes the vanishing act
with a flurry of shovelling legs.

In the swales between the dunes,
a crust of clay and sand has formed.

And in the years between rains
it lies sunbaked and cracked.

These miniature canyons are home
to Australia's tiniest marsupials -

the planigales.

They weigh as little as six grams,

and their heads are flattened

to squeeze through the narrow spaces
in search of insects.

But small mammals

also make attractive prey
for the desert snakes.

At moments like this,

the cracks offer protection
against more than the desert sun.

Reptiles are the major predators
in these parts.

And the most formidable of them all
is the perentie -

a giant goanna, two metres long.

Much of its prey hides from the sun,

but the forked tongue picks up
even the faintest traces of scent.

The snake is extremely venomous.

Bashing it breaks the back
and leaves it helpless.

A meal this size can last perenties
a month or more.

Storing food in layers off at

enables them to thrive
in this unpredictable region.

The desert dunes overlie
and rechannel ancient river courses

that once drained
into a huge inland lake.

What shimmers now is salt left by
thousands of years of evaporation.

Today Lake Eyre
is the driest place on the continent

and among the hottest.

It lies 15 metres below sea level

and temperatures can soar
to a scorching 60 degrees.

Yet even at this harsh extreme
some animals flourish.

Lake Eyre dragons
survey their salty domain.

Their eyelids shaped like sun visors
against the blinding glare.

They feed on ants which harvest
insects blown onto the salt.

The ant mounds
also serve as lookouts

to spot potential mates or rivals.

To avoid actual battle,

the dragons have evolved
a most eloquent body language.

Head bobs, push ups and arm waves
sort out the hierarchy

and signal readiness for mating,
or reluctance.

This male has proved his dominance.

Now he can feed undisturbed,

walking on the heels so as to keep
toes from getting burnt.

The dragons manage to thrive

in conditions that would defeat
most other creatures.

And most of the time
their domain remains undisturbed.

But a few times each century
Lake Eyre becomes a sea again.

Most of Central Australia
drains into Lake Eyre.

Usually, run-off from light rains

evaporates long before
it reaches the lake.

But occasionally a tropical cyclone

dumps huge rains
across the remote channel country.

It's these unpredictable
heavy drenchings

that are the crucial events
in the life of the arid country.

Waterfalls in such abundance

that it soaks deep
into the parched earth

and replenishes the hidden stores

which keep the plants and animals
going when the dry times return.

The downpour is a welcome chance

for the desert animals
to drink their fill,

and for these galahs to wash
the dust out of their feathers.

In this region
of little and erratic rain,

the survivors are those
who, like this spiny-tailed gecko,

make the most of every opportunify.

Normally it emerges only at night.

A praying mantis sips the droplets
that gather on its arms.

The thorny devil drinks
in a most ingenious fashion.

The sculpting of the scales
creates fine channels

which draw the water
to the corners of the mouth.

The rain is heavy enough
to sink deep into the sand.

A metre or so down

it wakens a most surprising animal
to find in the desert-

a frog.

Yet frogs live here in abundance,

for they cope with drought
in a remarkable way.

They escape underground for years,

cocooned in a second skin
to keep their body moist.

That shroud provides the first meal

when the kiss of water ends a sleep
that may have lasted five years.

Then comes a brief but glorious
spell of freedom -

feeding and breeding

until the returning dry sends the
frogs back into their time capsule.

The desert plants have their own ways
of making the most of the rain.

Many mulgas are shaped
like inverted umbrellas.

The rain is funnelled down
the leaves and branches,

then cascades down the trunk.

The water soaks in
around the base of the tree

and recharges the underground stores.

The cracked clay between
the sand dunes soon becomes saturated

and forces the planigale
to seek higher ground.

There's been so much rain here
in the channel country

that the run-off races hundreds of
kilometres down the dry creek beds

towards the arid heart.

The waters replenish
the subterranean reservoirs,

carrying the benefits of the rains

a long way from
where they actually fell.

Once again, masses of water
are surging towards Lake Eyre.

So suddenly did the rivers rise

that they caught
this gecko unawares.

It's a marvellous transformation

from bone-dry sand
to water churning with fish.

They're bred from stocks
in isolated water holes

flushed out by the rains.

These cormorants are among
the legions of water birds

which follow the newly flowing rivers
into the flooding desert.

The rivers carry so much water,

they flood out across plains
that are among the flattest on earth.

The warmth of the sun
and the wealth of fresh nutrients

brings everything to life.

Dragonflies and insects of all kinds
are in a frenzy to reproduce,

to make the most of the good times
while they last.

The touch of water
stirs dormant eggs into life

and the claypans
soon teem with shield shrimps.

Theirs is a most fleeting existence,

forth is shallow water
won't last long.

Two weeks after hatching, they mate

and lay eggs
that may lie dormant for 25 years.

The budgerigars know the rain
will produce a flush of food.

And they gather in trees
lining the flooded rivers

to form pairs and start families.

These nomadic little birds

are well tuned to the
shifting fortunes of the interior.

They mature quickly

and the males produce sperm
when they're only a few months old.

The flooded rivers become flyways

for ever more invasions
from the continent's wetter margins.

Long line of water birds follow the
shining trails deep into the heart.

The wave of life
reaches its crest in Lake Eyre,

transformed again
into a mighty inland sea.

Water now stands metres deep

where the dragons perform
their courtly dance.

They've fled to the shores,
and the lake belongs to the birds.

Close to shore, red-necked avocets

sweep through the mud
for brine shrimps.

Further out, pelicans flock together
to round up the teeming fish.

The floods have turned the salty
desert into a vast bowl of rich soup

that supports breeding colonies
of enormous size.

Just in this one place alone,
15,000 pelicans gather to breed.

In their regular habitats, pelicans
and gulls breed only once a year.

But here they'll keep producing
clutches till the food runs out.

There are broods
at all stages of growth,

from naked hatchlings to
young pelicans ready to take wing.

With no predators to worry them,

the greatest threat
comes from the relentless heat.

Inevitably some will perish.

But for a time Lake Eyre offers what
counts most- an abundance of food.

Elsewhere the rains have painted
the desert with glorious colour.

These are the ephemeral
short-lived deserf plants.

They sit out the dry years
in time capsules -

dormant seeds
which only rain can unlock.

Like this Sturt's deserf pea,
their flowering will be brief.

And in their urgent need
to attract pollinators,

they provide copious nectar.

The plants
set great quantities of seed,

so there'll be enough
to last till the next rains.

The flowers vanish
as swiftly as they bloomed.

Their abundant seeds will feed many
creatures for a long time to come.

Most of the desert animals come out
only in the cool of the night.

Avoiding the daytime heat
is one way these hopping mice

have made themselves at home
in the sandy desert.

They also get
their moisture from seeds.

And they've evolved a speedy hop
to escape their enemies.

The hopping mice
almost vanish in the dry years.

But plentiful food
stimulates them to multiply rapidly.

They're very social creatures.

As many as 10 live together.

And their communal burrows
are marvels of design.

As well as a main entrance,
there are several escape holes,

and the main living area
is a metre or so down

to avoid the extremes
of hot and cold.

Young are born
about four weeks after mating,

and part of the burrow
becomes a nursery.

There are usually four in a litter,

and mothers suckling one brood
may already be pregnant with another,

to reproduce even more quickly
in this time of plenty.

Long after the rains,
the water that soaked into the sands

sustains the arid region's
most characteristic plant.

Spinifex is a uniquely
Australian grass,

and covers a third of the interior.

This grasshopper mimics the foliage -

one of many creatures thriving
within the spiky ramparts.

Deep taproots reach the moisture
metres down,

and surface roots seek what
few nutrients the soil has to offer.

As a result, spin if ex grows outwards
in ever-widening rings.

In some places,
the tussocks are linked

by these intriguing
tunnel-like structures.

The runways are built by ants,

using grains of sand glued together
with drops of spin if ex resin.

The covered trails shield the ants
from sun and predators

on the way to their food supply
in the spin if ex.

The ants protect
the source of that food

with more sand and resin shelters.

Within them, minute
sap-sucking insects are at work.

And this is the purpose
of the ants' striving.

Sugary drops
that are the waste product

of the insects feeding
on the spin if ex sap.

Together, these tiny droplets
provide all the energy needed

to drive an entire ant colony.

Using some of that energy to build
runways is a wise precaution.

Ants without that protection
may fall victim to the thorny devil.

On higher ground,
there's sufficient vegetation

to supporf one of Australia's
creative artists -

the western bower bird.

It shapes stalks of grass
into an elegant bower,

and decorates them
with desert fruits and berries.

The calls lure a female to the bower.

It's sole purpose is to impress her

And to serve as the arena

for the male's seductive display
of song and dance.

When evening comes
and the sands cool,

the pace of life
among the spin if ex quickens.

Scorpions and other creatures

that have spent the day
shielded from the sun

come out to hunt.

There's much food about,
but also danger from other hunters.

The stripe-faced dunnart,
a ferocious marsupial carnivore,

tackles almost anything -
even a venomous centipede.

Dunnarts belong
to an ancient marsupial group.

Although females do have a pouch,

it's too small to hold
six growing young for long,

and some occasionally
lose their grip.

Hanging on to mother
is vitally important,

for dunnarts are always
moving their home range

to keep up with the shifting supplies
of insect food.

There's no advantage for dunnarts
in having a regular nest or burrow,

but forth is little creature,
a permanent home makes much sense.

The pebble mound mouse
has reliable food

of seeds and tubers nearby.

And making a shelter
from heat and enemies

is well worth
even this prodigious labour.

Some of the stones
are bigger than itself.

The stones are piled in a circle
around the entrance.

On dewy nights,
they collect moisture to drink.

The arid landscapes are a patchwork

made by millions of years
of shifting and leaching soil,

from sands to stony ground.

Some retain more of the recent rains,
some less.

The variations shape
an astonishing diversify of life.

The mulga
is the characteristic desert tree.

In favoured places,
it produces a nectar

that's promoted
an extraordinary animal response.

The nectar flows
from small leaf glands,

and the ants it attracts
keep leaf-eaters away.

Many ants come to feed
on this mulga honey,

but because the flow
varies considerably,

certain species have evolved
an ingenious way of storing it.

In these unusual colonies, a special
caste never leaves the nest,

but serves as living stores,
their bellies hugely distended

into translucent honey pots.

When the nectar flow dries up,

the colony taps into
the storage ants.

Stroking stimulates them
to release the sweet liquid,

a tiny drop at a time.

Nursing ants
only digest a little themselves

and feed the rest
to the larvae in their care.

These busy insects
are the most numerous inhabitants

of the arid lands.

About half of Australia's 5,000
species of ants live here.

Through some remarkable interactions
with the plant world,

ants play a major part
in shaping the environment,

carrying vast amounts
of plant material,

and turning over the desert's
meagre stores of nutrients.

But ants also exploit seeds,

and so short-lived plants
produce huge quantities.

Some, at least, will escape
the columns of foragers.

Some of the permanent plants

actually turn the ants' appetite
to their advantage.

Desert trees won't thrive too close
together in these poor soils,

so the seeds need to be dispersed.

Birds sometimes help by distributing
seeds in their droppings.

But not these galahs -
what they eat, they digest.

The remainder drops
close to the trees.

Were they to sprout here,
they would compete with their parent

for nutrients and moisture.

So ants have been enticed
to carry them away.

The seeds themselves are ant-proof,

but they're packaged
with an attractive food -

oil-rich bodies called elaiosomes.

In the underground chambers,
nurses and other workers

labour together
to remove the elaiosomes

and distribute the food
to the rest of the colony.

The seeds are just waste,

and dumped on a rubbish heap
in a distant gallery,

there to await the germinating touch
of the next rains.

Some trees use the wind
to get their seeds away.

Dispersing seeds gives the saplings
more space to grow extensive roots

and make the most of
the little moisture in these soils.

While the desert rivers
have long stopped flowing,

masses of water run deep
within the sandy beds -

enough to sustain
the mighty river redgums.

All that's left on the surface
is a chain of pools,

and most of those will vanish soon.

But the moisture flowing
in the hidden rivers

supports generous stands
of the river reds

through even the driest times.

Clouds of corellas roost in the gums
on their travels around the interior,

following the movable feast
of seeds and fruits.

It's not hard to think
of these antics as pure play,

a means of whiling away
the long hours between feeds.

Come breeding time in late winter,
the flocks break up,

and the corella couples
start looking for nesting hollows.

In this season of plenty,

every suitable hollow
is soon occupied.

This pink cockatoo
already has chicks in the nest.

It approaches cautiously
so as not to alert predators.

The parents take it in turn
to feed their youngsters.

There's still an abundance
of seeds and fruits to collect,

and the birds make many trips a day

to pump the mash
into the ever-beckoning young beaks.

The chicks are now a fortnight old.

In another month,

they'll be strong enough
to follow their parents and fly.

Cockatoos are hardy
and resilient birds,

well-designed to cope
with the rigours of a rid life.

But they can't do without water.

This deeper pool will remain filled
well into the dry times,

and it becomes the focus
for much of the animal life

of the surrounding plains.

Red kangaroos
can go without water for months

while there's fresh growth.

But when that's gone,

they need to come in for a drink
once or twice a week.

Those other large plains dwellers,
the emus,

need water nearly every day,
once it gets really hot.

With so many kangaroos
crowding together,

tussles often break out
among rival bucks.

When nightfalls,

the cockatoos find resting places
in the trees nearby.

And the big reds start moving back
to their home ranges,

to feed in the cool of the night.

Grasses that grew tall in the wake of
the rains have dried out,

and the green pick that the kangaroos
need for moisture is harder to find.

The rising sun swiftly sends the
temperature soaring to 40 degrees,

and the kangaroos move
to what meagre shade they can find.

Such large and warm-blooded animals

should have real problems
in this kind of heat,

yet the kangaroos cope
remarkably well.

Oneway they keep cool
is to lick parts of their body

where the blood vessels
run close to the surface.

While the reds shelter in the shade,

the emus
carry their own heat shields.

A double layer of feathers
insulates them very efficiently,

and they can keep foraging
through the heat of the day.

As the dry tightens its grip,
food and water start to run out,

and the big reds
have to move on or perish.

The awkward shuffle
of their feeding gait

shifts into an effortless,
fluid bounce.

The energy of each hop
is stored in the hind leg tendons,

like a spring, to provide
the propulsive force for the next.

For those that leave too late,
the end is inevitable.

The diminishing resources
simply won't sustain the numbers

that flourished
in the time of plenfy.

It won't be long before the mud
in this pool is baked hard again,

too hard for the animals to penetrate
to the moisture below.

Soon the females
will stop producing milk,

and the joeys will die.

But if the does manage to survive
till conditions improve,

they'll quickly breed again.

For a time, the great die-off
provides a feast

for the hunters and scavengers
of the arid country.

Soaring on wings
spanning two-and-a-half metres,

the mighty wedgetailed eagle,
Australia's largest bird of prey,

scans the drying country
for dead and dying animals.

Eagles feed on carrion,
as well as live prey.

But even carrion is becoming scarce,

and hunger drives the birds
into fierce competition

for the little food that remains.

Two years after it began to fill,

Lake Eyre, the great sea
at the heart of the continent,

has dried to salt again.

Rows of dead fish
mark the receding shores.

The legions of birds
that flourished here have vanished,

the last of their broods abandoned.

These cormorant chicks
had the misfortune

to be at the end of the line
when the food ran out.

Nothing can save them,
or the pelican broods.

But though the images
speak of death,

they belie the fact
that this so-called dead heart

can also be a place
of extraordinary ferfility.

Even while the flood of life
that came with the rains ebbs away,

the underlying pulse
continues to beat strongly,

and the permanent
inhabitants reappear.

The Lake Eyre dragons
are coming back

now that the country is returning
to its normal state of drought.

Lack of food
Ieft the last of the pelican flights

without the strength
to make their escape.

The winds suck away
the last traces of moisture

and leave the plains bone dry.

But deep beneath
the waves of sand and dust,

the hidden aquifers still run -

the lifeblood
that keeps the arid heart beating.

Even on the salt beds of Lake Eyre,
seemingly so dead,

life continues to proclaim
its vigorous existence.

The Lake Eyre dragons
have reclaimed their dominion.

The males reassert their dominance

with inflated impressions
of their size.

Soon the hierarchy
will be sorted out.

Each dragon will have its place
in which to feed and breed...

...to live and die.

The challenge in the arid centre
is not so much lack of rain,

as its unpredictability.

Over millions of years,
plants and animals

came to meet that challenge
in remarkable ways.

More than 50,000 years ago,

man set foot on the continent
for the first time.

And his response
to its challenge changed,

dramatically and forever,
the nature of Australia.

Human song first sounded in Australia
at least 50,000 years ago.

It heralded great changes
for the island continent.

The origins of the first Australians
are lost in time.

They came from somewhere in Asia,

gradually drifting south
over many generations.

A final voyage across a strait,

narrower than now
because the sea was lower,

brought them to north Australia.

Here they found
a mix of the known and the new-

swamps where crocodiles lurked,
like those of South-East Asia,

but also much that was strange.

Like the regions
of their forefathers,

tropical Australia
was ruled by monsoons,

but here, the annual swing
from flood to dry

was far less predictable,
far more savage.

The newcomers had to learn new ways,
interpret new patterns

and weave them into a system
of beliefs to explain this new land.

They identified
with certain animals...

...and made them
powerful tribal totems.

The first Australians
were coastal wanderers.

Their descendants
on the northern shores

still call themselves
saltwater people.

They never moved far
from the familiar sea -

that never-failing provider
of good things to eat.

Among the skills imported
by the early people

was a practised use of fire.

Through wielding flames
to clear the land and aid the hunt,

they went on
to change the face of Australia.

Before people came here,
lightning was the only source of fire.

They believed lightning was made
by Namarrgon, the 'Lightning Man'.

Namarrgon's stone axes hit the clouds
to make sparks and thunder.

These are the storms of the build-up,
the time before the wet.

The Aborigines call it Gunumeleng -

one of the many seasons
they came to recognise.

Gunumeleng is also signalled
by fainter sounds,

calling freshwater crocodiles
to their nest.

The cries come from inside eggs
buried in the river bank

some three months earlier.

They summon the females
to excavate the nests,

so helping
to release their offspring.

Not all the eggs survive.

Some are dug up by human foragers,
who find them delicious.

But enough are left to ensure
there'll continue to be crocodiles

and supplies of eggs.

Though capable of making it
to the water on their own,

it's much safer and quicker
for Mother to carry them.

The sound of sand being scraped away
and the calls of the newly hatched

stimulate the rest of the brood
to break free.

As soon as the maternal jaws
release them,

the young crocodiles
launch their lifelong hunting career,

starting on insects
and working their way up.

But they also make attractive morsels
themselves,

and the mother keeps watch,
especially for other crocodiles

coming to investigate
with cannibalistic intent.

Northern Australia lies on the edge
of the monsoonal belt,

and the build-up is a fickle time.

Dry spells alternate
with drenching rains.

Early falls soak in,
then the soils saturate,

pools fill, rivers flow.

They flow out of the great Kakadu
escarpment looming over the plains -

the edge of
a vast and ancient plateau.

Its worn and cragged roof
makes an enormous catchment

that feeds
permanent pools and rivers.

Millions of years of monsoonal rains
scoured and sculpted the sandstone,

and rivers carved deep gorges.

It's Gudjewg now-

the wet season proper
in January and February.

It's a barren and forbidding place
where Aborigines rarely come,

but it's also the source
of much ferfility,

for the waters wash sediments
down to the lowlands.

The cascades feed broad rivers which
meander across the northern plains,

and the rising waters set
the rhythm of life for many animals.

Pig-nosed turtle is one of them.

As the river rises, it cues
a new generation into the world.

They spend most of their time
submerged,

but they have to come out
to bury their eggs.

Three months earlier,
they dug their nests in the river bank.

The eggs of reptiles like crocodiles
drown if they're flooded,

but pig-nosed turtles actually wait
until they're completely immersed

before breaking out.

The sudden drop in oxygen
passing through the shell

gives them their cue.

Eager for air,

they emerge into conditions
best suited to their survival -

fast-flowing water to aid dispersal,
and a wealth of food.

The rising waters also stimulate
the magpie geese to gather and breed

and tell the people there's
an abundance of goose eggs to collect.

The spike rushes
grow tall in the swamps,

and the geese trample them
into floating nests.

Crops of wild rice shoot up,

and in the steaming heat,
their seeds ripen swiftly

to provide rich nourishment
for the goslings.

But it won't last.

Parents and chicks
are racing against time,

for the youngsters
need to grow strong enough to fly

before the swamps begin to dry out
and they have to move elsewhere.

The breeding of these ancient birds

follows the rise and fall
of the waters,

and their seasonal wanderings

became part of the knowledge
that guided Aboriginal walkabouts.

The season rolls on.

The storms of Gudjewg sweep in
almost daily now...

...and with ever-increasing force.

Hot winds, heavy with moisture,
drive in from the north-west,

pile the clouds into mountains...

...and hurl sheets of water
across the landscape.

Day after day,
this is the pattern of Gudjewg.

The very sky turns to water.

As the plains became impassable

to all but water birds
and aquatic creatures,

the people moved to higher ground,

into the shelter of
the escarpment's caves and overhangs.

The long, wet days gave time
to reflect on their place in this world.

In painting the rock walls,

the people celebrated their
deep sense of affinity with the land.

The record goes back unbroken
for tens of thousands of years.

The torrential downpour sends so much
water rushing across the plains

that even higher ground disappears
under the swirling floods.

The swiftly rising waters
send creatures scrambling

for whatever precarious perch
they can find.

This sand goanna will need to hang on
for many hours

before the floods subside.

Even capable swimmers

like highly venomous king brown snakes,
and water goannas,

may find the currents too strong.

A mass of termites.

Odd companions, a python
shares its refuge with a water rat.

In this common crisis, normal
predatory instincts are suspended.

The flood plains merge
into one vast, shallow lake.

The spreading waters
replenish their ferfility

with sediments
washed down from the escarpment.

But while the rains recharge
the Top End's biological power,

they also bring hardship
to many animals.

Rocky outcrops become islands

and maroon the wallabies that
normally graze down on the plains.

Until the floods subside,

these short-eared rock wallabies
will have a lean time of it.

Overtime,
the lives of animals and people

wove into a complex fabric
of myth and custom.

The rock paintings became the icons
of Aboriginal belief

as well as a practical inventory
of their most important creatures.

The rainbow serpent,

mythical carver of rivers and gorges
as it slid across the landscape,

intertwines with pictures of animals
hunted for food.

The record also traces
changing climate.

As sea levels rose
and estuaries came closer,

images of barramundi fish
featured more.

In 2,000 generations
of human occupation,

the view from the escarpment changed

as flood plains
extended and retreated,

but the relentless rhythm
of the tropical monsoons

continued to rule all of life here.

The mating call
of the green tree frog

adds to the cacophony that marks
the height of the wet season.

They need standing water,

and there are now plenty of pools
where the females can spawn.

She lifts her rear end
to scatter the eggs.

The male, clasping her firmly
from behind, covers them with sperm.

Of the hundreds of eggs,
only a few will survive.

The rest will feed other creatures.

Deep within the escarpment,
other animals breed.

The walls of some caves
crawl with bats.

More than 100,000 bent wings
crowd together,

all of them females and their young.

The females came here
early in the wet to give birth.

Now their offspring
are on the verge of flight.

But for the moment,
they're still left behind in a creche

while the mothers make their
evening exodus, streaming out to feed.

The creche is far from safe.

Below the bat-covered walls,
green tree frogs lurk,

waiting for a baby to fall.

The young bats are only tiny.

Even so, they make quite a mouthful
for the frog,

which is about the size
of a man's fist.

The dense flow of bat flesh
attracts other predators.

Pythons and venomous snakes
cast around in the stream

like lethal fishing rods.

The snake throws a deadly coil
around the victim,

then dislocates its jaws
to swallow the bat whole.

The meal lasts the snake many weeks.

The streams of breeding bats
are an endless source of food

at this time of Gudjewg.

Their comings and goings
meld into the flow of the seasons -

part of the nature of Australia
for 25 million years

when bats first flew in from Asia.

They're particularly abundant
in the tropical north,

flying foxes especially.

At dawn, tens of thousands
return to their tree camps

to roost for the day.

They're the largest of the bats,

very different
from the small insect-hunters

that inhabit the caves.

Their flesh is as sweet and succulent

as the flowers and fruits
upon which they feed,

and highly prized by human hunters.

Flying foxes, also called fruit bats,
are found throughout South-East Asia,

and raiding their camps
remained an important part of life

for the Aborigines
of northern Australia.

The fruit bats
have their own seasonal rhythms.

As the monsoonal rains fall away
and the end of the wet draws near,

males begin to feel the urge to mate,
and females respond...eventually.

Having to mate upside down

might seem to add
an extra dimension of difficulty,

but for the fruit bats,
there's no other way.

The pair may mate four times
in half an hour

and several more times
during the day.

During that time, the immediate space
around them is inviolate territory.

Soon, the bats shift camp

to follow the move able feast
of flowers and fruits

as the season turns.

With the heaviest rains passed,

the Aboriginal year
moves to Banggerreng -

a time of brooding calm
pierced by sudden storms.

The waterlilies flower
in the paperbark swamps,

and on their broad leaves,
jacana eggs are about to hatch.

While the cock bird broods the eggs,

his mate
jealously keeps other hens away.

A few days later, the jacana chicks
take their first tentative measure

of this floating, leafy world.

The father has a wonderful way
of keeping his chicks safe.

At the first sign of danger, he calls
and sweeps them under his wing.

Only their legs
betray their presence,

already with the long toes that make
jacanas seem to walk on water.

In these closing days of the wet,

the humid air is heavy with the scent
of flowers, vibrant with insects.

In a final spurt, the spear grass
shoots to twice a man's height.

But the storms of Banggerreng
will soon knock it down.

For the early people
and their descendants,

this was a good time of year
to collect wild honey.

As the season turns to dry,
fire begins to dominate the daily round.

The art of making it
came with the ancestors.

Using it became
an ever more important skill,

on the small scale and the large.

Though the native bees are small
and have no sting,

flame and smoke help clear the way
into the sweet heart of the nest.

Fire sticks were also put
to larger use,

and the effects reached into
the very essence of the landscape.

When the winds turn cool
and blow from the south-east,

it's Yegge -the burning time.

Fire cleaned the country
of the spear grass,

smashed into an impenetrable tangle
by the storms of Banggerreng.

Natural fires, sparked by lightning,

mostly flared
towards the end of the dry.

The Aborigines burnt early in
the season and altered the landscape.

They lit their first fires
when dew still fell.

It dampened the flames at night.

Over the years, Aboriginal burning
created a mosaic of plant growth

that fostered a range
of valuable game.

The smouldering aftermath

also brings immediate benefits
to the hunter gatherers -

human and animal alike.

Fried insects make rich pickings

and bring game
within a spear's throw.

Alert eyes spot barbecued meals
of small lizards and snakes.

A scatter of fresh leaves
protects the human feet.

The scavenging birds

have nothing between theirs
and the glowing cinders.

The patterns of Aboriginal burning

brought lasting change
to the nature of Australia,

evident on the small scale
through the hunting birds

that prosper as fire-followers,

and on the larger scale
through a shift in vegetation,

with fire-tolerant eucalypts thriving

where plants sensitive to scorching
could not.

The wood lands seem dead after fire.

But within days,
the gums green up again.

The spread of the eucalypts
was aided by another force,

less obvious and dramatic than fire,
but just as powerful.

These castles of clay
conceal that hidden power.

They're the strongholds
of the termites.

And it was fire
that destroyed the bark's defences,

and opened the way for termites
to enter the tree.

Deep within
lies the colony's pulsating heart-

the termite queen.

She produces a ceaseless flow of eggs
to keep the colony growing

and issues a stream of chemical
commands to govern her subjects.

Workers stack the precious eggs
in nurseries

and tend them till they hatch.

Other workers look after the larvae,

preparing them for their
allotted task as workers, soldiers,

and once a year,

they tend a special brood
of future kings and queens.

Workers form the largest class,
labouring endlessly,

turning the eucalypt's
structural heartwood

into energy that drives
the entire colony.

Their sharp jaws
slice into the tough fibres,

and the hindgut breaks it down
into digestible nutrients.

Some goes to feed other termites -
the queen, soldiers and juveniles.

The massed jaws
of the worker brigades

swiftly excavate the heartwood,

chewing their way
up inside the main trunk

and out into the branches.

The waste is moulded
into more galleries and egg chambers.

Within a few years,
the eucalypt is completely hollow.

In places, breaking branches
open away to the outside,

branches that provide Aborigines
with hollow wood

to craft into didgeridoos.

Now the legions move out,

digging tunnels
to seek fresh supplies

in the surrounding trees.

They too are hollowed out
and the colony grows ever larger.

Strange as it may seem,

not only do the eucalypts survive
this attack on their very heart,

they actually benefit from it.

The termites might appear
to be parasites,

but, in fact,
the hollows they chew out

are a kind of payment
for their board and lodging.

Hollows attract birds
and other animals

to nest and shelter.

Their spillings and droppings
make valuable fertiliser.

The trees absorb these bonus rations

and grow well in the soils
of this higher ground,

which are otherwise extremely poor.

The dollar bird
takes insects on the wing.

It migrates from New Guinea

and joins the local birds
to take advantage of the nest holes

created by the termites.

Individually,
the fragments don't amount to much.

Together, the leftovers and litter
of nesting birds -

like this forest kingfisher-

add up to a feast
when taken into the bowels of the tree.

Over time, it gives eucalypts
a great competitive advantage

over trees that don't have
this curious partnership with termites.

As well as birds,

half the local mammals
use hollows as lairs,

turning the trees
into a well-stocked larder.

Aboriginal hunters
need only a fire stick

to smoke the game out.

Night reveals other hunters.

Some holes excavated by termites

make nurseries for quoits
and their young.

When they're nearly full-grown,

the youngsters go piggyback
when Mother goes hunting.

For the young quolls,
catching insects and keeping them

are the first big steps
on the road to independence.

The adult quoits tend to use
the same hollow all year round,

and when they come home,

the waste they excrete
helps to nourish their host-

an organic form of rent.

But eventually the termites
weaken the tree so much

that fire or a storm
sends it crashing.

The termite castle smashes open

and armies of green tree ants
come racing in to devour the workers.

The sudden onslaught temporarily
overwhelms the termite soldiers,

but soon they'll repel the invaders.

And if the queen survived,
the colony will rebuild.

The season moves to Wurrgeng -

hot, still and no rain.

The flood plains are dry.

The streams stop flowing.

The waters withdraw
to the deeper swamps and billabongs.

And the magpie geese follow.

For the first Australians,
the sight of such vast flocks

meant more than abundance.

Watching them, stalking them,

inspired dances of a natural grace
matched only by the birds themselves.

Trumpeting, tossing sprays of leaves,
the brolgas dance around the year

as parf of the courtship
at breeding time

and to enhance the bond between pairs
wherever the birds flock together.

The dry tightens its grip,

but the mud around the swamps
remains soft enough

for the brolgas' long beaks
to spear up tubers.

In a week or so, it will be too hard,
and the birds move on.

These stately waders
breed in the wet season

when it's easier
for growing chicks to find food.

By contrast,
hunting birds like sea eagles

build their nests
and have their chicks in the dry,

snatching up nesting material
with the same easy swoop

used to catch fish.

Wurrgeng is a hard time
for the water creatures.

The diminishing lagoons
cram them together

and make them easy to catch.

The eagles hook up fish and turtles
in plenty

and they keep their young well fed.

When the wet season returns,

it'll bring an abundance
of other game,

especially newly hatched goslings,

and there'll be plentiful opportunity

for the young eagles
to learn to hunt.

The season changes to Gurrung -
the hottest time of the year.

The flying foxes
prepare to give birth.

The baby's head has just emerged

and the mother arches upwards
to clean it with her tongue.

The baby may stay like this
for more than an hour.

It's a tense time
for both mother and young.

Should the newborn fall,
it'll be to its death,

for many predators lurk nearby.

When finally all of the baby emerges,
Mother has to be ready to catch it.

And she does.

This youngster, at least, is safe.

She cleans off
the last of the afterbirth

and helps the infant find her nipples
located in the armpits

where it can cling in safety
when Mother goes flying.

Barbed growths inside their claws

help young bats
hook into their mother's fur

and their teeth curve inwards
to hang on to the nipple.

Independence comes swiftly.

Even at two weeks,

it's already trying for its own grip
on the tree.

Until the young bat's ready to fly,
at around three months,

the maternal wings
always remain ready to enfold it

and keep it safe.

The wings help the flying foxes
to keep cool.

They fan the air and, folded,
make an excellent heat shield.

The searing heat has sucked
all the moisture

from the swamps and flood plains,

and the only water left

is in the permanent soaks
and deeper billabongs.

Birds from all over the region
converge on these precious oases.

Red-tailed black cockatoos
wander from soak to billabong

in search of a drink.

Aborigines believed the flaming red
of the tails was fire -

the means by which the birds
carried it round the land.

While all around
the plains lie parched,

these Iast wetlands
provide rich bounfy.

Each billabong attracts
its own progression of visitors.

Each bird's bill is designed
to harvest different food

at different depths
in different ways.

This jabiru has caught a water snake.

As the waters recede,
the birds need to keep moving

to find the food that suits
their particular way of feeding.

These royal spoonbills come to feast

on the rich broth
of this shallow lagoon,

sweeping through the water

to sift out small fish
and crustaceans.

Pelicans flock together
on a deeper billabong

and round up shoals offish

and scoop them up
with capacious beaks.

Cormorants patrol alongside
ready to snatch any that escape.

There are as many fishing techniques
as there are birds.

A pied heron takes extraordinary
steps to secure a safe vantage point.

The waters fall ever further
exposing new crops of food.

The plant-eating birds
have their feast now.

And flocks grow by the thousands
every day.

The sound of the whistling ducks
is made by voices and wings together,

rising and falling as they move
between grazing and resting.

The massed song
is a spectacular celebration

of the great ferfility
of these northern wetlands.

Clouds of birds darken the sky
over these last waters.

Now's the time too

when magpie geese assemble
in their hundreds of thousands,

a sure sign that the first storms
of Gunumeleng are not far away,

that the season's coming full cycle.

The vanishing water
leaves great stretches of soft mud

with abundant bulbs and tubers
for the birds to rip up

with their hooked bills.

The massing of the magpie geese
is one of the biological events

that mark the turning of the seasons
in the Far North.

For the first Australians,
they became part of the calendar

which set the rhythm
of their own rounds and celebrations.

Knowing the nature of the land
was basic to their survival.

But in learning to live with it,

the skills they acquired
and practised over 2,000 generations

set profound changes in train.

Fire became the symbolic centre

of their spiritual
and ceremonial life -

their tribal temple.

Far from being a timeless people
in a timeless land,

their impact was as great
as that of any people on earth.

And the chief instrument
of that impact was fire.

Aboriginal burning altered
the mix of plants in the landscape.

The fire-tolerant eucalypts
extended their hold,

and the wood lands opened out.

As the Aboriginal people
grew in numbers

and spread across
the vastness of Australia,

the migrations were marked
by trails of fire

and the hunting birds
that followed them.

The fire skills perfected
in the monsoonal north

were carried to new terrain
and different climates.

The fire stick reached
into every plant and animal community

in every part of the continent,

from the coastal regions
to the dry interior.

Many animals
profited from the changes.

Many others vanished for all time.

In all this vast land,

there were only ever less than
1 million people at any moment,

yet in their 50,000 years,
the Aborigines' way with fire

changed the face of the continent.

Evil spirits
they called these willy-willys.

But they were tornadoes
of ash and dust

unleashed by the heat
of their own fires.

Now a new storm was about to break-

the whirlwind
of the European invasion

would race across the continent
with unprecedented speed,

and pose the most severe challenge
yet to the nature of Australia.