[soft regal music] [light music] - [Narrator] The blistered world of the Kalahari Desert is a haunted realm.

Dust devils patrol a seemingly empty landscape, and scores of tracks dimple a vacant terrain, as if laid by ghosts.

But in this land of enigma, wildlife does exist.

Ever taunted by the promise of rain, they wait in the wings for the cue to emerge.

[intense music] Finally, forces mingle in just the right combination.

Summoned by storm clouds, millions launch on epic journeys, slipping from their hiding places where some have spent years.

It's a world set in motion by a few drops of water.

Some have made this trek before; for others, this will be their first, a test of supreme courage through a desert that shows no mercy.

[intense music continues] [light regal music] The Kalahari.

It is a magnificent contradiction.

Deemed a desert, it also holds vast grasslands, and immense salt pans as deadly as the moon.

It is a land of riddles.

Tracks hint at huge herds, but where are they now?

In hiding places and havens, both near and far.

Each one waits for its own summons, a complex set of conditions.

And in years when all the right elements come together, they produce an explosion of life.

Into Botswana's Kalahari sands runs a great river, the Okavango, creating a lush paradise a thousand miles from the sea.

[soft music] Beyond it lies the bed of an ancient lake, once the largest in Africa.

Now all that is left is its immense footprint, known as the Magkadikadi Salt Pans.

[soft rhythmic music] Zebra and wildebeest are born to the Kalahari's relentless cycles of dry and wet, scarcity and plenty.

Yet their limit has been reached.

For many years, sparse rains have left the Boteti River bed mostly dry.

A spillway of the Okavango River, it has not flowed for 20 years.

Even so, it remains a lifeline to a population on the brink.

Wildebeest plunging down a river bank are not greeted by a rushing deluge or eager crocodiles.

Just more sand.

Nevertheless, thousands of animals that depend on surface water for survival must trek to the Boteti during the dry season, to drink from its dwindling seepage pools.

Crocodiles originally came down with the river from the north decades ago.

Now, stranded in a dry land they have held on, and even bred, in small mud pools and riverbank caves.

[frogs grumbling] Months after the last rains fell, some animals devise ingenious strategies to find clean water in the dry riverbed.

Zebra scrape away the sand until fresh water seeps through.

[wings flapping] Hundreds of sandgrouse take advantage of the clean pools made by the zebra and wildebeest herds.

The male sandgrouse has highly absorbent breast feathers, a remarkable adaptation that allows him to carry water back to his young.

In the desert scrub where they live, the birds are well camouflaged, but here, they are vulnerable.

The martial eagle watches for any sign of weakness.

Sandgrouse only spend seconds drinking and dunking their feathers before flying back to their nests, which can be up to 50 miles away.

With their massive feet, elephants often create and enlarge water holes.

They can also bore holes with their trunks as deep as six feet into the sand to reach clean water.

[elephant grumbling] Every day, the herds must make an arduous journey many miles away from the dry riverbed to feed.

Having exhausted the grass near the Boteti, the zebra's trek to grazing grows ever longer.

Eventually, most of their day and almost all of their energy is spent en route, giving them barely enough time to eat before they must turn back to drink again.

They also face tremendous competition.

Termites consume huge quantities of grass.

In some places, they eat far more than the herds, leaving behind barren wasteland.

Termites need little water, getting enough from subterranean moisture and the plants they eat.

So the distance between water and food is short.

There are no shortcuts for the zebra in the dry season, just endless journeys in the heat and dust.

[animals chittering] While the rest of the herd grazes far away, an abandoned foal is trapped in a desperate struggle.

[zebra braying] [water splashing] [elephant grumbling] Lost and confused, the foal is attracted to the only other creature it sees.

It follows the elephant as if it were its mother.

[elephant growls] [zebra chittering] [soft music] [zebra chittering] Although it has been rebuffed, this orphan has nowhere else to turn.

It stubbornly clings to the elephant, though it has no hope of winning him over.

As conditions worsen, the sandgrouse seek out the last remaining pools.

At least the birds can come and go.

It's the end of the line for the catfish.

Their flailing whiskers seem to telegraph a message of doom to the lonely foal.

But suddenly, it is rescued by familiar calls The herds have returned from their trek to the grasslands.

Yet coated in mud, the foal looks darkly dangerous.

It has become an unwelcome stranger among its own kind.

[zebras chittering] [baby chittering] Through gathering clouds and a distant rumble of thunder, the herds know their moment has arrived.

Heading east, they will cross a hundred miles and more, chasing the rains for their promise of new grazing and fresh water.

[flies buzzing] [downcast music] But for some, it is too late.

She can smell the rain on the wind, but, starving and weary, her strength fails just as the hour is at hand.

[thunder rumbling] But the foal is in luck.

Here's a chance to wash away its shadow coat.

The change in weather stirs the termites, deep in their castles.

Masters of their own environment, they maintain an air-conditioned haven in the heart of the desert.

With hundreds of thousands of insects in each colony, termites probably comprise the single largest animal mass in many parts of the Kalahari.

Only specialized predators can assault their clay fortresses.

The pangolin is equipped with powerful claws, armor, and a tongue half as long as its body.

[intense music] In a chamber deep inside the mound, dwells the mother of millions, a giant egg laying machine.

The queen is so big, she can hardly move under her own power.

She will not even fit through the exit unless the workers widen the door.

[intense music continues] The pangolin has damaged the colony, but the queen is unharmed.

The termites numbers will quickly recover once the structure is repaired.

Dawn finds the last of the zebras leaving the Boteti.

In the open grasslands, they will escape from a harsh existence.

[animals chittering] On the wings of the storm comes an astonishing spectacle.

Flamingos stream through the desert skies by the tens of thousands.

They have flown from their coastal feeding grounds without rest.

[thunder rumbling] How they know the rains are beginning from a thousand miles away is a mystery.

With the grassland waterholes restored by the rains, the zebras at last have water and grazing in the same place.

[animals chittering] The herds fan out over thousands of square miles of rejuvenated grasslands, while the flamingos fly to their ancestral home.

In primordial times, when this was a wet region, most of southern Africa's flamingos may have lived permanently around the ancient lake called Makgadikgadi.

Today, they return whenever that lake is reborn.

[soft music] [wings flapping] [lightning crackling] [thunder rumbling] The shallow lake is rising, ephemeral but potent.

[soft music] When mixed with water, dormant animals on the ancient lake bed come to life, producing the favorite food of flamingos.

Beneath the insects, blue-green algae emerges from microscopic spores.

In its dormant state, it can endure a hundred years without rain.

Blue-green algae is also the only food eaten by the lesser flamingo.

The paler and much larger greater flamingos whisk up brine shrimp from the muddy bottom as well as other invertebrates.

If the heavy rains continue, the flamingos will breed at the nesting sites they have used for thousands of years.

[soft music] [animals chittering] Unleashed with the rain are countless subtle signals.

A rise in humidity.

A shift in temperature.

A softening of the earth.

[hooves thudding] Complex messages for spore and seed to shake off their long slumber.

[rain pattering] [thunder rumbling] All the elements finally come together, promising a great awakening and a new generation of life.

Torrential rain will unlock the self-made tomb of one of the Kalahari's most surprising residents.

From deep underground, sealed in a protective suit of his own design, he surfaces.

[soft music] The African bullfrog, as big as a dinner plate, appears to have two large ambitions: to feed and to breed.

[thunder booming] The desert provides for him: Winged alates, the cream of their kind.

The only termites able to mate, these potential kings and queens have been specially prepared for this moment.

But now their plump bodies are coveted by every creature in the bush.

Slow and awkward, the alates have no defenses outside the mound.

Out of the millions of alates, just a few may live to mate.

A female shrugs off her wings and sends out her signal, an alluring scent.

She and her mate burrow into the rain softened soil and, with a lot of luck, could start a new colony.

From rain-filled pools, comes the booming call of bullfrogs.

This big frog's song should deter other males.

But it hasn't stopped a smaller frog from winning a mate.

[frogs croaking] The female's job is simply to lay eggs.

Incredibly, the male alone will take responsibility for raising and guarding the thousands of tadpoles.

[frogs croaking] Kites, eagles, buzzards and falcons, all time their migrations from distant lands to cross the Kalahari just as the termite alates emerge.

Fat is such a precious commodity in the wild, that these winged butterballs fall victim to every sort of predator.

The sand lizard must catch them before they take to the sky.

Marabou storks track the rains across the desert in search of alates.

Standing more than four feet tall, the enormous storks fill up on tiny morsels.

[animals chittering] The bounty of termites brings Africa's Bateleur eagle together with the Russian Steppe eagle.

Discarded wings litter the ground.

Remnants of a passing feast, they bear witness to the important role the termites play in feeding the multitudes.

In the rains' wake, the desert blooms.

And a profusion of life, from the magnificent to the minuscule, bursts forth across the Kalahari.

On a small scale, insects perform the same tasks that occupy all, feeding, breeding, and finding shelter before the water disappears.

Some animals only take a few days to complete the cycle; others will need months.

The longer the process, the greater the risk.

But all the Kalahari's creatures are pitted in a race against time.

A few weeks ago, this waterhole was a barren patch of earth.

Now it bustles with a tadpole mob.

Feeding on algae, they suck up all within reach.

But their ever-watchful father eats nothing.

As their sole protector, he must ensure the safety of his offspring.

He attacks any predator that dares comes close, even animals much larger than himself.

[water bubbling] [animals chittering] With water and algae running short, the father frog comes up with a remarkable solution.

[soft curious music] He digs a channel to the next pool.

Upon the bullfrog's signal, the tadpoles rush through.

And immediately, they attack this new source of food.

[animals chittering] By the time they're two inches long, the tadpoles have sucked up every edible morsel from the pools.

Fortunately, their new legs open up new possibilities.

Plentiful water and a superabundance of insects draw hundreds of thousands of quelea finches to the Kalahari.

In some breeding colonies, staggering numbers of tiny woven nests weigh down acres of acacia trees, promising a future population explosion.

[animals chittering] The frogs' diet has expanded to include almost anything that moves.

[animals chittering] For three weeks, the male frog has fasted while his tadpoles have fed ceaselessly.

Now he snaps up whatever comes his way.

Snakes, rats, other frogs, and yes, sometimes even his own young.

[soft curious music] A bullfrog is aggressive as well as gluttonous.

When confronted, he puffs himself up to a formidable size and fears almost nothing.

[zebra braying] [animals chittering] Master of the pool, he will remain vigilant.

Compared to life at the Boteti pools, this must be a paradise for zebras.

Free from the exhaustion of just staying alive, here for a time they play, fight, and mate.

[elephant trumpeting] Who now would call this place a Thirstland?

The dry season has lost its sting, its memory drowned by a world awash in plenty.

Elephants wander widely from one replenished water hole to the next, enjoying fresh forage as they go.

[animals chittering] Zebras must make the most of the abundant water and grass for these days are fleeting.

[zebra chittering] [soft curious music] The hungry young bullfrogs will try just about anything.

[soft curious music continues] The rove beetle is protected by its repulsive taste.

The wiry orange larva of a beetle is hotly contested.

Though toothless and legless, it defends itself admirably.

[soft music] The larva puts up a good fight even after its capture.

[soft music continues] Most of the little hunters will eventually become the hunted.

The woodland kingfisher preys mainly on insects, lizards.

And little frogs.

Only a few fat frogs will be left in the end.

The phenomenal rains have created spectacular breeding for the flamingos.

[soft music] Nearly 50,000 chicks gather in living islands.

Miles of shallow lake surround them, providing food and protection from most predators.

Three separate waves of breeding have produced chicks in various stages of development.

The first have already fledged while the second are still immature.

[soft music continues] The third wave has yet to hatch.

Thousands of eggs are being brooded in the flamingos' distinctive nests, a potential catastrophe.

For all around are signs that time is running out.

The water is receding rapidly.

Soon their nest site will turn back into a toxic salt pan.

The grasslands, too, are quickly drying out, a signal that it is time to leave.

[wings flapping] The acacia trees writhe with quelea finches which have multiplied in the billions.

Before they go, a host of finches reap a bountiful harvest, an ocean of grass seed.

[soft music] [wings flapping] After their season of renewal, the herds retreat to the Boteti pools.

They will not visit these rich grazing grounds again for many long months.

With the departure of the herds, the grasslands seem deserted.

But a few creatures remain.

They have their own ways of coping with the harsh times to come.

[soft music] Before the beds of their pools harden completely, the last of the bullfrogs dig themselves in.

Soon this one will be encased in a moisture-sealed coat and entombed in earth as hard as rock.

It may be many years before he reappears.

The dry season lays claim to the Kalahari once again.

On the salt pans, water and time are running out, marooning the chicks in a hostile landscape.

The only water left is north of the nesting colony, at the pan's edge.

Most adults have flown to this last haven.

But the unfledged chicks must make this journey on foot.

They will walk more than a hundred miles.

And many will die.

[soft music continues] The waters on the surface of the pan have become a supersaturated solution, crystallizing into layers of pink salt.

Forced to leave, all the flamingos gather at the pools on the pan's edge, far from their young.

These waters are their only source of food, but they too are rapidly shrinking.

The water around the nesting sites has vanished altogether.

In its place, a searing, caustic plane stretches to the horizon.

Vultures hover over huge creches of chicks, an omen of the life and death struggle about to begin.

Spurred on by the adults, thousands of chicks now embark on a forced march.

[chicks chittering] It is one of the greatest endurance tests in nature, hatched in paradise, some chicks will spend the rest of their brief lives in hell.

[soft music] Hobbled by mud and tender age, their cause seems hopeless from the outset.

[soft music continues] [waves crashing] Now, the flamingo nesting site seems only fit for the dead.

[bird cawing] And those that prey upon them.

[bird squawking] [wind blowing] But life has not forgotten the Magkadikadi.

It is only hidden, camouflaged as grains of sand, the eggs and spores of the lake's tiny creatures lie dormant, waiting for the rains.

Even in this desolate land, the Kalahari safeguards its seeds for future regeneration.

[soft music] Days turn to weeks.

Yet still the chicks persevere.

[soft music continues] Every evening, the parents fly many miles, seeking their chicks in a vast wilderness, bearing food to sustain them.

The young birds stagger on, following their parents' lead.

But the adults' approach changes with the wind, and the chicks drift off course, sometimes doubling the length of their agonizing march.

They trudge across the burning ground, sharp salt crystals slashing their feet.

And some of the smallest chicks are doomed by a crueler burden.

On the tips of their wings balls of mud have set as hard as concrete.

[chicks chittering] In some years, 50,000 chicks set out, and not a single one succeeds.

It is no mirage.

This year many of the chicks have made it across the great salt pan.

[soft music] They have survived the journey of their lives.

But here at the edge of the salt pans there are other dangers.

[soft music] As soon as the youngest fledge, all must take flight for the coastal feeding grounds a thousand miles away.

There they will wait for the mysterious signal that calls them back to breed in the desert again.

[soft swelling music] [birds squawking] Even as dust devils dance, the promise of the Kalahari endures.

For in time, the rains will quench the great Thirstland and summon the multitudes once more.

[light music] [soft regal music] [light music]