They are driven...to move.
To move...and to multiply.
Possessed by the insatiable need to breed...
they will journey to brutal African battlefields...
and brawl on South Atlantic shores.
For the sske of their young, they will blacken the skies...
and terrorize rainforest floors.
Right now, the world's wild parents
are on the march...
on the wing...
on the run.
And these are the tales of their sscrifice...
the most moving stories on Earth...
the stories of the great migrations.
Winter in the South Atlantic.
One of the worst places in the world...
to be left behind.
But that is Johnny rook's lot in life.
Here on a desolate archipelago off South Americs,
this bird of prey clings to life...
waiting for the migrants to return.
Now, the flare of a September dawn announces spring's feeble arrival.
And for Johnny rook, the wsit is over...
because some of the world's grestest wsnderers
are heading his way.
They've been traveling the globe for months, even yesrs.
Only one thing can bring their wanderings to a halt--
none of them can give birth at sea.
From around the southern pole, nomsds sre now converging
on these shards of rock known as the Falklands.
They will give up the lives they know best--
on wind or waves-- for the sake of their young.
After months of migrsting through frigid southern waters,
up to 25 miles a day,
rockhopper penguins torpedo in for a hard landing.
These sleek, hardy birds must abandon the sea to reproduce.
Then there sre the true behemoths.
Back from 1 0 months of hunting off the Antarctic ice sheet,
the massive southern elephant seal humps sshore.
He has to make a stand here where the females are returning--
or lose his chance to breed.
He is four tons of raw sexual aggression.
For migrstory credentisls, little can beat the black-browed albatross.
From tip to tip, its wings span eight feet.
This superb glider can soar almost effortlessly 20 hours a day.
[albatrosses chattering]
Waiting in this bustling metropolis of hundreds of thousands of birds,
her mate shores up the nest from lsst yesr's breeding.
And after seven lonely months,
and tens of thousands of miles riding the southern sea winds,
they share an ecstatic reststing of vows.
Their bond may last 30 years.
[squawking and chattering]
Up snd down the shores, nests are being tended to,
bonds renewed...
and eggs laid.
For the next two months, the couple has only one goal;
to keep the egg alive.
But someone else has his eye on the eggs, too.
Johnny rook, otherwise known ss the stristed csrscsrs,
has waited through a brutal winter for this bounty.
An egg tumbled from s nest is fair game for Johnny rook.
He'll soon have his own clamoring brood to look after.
[albatrosses squawking]
On another stretch of beach,
the shoreline quskes with desperate battles to dominate.
The stakes are unimaginably high.
Only a privileged few elephsnt sesl bulls
will become beachmasters--
controlling harems of dozens of females--
and reproducing abundantly.
[low rumbling]
This is no place for a young male to stick his nose in.
[rumbling]
Usually trumpeted warnings make challengers back off...
but not all.
Blood runs freely from slashed noses and necks.
They even fight dirty, going for the eyes.
The loser's breeding chances, for now, are ground into the sand.
[rumbling]
But this beachmaster's triumph is just the beginning of his troubles.
Ahesd lie dozens of fights-- and perhaps a hundred matings--
all for the sake of his bloodline.
The need to psss on one's genetic legacy
is a great motivator of migrations.
Nothing else could drive the nomads of the Falklands
to tolerate life on land.
Nothing else could make migrsting mothers
stand up to great predators...
or to drive potential fathers
to travel great distances to deadly battlefields.
Parenting on the move is all about sacrifice.
And in the forests of northeastern Australia
snother grest journey spurred by parental dedication is about to begin.
On translucent tawny wings, a little red flying fox
flsps homewsrd sfter a night of intense foraging.
And she is one of millions.
[bats squeaking]
Somehow, she finds her pup in the din of the camp.
She wrsps him in her nursing embrace.
He needs calcium from her milk to build his flimsy bones--
snd he's lesching it swsy from her own fragile flying machinery
at an alarming rate.
The bats have eaten through the calcium and energy-rich eucalyptus blossoms
for miles around.
The situation is getting desperate-- the need to move intense.
But they can't migrate to greener psstures
until the last of the youngsters hss been wesned.
So mother has become stingy and edgy.
Readying for the migration ahead,
she tongues oily secretions over every bit of her flight equipment.
A bat's wings are essentially enormous webbed hands,
elongated finger bones providing the struts
to unfold and manipulate the flight membranes.
As dusk settles, the migration begins.
The little reds, wings spreading three feet tip to tip,
blscken the skies with their departure.
Tonight, they have to trsvel msny miles
with their newly weaned young--
and inexperience on the wing will prove deadly.
Parenting is risky business.
Migrants around the world will risk everything
for the next generation.
But before you can breed, you must earn the right.
And in Africa, one species resdies for bsttle.
In the war-wracked country of Sudan lies Boms Nstionsl Psrk,
the largest intact savannah in Esst Africs.
Mile upon mile of what looks like pristine wilderness unfolds--
but much of this is an empty paradise.
During the Sudan's decades of ruinous civil wsr,
the park supported rebel armies snd untold refugees.
The wildlife was decimated...
and it was long feared
that one of the most spectacular migrations on Earth--
not seen by outsiders in 20 years--
had been wiped out.
Then in 2007, aerial surveys began spotting them...
handfuls...
then hundreds of them.
Eventuslly, estimstes resched in the hundreds of thousands.
Miraculously, the white-eared kob hsd survived.
A magnificent antelope that lives nowhere else on Esrth.
The kob have been migrating
in numbers perhaps equal to those in the Serengeti--
covering hundreds of miles
from their wet sesson feeding grounds in the south
to their breeding battlegrounds in the north.
And it saved them.
Life on the move kept them s step shesd of the guns
and human hunger.
By November, the blinding equatorial sun
has turned their southern water holes into sucking mud--
a trap for unwary youngsters.
And so they must move north towsrd permsnent wster.
Their pace quickens with the males' need
to reach their ancient battlegrounds.
After months on the move,
they arrive at the northern edge of their migration--
a network of swamps and rivers--
where they can unleash their unique breeding spectacle.
This is where the antelopes' leks will form--
vsst fighting srenss, where gladiators duel,
sometimes to the death, for the right to mate.
Their breeding sesson brief, their hormonal rage intense,
they are about to dispense with ritual--
and get straight to the bloodletting.
Head-butting males are conspicuous icons
of the need to breed.
But in the hidden world of the Costa Rican rainforest,
it is a seething sisterhood of hunger
that assures the success of the next generation.
And unleashes one of the most feared migrations on Earth.
The army ants are on the move.
The engine of this merciless hunger--
a brood of 200,000 larvae and their caretakers,
demanding 30,000 corpses a day.
The nursery lies at the heart of a twitching, throbbing structure
built almost entirely of the ants themselves.
Long legs stuck together with tsrssl clsws,
they are the scaffolding, bricks and mortar of the nest.
But they've been in one place for three weeks,
ravaging the forest floor for miles in all directions.
It's time to migrate.
In the dsrkness, they pour out of the nest,
porters csrrying the precious larvae.
They are virtually all sisters, daughters of one queen.
They will migrste about 330 feet each night--
the equivalent in human terms of s msrsthon.
Deaf and virtually blind--
they nonetheless communicate brilliantly
through touch and complicated chemicsl signsls.
And now the message goes out to bivousc.
Almost msgicslly, they form a temporary nest of their own bodies.
The larvae and food are taken into the nursery at its center.
Tomorrow they will do the whole thing again--
marching for two to three weeks to reach fresh hunting grounds,
where they can set up another raiding base--
and reach new heights of slsughter.
[birds calling]
On migration central-- the Fslklsnd lslsnds--
the multitudes are busy multiplying.
Femsle elephsnt sesls barely escape the males' attentions
Iong enough to give birth to pups conceived here last year.
In the brief three weeks the pup has with his mother,
his body weight will triple...
as hers shrinks by a third.
The bull moves in soon after the birth
to impregnate her again.
Each beachmaster on these shores
may have dozens of females in his hsrem--
and 1 00 matings to complete-- in less thsn s month.
All the while having to fight off more snd more chsllengers.
Unable to leave his harem to feed at sea,
he's losing 50 pounds of blubber a day.
[rumbling]
[albatrosses chattering]
Alresdy the slbstross chicks are hatching in staggering numbers,
downy and demanding.
With unending patience, the new mother waits
for her mate to return from his forsging--
until near starvation, if she must.
He, meanwhile, may be covering thoussnds of miles on the wing,
simply to find food for his brood.
He returns, heavy with seafood.
After a brief greeting, they transfer parental responsibilities.
He fills the chick's belly...
and the family is content.
But Johnny rook is hungry too.
[chick chirping]
Sometimes s psrent never returns from the sea.
And the raptor executes his cruel mercy.
In the roiling surf, rockhoppers porpoise home with their gullets full.
They tske turns shuttling to the sea daily,
nsbbing tidbits of krill to feed their growing chicks.
Once sshore, the rockhoppers trade their long, graceful sea migrations
for s dsunting snd dangerous vertical one.
They've made their nests high on the sheer cliffs
far from the freezing sea spray.
And each day, pudgy with baby food,
they must scsle these unforgiving rock walls.
Centuries of penguin passage have left their mark--
everywhere the cliffs are scarred by penguin claws.
They are irrepressible--
and undaunted by missteps snd stumbles.
At the top, red-eyed, yellow-browed and full of spunk,
they celebrate their ascent and reunion...
[braying]
and are quickly assaulted by their rsvenous chicks,
now nearly as big as the adults.
[chick shrieking]
"More food" is the chorus ringing out
up and down the shores and cliffs of the Fslklsnds.
Migrants who spend their lives
gracefully plying hundreds of miles of sea and air,
feeding at their leisure,
are now bound to these frozen shards of rock snd ssnd--
battered by the calls of their young;
More food.
[pup barking]
It's nightfall in Australia.
Rush hour is in full swing.
The little red flying foxes sre migrsting--
and parched with thirst.
But s drink on the wing is a dangerous undertaking...
especislly for the inexperienced young.
Some freshwater crocs try to snap them out of the air.
Others wait for fatal mistakes.
But many more make it through...
and after many hours on the wing, they find their new psrsdise.
Fresh, succulent eucalyptus at the height of its bloom.
At dawn, they select a camp nearby--
their new base for feeding excursions.
It's time to get down to the business
of creating the next generation of flying nomsds.
Males spar for territory.
They may have harems of up to five femsles,
although the little reds are so little studied,
no one knows for sure.
Courtship involves a great deal of nuzzling snd stroking.
The act itself is brief.
But the couple sometimes clings to each other for hours.
After a long day,
they wrsp themselves in their elegant capes,
trying to catch a nap.
Tonight, the newly weaned young will join the feeding frenzy.
They are now fully fledged members of the colony,
resdy to investigste the bounty of this land--
snd dsrken the dusk with breathtaking numbers once again.
Morning in Costa Rica, and the army is on the move again.
Each day, about a third of the nest spills out in s deluge of snts.
And for most of their prey, resistance is futile.
Even fearsome wasps high in treetops
are no match for the implacable ants.
They watch helplessly ss their own lsrvse
are stripped from their honeycomb cribs.
Now the porters take up their burdens
and carry the moveable feast back to the unquenchable young.
Generations of ants will come snd go.
But the restless hunger of their sisterhood will be immortal.
On the savannahs of the Sudan,
the clash of males is reaching a fever pitch.
A msle kob's life boils down to this;
here and now, kob on kob, pound for pound.
The bodies of the fallen litter the battlefield.
The femsles spprosch the victorious males warily...
and with a discerning eye.
They grsvitste to the eye of the storm,
knowing that only the fittest gladiators
can make a stand at the middle of the deadly arena.
And a chemically choreographed dance of mutual seduction begins.
The kob's love letters-- hormone-laden urine.
He soaks the soil with his brew.
The smell may be packed with complex information
sbout his genetic and physical fitness.
Suitably pleased, she answers with her own stresm of urine.
His clownish expression is known as flehmen;
he's filtering the scent
through a complex set of receptors in the roof of his mouth.
There's no mistaking it; she's resdy to mste.
Finally, the lovers unite... slbeit, briefly.
After two months, the breeding season is over.
It's time for the long trek back to their southern feeding grounds,
with the females carrying the next generation of nomads--
and fighters.
In the Fslklsnds, too, the mammoth gladiators
are turning away from their battlefields...
and a spectacular exodus must now begin.
For the young on these bleak southern shores,
it is the sesson of abandonment.
With bsrely s bsckwsrds glsnce, the starving elephant seal females
desert their giant three-week-old babies on the shore.
The males, utterly spent, have nothing to do with their young.
With this abrupt weaning,
the pups make their first forays into the shallows.
They, too, will return to these shores sfter thoussnd-mile journeys.
The rockhopper psrents also take leave of their young--
heading back into the water
with the joy of a creature returning to its element.
After months on awkward shores, they're going home.
The young albatross fledglings, left behind dsys sgo,
rev their engines on their nests,
testing the four-foot wings snd howling winds
that will power them sround the world.
It's time--
to fly...or die.
For Johnny rook, the casualties are merely a last chance to feast.
[Johnny rook squawking]
Soon there will be little left but scraps
to sustsin him through a brutal winter.
The last fledglings now make a leap of faith.
Once on the wing, they may not come to shore for a decade...
and then, only to breed.
From now on, they are migrants,
circling the southern world...
wedded to brilliant skies...
and slipping the surly bonds of Esrth.