A summer's day, 70 million years ago.
The Arctic. But not
the barren, icy landscape we know.
The Earth is a much warmer place
and in summer, round-the-clock sunlight
supercharges the forest vegetation.
A fertile feast for some of the planet's
biggest and hungriest creatures.
Dinosaurs.
There are thousands of vegetarians here,
all making the most
of the boundless food.
A spiky Ankylosaur.
She likes to feed alone.
Others are more sociable -
herd animals, who eat together,
like these Edmontosaurus.
This is one of the youngest members
of the herd.
We'll call him Scar,
a name he'll earn soon enough.
Since he hatched in the spring,
the sun hasn't stopped shining.
There's plenty to eat
and he has the company and protection
of his extended family.
Life is pretty good... for now.
But this will all change for Scar.
The 24-hour daylight will soon fade...
..and 24-hour night will take its place.
There are already signs
that summer is letting go.
The dark times are coming.
For everyone.
Patch is a young male Troodon.
This carnivore has feasted all summer
on baby Edmontosaurus.
Unfortunately for him, his favourite
food is now bigger than he is.
So Patch must look for other game.
As dinosaurs go, Troodon are clever,
born to hunt and kill.
So Patch has natural talent but, as yet,
not much clue how to use it.
What goes in must come out.
That much, Patch gets.
But he hasn't learnt
to cover all the exits.
Thanks to the bigger Troodon,
this is one meal that's gone begging.
A hungry and frustrated Patch
needs to get his act together,
and quickly.
The sun is weakening.
Winter is approaching fast.
Scar now has to deal with
something completely alien, unexpected
and very, very dangerous.
Something he has never seen before.
Nightfall.
Caught out,
Scar can't see danger coming.
He's in the dark, at the mercy
of whatever is out there.
This is no time
to be away from the herd.
Here in the Arctic, the first night
of autumn lasts just a moment.
Danger fades with the dawn.
But the encounter has left its mark.
Scar is wounded, but at least now
he's safely back in the herd.
But the coming winter will steal
a little more light from every day.
Soon, the sun will disappear completely.
Then the herd must leave
on a great march south
to find enough food and light
to survive the winter.
As the weeks pass,
the forest begins to wither and die.
This is no longer a land of plenty.
The competition for what food is left
is about to get much tougher.
The Edmontosaurus males
bellow a warning.
Something is coming.
Another dinosaur is here in force.
This is a herd of Pachyrhinosaurus.
Two-tonne headbangers.
The brains inside these thick skulls
are no bigger than a bird's,
but their reinforced heads
make excellent battering rams,
which they'll use against anything
that gets between them and their food.
For the first time in his life,
Scar is hungry.
The same goes for Patch.
While he is well equipped
to survive a cold, dark winter,
he still has to eat.
A Troodon's brain
is wired for high-speed pursuit.
His reactions are so fast,
it's as if he sees in slow motion.
But some meals
are still too quick for him.
Time is running out.
If he doesn't get the hang of this soon,
he'll starve.
With the cupboard bare, Scar must hunt
out every last scrap of nourishment.
The Ankylosaur is doing the same.
An experienced old hand at survival,
she's taken to eating rotten wood -
..the grubs and insect larvae inside
providing a little extra protein to keep
this three-tonne vegetarian on the move.
Scar, reared on a diet
of soft leaves and plants,
must develop a taste
for this new, harsher diet.
The warm summer paradise
is a distant memory.
It will soon be time to leave.
As every night
stretches longer than the last...
..it's the predators
that have the upper hand.
The adults corral their young,
using their own bodies as a last line
of defense against the night stalkers.
They know their enemies prowl
out there in the darkness.
After his terrifying narrow escape,
Scar is wary.
Nothing will entice him
to venture beyond the herd's protection.
Nothing, except perhaps a scrap of food.
Fear finally holds Scar back.
But for one young female,
the compulsion to eat
is more than she can bear.
Gorgosaurus.
At 30 foot long and two tonnes,
this is the T-rex of the North Pole.
Equipped
with highly sensitive night vision,
he is the consummate nocturnal killer.
The young dinosaur never stood a chance.
For Scar and the herd,
their summer playground
has become a winter killing field.
Their only hope...
..exodus.
The ever-shortening day
finally signals to the herd
the onset of the great annual migration.
It's time to head south towards the sun
in a grueling 1,000-mile trek
to find food, light and safety.
Only the herd's dead will remain -
life-giving sustenance for the predators
who will stay here
throughout the Arctic winter.
The three-month odyssey
will lead Scar and the other youngsters
through perilous terrain.
But with the herd to guide them,
many will see it through.
Across the Arctic,
Edmontosaurus hear the call,
coming together for safety in numbers.
Even rival herds of Pachyrhinosaurus
join the jostling masses.
The march of the dinosaurs...
has begun.
This is the start of a journey
which will take the migrating dinosaurs
through what is now northwestern Canada
to the fertile coast of the inland sea
that divides North America.
They will face perils every bit
as daunting as those they leave behind.
Many of them will not survive.
But not every herbivore
is making the journey.
Our female Ankylosaur
is too cumbersome and heavy
for the 2,000-mile round trip.
She will tough it out here at the Pole
and endure
the ravages of the Arctic winter.
Troodon are well adapted
to survive the winter.
But Patch must still learn how.
Feeding from the Gorgosaurus' kill
is a risky business.
But this could be
their last decent meal for months,
so it's a risk they need to take.
Patch knows
he's well down the pecking order...
..hoping for a few scraps at best.
But maybe it's better for him
to stay out of the firing line for now.
Because the king of the forest...
..will not stand for
anyone stealing his food.
In summer, the Troodon
would never fight a Gorgosaurus.
But in winter, a fresh carcass is
worth putting your life on the line for.
A reckless Troodon
inflicts a savage bite.
But he that strikes the king
must strike to kill
or pay the price.
Patch will stay hungry...
..as Gorgosaurus
reclaims what is rightfully his.
After one week, the migrating herds
have reached
the edge of the Arctic forest.
So far, Scar is keeping up.
But this open landscape
is a hostile, new world.
They're exposed to the elements
beneath a sky
that holds unfamiliar threats.
Scavengers...
..who know that this journey
will take its toll.
And soon
there's another surprise from above.
Scar has never seen snow before.
But the first flakes
rapidly become a blizzard.
There's only one way
to cope with the freezing temperatures -
keep moving at all costs.
The young are the most vulnerable,
their small bodies
easily overwhelmed by the cold.
If Scar can't keep up,
he will be left behind...
..to die.
An old male spurs him on.
With 20 winter migrations behind him,
this adult
has been through it all before.
He provides
some shelter from the weather
and sets a pace
the youngster can follow.
Scar's new companion
has problems of his own.
There is a tumor
growing in the veteran's brain.
This could be his last migration.
Back in the Arctic forest,
it's getting colder by the hour.
Patch's feathers are not quite enough
to keep out the biting chill.
Cold is not his only problem.
He's still not eaten properly.
And he needs to be in peak condition
for what's in store.
He's about to go head-to-head
with his rivals.
it's every male for himself
in a ritual that kicks off every winter.
It's nesting season.
As an adult, getting through the winter
is about
more than looking after number one.
Patch must now
also prepare for a family
and learn how to attract a mate.
200 miles to the south,
thousands of tonnes
of determined dinosaur
have battled their way
through the blizzard.
But in the whiteout,
they've strayed completely off course
and into deep trouble.
There are deadly predators in the water.
And Scar has never swum before.
In the far north, the Ankylosaur
is coping as best she can.
Her relentless foraging
leads her into the darkest corners
of the forest...
..where danger lurks unseen.
In winter, injuries can have
deadly consequences.
A fight could kill them both.
The Gorgosaurus
hasn't got the stomach for it.
The bite on his leg has become infected.
He must rest and
hope an easier victim comes his way.
Deep winter now begins.
As the sun sets,
so starts the longest night on Earth.
There will be no daylight
for four months.
Some may never see sunshine again.
The Edmontosaurus have been
moving south for almost a month,
keeping one step ahead
of the chasing night.
The herd marches on its stomach.
And they're now running on empty.
Starvation and exhaustion
are taking their toll.
To Scar,
the herd has always meant safety.
But now the weaker ones
begin to collapse and die around him...
..ending their lives
as meat on a volcanic wasteland.
The Quetzalcoatlus is the biggest
flying animal of all time,
with a 40-foot wingspan.
For these scavengers, the migrating
dinosaurs are their moveable feast.
At last, a tiny oasis of green
in the barren wilderness.
It's a rich reward
for those who have made it this far.
But there are too many mouths to feed.
The Pachyrhinosaurus
want the plants for themselves.
Hunger drives one Edmontosaurus
to fight his corner.
But there can only be one outcome.
A broken ribcage means a slow death
for the desperate animal.
But for the migrating herd,
there's no looking back.
The herd moves on, entering the most
dangerous part of the journey so far.
To the west, amid a massive collision
of continental plates,
the Rocky Mountains are being formed...
..violently.
As the land has twisted and buckled,
volcanic eruptions have blanketed
a huge area with ash...
..killing the plant life
and any chance of food.
And now, more trouble is stirring.
Another ash cloud pumps into the sky,
kicking off fierce storms.
The air spits and crackles
with electricity.
The fine volcanic dust coats the lungs.
And the toxic fumes
mask the tell-tale scent of predators.
And there is no shortage of them.
The herd is now walking
into a killer's lair.
Albertosaurus,
a relation of Gorgosaurus,
and all the more murderous
because they hunt in packs.
Each one
three tonnes of teeth and stealth.
It's been months
since these creatures last fed.
The winter feast will soon be served.
In the Arctic, Patch's head feathers
have turned a fetching yellow,
which lets the females know
he is ready to breed.
Being ready is one thing.
Being able is quite another.
In order to breed successfully,
a male must first prove
his home-making skills.
This older Troodon
has found a perfect spot,
nicely sheltered from the freezing wind.
Patch has got it half right.
But location is everything.
He's chosen the wrong place to build.
It's far too exposed.
With the arrival of a female,
the courtship ritual begins.
Instinct and natural rhythm take over.
Patch is dancing hard, but his efforts
aren't being appreciated.
This female
only has eyes for one Troodon.
And it's not Patch.
Dinner closes the deal.
The older male
knows the way to a woman's heart.
Patch learns another harsh truth.
When it comes to finding a mate,
there's always someone else
who's better at it.
To the south, the migration
of the Edmontosaurus herd
keeps them just ahead
of the zone of permanent darkness.
They have walked 600 miles -
more than halfway to journey's end
in the southern forests.
For a good many,
this is as far as they will get...
..because they're walking
into an ambush.
At the lip of the volcano,
ice is no match for fire.
Another eruption transforms the snowcap
into a deadly avalanche
of water, ash and rock.
Nature, which has so threatened
Scar's survival,
now comes to his rescue.
But he's lost
the most important thing in his world...
..the herd.
The volcanic torrent
has set like concrete.
A desolate blanket over Scar's new world
of total isolation.
If the herd has survived,
it has moved on.
At last, a lone voice returns his call.
It's the old dinosaur
who helped Scar through the blizzard.
But a distance behind them...
..an old enemy
refuses to lie down and die.
Scar and the veteran
continue south once more...
..unaware that they have company.
In the high Arctic,
night has now lasted for six weeks.
Having mated, this adult male Troodon
is doing his fatherly duty
and looking after the eggs.
He won't eat
until they hatch in the spring.
But Patch... Well, his nest is empty.
He did his best to mate, but his efforts
have only made him more hungry.
His courtship skills might be lacking,
but he knows an opportunity for food
when he smells one.
The scent of fresh blood draws him in.
Still hampered by his infected wound,
the Gorgosaurus has been
sustaining himself on small prey.
But he's on the mend,
and it won't be long
before this tyrant is ready to spread
terror through the forest once more.
Not far away in the winter dark,
the Ankylosaur
is still thinking of her stomach.
She's utterly helpless.
Far to the south, Scar and his
traveling companion trudge on alone.
A fresh sign of another dinosaur.
But is it friend...
or foe?
The old Edmontosaurus struggles
to take in this vital nourishment.
As his brain tumor grows,
he's becoming disoriented
and unpredictable.
Thrown together through disaster,
this small band of the young,
the ill and the injured battles on.
But the next day
brings a glimpse of hope.
Vast numbers of Edmontosaurus
still soldier on -
a moving fortress that will provide
safety for the stragglers once again.
If they can reach it in time.
As the short day ends,
they've fallen even further behind.
The Pachyrhinosaurus is struggling most.
There is nothing
Scar or his companion can do for her.
She must be abandoned to her fate.
Scar's confused companion
now does the unthinkable,
veering away
from the tracks left by the herd.
Scar senses something is wrong...
..but it's in his nature to follow.
The old dinosaur stops to rest
and to seek shelter
from the freezing wind.
Normally, these animals
would huddle together for warmth.
But not this time.
It's a shock for Scar.
One of his own has turned on him.
He is bewildered and confused.
And wounded.
Back in the north,
a warm weather front passes through,
lifting the temperature above freezing
for the first time in weeks.
Patch works on mastering
another of his natural gifts.
His hearing is so sharp
that even under two feet of snow
his prey can run...
..but it can't hide.
Patch has finally become
an effective hunter.
Maybe he'll soon be ready
to prove himself in the mating game.
The Ankylosaur has been trapped
upside down for three days.
With her soft belly exposed,
she's become
a target for marauding Troodon.
They sense
that she can still inflict injury.
Theyll bide their time
and wait until she weakens.
For the vulnerable
young Edmontosaurus...
..there is no rest.
Scar's confused old companion
has wandered off.
He no longer offers
any protection or guidance.
Unfortunately,
he's the only ally Scar's got.
The old Edmontosaurus
once kept Scar going
and probably saved his life.
Now he no longer even recognizes him.
Scar turns to his one-time saviour
for protection.
But he's wasting his time.
Scar is on his own once more -
..his instincts his only protection.
The Troodon are closing in
on the Ankylosaur.
Gang members
taunting a weakened victim.
Even Patch is plucking up the courage
to move in.
It's a crushing blow
for the king of the forest.
One there's no coming back from.
The tables have turned.
Scar has been slogging
through the wilderness for three days,
with only a frustrated scavenger
for company.
With every step, he becomes weaker
and more vulnerable.
But then his efforts
and struggle against all the odds
are finally and spectacularly rewarded.
He has found the herd.
But they have already crossed the river.
And it's cost them dear.
Scar faces a stark choice -
..death from below...
..or from above.
It's the end of the line.
The Pachyrhinosaurus
may have fallen behind,
but she got here in the end.
She gathers a last meal
before the final push across the river.
With an armoured giant
to shelter behind,
Scar is no longer
the easy target he once was.
His companion knows
the safest way to cross the river -
..as part of a herd.
But Scar must take care.
His companions are almost as dangerous
as the predators in the water.
For Scar, it's now or never.
Scar has proved himself a true survivor.
The fearful and naive young creature
of the Arctic forest has grown up
and come to the end of his epic journey.
At last, he rejoins the herd,
having earned his place amongst
the most indomitable dinosaurs on Earth.
They've marched over 1,000 miles
through the greatest hardship
to reach this safe haven.
With enough food to last until spring...
..when, at last, the sun will rise again
in the far north...
..bringing back a feast of plenty.
Few will go hungry.
And new parents will bring the next
generation of dinosaurs into the world.
And then the herds
will set off once again,
leaving their winter sanctuary...
..to return north to the
Arctic summer paradise
where, for each and every one of them,
the great journey began.