The ancient forests of North America.
Mysterious, wild... a world of giants... where great bears and wolves prowl.
But hidden in the shadows there is a miniature, almost magical world.
A place where nothing is quite as it seems.
The home of extraordinary, tiny creatures.
And the moment one little chipmunk has been waiting for.
The arrival... of acorns.
When you're just 6 inches tall the world looks very different.
This chipmunk is only 2 months old... and is already facing what will be the greatest challenge of his life.
He has to collect enough acorns to get him through the coming winter.
He'll need at least a hundred so every acorn counts.
He will only survive the coming winter by escaping underground.
But he can't hibernate like a bear.
His body is too small to store enough fat.
Instead, he needs a store of food.
For his first year the youngster's done well.
But he's being watched.
This is an older chipmunk... worldly wise and sneakier too.
Older chipmunks are notorious thieves.
After all, why work when you can steal from someone else?
For the youngster, life without his store of acorns... will spell disaster.
But he isn't the only little creature... struggling to grow up in the big, wide world.
On the other side of the continent... lies one of the harshest environments on Earth.
The Sonoran Desert... in America's wild west.
A place of legend.
For the first human settlers... survival in this unforgiving desert was on a knife edge.
So imagine how hard it must be... if you stand only 3 inches tall.
A tiny grasshopper mouse.
This caring mother was left to raise four hungry mouths alone.
They're not yet ready to make it on their own.
Except for one.
The eldest son is bolder... and increasingly drawn by the call of the wild.
Every night, his mother goes out to find food.
Hiding in the shadows is a host of enemies.
There are more venomous creatures here... than anywhere else in the U.S.A.
No place for the timid.
But she's not your average mouse.
It's why old-timers call her by an earlier name:
The sting of a scorpion can kill a human... but a scorpion mouse has a superpower.
Her body is immune to the venom.
She specializes in hunting deadly prey.
To defend her territory she stakes a claim with a warning howl.
This young scorpion mouse has a lot to live up to.
He knows nothing of the dangers outside his door.
But barely 3 weeks old... growing curiosity means he's about to face them.
Back in the wild wood... the young chipmunk is still preparing for the coming winter...
unaware that his store is being ransacked.
For the thief, it's a dash back home...
to stock up his own store...
before heading straight back to the scene of the crime.
Out in the woods, the young chipmunk is about to face a new problem... and this one's a giant.
This half-ton moose is hungry for acorns too.
Arriving back at his burrow... the young chipmunk is in for another surprise.
His store is now almost empty.
And that's not all.
The burglar is back... and he's a seasoned fighter.
An older stronger chipmunk can kill a youngster.
All he can do is run for his life.
And without a store of acorns... how will he survive the coming winter?
In the Sonoran Desert... the young grasshopper mouse faces his first night out alone.
There are more rattlesnakes here than anywhere else on Earth.
The mouse's superfast reactions have saved him.
But he still has a lot to learn about the dangers of the desert.
For the moment, a dry riverbed seems a safe refuge.
But tonight, a powerful force threatens.
One so rare a mouse could go its whole life without seeing it.
When the rain arrives... a year's worth can fall in a single night.
Small animals lose heat faster than big ones... and if he's not careful, his wet fur could lead to a fatal chill.
Months of blazing sun... have baked Arizona's earth as hard as stone.
The water can't soak away.
Instead, it gathers momentum... as it races downhill.
In the northern woods winter is just a breath away.
Once the freeze sets in... the young chipmunk won't last a week without a store of acorns.
And the days are getting shorter.
The urgent need to replace his stolen store... forces him into unknown territory.
The sound is irresistible.
This is the home of a silent hunter.
A great horned owl.
Over 20 times the size of the chipmunk.
He may have escaped, but his store... is still almost empty.
High noon in the wild west.
So hot, the last drop of rain is long gone.
The highest temperatures are down at mouse level... where it can reach a blistering 140 degrees Fahrenheit.
It's a side of the desert, a nocturnal mouse should never see.
Except for those washed up, exhausted... and swept very far from home.
In daytime... the desert is a real-life Jurassic Park...
where heat brings giants to life.
But this realm of reptiles is ruled from the air.
"Eyes like a hawk"... is no empty phrase.
Their vision is thought to be eight times as good as ours.
They're the only birds of prey that hunt in packs.
It's hard to outwit this intelligent team.
Long feather-free legs are ideal for extracting mice... from those hard-to-reach places.
But even these clever hunters... can't solve this puzzle.
The mouse has no choice but to hold out till dusk.
In the forest, the chill in the air... spells trouble for the smallest creatures.
A tiny body gives no defense against the cold.
There's only one way this young chipmunk can survive now.
He needs to find his stolen acorns and get them back.
He's found the thief's burrow.
He's caught in the act.
It's flight or fight.
He chooses fight.
The youngster's won.
He can reclaim his stolen acorns... while the thief nurses his wounded pride.
At last, his store can be returned.
And not a moment too soon.
Winter is here.
The young chipmunk has made it just in time.
Sundown in the wild west.
Now is the time for the young scorpion mouse to venture out.
When close enough... a lost mouse can follow its nose all the way home.
There comes a time when every youngster faces a difficult choice:
An easy life...
Independence has its dangers.
But what would life be without a challenge?
Even if it means fighting a venomous... two-headed monster.
He closes his eyes to protect them... but he can still see with his whiskers.
But as they say, what doesn't kill you... only makes you stronger.
Their mothers give them the start they need.
But it's their own experience that finally makes a man of the mouse.
He's finally ready to leave his home forever... and to wander the desert alone.
Compared to us, little creatures live at breakneck speed.
Their lives are brief, but burn brightly.
Here, in the temperate forest... the big freeze sets in.
For the large animals, this is a time of hardship.
For a chipmunk, it's a chance to take a well-deserved rest.
The start of six months of peaceful sleep.
And when he gets hungry, he'll wake, briefly... and feed on his store of acorns.
Little guys don't always finish last.
And in a land of giants... heroes come in all sizes.