Original subtitles

Alaska.

America's last frontier...

..and greatest wilderness.

Immense.

Unspoiled.

Awe-inspiring.

Home to half the world's glaciers...

..America's highest mountains...

..and ice sheets that stretch to the North Pole.

Inhabited by the world's largest land predators...

..herds of ancient beasts...

..and leviathans from the deep.

The land is hostile

but its richness and diversity is unparalleled

in the northern hemisphere

All must be resilient and adaptable

if they're to survive a year in the wild of Alaska.

Alaska is the largest of America's 50 states.

It is seven times the size of the UK

but home to fewer than a million people.

There are three million lakes...

..12,000 wild rivers

and 44,000 miles of coastline.

That's more than the rest of the US combined.

It is the gateway to the Arctic.

Half a million square miles of wilderness

that stretches from Canada in the east

to Russia in the west.

Winter here is one of the harshest anywhere.

Temperatures can plummet to -60 degrees Celsius.

Snowfall measured in feet, not inches.

And in the far north the sun sets for two months,

casting a huge swathe of the state into darkness.

The only light coming from the Aurora Borealis.

Winter lasts seven months.

That's longer than spring, summer and autumn combined.

Creatures must battle to avoid starvation and predators.

To survive here is tough.

But Alaska has one of the world's toughest.

Musk ox roam the Arctic tundra.

Vast treeless plains where winters are long and brutal.

Out here they're exposed to the worst that nature can throw at them.

But these conditions are nothing new for musk ox...

..as they're relics of the last great ice age.

They migrated here from Siberia with giant bears and woolly mammoths

over 150,000 years ago.

The other giants went extinct.

Only musk ox survived.

Standing five feet at the shoulder

and weighing almost half a tonne,

they need a steady supply of food.

But there's a problem.

The Arctic blast has frozen the snow solid,

trapping the vegetation below,

starving these giants of vital nutrition.

MUSK OX GRUNTS

It's like digging through concrete.

Even their toughened hooves are useless.

As hunger kicks in

they become irritable.

MUSK OX GRUNTS

Musk ox are naturally jumpy and defensive.

MUSK OX GRUNTS

One is startled...

..and they bolt.

When musk ox sense danger, they retreat to the high ground...

..where they close ranks.

..horns facing outwards,

prepared to fight off aggressors

such as Alaska's 11,000 wolves.

It's a defence strategy that's helped them survive

two million years.

But this time it's a false alarm.

A waste of valuable energy

when food is in such short supply.

Many of the females are in the early stages of pregnancy.

They must protect their fat reserves...

..as it's only going to get colder

and birthing season is still a massive six months away.

Musk ox are not the only ones struggling to find food.

Harsh storms batter the west coast...

..turning it into a frozen wasteland.

Arctic foxes have evolved to live out here.

They're one of Alaska's most resilient creatures.

But even they're finding it hard this year.

And they must compete with the world's largest

and most formidable land predator.

Alaska in winter.

Temperatures drop low enough to freeze the ocean...

..trapping many of the state's 2,500 islands in thick sea ice.

One of the most remote Alaskan islands is St Lawrence,

which lies just 40 miles off the Russian coast.

WIND HOWLS

Much of it is deserted.

Only scavengers are active.

BIRDS SQUAWK

Arctic foxes are well adapted to live out here.

Each winter their coats turn from brown to white

to help with camouflage

and double in length for warmth.

Their small squat bodies and a thick layer of insulating fat

conserve heat.

Furry feet enable them walk on ice and snow without sticking.

These adaptations help them go longer between meals...

..which is vital if you live in a place with so little to eat.

Throughout the winter they're solitary

and travel great distances to find food.

But in the right circumstances they will gather.

The remains of a bowhead whale

that was killed by hunters in the autumn

attracts foxes from all over the island.

A feast like this will keep them fed for months.

That's assuming they can get their teeth into the frozen flesh.

And that it's not discovered by the world's largest land carnivore.

Polar bears are most at home on the Arctic sea ice.

They use it to travel huge distances between islands and the mainland...

..and from where to hunt their main prey...

..seals.

But they're also scavengers...

..and can smell food 20 miles away.

If one of Alaska's many polar bears were to discover this carcass,

they would soon take possession.

Feeding quickly, the foxes must remain constantly alert.

They'll need all the help they can get

if they're to make it through to spring.

Winter still has four months to run.

While freezing temperatures grip the north...

..storms batter the south.

1,000 miles from St Lawrence Island,

in Alaska's south-east,

lies Glacier Bay.

This coastline is dominated by an oceanic climate.

Winters here are warmer but no less severe than in the north.

Wet, warm air blows in off the sea.

Rises...

..cools

and falls as snow.

More than seven feet every year.

BIRD SINGS

Over thousands of years,

much of this snow has thickened to form glaciers.

Slow moving rivers of ice,

hundreds of feet thick...

..that carve steep sided valleys out of solid rock...

..as they grind their way down to sea level.

On the coastline,

higher temperatures stop the streams freezing over...

..throwing a lifeline to one of Alaska's most resilient

little birds.

The American dipper.

BIRD SINGS

Each winter, dippers leave their frozen mountain streams

to feed on the coast.

Pushing her wings upwards and outwards,

she quickly drops below the surface.

Dippers feed by diving down to the riverbed...

..where they pick amongst the debris...

..to disturb insects and fish.

She emerges with an insect larva,

splitting it open by hitting it on the surface.

But it'll take more than scraps like this

to keep her alive through the winter.

She heads out to hunt in open water.

And is rewarded with a fish.

Which she kills by beating it against a rock.

She spends up to half the day feeding

in water just a few degrees above freezing.

So to keep well insulated she preens her 4,000 feathers

and the thick layer of down underneath...

..then fluffs up and squats down

to help keep her feet warm.

Before heading back to the sea to do it all over again.

The mountains and valleys inland from the dipper's stream

are cloaked in coniferous woodland.

Up here, heavy snow continues to fall...

..carpeting the forest floor.

It makes it difficult for Alaska's smaller animals

to forage on the ground.

To survive here you must be prepared for the worst.

American red squirrels are active all winter

and rely on food they cached in the autumn.

Sitting on his favourite perch,

a male hungrily rips open a spruce cone

to eat the energy-rich seeds inside.

He can get through 40 cones a day.

If he is to survive the winter, he must have a cache of 10,000 cones.

Storing them is one thing, keeping hold of them is another.

An intruder trespasses on his territory.

He's got an eye on the cache.

He edges closer...

..but is spotted.

The territory owner warns him by drumming.

DRUMMING NOISE

When that doesn't work, he chases him off.

His hoard safe, He quenches his thirst.

He has to be on constant alert if he's to make it through to spring.

BIRDS SQUAWK

In a remote valley on the tundra,

1,000 miles north of the squirrels...

..a group of Arctic specialists has plenty to eat...

..regardless of the freezing conditions.

Snowshoe hares rarely travel far from their birthplace.

They feed on twigs, bark and buds of stunted willow trees.

But despite their camouflage,

they're still vulnerable to predators.

Lynx are Alaska's most skilful and secretive hunters

and snowshoe hares are their number one prey.

Late February and four months into a brutal Alaskan winter.

But even out here it's possible to thrive

if you've adapted to the conditions.

Snowshoe hares are perfectly designed for life in the Arctic.

Their white coats help them blend in.

Their huge back feet, which give them their name,

let them move around easily on top of the soft snow.

Essential, as hares are the favourite prey

for one of Alaska's top predators.

Lynx.

They're stealth hunters with incredible hearing,

excellent eyesight

and, like hares,

they have big furry paws that act like snowshoes.

But hares have eyes high on top of their heads,

giving them almost 360 degrees of vision.

They also have acute hearing.

When one senses danger...

they bolt.

Four out of five lynx hunts end in failure.

Hares are not the only Alaskan animal to gain safety in numbers.

Back on St Lawrence Island, 100 miles off the Alaskan coast,

winter storms have buried the whale carcass under six feet of snow...

..forcing the Arctic foxes to dig deep.

But they can't stay down for long.

They take it in turns to keep a look out for polar bears.

This group of ten foxes may have travelled many miles

to join the feast.

FOX SNARLS

With the coast clear, it's time for a clean up.

Scrubbing removes dried blood and oil from their fur.

Fluffing-up traps air and helps them keep warm.

Essential grooming that could mean the difference

between life and death.

The sea ice surrounding St Lawrence Island is now nearly six feet thick.

It stretches over 1,000 miles,

all the way to the North Pole.

This may look like a frozen desert

but there is life.

Ringed seals haul out on it to warm up.

And polar bears roam across it to hunt.

Each winter, polar bears fatten-up by feeding on seals

ahead of the lean summer months.

The sea ice lets them travel further,

giving them access to more prey.

Without the ice, polar bears simply could not exist.

Thankfully for them this winter is a cold one

and the sea ice will be here for a few months yet.

Inland, the long winter means ever-deepening snow.

Those animals not able to dig through it

are forced to search further and for longer.

WIND HOWLS

OX GRUNT

The musk ox herd has moved to higher ground

where the wind-blown snow lies thinner,

making access to food easier.

Up here, the wind chill reduces the temperature

by a further ten degrees.

Musk ox have adapted to survive such a battering.

Their massive bulk helps them conserve heat.

Their fur is made up of two layers.

A long thick weather resistant outer one

and a deep inner fleece.

Called qiviut, it's eight times warmer than sheep's wool.

So little heat escapes

that their bodies can remain cloaked in ice right through the winter.

OX GRUNTS

Access to food is essential...

..particularly for pregnant females.

The next three months will be crucial both for them

and their unborn calves.

Especially as winter tightens its grip.

Temperatures drop to -30 degrees Celsius.

Ice crystals fill the air.

The longer winter drags on,

the more difficult it is for those roaming the land in search of food.

Alaskan moose are the world's largest.

At seven feet tall, they can stretch up to ten feet high,

giving them access to nutritious buds and young shoots.

MOOSE GRUNTS

During a long, harsh winter,

moose can't eat enough calories to stay alive

so must rely on fat they put on during summer and autumn.

If they use up these fat reserves,

they start consuming their own muscle

and will quickly starve to death.

Young moose are particularly vulnerable.

They allocate most of their food to growth,

and come into winter much leaner than the adults.

Many don't make it.

A scavenging magpie grabs what it can of the frozen flesh.

The death of one animal bringing life to another.

While it's still freezing in the north,

in Alaska's south-east temperatures are starting to rise.

Sediment-laden meltwater pours from the land into the sea.

Strong winds and high tides stir up the nutrients,

turning the Gulf of Alaska into one of the most fertile bodies of water

on Earth.

It's incredibly rich in life.

Both above...

..and below the surface.

The shallow waters along the edge of the bay

make this the perfect nursery for young Pacific herring.

Called fingerlings,

they're only five inches long

and feed on microscopic plankton that floats in the water.

For protection they form huge schools of over a million fish.

And for good reason.

As the Gulf is home to Alaska's biggest, most effective predator.

BIRDS SQUAWK

Late winter in the Gulf of Alaska.

BIRDS SQUAWK

Young Pacific herring are under attack...

..from harbour seals...

..and steller sea lions.

In an attempt to avoid the onslaught,

they head deep.

But are chased down.

In the confusion, the herring are split up.

Some rushing back to the surface.

But even here, there's no respite.

BIRDS SQUAWK

As they're ambushed from above by a raucous flock of sea birds.

But for the young herring, the worst is yet to come

as they're now under attack from one of the world's largest predators.

Humpback whales.

Every year, a small number of humpbacks

overwinter in these waters.

They gorge on the shoals of young herring.

Humpbacks hunt by diving deep,

then explode to the surface...

..their huge mouths gaping.

They devour thousands of herring at a time.

WHALE SONG

Over the next few months, their numbers will grow...

..as humpbacks from across the Pacific Ocean

return to feed in this quite unique bay.

EAGLE SCREECHES

An American bald eagle is attracted by the commotion.

Bald eagles normally hunt larger prey

but perhaps hungry after the long, hard winter,

this one seizes the moment.

South-east Alaska has around 20,000 bald eagles.

Roughly one-fifth of the world population.

As winter draws to a close, they return to their nest.

EAGLE SQUAWKS

Reunited with their lifelong partners,

they quickly start re-building work.

This is the most challenging time of the year for them.

Lower temperatures and bad weather increase energy demands.

Shorter days reduce hunting time.

And with such a limited breeding season,

it's going to be a battle to raise a family.

Alaska in winter is one of the most hostile places on Earth.

Food is scarce.

Conditions are brutal.

Only the fittest and best adapted made it through.

With the northern hemisphere swinging back round towards the sun,

life can once again flourish in Alaska.

Next time, spring.

Migrants start to return.

Those animals that spent the winter in hibernation

emerge hungry

having not eaten for eight months.

But spring in Alaska is short

and predators are many.

It's going to be tough for both parents

and newborn.

Subtitles by Ericsson

Alaska.

America's last frontier...

MUSK OX GRUNTS

..and greatest wilderness.

BIRDS SQUAWK

Immense.

Unspoiled.

Awe-inspiring.

Home to half the world's glaciers...

..America's highest mountains...

..and ice sheets that stretch to the North Pole.

ARCTIC FOX SQUEALS

Inhabited by the world's largest land predators...

..herds of ancient beasts...

..and leviathans from the deep.

The land is hostile

but its richness and diversity is unparalleled

in the northern hemisphere.

All must be resilient and adaptable

if they're to survive a year in the wild of Alaska.

Alaska's been in winter's grip for seven months.

Animals have scraped by...

..barely able to eke out a living.

Finally, there's a glimmer of hope.

Days are growing longer...

..and rising temperatures have triggered one of the most dramatic

transformations on the continent.

The sea ice is melting.

The big break-up has begun.

By April, waves are back,

pounding the shore of Alaska's largest northerly island.

St Lawrence lies 100 miles from the Alaskan mainland

but shares a climate with nearby Siberia.

It's bleak here...

..but not lifeless.

ARCTIC FOX SQUEALS

Five months ago, this female Arctic fox was part of a group...

..kept alive by the frozen remains of a whale carcass.

But now they've exhausted every food cache

and this female needs a fresh supply of meat more than ever.

ARCTIC FOX SQUEALS

Murres abandoned St Lawrence in the autumn

when their feeding grounds froze over.

Now they're returning in droves.

Around three million sea birds nest here in the spring.

But this year there's a problem.

Access to the cliffs is hindered by ice.

The murres will have to put any plans for breeding on hold.

This delay is bad news for the hungry fox.

It's mating season.

She's paired-up with a male and due to give birth in seven weeks.

If she doesn't eat soon,

her body will reabsorb her developing embryos.

A desperate act to preserve every scrap of nutrition.

Salvation may be buried under the snow.

Arctic foxes have such keen hearing,

they can find voles even when they can't see them.

But voles are canny.

If they don't move, the fox can't get a fix.

By paddling her hind feet, she may panic them into moving.

But there's still a thick layer of frozen snow to get through.

She needs a regular supply of voles each day whilst she's pregnant.

It's a deadly game of hide-and-seek.

And right now...

..the voles are winning.

Whilst spring drags its heels on St Lawrence...

..it's making headway on the mainland.

It still drops below freezing at night.

But there are only eight hours of darkness.

Barely enough time for the Aurora to shine.

Daybreak wipes the dazzling display from the sky...

..and replaces it with one on the ground.

GROUSE RATTLES ITS TAIL

Male sharp-tailed grouse gather here each morning

for a ritual called a lek

so that females can choose who to mate with.

And they're very fussy.

Only the fittest, most attractive males will do.

GROUSE SQUAWKS

If he's to coax one down from the aspen,

he needs to catch her eye.

Tricky when a younger male wants to hog the limelight.

If he loses this spot, the hens won't give him a second look.

He stands his ground

and it works.

Now he's got her attention.

Time to pull out all the stops.

He rattles his tail quills,

flashes his throat pouch

and throws in some of his finest moves.

Proof that he's fit, healthy and unencumbered by parasites.

But she's not convinced.

She always compares multiple males before selecting a mate.

If he's to sire any chicks this year,

he'll need to up his game and try again tomorrow

Whilst grouse fight for the right to produce this year's offspring,

500 miles away in Katmai Wilderness Area,

some animals are already raising theirs.

Female bears look after their young for nearly three years.

This family is fresh out of hibernation...

..and they're hungry.

When these twins were born 15 months ago,

they were blind, helpless and weighed a little under a pound.

They're already eighty-times their birth weight.

Big enough for a tussle.

But small enough to be vulnerable.

The beach is a good place to find breakfast.

But it's also dangerous.

There are other hungry bears out here.

And adult males will kill youngsters they don't know.

They need to stick close to mum.

She's the only thing keeping them alive.

It's May in Alaska.

The time when bears leave their winter dens

in the Aleutian Mountains

and head to the coast to find food.

In spring, warm, wet air blows over the sea,

cools

and casts a veil of fog over Hallo Bay.

But it won't deter this brown bear from teaching her twin

the art of clamming.

There's a lot to learn about surviving in this wilderness.

Young bears must learn where to find food

and how to harvest it.

Clams thrive here...

..but they're buried in the sand.

Bears have more scent receptors than a bloodhound...

..so it's just a case of sniffing them out.

Four-inch claws make light work of digging...

..letting her guzzle hundreds of clams at low tide.

Valuable extra protein for a bear that hasn't eaten for months.

The cubs should be paying attention

but seem more interested in where the world's gone.

And with a milk bar so close,

it's hard to resist the easy option.

She's having none of it.

Maybe hunger will make them focus.

Almost 50% of bear cubs don't even make it past their first birthday.

One of the reasons is wanderlust.

Cubs are keen to explore every new sound and smell.

But it's easy to get lost in the fog.

And bumping into the wrong bear could be fatal.

Luckily, it's mum that looms from the gloom first.

The twins must learn fast.

Or one day naivety will get them killed.

Warm air from the Pacific is opening up feeding-grounds

all along Alaska's southern coastline.

350 miles east of Hallo Bay

lies the Copper River Delta.

The drainage basin for 24,000 square miles of Alaskan wilderness.

Meltwater bathes the mudflats in minerals...

..feeding a habitat teeming with marine invertebrates.

Food for hungry sandpipers.

The delta is a vital pit-stop for almost five million shore birds...

..all racing to reach their breeding grounds in the north.

BIRDS SQUAWK

Dunlins mingle with flocks of western sandpipers.

Some have travelled from as far away as Peru.

All have just two months to find a mate,

lay eggs and raise a family.

They must refuel as fast as possible.

There's still an 800-mile journey ahead.

Slender bills with sensitive tips

help them find tiny worms and molluscs.

Most feed for three days straight,

only stopping at high tide.

Only then will they have enough energy

for the final leg of their trip.

It's not just migrant birds that are in a rush to raise a family.

160 miles north of the delta...

..in a valley sheltered by the Talkeetna Mountains...

..one of Alaska's permanent residents must also act fast.

Arctic ground squirrels sleep through the winter

in cosy burrows lined with fur and lichen.

But now, according to their body clocks,

it's time to rise and shine.

It's this male's first glimpse of daylight for eight months

but he can't hang about.

SQUIRRELS SQUEALS

Noisy neighbours are popping up everywhere.

Male squirrels emerge before females to establish territories.

Firstly, rivals must be driven out.

Sometimes shouting's enough.

SQUIRREL SQUEALS

But when verbal warnings aren't heeded,

things get physical.

By keeping rivals at bay,

he increases his chances of meeting females.

And he'd rather be a lover than a fighter.

At last, a female.

She'll only be receptive to mating for four hours in any given year.

Get his timing wrong,

and he'll be painfully rejected.

Success.

He's at first base.

Now all he has to do is keep an eye on her

and be patient.

He won't help raise his offspring.

But waiting for the right moment to conceive them

is a chance to get to know each other.

Every day, the sun has a little longer to warm the ground.

Snow melts and rivers begin to flow.

Ice jostles and jerks its way downstream.

Even in Alaska, ice doesn't sit still forever.

As mountain streams thaw out,

American dippers move in.

There's plenty of food here to feed their growing family.

But the creek's become flooded with meltwater.

A gentle cascade is now a raging torrent.

Their nest and the chicks inside

are in serious danger.

This American dipper spent winter on the coast...

..where open water allowed her to ride out the cold snap

on a diet of fish.

But every spring she returns upstream to her favourite creek...

..to raise a family.

They've hatched four chicks.

But this year there's a problem.

The sudden thaw has flooded the creek with meltwater.

She had nested on the edge of a waterfall to keep predators at bay.

But now a tonne of water crashes down every second.

A thick outer shell of moss protects her chicks from the spray.

But access into the nest is treacherous.

Only strong toes and a powerful grip

stop her sliding to oblivion.

Chicks need feeding every four minutes,

keeping both parents very busy.

They scan the shallows from their favourite boulder.

Highly oxygenated water supports an abundance of bugs...

..which the dippers hunt,

either by snorkelling in the gravel bed...

..or by diving for richer pickings further down.

They hunt for an hour at a time,

making up to 35 feeding trips between them.

To help them stay waterproof, they spread oil from their preen gland

through their feathers...

..before taking the plunge again.

Dipper chicks stay in the nest

for longer than most other birds their size.

They won't fledge until they're almost fully developed.

That's over two weeks away.

And with the thaw still in progress,

the river will keep creeping towards their nest.

1,000 miles north-west of the dippers,

just outside the Arctic Circle,

rising temperatures are both a blessing and a curse.

Musk ox still haven't shed their thick winter coats

and they're feeling the heat.

MUSK OX GRUNTS

Resting on a windy ridge helps a little.

Back in the depths of winter,

females were pregnant...

..food was scarce

and woolly coats were the only thing that kept them alive.

Surviving until spring has its own rewards.

After an eight-month pregnancy,

musk ox cows have given birth.

Calves are up on their feet within hours of being born.

And for good reason.

They need to suckle at least 20 times a day.

Mums use all their energy for making milk

so there's none left for growing a summer coat.

And until there is, they can't shed their winter ones.

Any physical effort gets them hot and bothered.

And calves caught dawdling are given short shrift.

It may not feel like it now,

but this calf will find safety in the herd.

Come winter, they'll rely on the adults

not just for food and warmth

but for protection from ravenous wolves as well.

If they're to survive, best stick close to mum.

Whilst musk Ox calves fatten-up in the north,

600 miles south, on the Seward Peninsula,

there are new arrivals of different kind.

Sandhill cranes,

fresh in from California.

Cruising at an average altitude of 5,000 feet,

they've been riding the thermals for over 2,000 miles.

Now, with their breeding ground in sight,

they spiral back down to earth.

The breeding season starts as soon as their feet touch the ground.

Cranes form lifelong partnerships

and nothing puts them in the mood for mating more than a dance.

Youngsters head off to do their own thing.

No-one wants to see dad dancing.

It starts with a wing stretch.

And once he's got her attention...

..it's time to dance.

It's not about how elegant you are.

It's about relaxing and letting go of inhibitions.

CRANE SQUAWKS

Dancing strengthens the pair-bond.

If you can bust a good move,

you're also likely to have the skills required

to drive predators away from your nest.

MUSIC

CRANE SQUAWKS

MUSIC

They renew their commitment to each other by singing.

Which may also stimulate ovulation.

CRANE SINGS

And after all that song and dance...

..mating is over in under four seconds.

Sandhill cranes build their nest on the ground,

which makes them vulnerable to predators.

If they're to hatch any chicks,

these big birds will need to keep a low profile

for the next 30 days.

Alaska is home to 30,000 brown bears.

2,000 of them live in Katmai Wilderness Area.

Adults are normally solitary.

But in spring,

meadows brimming with sedge grass draw them together.

Sedge contains a lot less protein than meat or fish

so bears need to eat a lot of it just to maintain their weight.

Regular naps aid digestion.

With the gathering comes an opportunity to woo a mate.

Competing males try to give each other space.

Submissive body language keeps low-ranking bears out of trouble.

Any that don't read the signs

end up in a brawl.

BEARS GROWL

Young bears avoid trouble by staying on the side lines.

These two are almost three years old.

They've been nurtured by their mother since they were born.

She's gone grazing with the other bears on the meadow.

They don't know it yet

but she won't be coming back.

Two young bears have been abandoned by their mother...

..and are now facing life on their own.

She's been their teacher and their comfort blanket

for the past three years.

But the time has come to break up the family.

She has a new admirer.

He'll trail after her until she's ready to mate...

..fighting any other bears that get in the way.

There's no way her cubs will get past 900 pounds of muscle

and escape with their lives.

They may have parted ways with mum,

but they've still got each other.

Which will help smooth the way

as they set-off on the road to independence.

Their mother will be fertile for up to 30 days.

Footloose and cub-free,

she may mate with several males in that time.

If she has twins again,

it could be that each cub has a different father.

But she won't know till spring...

..as her fertilised eggs don't start to develop

until she's back in hibernation.

In that way, she can save raising new cubs until next spring,

when there'll be plenty of food about.

Other animals already have hungry youngsters to feed.

And Eagle Beach, 700 miles east of the bears,

is the perfect place to find baby food.

This male bald eagle returns here every spring.

And not just for the hunting.

But because this is where he's always raised his family.

He returned here three months ago with his partner of 13 years.

Their nest survived the winter gales

but was in need of some repair.

They quickly get it up to scratch

and today is a big day.

The female hatched her solitary egg this morning...

..and by the sound of it the chick's doing well.

EAGLE CHICK CHIRPS

For the next two weeks, the male will do most of the hunting.

There are fish here, if you know how to get them.

Sand lances hide in the sand to escape predators at low tide.

Finding them is simple if you're as clever and well-equipped as a raven.

Each fish is a high-fat, high-energy snack.

Perfect food for eagle chicks too.

But this dad hasn't got the hang of digging them up.

There is another way.

He looks to cash in on the raven's success...

..and launches a raid.

In a split second...

..the raven loses half his catch.

One for him.

The rest he'll take back to the nest.

The female spends most of the day brooding her new hatchling,

but the return of her mate gives her an opportunity to stretch her wings.

And a chance for him to feed his progeny for the first time.

Last year's chick was weak and died after only two days.

This one seems stronger.

But it will need feeding at least eight times a day.

If this family are to avoid another tragedy,

the next few weeks are critical.

Spring in Alaska arrived with the melt...

..and triggered a season of rapid transformation.

THUNDER

The race was on to start a family.

Sandhill cranes saw eggs become chicks.

Dippers saw chicks become fledglings.

Musk Ox calves survived the school of hard knocks.

And two young bears learned to cope without mum.

Spring saw many flourish

but did it all come too late for the Arctic foxes

to raise a family of their own?

Next time, summer is coming...

..and new challenges begin.

Youngsters must grow up,

fatten up...

..and stay out of danger.

Summer is when the clock starts ticking

and the countdown to winter begins.

Animals must make the most of the good times

or it'll all be for nothing.

BIRDS CHIRP

Subtitles by Ericsson

Alaska. America's last frontier...

..and greatest wilderness.

Immense.

Unspoiled.

Awe-inspiring.

Home to half the world's glaciers...

..America's highest mountains...

..and ice sheets that stretch to the North Pole.

Inhabited by the world's largest land predators...

..herds of ancient beasts..

and leviathans from the deep.

The land is hostile, but its richness and diversity

is unparalleled in the northern hemisphere.

All must be resilient and adaptable if they're to survive

a year in the wild of Alaska.

Summer has arrived.

With the northern hemisphere tilted towards the sun...

..days are long, the air is warm...

..and snow has been banished from all but the highest peaks.

The far north is bathed in gold, even at midnight.

BIRD SQUAWKS

But things are about to change.

Animals are in a race against time.

What they do now,

could mean the difference between life and death

when snow and ice return.

The ebb and flow of the seasons is mirrored on the coast of

Katmai every day.

Where three million acres of wilderness meets

the Pacific Ocean in a deep crescent known as Hallo Bay.

Here, tides rise and fall for seven sandy miles.

Leaving opportunity for brown bears in their wake.

It's rare for a mother bear, to bring cubs so small to the bay.

But she's hungry... and combs the beach for food.

Her cubs are just six months old and more used to the safety of their

den than wide open spaces.

Everything out here is new...

EAGLE SQUAWKS

..and very scary.

Bald eagles aren't a threat but there are good reasons to be jumpy.

Many brown bear cubs die in their first year.

And many are killed by other bears.

Right now the coast is clear.

It's a chance for

this female to tackle the other big cub killer... malnutrition.

So far mum's milk has provided her cubs with all of their nutrients.

But a recent growth spurt has fuelled an urge to try solid food.

Crabs, clams, almost anything will do.

But the search is futile.

The cubs do their best to help.

They're learning fast, but they're hungry.

What this family need is a feast of epic

proportions.

And there's one heading their way.

Over 300 million salmon are coming home...

..to spawn in the same rivers that they were hatched in.

Once they hit shore and head upstream many will

become food for bears.

But there's no telling when they'll arrive.

Until then food is scarce. And this family will grow weaker by the day.

700 miles north-west of here and just 40 miles off the

Russian coast summer visitors to St Lawrence Island have

already arrived.

Every year, over three million auklets nest in colonies

along the coast.

They look for a suitable spot to lay a single egg.

Unaware that there are predators waiting.

It's midsummer in Alaska.

And on St Lawrence Island, an arctic fox is on the prowl.

The coast is alive with the clack and clamour of over

three million auklets.

It's just what he's been waiting for.

St Lawrence is smothered in snow for almost eight months a year.

With auklets absent, food is hard to come by.

If there's nothing to scavenge

foxes are forced to hunt for voles under the snow.

It's a great deal of effort, for very little reward.

But now auk is back on the menu.

And he has a new camouflaged coat to hunt them in.

Eggs are good. But an adult bird is even better.

His mate is pregnant and she needs a regular

supply of protein.

They can't rely on speed in this terrain.

Only stealth will net them a meal.

But there are eyes everywhere.

And when a few birds panic, it sets-off a chain reaction.

Once their chicks hatch, the auklets won't be going anywhere.

FOX CALLS

The foxes need to bide their time...

..keep their distance...

..and wait for the auklets to settle in.

Alaska has over half a million square miles of wilderness.

It's big enough to fit two Great Britain's in, end to end.

One thousand miles south-east of St Lawrence Island

on the pacific coast of south-east Alaska...

..summer is in full swing.

Warm air frees billions of gallons of water from glaciers.

Feeding a multitude of rivers and lakes.

There's more wood here than in any other forest on Earth.

Good news for a family of beavers.

Yearlings help their parents with chores.

This family has enjoyed a surplus of food all summer.

But now, they must prepare for lean times ahead.

They harvest as many green sprigs as they can...

..ferry them across the pond...

..dive, and store them underwater.

Down here, they'll stay fresh. Providing food, even

when the pond is frozen over.

Bigger branches are used to reinforce the lodge.

This is their fortress. And it needs to be strong enough to keep

predators out.

Beavers rely on deep water for safety.

So, to ensure there's always plenty of it they build dams.

The rush of water is like an alarm bell to a beaver.

Holes must be plugged up.

Timber is gathered from the surrounding forest.

And by clearing forest, they create new habitat.

Grass grows in patches of light where trees once stood.

Providing Sitka deer with tender stems to nibble on.

Pollarded willow put out new shoots within easy reach of a porcupine.

She can devour up to a pound of leaves every day.

But not all beneficiaries of

the beavers' building work are so benign.

Black bears also forage here.

Plants make up the bulk of their diet. But the scent of beaver

could prove too good to ignore.

Forays onto land are unavoidable.

The further they go, the bigger the risk.

But beaver security is always on high alert.

The alpha female sounds the alarm...

..and sends every beaver within earshot bolting back to the water.

Soon, it's like they were never there at all.

Black bears prefer to eat meat, but they have

plenty of other options.

Unlike the bigger brown bear, they evolved in these forests.

Their ancestors were consummate climbers.

And it's a skill that's been handed down.

Cubs can climb as soon as they can walk.

It gives them access to forage that other animals can't reach.

Come autumn, there'll be a glut of nuts and berries to choose from.

Until then, aspen pods will curb their hunger pangs.

If they can keep hold of them.

It's only a snack. But mum knows where more

emergency rations are.

She'll need to make full use of this forest if her cubs are going

to make it through until autumn.

About 17 million acres of forest cloaks Alaska's southern coast.

Where over 60 inches of rain fall annually.

Many plants are green here, all year round.

But summer adds a splash of colour to the undergrowth.

Plants take advantage of the long days...

..and burst into bloom.

Drawing in pollinators, from both near... and far.

At just three inches long and weighing little more than a penny

this female rufous hummingbird has

flown over 3,000 miles from Mexico to nest in south-east Alaska.

No other hummingbird breeds this far north.

Males play no part in raising their young.

She's raised this chick all on her own.

Hatched from an egg the size of a jelly bean

in just three weeks she's already outgrown the nest.

They require more than their own body weight in nectar each day.

And if this chick is to fledge successfully, the next

24 hours are critical.

It's July in Alaska...

..and the forest resonates with the drone of tiny wings.

Rufous hummingbirds must soon depart for their wintering grounds

in Mexico.

But the trip of almost 3,000 miles can't begin...

..until this year's youngsters have fledged.

By beating her wings at up

to 60 times a second, a chick warms up for her maiden flight...

..whilst her mother hunts for more fuel.

Nectar is a precious resource...

..that other hummingbirds aren't always willing to share.

But this mum has a cunning plan.

There are sapsuckers nearby.

They're also busy raising chicks.

Adults drill into trees, to release sap which they

lap-up... along with any insects stuck in it.

It's rocket fuel for growing chicks.

So when no-one's looking...

..the hummingbird launches a raid.

She must drain as many wells as she can, before the sapsucker returns.

Hovering takes the youngsters a little while to master.

But in order to fledge she just has to manage a straight line.

The chick has a few more weeks to strengthen her flight muscles...

..before she flies all the

way to Mexico on her own.

At the end of July, summer turns a corner.

South-west Alaska loses half an hour of sunlight every week.

Temperatures plateau...

..and start to drop off.

Animals sense the change.

Bear cubs are born with very little fat.

But they need a thick layer of it in order to survive hibernation.

Their mum's milk is rich but it's not enough on its own.

The whole family needs solid food.

Their fate, and

the fate of all brown bears in Katmai, depends on the salmon.

Pacific salmon make one of the most incredible journeys on Earth.

Every year, over 300 million of them

head towards Alaska's shores.

Often travelling thousands of miles to spawn in one of 12,000

wild rivers.

The salmon must find the one that will lead them to their birthplace.

With a coastline that stretches for 40,000 miles

their journey demands stamina and remarkable navigation skills.

Predicting where they'll turn up first is impossible.

All the bears can do is wait.

Mum checks for signs but there's barely a ripple.

Her cubs are eager to play.

But their mum has put all her spare energy into making milk.

For her, the salmon run can't come soon enough.

But instead, her worst nightmare arrives.

A big, hungry male.

He won't catch anything here.

And he's a real danger to the cubs.

It's rare but when males are under pressure they can resort

to cannibalism.

She'll protect her cubs furiously.

But there's no fish worth fighting for here.

Better to be of sight and out of mind.

In summer bears leave their favourite stomping grounds

and move towards shallow creeks, where salmon will be easy to catch.

Leaving much of Katmai deserted.

Solitude is what this mum needs.

The cubs learn by copying her.

She checks for danger. And so do they.

There are no bears here...

..but she catches wind of something.

All she has to do is track it down.

The cubs sense her excitement.

Finally, it's a salmon.

The first the cubs have ever seen.

Self-preservation kicks in.

Fish like this provide essential

energy that bear cubs can convert into fat.

One fish won't feed a family of four.

But nearby, there's a sign that it could be the first of many.

Just 100 miles from here,

but on the other side of the Alaska Peninsula lies Bristol Bay...

..where a deadly combination of high winds and high tide has left

an early run of salmon stranded.

Whimbrels are first to discover the bounty.

Tender fish

is an easy treat for birds more used to probing the sand for crustaceans.

Further up the bluff is a colony of Arctic ground squirrels.

Most females have pups.

They're over six weeks old, fully weaned and can't

rely on mum for food any more.

But they must double their weight or they won't survive hibernation.

Males gather grass to stockpile in their burrows...

..whilst youngsters munch through as much seed as they can.

Nothing is wasted.

Even the skin of a dead relative is valuable extra protein.

They don't like to wander too far from their boltholes...

..but they can smell fish in the air.

It's an opportunity too good to miss.

They need to build-up their fat reserves...

..and oily fish has a lot more calories than grass seed.

Come autumn, young females will

settle down to sleep with their mothers.

But young males must first find a territory of their own.

They're going to need all the energy they can muster.

And only the fittest squirrels will survive.

Whilst a twist of fate has landed the squirrels with welcome feast...

..it's nothing compared to what's just arrived over 800 miles

away on the other side of the gulf.

After four years out in the open ocean

thousands of Chum salmon have finally

arrived in south-east Alaska.

Nothing will stop them now.

Their spawning ground is in the mouth of a river,

just beyond the high-tide line.

They don't waste any time.

Each female makes a small pit in the gravel...

..where she'll lay up to 4,000 eggs.

Once they've been fertilised...

..she covers them over...

..and stands guard until she's too weak to continue.

A voyage that's all about life, ends in the death of the salmon.

As soon as they enter freshwater, salmon stop eating.

Their stomachs slowly disintegrate.

GULL SQUAWKS

And they finally succumb to the inevitable.

All the gulls have to do is wait.

Whilst the journey is over for some travellers

for others, the advance continues upstream.

Pink salmon spawn further inland...

..where predators lurk, ready to pounce.

It's the end of July...

..and a big wave of salmon has just hit Alaska.

Thousands of fish fight their way

upstream, driven by an irresistible

urge to reach their spawning grounds.

This is what brown bears have been waiting for.

It may be this adolescent's first season away from his mum.

The perfect opportunity to hone his hunting skills...

..and take advantage of the glut of food.

But his lack of experience quickly shows.

Many young bears copy their mother's fishing methods.

In his case it's the dash, splash and grab technique.

It's one he's yet to master.

Perhaps gaining some height will help?

Apparently not.

The snorkelling method is another way to catch a salmon.

Especially when they're in such large numbers.

But seeing them is one thing.

Catching them is another.

The deep water isn't helping. It gives the salmon an easy getaway.

Eventually he spots a carcass floating downstream...

..only to discover that the best bits have already been eaten.

He craves fat...

..and the fattiest bits on a salmon are the skin, brain and eggs.

With so much food about, anything substandard is quickly rejected.

Eventually perseverance pays off...

..and he nets himself a large female pink salmon.

Flush with success he goes for another...

..and almost loses the first.

Perhaps he should learn to finish what's on his plate,

before going in for seconds.

Summer arrived with the auks...

..and filled Alaska with light...

..warmth and improving prospects.

It was a season rife with possibilities.

Where hard work and persistence paid dividends.

And where the death of one generation brought hope to another.

But now, change is in the air.

Autumn is coming.

Next time...

The salmon season goes into overdrive.

And animals battle it out for a share of the spoils.

Young must come of age before winter puts Alaska in lockdown.

With freezing temperatures imminent it's do or die for many

predators... including the biggest killer of all.

Subtitles by Ericsson

Alaska.

America's last frontier...

..and greatest wilderness.

Immense.

Unspoiled.

Awe-inspiring.

Home to half the world's glaciers,

America's highest mountains

and ice sheets that stretch to the North Pole.

Inhabited by the world's largest land predators,

herds of ancient beasts

and leviathans from the deep.

The land is hostile,

but its richness and diversity

is unparalleled in the northern hemisphere.

All must be resilient and adaptable

if they're to survive a year in the wild of Alaska.

Autumn is the season when Alaska's wildlife

must make the final preparations before winter.

Summer saw the groundwork done by the adults.

Time is now running out for the youngsters.

Days are growing short.

Snow and freezing temperatures are imminent.

Many young must soon start their lives alone.

Those not prepared will perish.

Nowhere is the struggle for survival more apparent

than in the Katmai Wilderness Area.

Three million acres of wildness.

Home to the highest density of brown bears in the world.

They're here to gorge on the millions of salmon

that are coming to the end of their epic migration.

A journey that takes them back to the very same

rivers where they were born.

Having travelled thousands of miles to spawn,

the final leg is by far the most dangerous.

Brown bears need to build up a thick layer of fat for hibernation.

The salmon are their salvation.

Competition is fierce.

But the salmon don't only attract bears.

Katmai is also home to American Wolves.

This adult female finds a good spot.

And starts to hunt.

But the salmon are too quick for her.

Then she gets company.

A mother bear is also actively hunting the same stretch of river.

Never stand in the way of a mother bear...

..especially one with two hungry cubs to feed.

The wolf may also have young.

She can't risk getting injured in a fight...

..so reluctantly gives up her spot.

Back in the spring,

these two cubs emerged from hibernation.

They scraped by on a diet of clams and milk.

If they're going to survive winter, they must start

packing on the pounds.

Their mother replaces the wolf on the bank.

One lunge and she does what the wolf couldn't.

The lump on the salmon's back identifies it

as a male Humpy, or pink.

She quickly devours it without sharing

and moves on,

the cubs dragging along behind...

..leaving the wolf to pick up the scraps.

She now wants to fish the prime spot at the river mouth.

But it's taken

by a 1.000 lb male,

over 200 lbs heavier than her.

Upstream, the river is deeper, making fishing near impossible.

She must feed the cubs...

so puts herself in danger.

A growl

and a charge...

..but he's not budging.

Undeterred, she grabs a fish...

..which draws in the big male.

Fortunately, there's plenty of fatty salmon in the river to go round.

But this won't be the case for long.

She must reap the harvest while she can.

Brown bears are not the only ones fishing in the Gulf of Alaska.

Humpback whales have returned.

They've adapted their hunting technique especially for here,

and they're hungry.

It's autumn

and one of Alaska's most iconic migrants has returned.

These humpback whales spent the winter

in their calving and mating grounds off Hawaii and the Gulf of Mexico.

Following their 3,000 mile migration,

they've arrived at their feeding grounds in the Gulf of Alaska.

They've not eaten for six months,

so waste little time.

They have a unique way of fishing,

one not seen anywhere else in the world.

Herring shoal here in their millions,

for protection from seals and Steller sea lions.

But this shoaling actually works against them

now the humpbacks are here.

Once the whales have their sights on a shoal,

they dive.

And start to sing...

..as loud as a jet aircraft.

The sound panics the herring

and drives them up towards the surface.

One whale starts blowing bubbles

surrounding the herring...

..a vertical barrier as high as a four-storey house,

which the herring won't swim through.

The trap is set,

the whales move in for the kill.

Together, they devour thousands of fish at a time.

At over 45 feet long and nearly 30 tonnes,

they have quite an appetite,

so quickly regroup to do it all over again.

This North America coast is the only place in the world

where humpbacks combine bubble netting with singing.

They've learned that by engaging their feeding siren,

they can turn these waters into the perfect place to hunt.

500 miles north-west of the whales,

on the northern edge of the Gulf of Alaska

lies Prince William Sound.

3,500 miles of rugged coastline...

..home to one of the highest concentrations

of sea otters in the world.

Here because these nutrient rich waters provide them with an endless

supply of food, which is vital for their survival...

..as unlike most marine mammals,

sea otters don't have an insulating blubber layer.

Instead, they burn calories to keep warm.

To do this, they must eat a quarter of their body weight every day,

so regular feeding is essential.

They can dive for four minutes at a time...

..feeding on clams, snails, starfish and sea urchins.

But body heat alone is not enough to survive out here,

so sea otters have the added protection

of the thickest coat of any mammal.

Up to one million hairs crammed into every square inch

compared to the average human,

that only has 100,000 hairs on their entire head.

But looking after this coat takes time and effort,

so when not foraging, they spend hours grooming...

..drying their fur...

..removing salt and excess oil.

Fluffing it up traps air,

providing four times as much insulation

as the same thickness of fat.

Essential, as it's the only thing that lies between them

and the freezing cold Alaskan water.

The next six months are the most difficult,

especially for mothers with pups.

Calm days will soon be replaced by storms,

disrupting feeding,

increasing the chance of separation and drowning.

One in five sea otter pups won't see their first birthday.

Starvation is the biggest killer.

They must stick close to Mum if they're to survive.

As autumn advances, parental guidance is crucial.

But for some it lasts much longer than just one season.

Over the past three months,

this mum has kept her two cubs secreted away in the forest.

Unlike brown bears, black bear cubs don't rely

on a diet of salmon for their survival.

Mother's milk and vegetation is more than adequate.

But Mum can't resist the lure of a salmon lunch

and it's the best way for her to get nutrition to produce milk.

She leads them to the river for the first time.

They're understandably cautious.

Brown bears also fish here

and pose a serious threat to the cubs.

She expertly catches a fish...

..then slinks back into the safety of the forest to feed.

They'll spend the next three years by her side

before heading out on their own.

That break-up can be traumatic...

..with youngsters sometimes reluctant to leave.

This three-year-old cub nestled in the rocks

waits expectantly to be fed.

His mother rebuffs him.

A clear sign it's time he started hunting for himself,

as she can no longer catch enough fish to feed them both.

He's not going to give up without a fight.

His begging becomes more aggressive.

But she stands her ground.

Eventually he gets the message...

..and the family breaks up.

Just 60 miles north of the bears in the Tongass National Forest,

another youngster is about to take a leap into the unknown.

It's mid-Autumn in the Tongass National Forest.

And a very big day for a young bald eagle.

He hatched in early June.

Since then, his parents have worked tirelessly.

And he's grown quickly.

His fluffy white down turned grey.

He grew flight feathers.

And learned to feed himself.

He was fully feathered in 56 days...

..and almost as big as his parents.

With age came a change in attitude.

He no longer waits to be fed.

And drives them off to fetch more.

His parents continued to make food deliveries.

But didn't hang about.

Now, he's starting to explore his environment.

Stretching his wings to strengthen his flight muscles.

He's about to make his maiden flight.

A huge leap of faith.

The ground being 150 feet below.

After a brief hesitation...

..he's off.

He doesn't go far...

..returning to snatch food from his parents.

Survival is instinctive.

Good manners are not.

Parental duties over, they leave...

..forcing the youngster to start looking after himself.

Just as the first autumnal storm approaches from the Arctic.

On the island of St Lawrence,

40 miles off the Russian coast...

..three Arctic Fox cubs play.

They're only 12 weeks old.

This den site has been their refuge since they were born.

But not for much longer.

They've already grown their thick adult coats.

And now resemble Mum...

.and Dad.

They're perfectly camouflaged amongst the rocks.

At this age, life is simple.

They pass the days play fighting...

..which helps improve hunting techniques.

Strength and speed.

The braver they become, the further they venture.

The more adventurous of them, even attacking and killing fungi.

All of which is vital.

Their lives have reached a critical point.

The nesting sea birds are starting to migrate.

Their parents are no longer returning with food.

A clear sign that it's time for them to start life alone.

One by one, they drift away.

And the den lies quiet

until next year.

It's not just on St Lawrence that food is drying up.

In Katmai Wilderness area, the salmon run is starting to dwindle...

..heaping pressure on this mum and her three yearling cubs.

She watches as bears downstream catch the last of the salmon.

But it's too dangerous for her to take her cubs into the melee.

Nor can she leave them alone on the beach.

She's trapped upstream...

..while the others hold the best fishing spots.

Her cubs are hungry.

She must revert to plan B.

Low tide gives her access to mussel beds and razor clams.

Slim pickings, compared to the salmon the other bears are catching.

But every morsel is vital...

..if they're going to survive their first Alaskan winter.

The sun tracks low across the autumn sky.

Winter is fast approaching.

North facing mountain slopes

won't feel the warmth of the sun's rays until spring.

Shaded rivers are already coated in frost.

In the Chugach National Forest,

in Alaska's south,

Coho salmon have at last reached their spawning grounds.

They haven't eaten since returning to the river,

and are now close to death.

But they still have one final act before they die.

And that is to breed.

The females dig deep depressions in the gravel.

Called a redd, this will be the nest for her eggs.

The males line up, waiting for the moment she lays.

Then they will rush in to fertilize them.

They may only get once chance...

..so fights are frequent and violent.

Even the largest males carry severe injuries.

Half starved, their bodies are in a state of collapse.

Wounds fester.

But still, they battle to keep control of a female.

Their attention elsewhere leaves them vulnerable to attack.

At around 10lbs,

this Chum salmon weighs roughly the same as the eagle.

It's far too heavy to carry away...

..so he drags it into the shallows.

But he's not alone.

And stealing a meal is easier than catching one.

As winter draws ever closer...

..and food becomes scarce...

..tensions rise.

But Alaska still has one last offering.

A spectacle that throws a lifeline to eagles

from across much of north America.

Late October.

Clear skies reveal the Aurora Borealis.

Temperatures drop...

..chilling both land and water.

Soon, most of Alaska's rivers will freeze completely...

..locking away vital food under a thick layer of ice.

But not here.

The Chilkat River in southeastern Alaska is different.

Upstream, water trapped underground is warmed.

It slowly percolates up...

..and seeps into the river.

Keeping a five-mile stretch of the Chilkat free of ice.

Even during the coldest winter.

The warmer water means salmon can spawn here later.

This attracts eagles from thousands of miles away...

..for one final feast before winter hits.

At 3,000 strong, this is the world's largest gathering

of bald eagles.

Such a glut of food means there is little reason to squabble.

And a chilling calm descends.

The salmon pay the ultimate price.

They've done what they came all this way to do.

Their cycle of life is now complete.

Every year, 300 million returning salmon

bring life to much of Alaska.

Even in death, they fertilize the land along river banks...

..nourishing the vegetation...

..providing food for grazers...

..that in-turn feed predators.

Nutrients from far out in the Pacific Ocean...

..creating life hundreds of miles inland.

With winter closing in...

..Alaska's wildlife must steel itself...

..ahead of seven months of ice and snow.

But it's these extreme conditions that have helped transform them

into some of the most resolute creatures on the planet.

So that when spring finally returns...

..they'll be ready to face another year in the wilds of Alaska.

Subtitles by Ericsson