Original subtitles

This is The Americas,

an extraordinary journey across Earth's great supercontinent.

The widest variety of life on the planet.

The untold story of our home.

Tonight on The Americas...

An adventure through the vast wilderness...

of Alaska and Canada.

Here, winter's beauty...

disguises her dangers.

But when snow and ice retreat,...

the North reveals landscapes...

teeming with life.

All animals here must endure or escape...

the extreme swing of the seasons...

as the North changes before their eyes.

At the top of the continent lies a frozen frontier,...

larger than the rest of the United States.

The night reveals just how few of us...

live up here.

From the East Coast to West,...

three million square miles...

of wilderness.

A late November dawn in Canada's Hudson Bay.

By now, this place should be frozen solid.

But this year, it's still too warm.

And for a polar bear,...

that's a problem.

He's a seal hunter.

But those seals...

are way out on the sea ice.

And right now,...

the ice still isn't thick enough to walk on.

He's forced to wait until it really freezes up.

A few dead leaves won't fix an empty stomach.

In just ten years,...

the bear population has fallen by over a third.

Waiting for winter...

is becoming a dangerous game.

While polar bears occupy the shore...

the forest belongs...

to wolves.

Winter is their prime hunting season...

when the deep snow slows down their prey.

A moose would feed this 17-strong pack.

As a second moose is flushed out,...

the pack splits.

It's a costly mistake.

Nine out of ten hunts fail.

And with this blizzard rolling in...

They've missed their chance.

But that doesn't mean they'll go hungry.

In this weather,...

the exposed coastline will claim casualties.

The pack must find them first.

They're nervous.

This is not wolf territory.

A dead polar bear is an unexpected feast.

They must feed quickly.

This is no-man's-land.

It's now that Canada's top predators...

come face-to-face.

As winter descends on the shoreline of Hudson Bay,...

the rulers of the forest...

confront a king of the ice.

The wolves have strength in numbers.

But at 800 pounds,...

this bear has a massive weight advantage.

And this time, that's what counts.

As winters arrive later,...

polar bears trapped on the shore...

are growing more desperate.

But the fortunes of all who live here...

are about to change.

For six months,...

winter buries much of the Fr North.

Now the wolves will get their kill.

And Hudson Bay...

is finally frozen solid.

For polar bears,...

the path to seal hunting grounds...

is clear, at last.

The North's extreme seasons are caused by the tilt of the Earth.

For months, the Arctic is plunged...

into darkness.

But still, the sun makes its presence felt.

A magical display.

The aurora borealis.

These are the traces of a solar storm...

as radiation from the sun...

reacts with gases in the Earth's atmosphere.

Green for oxygen,...

purple for nitrogen.

In Canada's Yukon forest,...

temperatures in early February...

drop to minus 30.

There's so little food in winter,...

you're best to either leave...

or hide away until spring.

Unless...

you're a snowshoe hare.

Wide awake and perfectly at home...

here in the frozen forest.

They survive the winter on nothing more than twigs...

and bark.

But they're smart,...

only picking plants that provide the most protein.

He's about as tall as the snow is deep.

But he's got something that makes living here...

seem like a walk in the park.

Enormous webbed feet.

They're built-in snowshoes,...

so he's always ready for a sprint start.

And he needs to be.

He's not alone in these woods.

A Canada lynx.

In winter, a lynx has one main source of prey.

And he's... it.

His ears rotate independently,...

always listening out for the ominous crunch...

of footsteps in the snow.

Spotted.

Lynx are agile hunters,...

though not quite as light on their feet...

which buys the hare precious seconds.

But no hiding place will be safe for long.

Deep in the Yukon,...

a snowshoe hare freezes...

not from cold, but from fear.

Canada lynx don't give up on dinner easily.

So escape must be timed to perfection.

With the help of those snowshoes,...

he can hit a top-speed of 30 miles per hour.

A clean getaway.

And that's unusual.

Canada lynx rarely miss.

This is one lucky bunny.

When the breeding season arrives,...

there will be more hares to take the heat.

Until then,...

he'll need to stay on his toes.

By late winter in Alberta, 12,000 feet up,...

the towering mountains of the Rockies...

are coated in layer upon layer of snow.

In places, more than 20 feet deep.

A playground for millions of visitors every year.

But be careful.

The spring sunshine weakens the vast shelves of mountain snow...

priming one of nature's most destructive events.

Avalanche.

A million tons of snow and ice...

race downhill at speeds over 100 miles an hour.

More than 2,000 avalanches are reported in the Rockies every year.

Many more go unwitnessed.

As the planet warms,...

avalanches are becoming ever more...

unpredictable.

In the shadow of the Rockies,...

even in late April,...

snow still falls across these vast grasslands.

But make no mistake.

Spring has arrived.

And so have a group of determined dancers.

But will all this be enough to melt the heart...

of an ice queen?

Standing high over the plains of Alberta,...

the Rockies channel warm winds down their eastern flanks,...

winds known as "snow eaters".

As they descend, they heat up,...

raising the temperature of the plains below...

by as much as 20 degrees.

Out on the prairies, pretty much everyone...

is an early riser.

None more so than sharp-tailed grouse.

They're here to catch the very first rays of sunshine,...

but they can't resist any spotlight.

- ♪ Gimme some lovin' ♪ - ♪ Gimme, gimme some lovin' ♪

♪ Gimme some lovin' Every day ♪

The males gather every April for a mating dance-off.

The females are the judges,...

and the prize is...

well, bet you can guess.

As dawn breaks, it's show time.

Stomping their feet 20 times per second...

with a shake and a shimmy,...

it's all about seduction.

They look their best at this very moment.

And they know it.

She'll be looking for style.

And stamina.

Very nice.

He's not bad either.

The choice is bewildering.

But without a clear winner,...

fights break out on the dance floor.

With all this testosterone flying around,...

she's losing interest.

They seem to want the fight more than the prize.

The males need to up their game.

By June,

under a sun that no longer sets,...

even the most stubborn snow melts away...

to reveal lush grasslands.

New life transforms the Frozen North.

This is America's largest wildlife refuge,...

30,000 square miles of Alaska.

The Arctic Refuge.

In summer, one animal dominates these plains.

Caribou.

You might know them as reindeer.

They're nomads,...

following the retreating snowmelt,...

sometimes for a thousand miles.

The longest land migration in the world.

Every summer, for centuries,...

caribou have been coming here to have their calves.

This little male is only three weeks old.

But he can already run faster than an Olympic sprinter.

It's easy to lose track of whose mom is whose.

Wanting to explore...

can get you into trouble around here.

Anyone who can't keep up with the herd...

will be left behind.

But their unique calls and scent...

usually mean they can find each other.

Come wintertime, he will be independent.

But until then,...

Mom is his whole world,...

whether she likes it or not.

As the herd eat their way through more than a thousand tons...

of tundra grasses every day,...

they move further west across the coastal plains.

But hunger is driving them towards danger.

The snow that blanketed the Frozen North...

now descends from the mountains...

as billions of gallons of meltwater,...

channeled into raging torrents,...

cutting across the caribou's path.

These rivers are deeper and faster than ever before.

And the feeding grounds lie on the other side.

This crossing is more than a young calf is ready for.

But survival depends on it.

The current takes them by surprise,...

sweeping him off his feet.

This mother now has a tough choice to make.

On the riverbanks of Alaska's Arctic Refuge,...

this caribou mother scans the water...

for any sign of her missing calf.

The herd is moving on.

Her instinct to follow them...

is just too strong.

Downriver,...

the calf is still alive.

He has a fighting spirit,...

but he's exhausted.

Mom's nowhere to be seen.

As the herd slows down to feed,...

all a lost calf can do is try to catch up.

Female caribou rarely adopt lost or orphaned young.

Mom recognizes a familiar bleating.

Reunited.

You have to grow up quickly in the Far North.

These ancient routes will soon be ingrained in his memory.

His destiny is to endlessly wander this vast...

American tundra.

As summer warms the North,...

hundreds of these swollen rivers...

carry soil and nutrients from the land...

to the sea.

And for some,...

this becomes a time of plenty.

In July, on Alaska's isolated Round Island,...

a strange sound is carried on the wind.

Just listen.

This is the surprising song...

of male walruses,...

known as "chiming".

It's made by pockets of air in their throats.

Usually, they sing to impress females during the winter mating season.

But there's no ladies in sight.

Which probably suits the ladies just fine.

On Alaska's warm summer evenings...

Perhaps this is nothing more than their very own lullaby.

For walruses, the short summers are all about downtime.

But in the shallows of Alaska's mainland...

there is no time to rest.

Pink salmon gather at the starting line of a race...

that will test them to their limits.

Driven by an urge they cannot ignore,...

salmon arrive at the entrance of the very same stream...

in which they were born.

Now, two years later,...

it's their turn to breed.

All 200 million of them.

This female is carrying at least 2,000 eggs.

Returning to the same spot in which she was born...

will give her offspring the best chance of survival.

But ahead of her...

lies a killer assault course.

She must succeed...

or die trying.

Prince William Sound, Alaska.

As the tide races out,...

countless pink salmon...

are waiting.

The scent of their spawning grounds grows stronger.

Now it's a race to cross the shallows...

before the tide cuts them off.

One wrong turn and it's game over.

For gulls,...

the banquet has begun.

They can be picky at this stage...

only selecting the most tender flesh.

This female has made a serious error...

and is now dangerously exposed.

Her determination seems to confuse her attacker.

This is only the beginning.

Every salmon is now on borrowed time.

From here on out, they barely eat or rest,...

as they forge upstream.

This journey takes a grim toll,...

as their bodies begin to shut down and decay,...

some faster than others.

Finally, they arrive at their spawning grounds,...

but it's not over yet.

This female needs to construct a shallow nest,...

known as a "redd".

She flicks away fine sediment...

to prevent her eggs from being smothered.

She will fiercely defend her nest from other females.

By now, some males look like the swimming dead.

They're "zombie" salmon,...

desperate to mate before they die.

Kind of gross.

After all she's been through,...

she's not going to settle for anything less than perfect.

Males fertilize eggs in as many redds as possible,...

but this will be her only chance.

She will only release her eggs when she's ready.

It's the moment that will seal her fate.

Spawning and dying on the same stretch of river as her mother...

is a female salmon's destiny.

Though their journey ends here,...

these salmon leave behind millions of eggs...

that will become the next generation.

Life,...

dictated by the seasons.

In just two months, winter returns.

Some begin the long trek south.

Others surrender to many months in the den.

But there are those who are perfectly at home...

in this snowbound world.

A place...

full of magic.

One thing is certain here in the Frozen North...

nothing stays the same...

for long.