Original subtitles

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The Yukon is a true wilderness...

One of the last on earth.

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At its heart runs a river,

where salmon make an epic journey to reproduce...

Only to face powerful predators,

whose survival depends on this seasonal migration.

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It's a place where giants battle...

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And surprises hide in the smallest places...

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Where the primeval mountains

tell the story of our planet.

Carved in stone...

By the power of water...

And the violence of ice.

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This is the Yukon, a place of rebirth...

And extraordinary journeys across an imposing land.

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A land now under threat

from rapid and unprecedented change.

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It's early fall.

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A September sun rises low over the Chilkat Mountains.

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There's frost in the air.

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A solitary sockeye salmon is almost home,

desperate to reach the same patch of river

where it was born...

The spawning beds where it will lay its eggs.

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It's traded its ocean silvery blue for a fiery red

to attract a mate.

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From the North Pacific, salmon of several species

climb the rivers into the interior

in a series of migrations,

swimming against the strong currents and

leaping many rapids.

It's an extremely tough journey,

and the fish need an enormous amount of strength --

and luck -- to make it home.

And winter is closing in.

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Theirs is the longest freshwater migration

of any salmon in the world...

Almost two thousand miles

up the mighty Yukon River.

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The Yukon River is the third longest waterway

in North America.

Starting in the Coast Range Mountains,

it flows almost 2,000 miles northwest through

the Yukon Territory and across Alaska

towards the storm-tossed Bering Sea.

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The Yukon watershed is huge...

over 320,000 square miles.

That's 25% larger than Texas.

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As it crosses the Yukon Territory,

it carves its way through narrow channels and

meanders through wide-open valleys.

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The salmon are determined...

But tired.

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The energy expenditure is incredible.

After they leave the sea, they never eat again.

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It's a journey of life and death.

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This grizzly has been waiting for weeks...

Along with many others who line the shores.

A gauntlet of sharp claws and gaping jaws.

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And they finally get their chance.

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The bears need an enormous amount of food

to ready for the long winter ahead,

and the egg-laden salmon

provide a much-needed feast.

Only the luckiest salmon make it past the bears.

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In the mountains along the river,

herds of Dall sheep roam the peaks and crests.

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The lush days of summer are over.

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In autumn, grass is already scarce.

And though these sheep are expert foragers,

it's time to move on.

The ewes and their lambs slowly wander

from their summer pasture high on the mountains,

to their winter grounds at lower altitudes

on windswept, south-facing slopes.

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But all that is about to change.

The annual rut is about to begin.

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The ewes are en route to meet up

with a band of male sheep --

the only time in the year

when males and females meet.

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It's a journey fraught with danger...

Predators lurk everywhere.

But the sheep are well equipped to deal with the threats.

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Their hooves are perfectly adapted to the tough terrain.

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Their flexible toes quickly adjust to the

uneven surfaces of the mountain.

Should a wolf or bear appear,

they're capable of dashing across the rocks to escape.

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But if attacked,

these gentle-looking animals are known to

butt wolves over the edge of cliffs.

Within two weeks of their birth,

the lambs started nibbling on

the sparse mountain greenery.

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Now, at four months of age,

they're close to being weaned.

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But some don't want to give up on the sweet milk just yet.

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To survive, the lambs have to grow rapidly.

The coming winter will be brutal.

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40-50% of lambs won't make it through.

(bleats)

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Icy death is a tough reality in the Yukon.

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The Yukon is home to some of the most

majestic mountain ranges on earth.

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This is the upper end of the massive American Cordillera...

A rocky spine...

The backbone of the Americas...

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Stretching from the Arctic...

All the way to Tierra del Fuego at the tip of South America.

It encompasses the Coast Range Mountains,

the Rockies, the Sierra Madre

and the Andes.

The North American end of these ranges

started forming around 200 million years ago...

Born when the continents were young

and undergoing dramatic, violent change.

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The North American and Pacific plates collided,

causing the earth's crust to fold and bend,

sculpting the landscape with immense tectonic energy.

Volcanoes erupted through fissures in the crust,

spewing lava and ash.

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Over millions of years, this volatile mass

of molten rock cooled and hardened.

The majestic mountains of the Yukon are

silent monuments from that time of transformation.

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Deep in the interior, further upriver,

the grizzlies are still waiting for the salmon to arrive.

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In the meantime,

the bears get their sugar fix.

While they wait for the main course,

dessert is everywhere.

Cranberries... Blueberries...

Cloudberries...

But the bears need protein.

Protein the salmon can best provide.

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In this remarkable land where everything seems big,

the bears are not.

Grizzlies here only grow to about

two thirds of what their relatives

further downstream achieve...

about 600 pounds for a male Yukon grizzly

versus over 880 for a coastal Alaskan male.

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The grizzlies aren't the only ones waiting

for the fish to finally get here.

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Bald eagles also know the salmon are coming.

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(chirping)

While the grizzlies are smaller here,

bald eagles actually get larger,

the further north they live.

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With a wingspan of up to eight feet, they are

one of the largest birds in the Northern skies.

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Though relatively abundant now,

it wasn't always this way.

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In the 1960's, the species hovered

on the brink of extinction.

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The pesticide DDT weakened the shell of their eggs,

which cracked under the weight of the nesting parents.

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Successful hatching of chicks dropped to near zero.

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The ban on DDT and other conservation efforts have

brought the bald eagle back from the brink,

with around 115,000 birds

in Canada and the United States today.

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Juvenile bald eagles aren't "bald" yet.

Their heads don't turn white until they're fully mature

at around four to five years of age.

These birds must learn the art of salmon fishing

from their more experienced elders.

For now, they watch and wait

from the bottom of the pecking order.

Extremely territorial when breeding,

bald eagles are highly social outside nesting season

and congregate by the scores at the

salmon spawning beds.

Bickering over the best spots,

they keep a steady eye on the water.

(chirping)

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As night falls, the eagles sit quietly.

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In the early morning light, the river erupts.

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It's the moment the bald eagles have been waiting for.

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But the young bird is so inexperienced;

it doesn't know what to do with the writhing fish.

Salmon have thick leathery skin and tough scales.

The juvenile eagle isn't sure how to get at the

delicious flesh underneath.

Before he can figure it out,

an adult swoops in...

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And claims his prize.

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The salmon makes one final desperate struggle --

before succumbing to the eagle's powerful grasp.

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These large birds are surprisingly peaceful

with each other.

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(chirping)

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There's enough for everybody to eat...

and they don't mind sharing.

But not the choice pieces.

The young eagle must wait until the birds of higher rank

have had their dinner...

but there'll be plenty left.

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Magpies also join the feast...

and everyone gets the nourishment they need.

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It's a last moment of abundance

before the long, hard winter.

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(eagle calls)

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From its mouth at the Bering Sea,

the Yukon River extends over 3,000 km to its source

in the mountains of British Colombia.

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Its headwaters lie here,

at the toe of the Llewellyn Glacier...

Part of the Juneau Ice field in the Coast Range Mountains.

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The Juneau Ice field is home to 140 glaciers...

One of the largest ice fields in the world

outside the Arctic circle.

Like a frozen inland sea,

the ancient glacial ice can reach a depth

of over 4,000 feet.

The Coast Range Mountains protrude like

islands from the glaciers,

some towering over 7,000 feet.

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The ice field is ancient...

in some areas it's up to two and a half million years old.

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During the most recent glaciation a massive

dome of ice stretched from the

Pacific Coast all the way to the Atlantic Ocean,

extending in parts as far south as Manhattan.

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Around 10,000 years ago,

as the Laurentide Ice Sheet retreated to the east,

the western extent of this frozen slab,

known as the Cordilleran Ice Sheet,

also shrank...

leaving the Juneau Ice field...

a relic of the frozen past.

Everything here has been touched and shaped by ice.

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Mountains have been sculpted.

Valleys have been carved.

Scoured by millions of tons of ice,

plowing across this land...

advancing and retreating.

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Mountain range upon mountain range...

Stretching to the horizon.

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Raging rivers gouged deep canyons into the rock...

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Dividing vast plateaus.

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Here, in the Yukon's interior,

the temperature frequently plunges to

negative fifty eight in winter.

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In the summer, it can soar to eighty six degrees.

One of the greatest temperature variances on earth.

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Rocks and rubble mark the gradual retreat

of the ancient glaciers.

This moraine is home to one of the most

intriguing species in the Yukon.

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Tiny herbivorous mammals called pikas have turned

this glacier-scarred landscape into a cozy home.

They take advantage of the countless crevices

between the rocks of the moraine.

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Now, at the beginning of September,

it's their busiest time of year.

In barely three weeks,

this valley will be blanketed by snow...

Pikas don't hibernate.

They spend the winter awake...

nestled in the nooks and crannies

of the moraine underneath the snow.

They're stockpiling now for the lean times ahead.

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Pikas actually "make hay".

Each pika collects its own stockpile

of grasses and leaves,

and dries it on the rocks in the summer sun...

They store the hay in crevices...

safe from the elements, lasting all winter.

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The pikas are not alone on the moraine.

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They share their home with

a colony of hoary marmots.

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The marmots are highly social.

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They live in big family groups of up to 36 individuals.

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While the pikas are much more territorial

and jealously guard their hay piles --

the marmots like to lounge on the rocks together.

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They spend almost half their time sunning themselves.

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Unlike the pikas, the marmots hibernate together

in their large burrow beneath the moraine...

so they don't need to stockpile any food.

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The hoary marmot is an ancient species...

Fossils date back more than two million years.

The marmot was here in the Yukon at

the height of the last Ice Age.

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Now, marmot and pika habitat is in decline.

A warming world is replacing

their alpine meadows with forest.

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They're so well adapted to the bitter climate,

they're ill equipped for the world's rising temperatures...

They can die from overheating in just a few hours...

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Other alpine species might move to higher altitudes.

But marmots and pikas live so high on these mountains

that there's nowhere further up for them to go.

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They now run the risk of being the first species with the

sad distinction of going extinct due to climate change.

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Marmots and pikas share watchman duties on the moraine.

(Screeches)

Both call out to warn the others.

(Screeches)

Danger lurks all around.

From the sky...

(Bird call)

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And on the ground.

A young silver fox has taken interest.

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Its den is nearby.

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The parents didn't choose this site accidentally.

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In these sparsely populated mountain ranges,

this moraine is a hot spot for prey.

Silver foxes are a dark variant of the more common red fox.

They're the same species -

just have differently colored coats.

In North America,

most silver foxes live here...

in the far Northwestern reaches of the continent.

The fox is one of the most successful predators

on the planet.

It has colonized virtually every corner

of the Northern hemisphere.

It's extremely resourceful and an outstanding hunter.

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This juvenile silver fox and its sibling

aren't living up to their reputation just yet...

Playing and exploring are

so much more fun than hunting.

Every bush and puddle is infinitely more interesting.

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Not even the prospect of a meal of marmot can pull them away.

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But the marmots take no chances.

The presence of a predator can send them

to their burrows for hours.

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Without their calls and whistles

the hillside falls eerily quiet.

Every day the temperature is dropping.

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Rock ptarmigan don't have burrows in which to retreat.

They rely entirely on their feathers to

keep them warm...

and safe.

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Perfectly camouflaged,

they adapt to their surroundings

and molt their feathers twice a year.

They're mottled brown in the summer...

and snow white in the winter.

Normally, ptarmigan blend in perfectly with the moraine.

But not now.

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Fall is a dangerous time for the bird.

Already sporting half its winter white feathers,

it can be seen from miles away.

The ptarmigan need to be extra vigilant.

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A thin veil parts over the Yukon's rugged beauty...

Revealing the sharp, jagged ridge of a mountain...

honed by two glaciers advancing on either side.

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But not everything here was carved by ice.

Generation after generation of Dall sheep have

etched their presence into the rock.

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Dall sheep spend the winter on treeless ridges

where powerful winds blow away any light, dry snow...

exposing the grasses that will

keep them fed until spring.

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The sheep know exactly where they're going...

They've inherited their winter range from their ancestors.

Returning year after year...

The exact location inscribed in their collective memory.

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This knowledge now faces an unprecedented challenge.

Inconsistent temperatures, repeated thawing and

re-freezing creates a hard layer of ice,

making their winter grasses harder to reach.

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In the face of global warming,

the Yukon is experiencing change...

Rapid change.

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In recent years, the Juneau Ice-field has

wasted away dramatically because of rising temperatures.

Some glaciers have retreated over

one and a half miles since 1984.

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Scientists predict that the entire Juneau Ice-field will

be more than half gone by the end of the century and

vanish completely by 2200.

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Nobody knows what will happen to the waterways downstream,

which for thousands of years have sprung from the ice-field.

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The entire rhythm of life in the Yukon is at risk.

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And one of its most graceful seasonal visitors

faces new challenges.

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The Trumpeter swan once nested from Alaska and

northern Canada to areas south of the Great Lakes and

along the St. Lawrence River.

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Heavy hunting and destruction of its habitat

drove the Trumpeter swan to near extinction.

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By 1933, just seventy known living birds

remained in the wild.

Thanks to strict conservation measures the

Trumpeter swan has since bounced back.

There are almost 20,000 birds in the Yukon today.

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The Trumpeter swan is the largest living

species of waterfowl, with a wingspan

of over ten feet...

and an adult weight of 26 pounds.

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These young swans still have some growing to do

before they reach that imposing size.

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Now, in the middle of September,

they're about three months old.

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They have to perfect their flying skills before

the winter migration begins.

Departure is just a couple of weeks away.

Under the guidance of their parents

they'll have to fly across the Rocky Mountains...

Thousands of feet high...

To reach the Pacific coast of Washington and

British Columbia.

For the young, it is a race to fledge and fly

before winter closes in.

They will do the journey clad in grey.

It will be another year before they turn the same

brilliant white as their parents.

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After several weeks of continuous walking,

the Dall ewes and their lambs have almost reached

their winter range.

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But before they make a detour to one of

their favorite destinations...

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A mineral lick.

Here, high concentrations of salts and minerals

are accessible on the surface.

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The sheep lick or even eat the soil...

Ingesting much needed nutrients they don't get

from their herbivorous diet.

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The mineral intake is crucial for healthy growth,

especially for nursing ewes and lambs.

They become so engrossed in the licking,

they pay attention to little else.

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Catching a lamb would fill this young timber wolf's belly

for many days.

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But the young wolf is injured and dragging his hind legs.

He doesn't seem capable of staging an attack.

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The sheep seem to sense that, too.

They continue to feed on minerals, unperturbed.

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The sheep spend several days here...

eating their fill before moving on.

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They will meet up with the males soon.

It's almost time for the rut.

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Dall sheep aren't the only mammals getting ready to mate.

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Each fall the usually solitary bull moose

meet in epic clashes, fiercely competing for females.

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Male moose first grow their antlers from the age of one,

with a full new set growing each year in summer.

Soft, furry tissue called velvet

covers the rapidly growing bone.

Now, that his antlers are fully developed,

the bull sheds the velvet.

Strips of it still hang from them.

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The antlers fall off every spring,

and larger ones return with each passing fall -

reaching their most impressive size around the age of ten.

They can span almost six feet wide on a mature male.

The sole purpose of this elaborate crown

is the annual rut.

The smell of a cow lures this bull across the valley.

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His long legs, perfectly adapted

to wading through swamps,

aren't great for clambering across the glacial moraine.

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The bull tries to find a way to bypass the rocky barrier...

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If he falls on these sharp rocks,

it could easily be his death.

Even though the fall might not kill him,

a broken leg would make him an easy feast for any wolves

or grizzlies passing by.

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He decides to risk it all.

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His cousins, the Northern mountain caribou,

have no such problems.

They were made for this terrain.

Their strong legs and large hooves are

perfectly shaped against slippery ice and

uneven, loose rocks.

They migrate through here each spring and fall...

Hundreds of miles...

one mountain pass after another.

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In relation to their body weight,

their antlers are even heavier than the moose's.

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This bull is in magnificent shape.

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His antlers have stopped growing.

The velvet has just fallen off.

And they're still tinged red from his own blood.

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After spending the summer spread out in open alpine areas,

the caribou now congregate in larger herds...

and move towards their winter habitat.

They move to forest areas rich with spruce and lichen,

where the snow cover will be relatively shallow.

The woodland caribou need the seclusion of these

Yukon mountains to thrive.

But increased mining, oil and gas activity

disrupts their migration patterns and

threatens their very existence across the North.

If the ruthless exploration continues,

caribou could fade from this landscape...

within our children's lifetime.

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Before long, all the leaves are gone...

and color drains from the land.

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The first snow falls in the Yukon River valley.

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The salmon must complete their once in a lifetime journey

to their spawning beds before winter truly sets in.

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These chum salmon are the weakest jumpers

of all species of Pacific salmon.

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Against incredible odds they have made it here

over countless rapids.

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Their bodies visibly scarred from the harrowing journey

they summon their last energy reserves to mate.

Males grab the females with their hooked jaws...

encouraging them to drop their eggs into nests

called redds.

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The male sprays the eggs with his sperm.

She will cover the eggs and sperm with gravel and

remain with her redd until about two weeks later.

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The adults have accomplished their mission...

And they die in the very place

where they themselves were born.

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Only about two of each clutch of 4,000 eggs will

make it back here as mature salmon in four years' time.

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Ice begins to close over the river,

locking it in for the season.

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The trumpeter swans ready for their grueling journey

to a warmer winter home.

For the young swans born here this year,

it will be their first and greatest test of endurance.

As the lakes begin to freeze,

the flock gathers.

Multiple families having a last meal

before their long journey south.

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The time has come.

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The young finally take to the air.

Flying in formation with their parents.

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Their adventure has begun.

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It will be six months before they return,

when spring releases the river

from winter's icy shackles,

and life begins anew in the Yukon.

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