All language subtitles for S01.E02-YellowStone-Summer

NARRATOR: For six months Yellowstone
endures an unrelenting winter.

An ice world of hunters.

And hunted.

But now footsteps on
the slopes of a mountain

herald a change in the season.

The sun regains its strength.

Water flows again.

The race begins to recover
winter's losses.

To play.

Learn.

And breed.

But the summer ahead will be fleeting

and far from easy

in this unpredictable wilderness.

"YELLOWSTONE"

"SUMMER"

It's April.

The land lies exhausted by winter.

Everything is waiting for the return
of the sun's warmth.

The end of winter comes late

to the mountainous northwest
of the United States.

And in particular
it lingers in Yellowstone.

The heart of Yellowstone is
a high cold plateau

8000 feet up surrounded by the spires
of the Rocky Mountains.

After five months sleeping
in those mountains

a powerful presence returns.

This female grizzly bear

has awoken early to find food for
her two-year-old cubs.

But she may have brought
her family here too early.

The Tetons

on the extreme southern edge
of the Yellowstone plateau.

It's where the spring thaw
normally begins.

But this year it's come late.

Deep snow is still a novelty
for her cubs.

But she is much more focused.

Led by her nose
she risks her 300-pound bulk

on the thin ice of a bend
in the Snake River.

It doesn't look promising

but her cubs follow
with only a little hesitation.

With paws that can knock down an elk

she feels delicately in the water.

A fish frozen beneath the ice
by this cold winter.

One fish won't feed the family

but she knows there are
almost certainly more.

The cubs must learn to find them.

A little success for one of the cubs.

This mother bear's experience

gives her family a good chance
of survival until spring arrives.

They will return again and again
as the thaw releases more fish.

On the warmer plains and valleys
that surround the plateau

grazers are on the move.

They left the high country
to avoid the worst of the winter

and now begin the long journey
towards the heart of Yellowstone

in time for summer.

These elk are led by experienced adults

who have made this trip
many times before.

They are followed on their migration by
the most ancient of American grazers.

Pronghorn.

Though predators may follow
none can outpace them.

Over distance these are
the fastest animals in the world

taking a long migration in their stride.

Migrating elk and pronghorn must follow
the advancing thaw.

But higher up in the valleys
one animal is well ahead of them.

Bison are adapted for cold.

These herds need to be
in Yellowstone early

to have time to bring up their young
in the short summer ahead.

Calves born during the journey
will be tested.

Clues to why the herds are drawn
to the Yellowstone plateau

lie in its deep and unique history.

This plateau is the cratered bowl
of a huge sleeping volcano

and molten rock below the surface
still pushes the land up

to the cold of high altitude.

But it has not been the only force
to shape the land.

Millennia ago the volcano
was covered by an ice sheet

thousands of feet deep.

The few glaciers that border Yellowstone
are an echo of a time

when ice scoured
and smoothed the entire plateau.

When these great ice sheets retreated

they left pulverised rocks
in their wake

the foundation for fertile soil

and some of the richest
natural grasslands in America.

But in May this year

in the heart of Yellowstone
that grass is still beneath thick snow.

Something this ground squirrel
was clearly not expecting.

But as the sun's strength returns

spring bulbs start to push through
the late snow.

At last a sign
that winter is losing its grip.

Bluebirds too delicate to survive
deep winter here

now return to take advantage of
the first hatch of stoneflies

from a thawing river.

As six months of snow and ice
begins to melt

Yellowstone starts to come back to life.

Cascading snowmelt swells
the streams and rivers.

It's a hazard that
the migrating herds must cross.

Young are barely up to the task.

The Yellowstone River has increased
its flow tenfold.

In less than two weeks

the thaw has brought a remarkable change
to the heart of Yellowstone.

As the migrating herds arrive
in the plateau's river valleys

the spring is here.

This is why they have made the journey.

After the famine of winter

food is everywhere.

Birds have flown in from as far away
as the Arctic and subtropics.

Canada geese join flocks of
white pelicans to breed here.

A snow-covered wasteland is transformed

to an American Serengeti.

But it's a landscape like no other.

Geysers made Yellowstone famous.

Yellowstone sits above the molten core
of a volcano.

Underground water becomes superheated
and erupts into the air.

Strangely geysers and hot springs
can creep around the landscape.

The curious shapes of Grotto Geyser
are actually trees

entombed and petrified
by minerals dissolved in the water.

Hot water scorches and drowns the roots
of trees encroaching on the valleys.

It can keep the forests in check
and the rich pastures open.

Those pastures now produce the new grass
needed to make rich milk

and feed a bison baby boom.

The few calves born on the migration

are now joined by hundreds
of new youngsters.

The predators have been
waiting for this.

Coyotes have a voracious
reputation here

but on its own this one is certainly no
match for a healthy bison and her calf.

Pronghorn give birth to twins

each carefully cleaned
to hide their smell from predators.

While they are with her
they are relatively safe

and for now the coyote is content
with the afterbirth.

But the mother pronghorn must leave
her calves alone while she grazes

and with legs as wobbly as stilts

their best defence is to lie low.

She has young of her own to worry about
a demanding litter of nine

whose arrival has been carefully timed
to coincide with an abundance of food.

But they are not top dog here.

Yellowstone's top predator the wolf

dominated during the winter
but is far less visible in summer.

They prefer to stay close
to well-hidden dens

to protect their pups from rival packs.

This pack seem prepared to
allow their young a brief foray

to experience the world
beyond their den.

Even in Yellowstone

it is extremely rare
to see wolf pups like this.

Before long they are summoned
back into the forest by the pack.

It will be winter before
they are regularly seen again.

As May turns to June

Yellowstone sees its nursery season.

By early June summer is finally here.

In the flower meadows

plants turn sunlight
into the sugar of nectar

and that's what Yellowstone's smallest
migrating bird has been waiting for.

The Calliope hummingbird has made
the journey all the way from Mexico.

He'll make this flower patch his own

and he'll fight to defend it.

He'll even take on a far larger
Rufous hummingbird.

But his high-octane lifestyle
critically depends on the summer sun

and in Yellowstone
that's never guaranteed.

In the mountains surrounding the plateau
summer has not yet arrived.

At this altitude
it is still bitterly cold.

These mountains barricade Yellowstone
in a ring of ice.

And if the sun is swallowed by cloud

the cold can drive down
from the mountains

bringing with it
a punishing echo of winter.

It can snow in any month in Yellowstone.

The warm nursery meadows
of a few days before

are now buried by a June blizzard.

A curtain of snow dulls senses.

This mother grizzly bear
must now be especially careful.

A male grizzly will often kill cubs
if he finds them.

And though she would rather
sit out the storm she must move.

Panicky cubs could easily
be lost in a blizzard.

As soon as she feels it is safe

she settles to suckle and reassure them.

Bison can shrug off
this sudden change in the weather.

They are after all
built to survive a Yellowstone winter.

But this tiny hummingbird
is more vulnerable.

Flowers damaged by snow will die

and the nectar the hummingbird needs
goes with them.

Hummingbirds must be resourceful
to survive.

Bark wells dug by a sapsucker
a type of woodpecker

quickly fill with sugar-rich sap
as soon as the warm weather returns.

A little pilfering provides this
hummingbird with the energy it needs

until the new flower buds open.

Summer moves quickly.

By late June the blizzards of a few
weeks before seem a distant memory.

At last the summer is
well-enough established

for this hummingbird to take the plunge
and raise a brood.

The living is easy.

But it won't last long.

At this altitude the air is so dry

that rain evaporates
before it even hits the ground.

The water that flows off the plateau
is no longer being replaced.

Already there is drought in forests
beyond the meadows.

Yellowstone has vast
ancient lava fields.

This porous volcanic rock
holds onto very little water.

It is dominated by lodgepole pine

a tree that can cope with
the arid conditions.

The forest may be parched

but there is still water here
in lakes formed by ancient glaciers.

A visiting male otter
woos a female on the lake's shore.

But she seems a little distracted.

Her two pups are nearby.

They're about 10 weeks old

and the time is right to lead them
from the holt.

Males are not above
stealing food from cubs

so she makes it very clear
that he is not going to be joining them.

This female grew up on the lake

so she knows where to take the cubs
for a very special trip.

Yellowstone cutthroat trout

amassing in the mouth of a stream
that feeds the lake.

They're preparing for
their annual spawning.

But the trout must wait.

The stream is still running fast

too turbulent to lay their eggs.

It's a nervous time for them
and for good reason.

This osprey has a brood to feed
and will be back.

Now the otters are here too.

She chooses her moment
to lead the pups upstream.

Then leaves them to watch

and gives them a lesson in hunting.

A large trout like this full of eggs
is a trophy catch.

She chews its tail first
to make sure the fish can't get away.

While the pups are still demanding milk

the mother otter will often keep
the whole fish for herself.

Her pups are happy enough with caviar.

As the flow becomes slow enough
for the trout to lay eggs

there is a brief window of opportunity
to spawn

before the river gets too shallow
to swim upstream.

The female digs a trough
with sinuous flicks of her body

and the attending male fertilises
the eggs as they are laid.

Millions of new lives.

It's now early July

and what looks like more snow

is actually a blizzard
of seeds and insects.

There is more life in the park now
than at any other time of the year.

It's a turning point in the summer.

Through the coming month
the days will get hotter and drier.

The plants will grow less vigorously

and the pace of summer will slow.

The meadows are not so welcoming now.

The grass becomes less nourishing

as it puts its energy
into seeds and roots.

Bison lose the last of
their winter coats.

In the heat tempers fray.

To escape soaring ground temperatures

cowbirds choose a bison's back
as a cool place to feed

and catch the breeze.

Biting insects now become
a draining nuisance.

A grizzly bear escapes the heat and bugs

in the cool waters of a lake.

As the ground dries

bears find little food to eat
out on the Yellowstone plateau.

There is less to graze
and digging roots is hard work

so they start to head to
the cooler mountains beyond.

In the mountains

glacier lilies that finished flowering
a month before on the plateau

are only just coming into bloom.

Up here where spring
has only just arrived

bears can find food again.

As the thaw reaches up
into the mountains

a part of Yellowstone that few ever see
is briefly revealed.

From its first day above the snow

this pika is obsessed by food.

It's in a frantic race to restock
its winter larder

before the snow closes in again.

They're a part of a community
of small mammals

which live life on the edge up here.

Carefully chosen plants are harvested
and dried in haystacks

before being stored below ground.

This larder must be over 50 times
the pika's bodyweight

to get it through winter.

The summer is so short up here

that few animals can
permanently live any higher.

But higher is exactly where
the bears are heading

above the tree line

towards the barren rocks
of the peaks beyond.

It seems an unlikely journey
for an animal led by its stomach.

Why they do this
will only become apparent

as the summer draws to its close.

Meanwhile 2000 feet below them
on the Yellowstone plateau

the grasslands are facing drought.

Bison calves are more independent
of their mothers.

The adults' focus is now set
on a ruthless competition to mate.

A male bids to enter a herd
with females in season.

He uses dust to accentuate
all his size and power.

Another male already established
in the herd

answers the display.

(GRUNTING)

And waits.

The newcomer responds by scent marking
and moving even closer.

This challenge cannot be tolerated.

The resident male has won.

Having seen off his rival

next summer's calves will likely be his.

Victory in the dust of high summer.

But now there is a larger challenge
to the whole of Yellowstone.

These clouds don't signal rain.

They are vast smoke plumes.

Yellowstone is burning.

Throughout the summer

the dry lodgepole pines have become
like a tinder box

and lightning has struck the match.

The worst wild fires
will burn for weeks.

In 1988 a third of Yellowstone burnt
in a single summer.

Devastation.

Animals that depend on these forests
will starve this winter.

But Yellowstone itself has
a longer perspective.

Ashes fertilise the soil
and fire opens it up to sunlight.

As the forests regenerate

new life finds opportunity.

In August fledgling hummingbirds gorge
in fields of fireweed

that have risen from the forest's ashes.

For them the summer
is already nearly over.

They must chase the sun south
before winter returns.

But just as the first of Yellowstone's
new generation are preparing to leave

its last visitors are arriving.

Night after night

army cutworm moths have been escaping
the heat of a distant prairie.

They have been flying in
on favourable winds

hiding away in rock crevices
in the mountains.

This is why the grizzly bears
climb to the barren peaks.

Two miles up they begin
to search for the moths.

It's the end of summer

and the last snow of winter
holds on only here.

It offers a few refreshing mouthfuls
for travel-weary cubs.

Many of these bears learnt
about this site from their mothers

as a part of local bear tradition.

The family sets to work finding moths
digging into the loose rock.

Though each moth is very small

a bear that makes a successful strike

can harvest up to 40000
in a single day.

That's 20000 calories
and vital weight gained for winter.

Having spent all summer avoiding males

the mother now finds one
much too close for comfort.

Perhaps he's seeking a mate
but he is unwelcome.

Leaving her cubs she confronts
the male head on.

As she approaches to see him off again

she realises she has been injured.

A damaged jaw would be a disaster
for her and her family.

Clearly in pain

she leads the anxious cubs
to high ground away from the male.

She nurses to calm and reassure them.

The injury does not seem serious

but she decides to lead her family
back down from the mountain.

This will be the last time
these cubs feed here as a family.

By next year they will be independent

ready to face their world alone.

Sun has briefly brought warmth
to Yellowstone

long enough to fuel the raising
of new generations.

But just as summer reveals the full
extent of Yellowstone's diversity

a curtain of winter ice
is set to descend again.

The days are getting shorter

the sun losing its power.

Now there are just a few short weeks
to prepare for winter.

One final flourish of life

in Yellowstone's briefest
but most glorious season.

Autumn.