All language subtitles for BBC.Frozen.Planet.II.5of6.1080p.HDTV.x265.AAC.MVGroup.org

DAVID ATTENBOROUGH:
In the far north of our planet

lie vast frozen lands...

..of snow-covered forests...

..and open tundra.

During the months to come,

they will be transformed

by the greatest
seasonal changes on Earth.

But now, in midwinter,

conditions are so hostile that
life seems all but impossible.

But...

..not so.

In this world of extremes,
animals must go to

extraordinary lengths to survive.

HOWLING

February, northern Canada.

The harsh winter

has brought together
an extended family of wolves.

But this is no ordinary pack.

There are 25 of them.

A super-pack,

one of the largest ever recorded.

They're ravenously hungry.

They may have walked over 150 miles

since they last had a meal.

But now, at last,
the lead male and female

have picked up a trail.

It's been left by the only
substantial prey there is here

at this time of year...

..bison.

GRUNTS

They're formidable animals,

not easy to attack.

The bulls are ten times
the size of a wolf.

And they have horns

with which they could
rip any attacker to pieces.

Gathered together and on guard,

they appear invulnerable.

The wolf pack's only chance...

..is to try and break up the group

and isolate one of them.

To do that,

they will have to work as a team

and try to start a stampede.

Even in thick snow,
bison can run at up to 35mph.

The lead female wolf
leads the chase.

A kick from a bison's hind leg
could shatter her jaws.

But the pack must feed,
and they take turns to attack.

YELPING

The bison head for cover.

The deep snow slows down
both attacked...

..and attacker.

The herd splits into two.

But the wolves
are far from giving up.

Hours pass.

The thicker vegetation has turned

a straightforward chase...

..into a deadly form...

..of hide...

..and seek.

Discovered.

The lead female manages
to chase the smaller group

into the open.

GRUNTING AND YELPING

But here the bison are able
to close ranks once again.

The leading wolves wait for
the rest of the pack to catch up.

The super-pack is once
again at full strength.

Suddenly, two of the bison panic.

It's just what the wolves
have been waiting for.

One of the bison is tiring.

The lead female
gets a grip on its flanks.

The male joins her.

Together, they might be able
to bring it down.

The rest of the wolves
catch up and help.

After eight long, hard hours,
the hunt is coming to an end.

HOWLS

Victory is sounded to summon
the rest of the pack.

A single wolf
wouldn't stand a chance

of making such a kill by itself.

The only way they have

of surviving the winter
is as a super-pack.

HOWLING

These snow-covered forests
encircle the Arctic

from Scandinavia, through Russia,

to Alaska and the rest
of North America.

But close to the North Pole,

the winters are too long
and too cold

for even the hardiest of trees.

This is the tundra, and it stretches

all the way to the shores
of the Arctic Ocean.

Here, conditions are even more
extreme than in the forests.

During the two months
of winter darkness,

temperatures may fall
to minus 50 degrees Celsius.

The ground deep beneath the snow

has been frozen solid
since the last Ice Age.

There is no shelter of any kind.

Very few animals can survive here.

But this is one which does.

An arctic fox.

It has the warmest fur
of any mammal.

And it can survive

blizzards that may rage
for days on end.

It must nonetheless
eventually eat something.

But how is that something
to be found

when you're all by yourself
in this desolation?

Arctic foxes are wanderers.

And they can travel over 2,000
miles, from Norway to Canada,

in a constant search for food.

There might be something here.

A patch of grass,
kept clear of the snow

by the near-constant wind.

The slightest hint of scent

might indicate the presence of prey.

Less than a metre below the surface

may lie a hidden network of tunnels,

shown here using
a special filming burrow.

SQUEAKS

Tiny arctic lemmings.

With a carpet of edible moss beneath

and a thick blanket of snow above...

..the lemmings spend
their entire winter

hidden below the surface.

And here they breed.

SQUEAKS

For a hungry fox...

..a group of lemmings

could be a life-saving discovery...

..if it can catch one.

Lemming burrows may
extend for up to 15 metres.

Pinpointing the position
of one of the inhabitants...

..is not easy.

An acute sense
of hearing is essential.

SQUEAKS

And the arctic fox

has a special trick.

SQUEAKING

It doesn't always work first time.

And it does require dedication.

With less than 25 lemmings
per square mile of tundra...

..you have to persevere.

And at last,

one plump lemming.

The foxes' tenacity
and unique hunting skills

enable them to find prey
which few others could catch.

On the tundra's southern fringes,

winter is significantly less severe.

The slight increase
in annual sunlight

has enabled a stunted forest
to develop.

It's the northern edge of the
world's largest woodland...

..the boreal forest.

750 billion trees.

A quarter of all the trees on Earth.

And it encircles the globe.

These forests store
twice as much carbon

as a tropical forest,
and they play a crucial part

in regulating the climate
of the entire planet.

One of the most remote tracts

stands in the far east of Siberia.

It's cut off from the rest of
the world by towering peaks...

..and precipitous valleys.

And it is the last stronghold

of the world's rarest big cat.

The Amur leopard.

Hunting has brought it
close to extinction.

Only 120 are left in the wild.

And this is one of the very
few ever to be caught on film.

Each must patrol a territory
of over 100 square miles

to find enough to eat.

In the cold of March,

prey is at its most scarce.

But leopards are clever opportunists

and watch for clues.

CAWING

Crows.

They too are looking for food.

And their calls tell him
that they've found something.

CAWING

But he is not
the only predator here.

On one of the trees,
the marks of huge claws,

ten centimetres long.

They've been made
by a hunter twice his size...

..a Siberian tiger.

Fewer than 500 remain in the wild.

These two rare big cats
are sharing the same territory.

And fixed remote cameras

show that they even use
exactly the same trails.

But leopards know
they must be careful.

Siberian tigers are the
biggest of all the big cats,

and could kill a leopard...

..should they ever meet.

In winter,

many forest animals
rely on carrion for food.

CAWING

And that includes leopards.

But he can't let down his guard.

CAWS

The crows that led him here...

..may also have alerted the tiger.

GROWLS

The crows are disturbed.

Another mouthful might be risky.

CAWING

Survival sometimes
depends on knowing

when to leave.

Only a few choose
to take their chances here

in the depths of winter.

Elsewhere, vast swathes of
the forest remain eerily empty.

Above, there is
an otherworldly light show...

..the aurora borealis.

High in the sky,

electrically charged
solar particles from space

collide with the Earth's atmosphere

and create this ethereal display.

Meanwhile, in Canada, through
the six long months of winter,

life below ground
is biding its time.

The world's most northerly turtle...

..the painted turtle...

..seen here
in a special filming chamber.

They hatched last autumn
but have remained

in a state of suspended
animation ever since.

Their hearts have stopped beating...

..and only their brains
have remained active,

and even then, only very faintly.

Painted turtles wait underground

for this most important
of moments...

..the arrival of spring.

In April, the strengthening sunshine

triggers a miraculous
transformation.

The turtles' body temperature
rises just above freezing...

..and their hearts
start to beat once more.

Slowly, they return to life.

Thanks to this extraordinary
adaptation, these young turtles

get a valuable head start
in spring...

..and are one of the first
to emerge, ready to take

full advantage of the forest's
renewed abundance.

In just a matter of weeks,
the vast northern forests

flush green.

For Siberia's big cats, each
spring could bring new hope.

Cubs.

Each of them
increases the chance that,

even at this very late stage,
both species might recover.

By June, the northern forests
are full of life.

But several thousands of miles
further north, in the tundra,

the spring thaw
is only just beginning.

When it does,
under 24-hour daylight,

its impact is even more extreme.

Five million square miles of snow

disappear in a matter of days.

Ten centimetres beneath
the surface of the ground,

a snow queen is waiting
to make her appearance.

A Lapland bumblebee.

She's barely alive.

All the other members of her colony
were killed by the cold.

She survived,
as bumblebee queens do,

thanks to her larger size,
her particularly thick fur,

and a natural antifreeze
that she has in her body.

As temperatures continue to rise,

she begins to thaw.

BUZZING

She vibrates her flight muscles,

which raises her body temperature

to over 30 degrees Celsius
in just six minutes.

There is no time to lose.

She must now create
an entire colony.

First, the queen must find
a drink of nectar

to regain her strength...

..travelling as much as
three miles a day

to find the flowers
from which to collect it.

She works tirelessly.

As well as high-energy nectar...

..there's pollen to be gathered.

Back underground, she uses the
pollen to build a waxy cocoon.

And in it,
she deposits the tiny eggs.

Had she laid them
directly on the frozen ground,

the cold would have killed them.

And now she warms them

by pulsating her body.

She has also constructed
a little pot

in which she stores nectar

to provide her with a drink
when she needs it.

For the next three weeks...

..this single mother

works around the clock,
gathering nectar

to top up her pot...

..and vibrating her body

to prevent her developing young
from freezing to death.

Eventually, a new generation of bees

starts to emerge.

She leads each young
worker to her honey pot

and encourages it to drink.

By the end of the following week,

the number in her little colony
has increased to eight.

Her timing has been perfect.

The tundra is now in full bloom.

And the bumblebee families
help to pollinate

the largest wild-flower
meadow on Earth.

But the summer here is one
of the shortest on the planet.

And all of the tundra's residents

are now racing to breed.

SCREECHES

Alaskan snowy owls have
a brood of six fluffy chicks

and only eight weeks
in which to raise them.

The parents provide them
with 30 lemmings a day...

..for the chicks will need
to triple their weight

before they reach independence.

Unusually for an owl,
snowies hunt by day.

And over the next two weeks,

they take full advantage of
the Arctic's continuous light.

But this morning, the female
returns to an empty nest.

Her chicks are nowhere to be seen.

They're hiding.

CHIRRUPING

They're so big, the whole group
might be spotted by predators,

so they have scattered
across the tundra.

But that makes feeding them
all much harder work.

SCREECHES

Over 600 meals later,

the parents' labours
are starting to pay off...

..as the chicks stretch
their newly developed wings.

Just a month is left
before winter returns.

SCREECHES

Two weeks more,

and their transformation
is almost complete.

The chicks' wings
might at last be able

to do more than just
lift them from the ground.

Getting there!

Keep going!

Airborne!

The youngsters are ready
for independence.

And the exhausted parents
can take a well-earned rest.

The tundra has come to life
once again.

But in the longer term,
its very foundations

are now at risk.

BIRDSONG

The ground itself is giving way.

RUMBLING AND CRACKING

In some places, it's dropped
by more than 60 metres.

Grasslands that once supported
thousands of different species

have become wastelands.

Arctic temperatures are rising

as a consequence of climate change.

The deep soil
which has been frozen solid

for thousands of years,
the permafrost,

is now thawing at a rate
never witnessed before.

Without the ice to bind it together,

the ground becomes unstable.

In Canada, thousands of
tonnes of the tundra

have collapsed in a matter of weeks.

And in Siberia,
huge scars are appearing.

By the end of the century,
an area of Arctic permafrost

one third of the size of Europe

could have thawed.

The warming of the tundra

is having a profound impact
on its wildlife.

For millennia, caribou
have made annual migrations.

Every summer,

driven by the seasonal
changes of the far north

and following
long-established pathways,

they have trekked
almost 400 miles north.

This herd alone in north-east
Alaska numbers over 200,000.

Their destination

is a vast wilderness

known as the Arctic
National Wildlife Refuge.

These summer pastures
provide rich grazing,

just what's needed
to raise newborn calves.

GRUNTS

This one, fattening up
on its mother's milk,

would normally double its weight
in just a few weeks.

But now grazing time
is being disrupted.

INSECTS BUZZ

In summer, the tundra
becomes waterlogged.

These are excellent
breeding conditions

for mosquitoes
and other biting insects.

But as the climate warms,

there are concerns
that insects will breed earlier

and eventually reach
plague proportions

just as the caribou need to feed.

INSECTS BUZZ

Individual animals could lose

a quarter of a pint of blood
a day to biting insects.

GRUNTING

So the caribou may
end their grazing early

and head for cooler,
mosquito-free pastures.

But to get to such places,

they will have to cross rivers
swollen by seasonal runoff.

For a young calf, a deep river
crossing is very dangerous.

He does what he can
to stay close to his mother.

But he doesn't have the strength

to resist the fast-moving current.

GRUNTS

GRUNTS

He is one of the lucky ones.

Reunited with his mother,

he can continue
on his journey with the herd.

GRUNTS

But other calves
are less fortunate...

..and must now
fend for themselves.

Some are too exhausted
to take another step.

But this is not a safe place
to take a rest.

Grizzly bears.

For the past few weeks,

there has been little food
for them on the tundra.

And this one is extremely hungry.

GRUNTING

He's looking for the weak and weary.

And he's found one...

..too tired to flee...

..and too weak to resist.

The herd's finally reached

the northern limits of its range.

These coastal pastures
bordering the Arctic Ocean

remain cool enough to provide relief

from the swarms of insects.

Mothers and calves
can finally feed in peace.

For now, this
immense herd is stable.

But in the long term,
its survival is now uncertain.

The seasonal extremes
of the far north

have always tested
its inhabitants to the limits.

But climate change
could present them

with one challenge too many.

Only if we can mitigate its effects

will the remarkable wildlife here

stand a chance of survival.

Filming in the extremes
of the far north...

..the team's greatest
challenge was to capture

the epic showdown between
super-packs of wolves

and bison in midwinter.

GRUNTING

The crew travelled to

Wood Buffalo National Park
in northern Canada,

a remote wilderness
the size of Switzerland.

To stand a chance
of filming this drama,

they must take to the skies.

Drawing on local knowledge,

pilot Matt Erhardt
helps to pinpoint

one of the last
free-roaming herds of bison

and the wolves that
specialise in hunting them.

Some of the wolves
have run forwards.

Just have all your kit
ready to go.

With a positive sighting,

it's time to mobilise the film crew.

Cameraman Jamie McPherson
has rigged the helicopter

with a gyrostabilised camera system,

enabling him to capture
rock-steady images

from a safe distance.

You'd think filming
from a helicopter's easy,

because you can just
fly around and film stuff.

But you've got to be
incredibly careful,

not influence the behaviour,

not scare the wolves or the bison.

There we go.
Yeah, that is them.

It's a big pack. Yeah.

They're really chilled out
with the helicopter.

Really encouraging.

But before Jamie can start filming,

the chopper must first drop
the accompanying ground crew.

Good luck. OK.

We got put down

in this vast open space,

and now we're going to
try and hike in and see

if we can get close to them,

or hopefully they'll
get close to us.

To intercept the pack, the team
must scramble into position.

But trudging through
knee-deep snow

is hard going.

HE BREATHES HEAVILY

Every time I catch up with
Justin, he just keeps on going.

He's a machine!

Yeah, go ahead, Matt.

OVER RADIO:
They're starting to head

a little bit towards
the north-west,

so they're starting to
move away from you.

Oh, Goddamn it!

The ground crew
will have to dig deep

if they're to film
the fleet-footed wolves.

Over the following week,

Jamie manages to track
the wolf pack

from the comfort
of the helicopter...

..while down on the ground,

Justin and Will are having
a tougher time of it.

Ohhh! It's really
incredibly awkward getting around.

Even lunch offers
little consolation.

It's frozen bread,

frozen Brie and frozen pickle.

And with no wolf activity

visible from the air,

Jamie is soon grounded.

Yeah, I'm just
looking for an update.

Great...

WIND HOWLS

The winter weather
takes a turn for the worse.

It's snowing, and it's at
a temperature where it could

potentially stick to the blades

and become really dangerous.

For the next few days, the crew
are forced to sit it out.

Finally, the skies clear.

But after nearly three weeks
on location,

there's precious little
filming time left.

We've got one last shot

to get what we're looking for.

And just hoping that it comes
together at the last minute.

There, there's the trail there,

so they're on the west side
of that trail there.

Soon enough, they find the bison,

along with wolves

who appear to be in hunting mode.

The spotter plane just found
the wolves with the bison,

so we're scrambling to get
there as quick as we can.

There's something about

being in the presence of prey
and predator on the ground

like this which is very special.

Justin is in prime position
to capture the showdown.

As a chase begins,

Jamie picks up the action
from the air.

It'd be amazing
if we could get round that. OK.

In a stop-start pursuit

lasting an entire day,

Jamie manages to record
the full jaw-dropping drama.

They've definitely got
that female.

I think they're going to
bring it down.

Perfect, Jim. We got it.

With the hunt nearly over,

the crew reposition Justin
once more.

HOWLING

We got on the ground
just in time to capture

from a really far distance

the last moments
of the bison's life.

There's a moment of confliction

between your loyalty
for each animal.

One is filled with a mixture of
both celebration for the wolves

but a sadness. Both exist
somehow simultaneously.

Bearing witness to this
rarely seen age-old battle

between predator and prey
leaves the crew

with an appreciation of
just how challenging life is

in the frozen extremes
of the far north.

Next time...

..we meet the scientists
and people...

..who are dedicating their lives

to understanding
the changes taking place...

..across our frozen planet.

Changes that'll impact
the lives of each...

..and every one of us.

The Open University has
produced a poster

exploring how animals adapt to life
in the world's coldest environments.

To order your free
copy, please call...

..or go to...

..and follow the links
to The Open University.