All language subtitles for Planet.Earth.III.S01E06.Extremes.2160p.UHD.Blu-ray.Remux.HDR.HEVC.TrueHD.7.1.Atmos-CiNEPHiLES_ENG_Subtitles02

This is the entrance

to one of the greatest
of natural wonders.

Hang Sơn Ðoòng in Vietnam.

It's thought to be
the largest cave on Earth.

Here, 200 metres underground,

for just a few weeks a year,

sunbeams cast light

through a hole in the cave's roof.

There is just enough light

to enable plants to grow.

But travel deeper

and darkness returns.

And you reach the limit

of where life can exist.

These most extreme places
on our planet

are often hard for us to reach.

Indeed, this cave
was only recently discovered.

And it contains many surprises.

Cave pearls.

Once tiny sand grains,

now spheres the size of tennis balls.

And giant stalagmites...

...formed over centuries

by billions
of individual drops of water.

Underground rivers

have carved this great passage
through the limestone.

Over five miles long

and wide enough in places

to accommodate a jumbo jet.

And it is here,

in the cave's furthest chamber,

that life can be found.

Translucent cave fish...

...and shrimps.

Isolated for millennia,

feeding on little more

than the nutrients
from the jungle above.

The fish are completely blind

and find their way about
by touch alone.

These underground worlds

are at the very limit
of where life can exist.

But above ground,

our planet's most extreme conditions

are found at the poles.

Here in the north,

winter temperatures can drop

to -50 degrees Celsius.

For four months of the year,

there is barely a glimmer of sunlight.

But here, too,

life finds a way to survive.

A pack of Arctic wolves.

Their dense fur has protected them

through months of bitter cold.

But now the sun is returning.

This is Ellesmere Island.

The short summer

gives the wolves a chance

to rebuild their strength.

But here in the Arctic...

...life is never easy.

This pack is led

by an experienced female.

If she can't lead them to food,

the coming winter could be their last.

Prey is spread over such a vast area

that they must be
constantly on the move...

...in search of it.

But finding prey

is only the beginning.

Musk oxen.

They are five times
the size of a wolf.

The conflict between wolf and oxen

is an ancient one,

and has been waged since the Ice Age.

Each side knows the other's tactics.

The wolves try to isolate

the weak or the young.

A calf stumbles...

...and the pack leader

immediately closes in.

But the herd regroups,

horns at the ready.

Stalemate.

But it can only be brief.

This time,
the herd race to higher ground.

As they reach the top of the ridge,

the males turn

to defend themselves.

Stalemate...

...again.

Every unsuccessful hunt

leaves the pack weakened.

This could be an easier meal.

But something is not right.

This musk ox has died from a disease.

Outbreaks like this

are becoming increasingly common

as the climate warms
across the Arctic.

Despite their hunger,

the pack don't eat this carcass.

Another herd.

Another chance for the pack.

This time,

the wolves manage to split the herd.

That may improve their chances.

The lead female
makes sure that the oxen

do not reach the ridge again.

With one less defender,

the calf is more vulnerable.

A much-needed meal.

The wolves
must continue to make the most

of the remaining weeks of summer...

...so when winter returns...

...they're ready to endure

some of the harshest conditions

that exist on Planet Earth.

Such inhospitable extremes

are not only found at the poles.

As altitude increases...

...temperatures fall.

Here, too,

animals must make the most
of the seasonal change.

Particularly if you're ready to mate.

A male common frog

in the French Alps.

He has spent all winter

hibernating under the ice.

But now it's time to wake up.

Being cold-blooded,

he needs the sun to warm his body.

But once it sets in a few hours' time,

he could freeze to death.

So finding a mate is urgent.

The weather is good.

And he starts to sledge.

But this is not a one-frog race.

Dozens are rushing
to the breeding pool.

This many frogs out on the slopes...

...doesn't go unnoticed.

You can't afford any slips.

It was all going so well.

Made it.

But all the females
have already got partners.

There's only one thing for it.

Wrestling.

Not this time.

Another latecomer.

A female.

Could she be the one?

Sometimes being late

can pay off.

After all his efforts,

the male
is not going to let this chance

slip through his fingers.

This is the cedar forest

of the Atlas Mountains
in North Africa.

These Barbary macaques

enjoyed a summer of plenty,

but now they're paying the price.

Winter here can be brutal.

In some years,
over half the group perish.

But in this macaque society,

the more social the monkey,

the more likely it is to survive.

Keeping warm by huddling

can make all the difference.

But they can't huddle all day.

They must, eventually,
break apart to feed.

They spread out, searching for food.

But each night,

the group return
to huddle in the cedar trees.

No-one wants to be left out.

Especially the infants.

This baby, somehow, has got separated.

He must get back

to the life-saving warmth
of the huddle.

And soon.

But there is an obstacle.

A grumpy male

is giving the baby
a rather cold shoulder.

Maybe a more subtle approach.

The male decides to leave.

At last...

...an enthusiastic reception.

The male has had less luck.

It could be a long night.

Huddling might seem a simple
expression of affection,

but among these macaques
it's essential for survival.

And not just here.

5,000 miles away
in the forests of Mexico,

monarch butterflies, in millions,

also huddle for survival.

All of them have travelled
across North America

to escape the winter
that is coming there.

This forest,

at an altitude of 3,000 metres,

might seem to offer little comfort...

...for temperatures here

can drop below freezing...

...and that could
kill the butterflies.

But in fact, a thin layer of warm air

trapped by the tree canopy
protects them,

and will do so
throughout the winter...

...provided that the forest
remains undisturbed.

Unpredictable extremes
of weather, however,

can disrupt this delicate balance.

Strong winds
can push deep into the forest,

chilling the air.

Hundreds of thousands of butterflies

may be blown from the branches.

In some years, storms kill 75%

of hibernating monarchs.

This one has survived...

...but on the ground.

And night-time frosts are fatal.

It can't stay here and live.

It is too cold to fly,

but it must get back
into the tree branches somehow.

So it starts to climb.

It's the equivalent of a human

climbing up a skyscraper.

Safety at last.

As spring returns,

the monarchs wake
from their long slumber.

And now starts

one of the Earth's
greatest natural spectacles.

But this mass awakening
is under threat.

The changing climate

is creating more extreme weather,

and storms are becoming more frequent.

But, for now,

this miracle of nature continues.

Fire.

Unpredictable and destructive.

This is South Africa's fynbos.

Botanically one of the most
diverse habitats on Earth...

...with over 8,000
different plant species.

Yet, every two decades,

fire reduces the vegetation to ashes.

This may seem catastrophic.

But just days later,
plants burst into life...

...and transform the landscape.

Seeds and bulbs

have been waiting for this event.

90 million years of evolution
alongside fire

has made some plants
so closely adapted

that they can't germinate
without the presence of smoke.

Remarkably, around 50%

of Planet Earth's terrestrial habitats

depend on fire to remain healthy.

In Northern Australia, these savannahs

need seasonal fires to keep them open

and prevent the spread
of the nearby forest.

And they are a vital habitat

for this colourful resident.

The rare golden-shouldered parrot.

He and his lifelong partner...

...rely on grassland
for both food...

...and a nest site.

As usual, they've laid their eggs

in a hole in a termite mound.

And now there are four chicks.

The thick mud walls

don't only protect chicks
from predators,

but insulate them

from the heat of the scorching sun.

With fledging just days away,

the parents are working overtime.

They collect thousands of seeds
every day.

But they have a problem.

The fire season
is becoming more irregular.

If they are not ready to fly,

chicks have no escape.

But choosing to nest
in a termite mound

has a surprise benefit.

Their home is fireproof.

Concrete-like walls

keep chicks safe
from the flames outside.

The seeds of fire grass

are now easier for the parrots to find

on the blackened earth.

And they are the parrots'
favourite food.

So for both adults
and their fledgling chicks...

...fires are essential
for survival.

But their grassland home is shrinking,

and only about 1,000
of these lovely parrots

still survive.

It's through
the active management of fire

by humans that their world
now exists at all.

Humans are affecting habitats
across Planet Earth.

For wildlife, all too often,

the consequences have been disastrous.

Elephants are among
the most tolerant of animals.

They are very long-lived,

and knowledge
passed between generations

enables them to find food

and little-used sources of water

in times
of great environmental stress.

But even among elephants,

survival strategies
are now beginning to fail.

In Amboseli, Kenya,
years of extreme weather,

combined with overgrazing
by domestic cattle,

are turning these grasslands to dust.

This matriarch is over 40 years old...

...and she's already survived

some of East Africa's worst droughts.

But this year, food is in
extremely short supply...

...and her family
are struggling to find enough.

Her youngest son
is malnourished and weak...

...and is lagging behind
his mother and brother.

She leads them

to a pocket of acacia forest
that she knows well.

But broken branches and fallen trees

show that other elephants
have already been here.

There is very little left
worth eating.

Without food,

his mother cannot produce enough milk.

She has no choice...

...but to leave
her weakening calf...

...and try to find food
elsewhere.

So she...

...and her elder son
head off...

...without him.

He can only hope for their return.

But for him, time has run out.

There is nothing his mother,
or anybody,

could have done to save him.

With her elder son still alive,

there is hope for her family.

But only if they can adapt quickly.

Some families
are proving to be resilient.

They're travelling long distances

away from Amboseli...

...and finding new sources
of food and water.

And despite the drought...

...calves are being born.

But given the pace of change

and the challenges they face...

...how many
of Africa's elephants

will be able to adapt...

...and can they do so
fast enough?

The Gobi Desert.

A land of sand and snow.

For at least a million years,
this has been

one of the most extreme
habitats on Earth.

Yet footprints in the sand

reveal that there is life here.

A snow leopard.

Seldom seen...

...especially in such hot,
arid conditions.

They live up to 2,000 metres
above sea level,

and patrol vast territories.

They are rarely seen together.

A mother...

...with cubs.

Filmed here for the first time

in such intimate detail.

And they give us a glimpse
of their family life...

...such as it is.

Snow leopard cubs
stay with their mothers

longer than those
of almost any other big cat.

They remain together
for over two years...

...as they learn how to master
the extremes.

Which they do so well
that they are able to thrive

in some of the hottest, coldest...

...and highest places on Earth.

Some animals, over millions of years,

have evolved ways of surviving
extremely hostile conditions.

But as the extremes
become more extreme...

...evolution is being outpaced.

These extraordinary places
are still inhabited

by some of Earth's most resilient

and adaptable species.

But in our rapidly changing world...

...this is Planet Earth

as you may never see it again.