Original subtitles

The frozen seas are worlds unto themselves.

Beneath their ceiling of ice,

they have an eerie, almost magical stillness,

cut off from the storms that rage above.

In the winter, the feeble, slanting rays of the sun

bring little warmth,

and the temperature seldom rises

above minus-50 degrees centigrade.

For much of the year, it is dark and cripplingly cold.

Yet there is life here at both ends of the Earth--

the Arctic and the Antarctic.

For most animals,

whether they live in or out of water,

the winters, when much of the sea is frozen,

bring the greatest challenge.

The Northern Hemisphere.

It's February, and as the Earth tilts on its axis,

the sun's rays creep slowly northwards

and the Arctic emerges from its harsh winter.

The Arctic is a frozen ocean surrounded by continents,

and when the surface of the sea

between the continents freezes from shore to shore,

land predators walk out onto it to hunt.

It's early March,

and the sea is still covered with ice.

But there are patches of open water, polynyas,

that never freeze over.

Here, where tidal currents are squeezed between islands,

the water movement is so strong that ice cannot form.

Walruses spend the winter in polynyas.

Here they have permanent access to the air,

but they can also retreat to the sea

to shelter and to hunt.

Other sea mammals overwinter in polynyas, as well.

In this one, a young bowhead whale.

Here the current is really fast,

and the shifting ice is dangerous.

This whale became trapped

when ice encircled it last autumn.

There is no food here, but a whale must breathe,

and the only place that it can do so for miles around

is in this tiny hole.

It's living entirely on its reserves of fat,

but now they're dangerously low.

It will be some months yet before it can escape.

Elsewhere, other whales have also been trapped.

These are belugas.

Their tiny hole in the ice

has been kept open not by currents,

but by the belugas' continuous movements

as they rise to breathe.

Open water is now some 20 miles away.

It will be two months yet before the ice melts.

The belugas are extremely thin,

and most of them are horribly scarred.

But their wounds were not inflicted by the ice.

A whale would be a huge prize for any meat-eating hunter,

and these belugas, trapped by the ice,

are within reach of polar bears.

Well aware of the danger,

the belugas stay submerged as long as they can,

but they can only hold their breath for about 20 minutes.

Catching a 4-meter-long whale that weighs one ton

is no easy task,

even if that whale is weakened by starvation.

But a beluga is well worth waiting for.

Day by day, as the hole gets bigger,

it becomes increasingly difficult

for the bear to land a whale.

Keeping its fur in good condition and free from salt

is important for warmth,

and the bear uses snow like blotting paper.

These belugas have been attacked by many bears

over the last six months,

and some have been caught.

It may have taken a long time and a lot of patience,

but a catch, when it's made,

brings abundant rewards of energy-rich blubber.

Gulls rely on bear kills at this time of the year,

and the color of blood staining the ice

attracts them from a long way away.

The remaining belugas still have a long wait

before they're released from their prison

and the threat of slaughter.

Can you feel it?

You're exactly where you're meant to be right now.

You and me, we could do anything.

Us against the world.

Welcome to the Theatre des Vampires.

You have no idea what I'm capable of.

My word means something.

We need you...

...to lead the revival of humanity.

You deserve a happy ending.

Well, guess this is it, then.

Arctic foxes also rely on the polar bears

to hunt on their behalf.

They're the jackals of the north

and scavenge from bear kills whenever they can.

In winter and early spring,

they are wholly dependent on bears.

Only in the summer, when the sea ice melts,

will they regularly catch prey for themselves.

They're not strong enough to tackle adult seals

but can certainly take newborn pups or birds.

This canny individual is going to bury its prize.

It may need it during the uncertain times ahead.

The presence of bears affects the behavior

of almost all the animals here, big and small.

The bears tend to avoid

the fringe of fragmented ice bordering open water,

where traveling can be very laborious,

but that very fact makes this area, the pack ice,

a particularly good place for seals to pup.

Harp seals breed here.

Their pups are born with white coats,

which camouflage them very effectively against the snow.

Harp seals have a very short nursing period,

a necessity on this unstable pack ice,

but suckling is intensive.

The pup feeds for just 12 days

on milk that is 45% fat.

Then it's abandoned and has to fend for itself.

A male hooded seal.

This impressive nasal display

is used to warn away other males...

...and to win a mate.

Hooded seals also breed on pack ice.

Their pups suckle for only four days,

the shortest nursing period known for any mammal,

and all because the threat of polar bears

cause them to breed on the unstable ice.

Another Arctic seal opts for the solid ice further north.

Because it's easy for bears to hunt here,

these ringed seals must be particularly vigilant

and have to hide their pups.

Ringed seals are comparatively small,

so they can give birth to their pups

in little caves or lairs under the snow.

Here a pup is out of sight and protected from bad weather.

In late March and into April,

female bears emerge from winter dens with their new cubs.

The mother has not eaten for at least five months,

and she's hungry-- very hungry.

If she doesn't succeed in catching

a regular supply of seals,

her milk will fail... and her cub will die.

Bears have an extraordinarily sensitive sense of smell

and can detect seal pups hidden in the snow

from 2 kilometers away.

But a female ringed seal uses several lairs,

and a bear will almost certainly have to break into a number

before it finds one that is occupied.

This is a crucial time for the cub.

By watching its mother hunt and by copying her actions,

it's beginning to acquire

the rudiments of its own hunting skills.

Play is also important for developing muscles

and improving coordination.

As the days ays go by, the sun rises higher and remains above the horizon even at night.

The female bear continues to hunt

until her cub is too tired and can't keep up.

She's smelt something.

The pup escapes through a hole in its lair

that leads to the sea below.

Only one in 20 hunts is successful,

but this mother must find a seal pup soon

if her cub is not to starve to death.

As spring turns into summer,

the sun's heat begins to melt the sea ice.

Now the ocean is accessible

and the Arctic's summer visitors return.

Migrating birds arrive from the south

to nest and feed on the seafood that's now within their reach.

Brunnich's guillemots

are the northern equivalent of penguins,

but they have retained the power of flight,

for they need to reach cliff ledges,

where their nests will be safe from predatory bears and foxes.

Nonetheless, they are as at home in the water as in the air.

They dive down to a depth of 50 meters or more

to catch fish.

In June, the ice begins to fracture.

The cracks, or leads, form useful corridors

of open water for air-breathing animals.

Belugas, migrating to their feeding grounds,

use these leads to penetrate the ice-covered seas

and reach areas where their preferred food, Arctic cod,

has spent the winter.

The males regularly dive to about 500 meters to find fish.

The females and young, which have smaller lungs,

only go to about 350.

In late June and July, narwhals arrive.

The females, who usually lack tusks,

come first with their new calves.

The males follow a little later.

They also move up the leads

in search of fresh feeding grounds.

Bowheads.

Up to 18 meters long and weighing 100 tons,

these are the only large whales

that stay in the Arctic all year round.

They're not after fish.

They're seeking smaller prey.

Despite having the largest mouths in the animal kingdom--

the size of a small garage--

they eat tiny crustaceans, copepods,

straining them from the water

with the 4-meter-long strips of baleen

that hang from their upper jaws.

In the summer, they store enough energy

to last them through the following winter,

when food will be less abundant.

As the ice melts away,

the polar bears are forced to head for land.

They're excellent swimmers

and can cover 100 miles of continuous open water

if need be.

Off East Greenland,

there is little ice left by August,

so walruses haul out to rest on land.

At this time of the year, they are molting,

getting rid of their old, scarred,

and parasite-ridden skin.

A bathe in the cold water

brings some relief from the itching.

But even there, the odd scratch is irresistible.

They make daily excursions out to deeper water.

Down at 20 meters, they root around in the sediment

using their bristles to search out soft-shelled clams.

Once they find a clam,

they suck its flesh from the shell

with their powerful, muscular mouths.

Walruses can feed for about five minutes at this depth

before they have to return to the surface to breathe.

Elsewhere in the Arctic,

belugas are gathering in their thousands.

They congregate in just a few large estuaries.

Belugas of all ages and sizes come here.

There are even young calves.

Some are so young-- born only a week or so ago--

that they need help.

They swim on their mothers' backs

so that they can breathe more easily.

As the tide moves up the estuary,

the belugas follow,

swimming into surprisingly shallow water.

Like walruses, they also need to molt.

A combination of warm freshwater

and vigorous rubbing against the gravel does the trick.

They remain here for days or even weeks,

so it's likely that socializing

is also important to them.

After molting, they head back out to sea to feed.

It's now autumn, and the sea

begins to freeze over once again.

Thin sheets of ice form at the surface

and pile up, layer upon layer,

gradually creating an impenetrable barrier.

By late November,

the Arctic Ocean is sealed once again by ice.

The lights of the aurora play in the winter sky.

And at the other end of the planet,

in the Antarctic, there is the southern aurora.

Antarctica is now emerging from winter.

This is the coldest, windiest place in the world.

Temperatures are still hovering at a numbing minus-50,

and the returning sun has virtually no warmth.

Very few animals can survive such extreme conditions.

But emperor penguins can.

Standing on the frozen sea,

they endure the full force of the Antarctic storms.

Only by huddling together

can they survive the appalling winter months.

They take it in turns to bear the brunt of the gales.

They can only live here at all

because Antarctica is surrounded by the Great Southern Ocean,

and no land predators have been able to reach it,

so, unlike Arctic animals,

they're not threatened by polar bears.

The sea is still frozen, but one seal,

nonetheless, manages to stay here,

even throughout the winter.

The Weddell seal.

Underwater, it's protected from the storms above,

but it must have access to the air all year

in order to breathe.

And they keep their breathing holes open

with their teeth.

Only by continually scraping away at the ice

can they maintain access to the air,

but that means that their teeth get badly worn down.

Then they can no longer hunt and eat effectively.

Weddell seals die young.

The continent of Antarctica is so isolated and so high--

almost 5,000 meters in places--

that it's considerably colder than the Arctic.

Ice slides slowly down from its center

towards its rim in immense glaciers.

During winter,

the continent effectively doubles in size

as the sea freezes over.

Ice forms around its shores

and extends outwards for hundreds of miles

around the entire land mass.

Under the sea ice live small, shrimp-like creatures--

krill.

They have been here all winter.

During these dark months,

they feed by scraping algae from the ice.

Remarkably, they also shrink in size

and revert to their juvenile form to save energy.

As the temperature rises in spring,

the ice begins to melt,

and little air bubbles trapped within it are released.

Microscopic algae grow around these bubbles,

and the krill now graze on them,

gathering them up with their beating legs.

As the sun's rays grow stronger

and penetrate deeper into the water,

floating algae begin to flourish,

and krill leave the dwindling ice

and gather in swarms as they harvest this new crop.

Far to the north, beyond the blanket of sea ice,

chinstrap penguins have been overwintering

in the open ocean.

The occasional iceberg gives them the chance of a rest,

if they can get onto it.

But at this time of year,

where they really want to be is on land.

It's just getting there that's tricky.

It's spring, and the penguins are returning to breed.

Their need to get ashore is now urgent and imperative.

Doing so is all a matter of timing

and picking the right wave.

But their journey has only just begun.

Most of them will have to walk many miles

before they can find a nest site.

This is Zavodovski Island,

which has the largest penguin colony in the world.

About two million chinstraps breed here,

and they come to this island for a good reason.

It's an active volcano.

The heat from the crater and the fumaroles

keeps the slopes free from the ice and snow,

allowing these chinstraps to start breeding earlier

than those further south.

But then again, living on an active volcano

is not without its risks.

Unlike the emperors,

these penguins are able to lay their eggs on the bare ground.

Little wonder so many of them choose

to brave the mountainous waves in order to get here.

Further south, near the continent,

the blanket of sea ice is beginning to break up.

Icebergs are gigantic fragments of ice

that have broken away into the sea

from the front of glaciers.

During the winter, they were frozen into the sea ice,

but now they're set adrift once more.

As the bergs break up, they form brash ice.

It litters the backwaters of the Antarctic peninsula.

Minke whales make their way into these placid waters in summer.

This is the most abundant whale in the Southern Ocean.

Minkes are one of the smallest of all the baleen whales,

and like all others, they come here to feed.

The majestic humpback whales are also summer visitors.

They have traveled thousands of miles

from their winter breeding grounds in the tropics

to gather the food that becomes available here in summer.

In just four months, they accumulate enough fat

to provide them with energy

for the whole of the rest of the year.

All these animals have come here in search of one thing--

the krill.

Krill is the mainstay of the Antarctic food web.

It occurs in phenomenal quantity.

Billions of individuals in a single swarm,

and swarms can stretch for miles.

Fur seals also collect this rich, super-abundant food.

Krill swarms are very patchy,

but once found, feeding is easy.

Humpbacks engulf hundreds of thousands of them

in a single gargantuan mouthful.

When the going is good, the whales feed continuously,

each eating up to two tons of krill in 24 hours.

Further south, near the continent, the sea ice is still sound.

Here, where the ice remains for most of the summer,

emperor penguins make their home.

These have been feeding out at sea

and are now ready to make their way back to the colony

to feed their chicks.

Instead of heading straight for the ice edge,

the penguins hesitate some distance from it.

They're nervous.

They dive down and investigate the ice edge.

And for good reason.

Leopard seals patrol this border.

Leopard seals are the Antarctic's equivalent

of polar bears-- they're the top predators.

But they hunt most successfully in the water,

so, by and large, the animals they prey on

are safer out on the ice.

They have a lazy grace

that belies their ferocious nature.

Confident that the coast is clear,

the emperor penguins head for the ice.

But they certainly don't linger.

Now they have a long walk back to the colony.

Emperor penguin colonies are some way back from the ice edge.

In winter, they may be as much as 100 miles from it,

but as the summer progresses and the ice melts,

the edge comes ever closer to the colony.

So, by the time the chicks are fledged

and ready to take their first swim,

the water is close by.

This colony is in the lee of a headland,

and that prevents the ice

from being broken up by ocean currents.

The returning adults are so full of food

that they can barely walk,

but with no predator to threaten them now,

they can take their time.

Somehow, in this melee of 60,000 or so penguins,

a parent has to find its chick.

It returns to the place where it last left its chick

in the hope that it might still be close by.

But chicks tend to wander,

so the adult has to call to it.

The chick responds,

and they slowly home in on one another.

The plaintive entreaties

of the chick stimulates the adult

to regurgitate a mouthful of fish.

With the return of one parent,

the other is free to go to sea to feed for itself.

Aware of the leopard seal's presence,

the penguins press together at the ice edge,

unwilling to be the first to risk diving in.

Occasionally, the seal comes out onto the ice

and attempts to grab one.

But its most successful strategy by far

is to lie in wait.

It hides behind a corner of ice.

The emperors gain confidence and make a dash for it.

The first wave of penguins escape.

Once in open water, they will be safe.

But the seal is alerted by the noise,

and through the mass of bubbles, it makes its attack.

Almost invariably, it makes a kill.

Encouraged by the absence of the seal,

the remaining penguins make a break for the open sea.

In time, their chicks will fledge,

and when the Antarctic autumn is near its end,

these adults will walk across the newly formed ice

to endure yet another winter on the frozen sea.