Frozen Planet II

At the far south of our planet

lies the most hostile of the Earth's frozen lands.

Antarctica.

Here, temperatures can fall

to below minus 80 degrees Celsius...

...and winds blow up to 200 miles an hour.

Its icy centre is almost devoid of life.

But on the edge of Antarctica,

some creatures find a way

not just to survive, but to flourish.

Here are some of the greatest concentrations of life

to be found anywhere on Earth.

The continent of Antarctica

lies at the southern end of the globe.

Twice the size of Australia,

it's the largest, coldest expanse of land on the planet.

To the north of it, however,

across 1,000 miles of ocean,

lie the subantarctic islands,

where conditions are somewhat less hostile to life.

The largest of them is South Georgia.

Here, a million king penguins live and breed the year round.

A mother has returned after a month at sea...

...collecting food for her hungry chick.

At ten months old, chicks are the size of a human toddler,

and covered in no more than a downy fleece.

Until they get their waterproof feathers,

they themselves cannot go to sea...

...So they have to rely totally on their parents

to bring them food.

Their time together is brief -

just long enough to disgorge her crop of fish and squid.

All too soon,

parents have to return to sea to collect more.

But getting back there can take several hours.

Hundreds of parents make the commute together.

A beak can be used as an ice-pick

to negotiate the steeper parts of their trek.

This mile-long snow-covered trudge

is unique to this colony, and has never been seen before.

At last, the sea.

After several days on land,

their feathers need washing to be ready

for the long days of swimming that lie ahead.

But this is a dangerous place to loiter.

Leopard seals.

Three metres long,

more than three times the size of a king penguin,

these fearsome hunters are usually solitary.

But at this time of the year,

in this bay, there are as many as 30 of them.

If these penguins think that they're safe on land...

...they are mistaken.

Any one of these huge seals

can take as many as ten penguins a day.

Their best chance...

...Is to stay with the crowd.

There's safety in numbers.

Made it.

Only to return in a month's time...

...and once again face death head-on.

This is surely one of the greatest challenges

faced by any parent.

1,500 miles off the continent's east coast

lies another of the tiny outposts

that are vital for the survival of Antarctic wildlife.

The Sub-Antarctic Islands of the Antipodes.

In spring, the longer days turn each tiny speck of land

into a potential breeding ground...

...for the Antipodean wandering albatross.

Its wings are three metres across,

amongst the biggest of any bird.

This 14-year-old male

is now mature enough to start selecting a partner.

For the smaller, darker female,

choosing a suitable mate is of equal importance.

After all,

they may stay together for the next 50 years.

To make this crucial decision,

they use one of the most elaborate courtship rituals

of any sea bird.

He begins by sky-pointing.

It seems to be working.

Next, he attempts a move...

...known as the double head-bob.

The finale is the real decider.

Synchronised wing-spreading.

She seems impressed.

But another male appears...

...and shows off...

...his wings.

The greater the span,

the more attractive he could be.

But the first male won't tolerate

a rival cutting in.

Yet another hopeful joins in the competition.

And another.

This was not supposed to be a dance-off.

She prefers one tango at a time.

It seems that this is not going to be his year after all.

But he's caught the eye of another albatross.

Once again, he begins his courtship display.

But this is, in fact, another male.

Regardless, he continues to demonstrate his eligibility.

This could still be the one

with whom he will share the rest of his life.

On the Antipodes Islands, it's becoming increasingly common.

Today, there are three times as many males as females.

Females feed further north than the males,

in waters used by industrial fishing fleets

that catch and drown great numbers of sea birds.

As a result, the female albatross here

is now declining fast.

A same-sex partnership like this

may bring no survival advantage...

...but is apparently preferable to a life alone.

The wealth of life found around Antarctica's lonely islands

is evidence of the richness of the waters that surround them.

The Southern Ocean.

It may appear treacherous.

Its gale-force winds certainly create powerful currents.

But all this stirring has an important effect.

It brings up nutrients from the depths,

helping to create some of the richest seas on Earth.

And this provides food for the largest animal

to have ever lived.

The Antarctic blue whale.

It's more than 30 metres long...

...but it's rarely been filmed before.

Only the Southern Ocean

can provide the four tonnes of food

that the biggest of all blue whales needs every day.

This ocean giant was almost hunted to extinction,

but thanks to an international ban

on commercial whaling,

its numbers are now increasing.

The closer the seas are to mainland Antarctica...

...the colder they become...

...until, a few hundred miles offshore,

the ocean's surface freezes solid.

It forms a cover of sea ice

that is twice the size of Europe

and encircles the entire continent.

This is a stronghold

for one of Antarctica's most remarkable inhabitants.

It uses its teeth

to prevent its breathing holes from freezing over.

The Weddell seal.

The most southerly breeding mammal on the planet.

This ten-day-old pup

is still entirely dependent on his mother.

Out on the ice,

it may be safe from marine predators...

...but within its first two weeks,

it will have to venture into the underwater world

upon which its future depends.

This is the coldest water on Earth.

So it's not surprising

that a pup needs some encouragement.

It's time to leave the safety of the breathing hole.

To catch fish and then safely return,

this pup must learn how to find his way

through the maze of underwater ice caverns.

But after just eight minutes...

...his mother signals that it's time to head back.

She can hold her breath for an hour and a half.

But he is already starting to tire

and is running out of air.

On their way back to their breathing hole,

they hear a sound as loud as a fighter jet.

It is the call of a half-tonne male Weddell seal

announcing that he's on the lookout for a mate.

She, however, is still producing milk for her pup,

and so isn't sexually receptive.

But he doesn't stop trying.

To repel his advances,

she leaves her pup's side.

But the pup isn't strong enough

to haul himself out without his mother's help.

She tries to fight off the adult male.

She's wounded him so seriously

that he is unlikely to be back any time soon.

A gentle nudge from Mother

is all an exhausted pup needs

to make it to the safety of the sea ice.

Mothers stay with their pups for six weeks,

by which time they're strong enough to fend for themselves.

As spring arrives, the sea ice retreats,

and in a few places, Antarctica's coast

is exposed to the open sea.

And that attracts all kinds of animals.

Having spent the winter at sea,

chinstrap penguins can now come ashore to breed.

Soon, the coast becomes extremely crowded.