Hostile Planet

Bear: These emperor penguins are about to undertake

One of the greatest feats of endurance on the planet.

A single egg.

It's taken almost all this mother's energy to create.

Time to entrust it to her mate.

While she leaves to feed at sea.

Now it's up to dad.

He must carry the egg through the world's worst winter.

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Risk his own life to keep the chick growing inside alive.

Just one of the many remarkable stories of how

Life triumphs at the ends of the earth.

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When winter hits the polar regions,

The temperature can drop as low as

Minus 120 degrees fahrenheit.

Almost nothing grows.

Winds build into some of the strongest on earth.

You've got land and sea locked in ice.

And weeks of perpetual darkness.

Only a few remarkable animals have what it takes

To survive here, and every day is a struggle

Against the elements and each other.

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Now the poles are changing faster than

Anywhere else on the planet.

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And getting through the coldest days,

That's just the beginning of the battle.

Late fall.

Polar bears are grounded.

Once the sea has frozen over

They can head out and begin hunting.

But since the 1970s that's taking longer.

Hunger claws for an extra three weeks.

And this young male must face other challenges.

An older rival.

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The largest of all land predators.

Male polar bears lead a life of violence.

But today punches are being pulled.

Sparring partners test strength and skill.

Preparing for tougher times.

When the battle for food and mates will be real.

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But first, patience.

Wait for winter.

The magic number.

28.8 fahrenheit.

Sea water begins to freeze.

An ice kingdom is born.

Almost limitless hunting grounds.

The harshest season is when polar bears thrive.

The arctic plunges into 24 hours of night.

Around the poles the planet's magnetic field puts on an

Unearthly display.

In the north the aurora borealis.

And in the south the aurora australis.

Winter here looks heavenly.

But for these emperor penguins it's hell on earth.

All of them are male.

And if the eggs they're carrying are to survive,

All of them must stand strong.

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Each one takes their turn in the full force of the wind.

All the time balancing their eggs on their toes.

Just beyond the ices deadly reach.

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75 days of sacrifice finally over.

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It was worth it.

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Just 6 ounces, he's got a lot of growing to do.

Soon the ice on which they stand will all be gone.

This is canada's last land before the arctic pack ice.

Somehow an eight-strong pack of arctic wolves

Survives here.

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During the brutal winter

Finding food is a daily struggle.

But after almost three months of darkness a ray of hope.

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Arctic hares are one of the few other creatures

That survive here.

Gathering in huge groups offers protection.

And now the sun has returned,

The element of surprise is gone.

A lot of effort for no return.

There are bigger opportunities here,

But they come with greater risks.

Musk oxen.

One of the arctic's true survivors.

Bear: In their search for food the arctic wolf pack

Can cover 50 miles in a day.

These musk oxen have spent all winter

In this frozen waste land.

They're built to survive.

But just one adult would feed the entire pack.

To witness wolves hunt musk oxen in winter is so rare

It's never been captured on camera, until now.

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This herd has a youngster.

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But it's protected behind a united front.

Armed with slashing horns,

Adults weight up to 700 pounds.

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The wolves search for weakness in their defense.

Try to get them on the run.

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The mother won't leave her calf,

But her instincts work against her.

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In such a brutal landscape, one animal's survival often

Depends on another's fate.

In the south, the sun's power is increasing.

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It's been 12 weeks since he hatched.

In fewer than four months, all this will have melted.

By then chicks must be ready to swim.

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His life depends on how quickly he grows.

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In just 150 days his body weight must increase 70 times.

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Strengthening sun promises easier times.

But down here promises are easily broken.

Antarctica's freezing winds have become more ferocious.

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A hole in the planet's ozone layer is disrupting

The atmosphere, altering the weather.

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Even though dad hasn't returned from fishing,

The chick now needs so much food,

Mum must go too.

His instincts are to follow.

But it's a mistake.

He's walking away from safety.

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Unless he makes it back to the colony,

He will die.

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Bear: In antarctica a storm has hit the