Original subtitles

O

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.

In 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.

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 35 miles

an hour. 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.

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.

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.

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.

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 forest is covered with snow.

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.

Tiny arctic lemmings.

With a carpet of edible moss beneath, and a thick blanket of

snow above, the lemmings spend their days in the snow. They

spend their entire winter hidden below the surface. And here they breed.

For a hungry fox, a group of lemmings could be

a life-saving discovery. If it can catch one.

The 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.

And the arctic fox has a special trick.

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 fox's 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.

Crows. They too are looking for food.

And their calls tell him that they found something.

But he is not the only predator here. On one of the

trees, the marks of huge claws, 10 centimeters 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 carrying of the food.

And that includes leopards.

But he can't let down his guard.

The crows that led him here may also have alerted the tigers. Let's go.

The crows are disturbed. Another mouthful might be risky.

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 turtle's 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 fly away. Fresh 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 centimeters 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 her long tail. And a

natural antifreeze that she has in her body.

As temperatures continue to rise, she begins to thaw.

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.

Traveling 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 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 ensures

that the bees are fed. She 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 wildflower 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.

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 hour, snowy owls 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.

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.

Over 600 meals later, the parents' labors are starting to

pay off. As the chicks stretch their newly developed wings.

Just a month is left before winter returns.

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. The chicks' wings are so big,

they're so small, they're so small, they're so small,

they're so small, they're so small, they're so small.

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.

The ground itself is giving way.

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 tons 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 area of land. A vast

wilderness known as the Arctic National Wildlife Refuge.

These summer pastures provide rich grazing, just what's needed to raise newborn calves.

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.

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.

Individual animals could lose a quarter of a pint of blood a day to biting insects.

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.

So the

He is one of the lucky ones.

Reunited with his mother, he can continue on his journey with the herd.

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.

He's looking for the weak and weary.

And he's found one.

Too tired to flee, and too weak to resist.

The herds finally reach 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

superpacks of wolves and bison in midwinter.

The crew travel 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 Earhart

helps to pinpoint one of the last free-roaming herds of

bison, and the wolves have specialised in hunting them.

Some of the wolves have run forward, 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 the gyro-stabilised camera system, enabling

him to capture rock-steady images from a safe distance.

You'd think filming from a helicopter is 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.

Before Jamie can start filming, the chopper

must first drop the accompanying ground crew.

We've got to put down this vast open space, and 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.

Every time I catch up with Jesse, he just keeps on going. He's a machine.

They're starting to head a little bit towards the north

-west, so they're starting to move away from you. Oh,

goddammit. 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. Oh,

it's ready. Incredibly awkward getting around. Even lunch

offers little consolation. Frozen bread, frozen brie, and

frozen pickle. And with no wolf activity visible from the

air, Jamie is soon grounded. Yeah, we're just looking for an update.

Great.

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 sky is 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'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 spot operator just phoned

the wolves with the bison, so we're scrambling to get there

as quickly as we can. Do you see that line of dark willows

in Poposoff somewhere just behind that?

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 the chase begins, Jamie picks up the action from the air.

Let's try and get around the front and try and get them

coming towards us as well if we can get around there.

In a stop-start pursuit lasting an entire day,

Jamie manages to record the full jaw-dropping drama.

We've definitely got that female right now. They're going to bring it down.

Perfect, Jim. We've got it. With the hunt nearly

over, the crew reposition Justin once more.

We've 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.

We'll be right back. you