The animal world is full of spectacle and wonder.
But what's it like to be right in the heart of the action?
To find out, our team of spy creatures goes undercover.
They not only look like the animals they film,
they behave like them too.
Armed with the latest camera technology...
..they are heading across the globe.
From the heat of the tropics...
..to the lands that lie in the north.
From the islands of the southern seas...
..to the snow and ice of the frozen poles...
..our spies reveal the astonishing variety
of life that thrives there...
..from inside their world.
On their final assignment, our spy creatures explore the lands
of ice and snow beyond the Arctic and Antarctic Circles.
In this polar realm, animals find astonishing ways to survive
in an extreme and freezing climate.
It's winter on the remote island of South Georgia
in the Southern Ocean.
Spy albatross patrols the rugged coast for signs of life.
Even in this hostile land, animals still thrive.
A city of king penguins and their chicks.
200,000 in all.
They're one of the world's tallest penguins, standing 1m high.
Among the multitude, there's a special addition.
PENGUINS BRAY
Spy chick is here to reveal life in the colony.
In this barren land, the chicks must stick together.
Preening each other is one way of making friends.
Now a fully-fledged member of the colony,
he's free to find out more.
Both parents care for their chicks, feeding them fish
stored in their stomachs.
They're six months old.
It will be eight more months before they're fledged.
No other penguin devotes so much time to rearing their young.
Sheathbills are one of the few other birds to thrive here.
They scavenge on anything they can.
Even spy chick is worth a try.
Sheathbills are more an irritation than a threat.
The chicks have far bigger things to worry about.
Giant petrels.
He seeks out the weak and injured.
His aim is to create panic...
..separating a chick from the colony.
But parents work together to shield any chick in danger.
The petrel seeks an easier victim.
Not the time for a malfunction.
SPY CHICK WHIRS
Luckily, there's plenty of life left in spy chick.
In a colony so vast, the petrel will soon find
a more appetising meal.
Order restored, the chicks' lives are about to change.
Their parents' food stocks have run out.
There's nothing left to give.
It's time to go fishing once more.
The chicks won't see their parents again for at least three months.
Ahead lies the Southern Ocean,
and a round trip of over 1,000 miles.
The chicks must now face the full brunt of the weather alone.
It will be a long wait.
Their next meal is many months away.
As our penguin chicks hunker down for winter,
spring is arriving in the Arctic's far north.
Icebergs, cast adrift from glaciers,
are sculpted by rising temperatures.
What once was frozen sea now gives way to open water.
Only rafts of drifting ice remain.
But it's not just the ice that's on the move.
Spy walrus is perfectly suited for navigating these waters.
Based on a young walrus, it should be readily accepted.
This is just what it's looking for.
Atlantic walrus hold out on what little ice remains.
A new walrus is always of interest.
This small family pod has been at sea all winter.
They gave birth when the water was frozen.
Ice still provides a safe platform to rest on...
..but now there's not enough room for everyone.
Fortunately, the male is quite happy to snooze in the ocean.
LOUD SNORING
And he doesn't mind letting everyone know.
PARPING
GRUNTING
He needs his sleep.
Walrus can stay awake for four days when searching for food.
He can dose for ten hours at a time,
only waking to change position.
He's even happy to sleep on his front...
..despite needing a breath every ten minutes.
Male walrus are notoriously grumpy.
But most of it's just for show.
KNOCKING
This strange knocking sound is a warning to rival males.
It can carry ten miles or more.
Back with the walrus family, their ice raft is fast disappearing.
Time to find dry land.
But first, they check out the new visitor.
Walruses use their tusks for finding food and fighting.
But they have only friendly intentions here.
Inspection over, the family look for a safer place to haul out.
They're joined by spy gyrfalcon,
based on the only falcon found this far north.
In the water, the calf is vulnerable to predators.
For security, the family keep him surrounded.
They may travel over 200 miles without stopping or sleeping.
But today, they're not going far.
Their favourite beach is close by.
A popular spot with shallow waters rich in clams and other food...
..this will be their summer home until the ice returns.
There are some who choose to follow the retreating ice.
Spy falcon heads further north...
..the frozen realm of the world's most formidable predator.
Polar bears use the ice for hunting.
But each year the spring melt arrives earlier,
making conditions more challenging.
She must use the fragile ice as stepping stones.
To gain a closer look, another spy is needed.
It could be a risky mission.
The planet's largest carnivore has a fearsome reputation...
..and they like to hunt alone.
As a precaution, spy bear has a nifty trick.
Fortunately, polar bears aren't territorial.
They're more inquisitive than aggressive.
The bear continues her quest for seals...
..slipping into the water with hardly a stir.
Hidden between the ice floes, she can move quickly and silently.
But seals haul out where they can see bears approaching.
And this seal has met polar bears before...
..with the scars to prove it.
She must use what cover she can.
She takes a bearing and dives.
She aims for a surprise attack.
That means getting close.
But there's too much ice to cover.
She must change her technique.
Keeping downwind gives her the advantage.
But hunting on melting ice has its own problems.
She spreads her weight as best she can.
But this wasn't in the plan.
When the ice is melting, most hunts fail.
Rolling squeezes water from her fur,
vital for maintaining insulation.
Perhaps all is not lost.
She's picked up a scent.
A trail that leads to land.
She can smell food from 20 miles away.
But the trail ends here.
A whale carcass.
100 tonnes of blubber, and a beacon for every bear in the neighbourhood,
including our spy.
The hungry bear soon joins the feast.
When there's plenty of food, they don't mind sharing.
Here, there's enough to last them a year.
As the climate changes, such bonanzas become life-savers
for hungry bears.
Further south, beyond the sea ice, is Norway's Hornoya Island.
It's early spring and millions of seabirds are returning to breed,
having spent winter fishing at sea.
Among them is the island's most famous inhabitant.
Puffins are rarely seen on snow,
but here winter lingers far into spring.
To gain a head start, they must pair up as soon as they can.
But one puffin is very much on its own.
A spy in disguise.
It isn't lonely for long.
Puffins are sociable and inquisitive.
Spy puffin greets them with a head flick.
And they soon return the gesture.
He's surrounded by males searching for their long-lost partners.
They pair for life, but only spend time together
in the breeding season.
After so long apart, it's hard to recognise who's who.
Even spy puffin is given the once over.
The male waits by his old nest burrow hidden beneath the snow.
This is where his partner will return.
Could this be her?
Or maybe her?
Or even her?
There's only one way to find out.
They bob and head rub.
She's definitely the one.
But a male who's young and single is out to try his luck.
He'll happily muscle in on a devoted couple.
But no male gives up the love of his life without a fight.
Despite her commitment, a strong male might turn her head.
Her partner must prove he's still worthy.
The love rival loses.
Her mate has proved he's still a good catch.
Bonds restored, they join others as they go fishing.
Back in South Georgia, four months have passed and the chicks
are still waiting for their parents to return.
With warming seas, the fishing grounds are moving south,
meaning their parents must travel further.
Despite their fluffy appearance, some have lost 70%
of their fat reserves.
Close to starvation,
they must conserve the little energy they have.
But their wait may soon be over.
The first promising sign.
They've been away for a third of a year and are desperate
to feed their hungry chicks.
Another penguin cam is here to greet the weary travellers.
Their bellies are stuffed with squid and krill.
Over the next few days, hundreds of thousands will return.
But while they were away, things have changed.
Their beach has been invaded.
6,000 elephant seals now separate them from their hungry chicks.
Spy chick is waiting too.
It won't be easy - the bulls weigh four tonnes
and are easily riled.
The penguins will just have to wait.
As peace returns, it's the opportunity they need.
Safest to go on tiptoe.
So far, so good.
Maybe not so good.
It's now or never!
He's cleared the way - it's the break they need.
But that was the easy bit.
Somehow they must find their own chick
among all the identikit versions.
A seemingly impossible task.
Especially as their chicks have changed
over the last four months.
But they have a solution...
PENGUIN CALLS
..call and hope their chick answers back.
Each parent's call is unique.
Once identified, the chick can't contain his excitement.
After so long apart, it's a moment worth celebrating.
Food at last!
Preservatives in her stomach mean it's as fresh
as the day it was caught.
With full bellies and their parents around,
the chicks will be safe for another few months.
On the Arctic islands of Svalbard, young seabirds
face a different challenge.
It's now summer, and guillemots are among the many birds
raising their young.
An Arctic fox bears witness to this yearly spectacle.
Among the returning flocks, our spy is surrounded by little auks.
They nest among the boulders.
While Guillemots nest on the sheer cliffs above.
All this life brings opportunities for predators.
Spy fox is staking out a den of Arctic foxes.
These youngsters have been raised here over the last three months.
Now they're coming of age,
they play the games that hone their hunting skills.
High above, the guillemot chicks are ready to leave their nests.
Below is a drop of 300m,
and there's only one way down.
Somehow, they must make it to the sea.
The chick has never flown before.
But her father is with her all the way.
Falling short is the greatest danger.
But she makes a textbook landing.
More are encouraged to follow.
For the foxes, they're tantalisingly out of reach.
While the youngsters hope for better luck,
boulder cam takes over filming duties.
It's just one of the many spycams hidden here.
For now, the fox cubs bide their time.
Above, more novice flyers are warming up.
Ready or not, she must make the leap of faith.
She falls short.
An opportunity for the fox.
The chick is still 300m from the sea,
but her father's calls are beckoning her.
She's in a race for her life.
To keep up, another spy creature is needed,
one based on a snowy owl.
The chick might seem an easy meal...
..but this meal bites back.
It's running rings round this novice hunter.
But there's a long way to go.
To reach the sea, the chick must cross the boulder field.
And danger lurks wherever she turns.
But this bird has spirit.
And the boulders offer places to hide.
All the time, she's edging closer to the sea.
It seems her bravado is outfoxing the fox.
But she's not safe yet.
She's made it.
A hard lesson for the fox.
A happy reunion for the chick.
She'll return to the cliffs in five years' time,
when she is ready to breed.
By then, the fox cubs will be seasoned hunters.
While it's summer in the Arctic,
Antarctica is facing the lowest temperatures found
anywhere else on Earth.
Remarkably, emperor penguins choose this time to have their young.
This tobogganing version of penguin cam
is here to discover how they survive.
As temperatures reach 40 degrees below,
the chicks try to tuck themselves into their mother's pouch.
As the blizzard strengthens, their parents turn their backs
to the biting wind.
But even this is not enough.
To stay warm, they must huddle together.
A chick on its own won't survive for long.
Just in time.
But he urgently needs the warmth of the huddle.
His mother must find a place to tuck in.
In the jostle for position, accidents are inevitable.
His mother's only thought is to protect him from harm.
It's not the only danger he faces.
Here, winds can reach 100mph for days at a time.
Spy penguin is facing the full force of the weather.
While penguin cam is out of action, other cameras take over the filming.
Time-lapse unravels the huddle's secrets.
Somehow, they must share the warmth.
But the last to join are stuck on the outside,
taking the brunt of the storm.
But there's help.
Those on the inside take tiny steps
that move the huddle in waves.
Step by step, the penguins move
from the inside to the outside.
In this way, the warmest penguins
soon cover the coolest birds.
By rotating position,
no penguin is left out in the cold
and all get a turn in the warm centre.
The huddle is so efficient
penguins at the inner core often overheat.
Then the colony breaks down.
The coldest penguins now form a new huddle.
As others join, they soon become warm and snug once more.
When the blizzard ends, the penguins separate.
Our spy can join them once more.
The chicks have made it.
They now take a little ice and snow in their stride.
As Antarctica freezes,
it's midsummer in Ellesmere Island,
just 500 miles from the North Pole.
It's home to the Arctic wolf,
the world's most successful pack hunter.
Summer is pupping season.
After three months in the den,
they're big enough for the great outdoors.
There's so much to see.
Spy pup.
A new companion, perhaps.
A bow and wagging tail means come and play.
Already, they've made a friend.
The pups are big enough to meet the rest of the family.
Their older brothers and sisters now have young playmates.
Their parents share in leadership duties.
DUAL HOWLING
They rally the family to go hunting.
When all are ready, they leave together.
Spy pup tries to follow.
But it's no match for the agile wolves.
Spy snowy owl takes up the filming baton.
It can fly long-range and cruise at 15mph...
..perfect for tracking wolves on the move.
They have 75,000 square miles to hunt in.
The head into wind
to try to catch a scent...
..perhaps from prey 20 miles away.
It's a testing time for such tiny pups.
To discover what lies ahead,
our eye in the sky takes the lead.
Muskox are prime prey for Arctic wolves.
Downwind, the wolves are difficult to detect.
But muskox are easily spooked.
So they carefully take up position.
Selecting the young or infirm.
But the pups have yet to learn the rules.
PUPS YAP
Their cover's blown.
The herd cluster together...
..forming a protective circle around their calves.
The wolves surround them.
This time, the pups stay still.
The pack calculates its next move.
They split the herd.
As the pups watch and learn.
They've singled out the oldest animal.
But a fully grown muskox
weighs 400 kilos and can kill a wolf.
And its thick woolly coat is almost impenetrable.
Their aim is to tire her out.
Those at the front keep the muskox distracted.
Those at the back anchor her down.
Such battles can last an hour.
Exhausted, she gives up the fight.
It's enough food for the whole family,
including the pups.
But they must wait -
the hunters get the first reward.
Once they've had their fill,
the cubs are called.
They're curious.
It's the first time they've tasted fresh meat.
It's also their first lesson in survival.
Back at the den, spy pup is waiting.
The pups return with spoils from the hunt.
For all, the meal will keep hunger at bay for a week.
It's now time to relax once more.
Before our spy creatures' mission ends,
they return to South Georgia.
Spy king penguin is on duty once more.
It's the elephant seals' breeding season
and females with pups are everywhere.
It's a busy time for this beach master.
He has around 100 females to look after.
Each is in need of attention.
He doesn't want them to stray.
But while his back is turned,
he's vulnerable.
There are plenty of other males
hoping to steal them away.
This one isn't big enough
to challenge the beach master.
He has to be sneaky instead.
But the beach master is always on guard.
He roars a warning.
His nose amplifies the sound.
For the intruder,
the message is loud and clear.
It's followed up with a charge.
The rival backs down.
Spy penguin becomes the first casualty
as the rival makes his escape.
With a spy creature down,
backup is required.
Meet the largest spy yet.
To cope with his massive bulk,
he's an inflatable version.
His head is filled with water
for added stability.
He seems to fit right in.
While the beach master recovers from his brawl,
the young male considers his next move.
It's worth another try.
He must be as discreet as he can.
But that requires a willing partner.
He's been rumbled, and he knows it.
This is an act of war.
As the rival retreats,
the female leaves the battleground.
They must fight once more,
with spy elephant seal in the very heart of it.
ROARING
The beach master rises to full height.
Let the battle commence.
Fighting can be lethal.
Outmatched, his rival retreats again.
Another victory for the heavyweight champion.
He'll spend the whole summer fighting.
Every day is another battle.
Despite being in the danger zone,
our spy survived.
But the young pretender
still has some fight left in him.
Best he picks on someone his own size.
It didn't stand a chance.
It's a deflated end
for spy elephant seal.
AIR WHOOSHES
As ever, the sheathbill won't miss an opportunity.
For a moment, he's king of the castle.
Despite its early demise,
spy elephant seal was part of something remarkable.
With the help of new technology,
our spy creatures joined animal families to discover
how they survive in every part of the world.
Wherever they went,
they gave us an intimate view of animal life
and captured behaviour never seen before.
What they filmed made us smile.
And made us wonder.
They even touched our hearts.
But in the end, the animals told their own stories
while our animatronic team
brought new insights into the animals that share our planet,
with many adventures along the way.