The sun rises on Japan.
More than 6,000 islands on the edge of the Pacific.
Life here is at the mercy of Earth's most powerful elemental forces.
From the wilds of the frozen north...
BIRDS SQUAWK
..to the subtropical warmth of the south.
Animals along this chain of islands have had to adapt
in unique and sometimes bizarre ways.
Throughout this land,
people have developed an extraordinary relationship
with the natural world.
BEAR GROWLS
Trying to capture its fleeting beauty...
..and tame its spirit.
But these islands remain wild, mysterious and magical.
This is Japan.
BIRDS SQUAWK
In Japan's far south, there's a chain of tiny islands
stretching for 750 miles towards the tropics.
Isolated in the vast Pacific Ocean,
these islands are ruled by the sea.
Here, you have to live life with a different spirit.
And the further south you go...
the stranger life seems to become.
SHE SPEAKS JAPANESE
At the top of the chain lies the island of Yakushima.
A narrow channel is all that separates it from the mainland.
It's like a lost world.
Its steep slopes are mostly covered in forest
and some of the trees are thousands of years old.
A family of Japanese macaques.
They share this island with another animal...
..sika deer.
Deer and macaques live all over Japan...
..but here on Yakushima, the two species live side-by-side.
And the rowdier young monkeys do something very unusual.
They ride on the deers' backs.
MACAQUE SQUEAKS
Why they do it, and why the deer put up with it, is not entirely clear...
..but it only happens here on Yakushima.
There comes a point when the deer have had enough.
MACAQUE SQUEAKS
But there are advantages to hanging out with monkeys.
Every day, the macaques forage up in the trees.
The deer listen for their feeding calls and follow them around,
picking up what they drop.
It's food they could never reach themselves.
It's an easy-going relationship.
But even the best of friends can fall out over something trivial,
like a stolen leaf.
MACAQUE SQUEALS
No-one really knows why these two animals have such a close bond...
..but strange things can happen
when you are cast away on isolated islands.
Enormous volcanic forces created Yakushima
and many of the islands beyond it.
The sea level rose and Yakushima was cut off from the rest of Japan.
The deer and the macaques were marooned together
in this odd little world,
where life could follow different rules.
This part of Japan lies along a great rift in the Earth's crust.
It's one of the most geologically unstable places in the world.
It has 18 active volcanoes.
VOLCANO RUMBLES
Some of the largest in the world.
VOLCANO RUMBLES
Sakurajima is Japan's most active volcano.
VOLCANO RUMBLES
It has been erupting nonstop for the last 60 years.
Even so, over half a million people live next to this smoking giant,
never quite sure when it might get really violent.
BIRD CAWS
VOLCANO RUMBLES
Every few weeks, it belches out thousands of tonnes of ash,
covering the city.
It might not seem like the ideal place to live...
..but with a few simple precautions, life can be almost normal.
Rocks the size of tennis balls can rain down at any time.
It gives the school run an element of peril...
..but these children are used to it.
JAPANESE SPOKEN OVER TANNOY
The school day always begins
with a sweep-up of last night's shower of ash.
Despite the risks, people have been living in the shadow of Sakurajima
for thousands of years...
but there are advantages.
The volcanic soil is fertile and farms crowd the lower slopes...
..but the volcanic warmth brings unexpected benefits.
On this local beach, nobody goes swimming.
The water could kill you.
It's hot enough to brew tea.
There's not much life in the sea around here,
but the resourceful people of this island have found a way
to create a paradise.
A steaming sand bath.
People travel from all over Japan
to be buried up to their necks in hot sand.
They've been doing it for hundreds of years.
They say it improves circulation, and restores health and vitality.
If nothing else, it's a nice lie down.
When you live next to a volcano,
you might have to deal with its dangers,
but you can still relish its delights.
Heading south along Japan's island chain,
life becomes more and more influenced by the sea.
It brings something to these islands
that affects everything that lives here.
The Kuroshio Current -
one of the most powerful ocean currents in the world.
Japan's own Gulf Stream.
It surges up from the equator
and delivers 50 million tonnes of warm water every second...
..and brings a touch of tropical magic...
..creating the perfect conditions for coral reefs.
It's only the warmth of the Kuroshio Current
that allows coral to grow this far north in the Pacific Ocean.
The current also brings nutrients from the deep.
There's one very small resident who never strays far from the reef.
He's a bluestreak cleaner wrasse...
and he leads a very busy life.
He eats parasites and dead skin from other fish...
..but he has to wait for them to come his way.
And right now, no-one is stopping long enough
to give him as much as a nibble.
But then he spots something worth chasing...
..a batfish.
Like a customer at a spa, the batfish lies back
and waits for attention.
It opens its gills
and the cleaner wrasse bustles in to begin the treatment.
The batfish even changes colour...
probably to make parasites more visible.
Someone else has arrived at the reef.
The batfish is abandoned.
There's a visitor from the open ocean
that's worth dropping everything for.
A manta ray, two metres long,
has come back to a favourite stretch of reef.
He signals to the manta by flicking his tail...
..and the giant responds by unfurling itself for cleaning.
The manta keeps its feeding lobes rolled up while it swims...
..but a thorough clean keeps them parasite-free.
This enormous fish would never visit Japan
if it wasn't for the warmth that bathes the island chain...
and the helpful services of this resourceful little wrasse.
The Kuroshio Current brings more dangerous animals to the islands.
Sea snakes.
At one time, these snakes' ancestors lived on dry land.
They must still visit the surface to breathe.
But they are beautifully adapted to life at sea,
hunting for fish around the island reefs.
They have some of the most toxic venom of any animal,
so they don't have many predators.
But as they forage off the coast of one small island,
their greatest nemesis is approaching.
Yoko and Setsuko are hunters and they have a fearsome reputation.
These two 70-year-olds are on a shopping trip like no other.
Yoko and Setsuko live on the tiny island of Kudaka.
It's only three miles across and, with limited space on land,
the locals look to the sea to provide.
As the sun sets, the ladies' prey is approaching.
On certain summer nights,
venomous sea snakes move towards the island
and gather in coastal caves...
..looking for shelter and fresh water to drink.
But coming ashore on this island is extremely risky.
It takes some nerve to wade in with no protective clothing.
Sea snake venom can be ten times more powerful than a rattlesnake's.
Yoko has been hunting snakes for 40 years.
It's a skill that's been passed down
the generations here for at least five centuries.
The snakes will be dried in this smokehouse
using a secret process known only by the hunters.
Then they go into a special soup.
The catching and eating of sea snakes is a very old tradition
on the island of Kudaka, where the sea provides more than the land.
THEY SPEAK JAPANESE
It's part of a rich island culture that goes back many centuries.
Kudaka is just off the bigger island of Okinawa,
right in the centre of the island chain.
The seas are warm and bountiful, and the climate is perfect.
In the Okinawan village of Ogimi,
you are still considered young at 80.
Many people here live well beyond 100.
Okinawa is famous as a place where people live longer,
an achievement worth celebrating.
96-year-old Sumiko reckons it's all about staying active.
She cycles to her vegetable garden every day.
Others have their own theories.
THEY LAUGH
But the biggest influence of all, they say, is the Okinawan diet.
Maybe this is what keeps them young.
But there's one ingredient in their diet that can't be grown on land.
It's another gift from the bountiful sea.
Around Okinawa, the warm Kuroshio Current supports
one of the strangest ways of farming in the world.
The Tsuhako family have made their living from the sea for generations.
It's harvest time on the family farm.
ENGINE RUMBLES
This is a field of mozuku.
It's just humble seaweed,
but it has a reputation as a miracle super food.
It grows naturally,
but Okinawan farmers have set out an ingenious system of nets
to help it take root...
..and they have a very practical way of harvesting it.
Mozuku seaweed is one of the most sought-after dishes in all Japan...
..so every strand is precious.
This farming still relies on traditional Japanese wisdom.
It's what they call satoumi.
If you work harmoniously with nature,
the sea will always provide.
This is a man-made environment...
but strange creatures roam the mozuku beds.
Sea slugs. Some crawl...
..while others fly.
This harmonious way of farming only works if the conditions are perfect.
Warm water, plenty of nutrients...
and a wide, shallow sea.
It's only here in Okinawa that they can grow mozuku
on such a massive scale.
On these central islands,
the bountiful sea provides a charmed way of life.
But further south, life takes a different turn.
Islands become further apart in the vastness of the ocean.
With fewer human inhabitants,
these are some of Japan's most remote island outposts.
Increasing isolation brings a whole new set of challenges...
..and life has found ever more inventive ways to get by.
One-and-a-half million years ago,
the island of Iriomote was joined to the mainland.
When sea levels rose and cut it off, one animal was left stranded here.
Its descendants have been scratching a living in the island's
dense forests ever since.
A Ryukyu wild boar.
It spends its day grubbing through the forest soils,
digging up worms and roots,
just like wild boar the world over.
But life on this island is not always easy.
It might look like paradise,
but sometimes it's a struggle to find enough to eat.
In the face of hardship,
something remarkable happened to the Ryukyu wild boar.
Over the generations, it has shrunk
to half the size of its mainland cousins.
When you're small, you need less energy to survive.
They're now just knee-high - the tiniest wild boar in the world.
But it still has a phenomenal sense of smell.
BOAR SNIFFS
It's alerted this little pig to a valuable bounty.
A female green turtle has come back to the very beach
where she was born.
She's here to lay her eggs.
Then she's off, back to the sea.
A heavily pregnant and very hungry sow
has come to the beach looking for eggs.
But she's not the only one.
A male is already rifling the nest.
He certainly won't let her share.
She can only eat when he's had his fill.
BIRD CAWS
But each nest can contain more than 100 eggs...
..so there's enough to go around.
Cast away on these remote islands,
you have to be extra resourceful to survive.
On the tiniest islands, the challenges get more extreme.
These are places where even pint-sized pigs can't survive.
Islands like Tarama have been overrun
by very different life forms...
..creatures of the sea.
Blueberry hermit crabs,
tropical crabs that have settled on these little islands.
These crabs don't grow shells of their own.
They make do with cast-offs from other sea creatures
and they can only grow as big as their borrowed shell will allow.
Deep in the forest, there's a very different crab...
..one that only comes out at night.
A robber crab...
the largest land crab in the world.
On these islands, before people arrived,
there were no big mammals and a humble crab could become king.
They've become giants.
Some can live for 60 years and grow to nearly a metre across.
This female is only about 12 years old...
..so she still has a way to go
before she's a true colossus of the crab world.
But right now, she has a more pressing challenge.
For several weeks, she's been nurturing
thousands of eggs under her tail.
But her babies need to start their lives in the ocean...
..so this young mum needs to make
the most important journey of her life...
..and there are some very modern obstacles in her way.
CAR RUMBLES
DOG BARKS
There's a small village between her forest home and the ocean.
She must get to the sea in time
for one of the highest tides of the year.
But when she reaches the shore, she faces a dangerous situation.
Robber crabs have become so big and heavy they can't swim.
She needs to summon her nerve
and wade out far enough to release her precious eggs.
If she gets swept away, she'll drown.
She's done it.
She can get back to the safety of dry land...
..leaving her eggs to hatch in the warmth of the sea.
But all this warmth comes at a price.
Every summer, these Japanese islands
are swept by violent tropical storms.
They're born far out to sea and some grow into typhoons.
The hurricanes of the Pacific.
They draw energy from the warmth of the tropical sea
and their power is enormous.
If you're going to survive, you have to be fully prepared.
Over thousands of years, people have built up defences.
They've designed homes with high walls and sturdy roofs.
Houses are decorated with Shisa lion dogs,
ready to ward off evil spirits and impending disaster.
All along the southwest islands,
people and animals batten down the hatches as the storms build.
In the forests, the macaques run for cover
and huddle together for safety.
But at the most south-westerly point of the island chain,
one animal has come up with a more ingenious survival strategy.
Yonaguni, 750 miles from the mainland,
and often the first island to feel the full force of a typhoon.
This far-flung speck of land is home to a very resourceful caterpillar.
THUNDER RUMBLES
It has built a typhoon-resistant shelter...
..an ingenious design of leaves and silk,
woven together into a perfect defence against wind and rain.
When they hit land, typhoon winds can reach 150mph.
The giant cocoon has withstood the elements.
The caterpillar has been transformed
into one of the most striking animals on earth...
..an Atlas moth.
She has a wingspan the size of a dinner plate.
The largest moth in the world.
Now that the typhoons have passed,
she's come out for one purpose only - to attract a mate.
She gives off pheromones from her tail.
A male has picked up her scent.
He'll fly three miles to find her.
Once they've mated, their job is done.
They don't even have mouths, so they will never eat.
They only have a few days to live...
..but they have defeated the typhoon.
This is a place of extreme survival,
where the ocean, in all its moods, drives everything.
Nowhere is that more evident than at the very furthest extent of Japan.
Just below the surface lies a great mystery.
The waters around Yonaguni are so remote,
they've only been explored in the last few decades.
In 1986, a local diver discovered something totally unexpected.
He noticed strange features in the rock.
He saw straight lines and flat surfaces.
Here was what looked like a colossal underwater monument.
A terraced sandstone pyramid, 270 metres long and 25 metres high.
But who or what could have made it?
Were those steps created for people to walk on?
Some now believe these lines and surfaces
were formed by nature alone.
The simple shearing of rock
in an area known for tremors and earthquakes.
But others are convinced that this is a monument
built by a lost civilisation...
..10,000 years ago, when sea levels were lower.
If it is, this Atlantis of the Pacific
would rewrite the history of these islands.
We may never know the truth.
But whether it was shaped by a lost civilisation
or immense forces of nature,
in the end, it was swallowed by the rising sea.
All along this chain of islands, the sea is ultimately in control.
But life has adapted to its fickle ways...
making the most of opportunities while it can.
We're in a cave by the sea.
There's a 70-year-old lady down there catching sea snakes...
..with her bare hands!
One of the team's more unusual experiences
was on the island of Kudaka filming sea snake hunting.
A privileged insight into the lives of two extraordinary women...
..who maintain an ancient tradition.
The tiny island of Kudaka is just a short ferry ride
from the main island of Okinawa.
Producer David Marks and cameraman Robin Cox are keen to meet
one of the island's legendary snake hunters...
..72-year-old Yoko Fukuchi.
THEY SPEAK JAPANESE
"You're very cute," that's what she's saying.
It's a very quiet island.
Fewer than 200 people live here.
It's a place with a rich history and culture.
Rituals like this are performed all year round to appease the gods
and ward off misfortune.
THEY SING
Yoko and her friend Setsuko are not only hunters,
they were once Kaminchu, priestesses of high status
with special privileges to hunt snakes.
They were made Kaminchu on this same patch of ground in 1978.
The initiation ceremony was called Izaiho
and this was the last time it was ever performed.
As Japan has modernised, many traditions were lost.
After more than five centuries,
Yoko and Setsuko are now the last in their line
who know the old ways.
Sea snakes have been hunted here for centuries.
It's another tradition that may soon be lost.
Despite their age, Yoko and Setsuko are the only ones left
on the island who still hunt.
The team has been granted special permission to film them,
but they have to work in the dark so they don't scare off the snakes.
(I can see about 20 snakes in here.)
(She gets right to the back of the cave.)
For Yoko and Setsuko, this ancient way of hunting
requires intense concentration.
The nearest hospital is across the water in Okinawa,
so if the ladies were bitten they probably wouldn't survive.
As the snakes swim in on the surge of water,
the ladies pick them out with their torches.
But years of experience mean
they can sense the movement of the snakes in the dark.
Yoko's poised to strike.
She's got a massive snake in her hands.
The team want to get shots of Yoko actually catching the snakes,
but with such a cramped space to work in
they need some special technology.
What does it say?
It's not saying anything.
Basically, we're trying to get the camera and my smartphone to
talk to each other so we can put the camera in the water where the
sea snakes are, and we can turn it on and off and focus and do all
the things we need it to do with it, but at the moment it's not working.
Well, she got another one.
So while we've got all this ridiculous technological nonsense
going on, Yoko is just happily plucking the odd snake
out of the water every five or ten minutes.
It's working, yay. Look at that. It looks good.
With the technical problems solved,
someone has to actually get in the cave.
David has volunteered, but he'll need some protection.
Yoko is not wearing any gloves.
No, Yoko doesn't wear gloves,
but I'm not putting my hands in water with sea snakes
crawling everywhere without any gloves on.
YOKO LAUGHS
What's so funny?
Why are you laughing?
Why are you laughing, Yoko?
When the night's hunting is over,
the team discover they only got a few shots of Yoko's legs.
The next day, the team are invited to Yoko's house.
She's prepared snake soup for them to eat.
We're filming...
snake and now it's time to eat snake.
I'm resisting the urge to say it tastes like chicken.
It doesn't taste like chicken.
It's pretty smoky, isn't it?
It's a bit snaky.
For the team, it's an unusual meal, but it's a great honour.
This dish was once reserved only for the island's kings.
There is only one night of filming left.
The team haven't yet got the shots they need of Yoko hunting,
but they have discovered a second entrance to the cramped cave.
Unlike the ladies, cameraman Robin is taking all precautions.
Put the hood on. There you go!
He's squeezed himself into a tiny
hole and is now surrounded by venomous sea snakes,
but he's finally in a position to capture the action.
OK, she just got a pretty big snake.
Just saw it just swimming underneath my feet here
and then it went in a crack in the rock and she came and grabbed it,
caught it and stuffed it in her bag,
so I think we've got the shots that we were waiting for
and I think I can get out of here now, please.
It's been a successful night for Yoko and Setsuko too.
That was astonishing. Pretty amazing.
I mean, can you imagine...?
My mum, most evenings, has a glass of wine or two and watches some telly.
You can't imagine your mum knee-deep in water,
writhing with deadly snakes, picking them up and putting them in a bag.
Next time, we head to Hokkaido - Japan's northern frontier.
Life is ruled by its extreme seasons.
Survival means being tough...
BIRDS SQUAWK
BIRD SQUAWKS
..and forging unlikely alliances.
It's Japan's wildest island.