Original subtitles

Japan

is a land of wildly diverse environments.

From snow-covered mountains,

to steamy mangroves.

And animals have adapted to survive in them all.

Unique residents and enigmatic visitors are found here,

in Japan's islands of extremes.

Japan consists of around 7,000 islands

in the northwest Pacific Ocean.

They stretch for over 2,400 kilometers

and encompass a huge range of climates.

Everything from frozen seas

to lush forests

to sweltering mangroves.

The islands sit above three of the world's

seven tectonic plates.

As a result Japan is one of the planet's

most geologically unstable areas.

It can experience over 1,000 earthquakes a year.

And tsunamis can strike with devastating effects.

Four fifths of the land is covered by mountains,

forged by violent geological upheaval.

Among them, around 180 volcanoes,

over a third of which are active.

The islands are home to a vast array of wildlife

found nowhere else on Earth.

Animals have adapted to survive

in the multitude of different environments.

Often turning adversity to their advantage.

Nowhere is this more evident

than in the heart of central Japan.

Jigokudani is a mountainous region in the middle of Honshu,

one of Japan's four main islands.

Jigokudani means "Hell's Valley."

And in the depths of winter,

it seems an apt description.

In this volcanic hotspot,

water bubbles and boils

and sulphuric steam filters ominously

through the valley floor.

Heavy snow blankets the ground

for four months of the year.

It looks bleak and inhospitable.

But one particular animal thrives in Hell's Valley.

And exploits it to the full.

Japanese macaques, or snow monkeys,

are among Japan's most mythologized animals.

And the most adaptable.

Macaques live throughout Japan.

Although more at home in the subtropical forests

of the southern islands,

they venture into colder climes too.

Apart from humans,

they're the only primates that can live this far north.

Dense layers of fur allow them

to survive temperatures as low

as minus 14 degree centigrade.

Macaques can move their fingers

with human-like dexterity.

And have sophisticated hand-eye coordination.

In Hell's Valley, that's vital.

It means they can skillfully rummage through

thick snow for any traces of food.

Life here is greuling,

but one feature makes living in Hell's Valley worthwhile.

Hot springs,

where the water is a blissful 40 degrees centigrade.

Warm volcanic pools called onsens

offer relief from the savage cold.

Onsen water is believed to have healing powers

because of its high mineral content.

The pools are the perfect place to relax and unwind.

Grooming helps keep coats untangled and free of fleas.

It also helps maintain the bonds

vital in macaque society.

Macaques have a strict chain of command.

Each group is ruled by a dominant alpha male and female.

And the pools aren't open to all.

Dominant males are quick to react

to any sign of defiance.

Only high-ranking females

and young monkeys are allowed to bathe.

The alpha male vets all entrants.

And this subordinate is bathing where he shouldn't be.

The intruder learns the rules the hard way.

This is a lesson he won't forget.

As night approaches,

the temperature tumbles.

The troop leaves the warm waters

and slowly winds its way back into the forest.

They'll survive the night huddled together in the trees.

Come sunrise, they'll make their way back to the pools.

The climate in Northern Honshu tests

the macaques tolerance to cold to the limit.

Conditions further north are too extreme,

even for the world's most adaptable primate.

In the depths of winter,

Hokkaido, Japan's northernmost island,

feels the savage bit of Siberian cold.

Arctic winds whip the land and temperatures

plunge to minus 30 degrees.

The Shiretoko Peninsula in northern Hokkaido

borders the coldest sea in east Asia,

the Sea of Okhotsk.

During winter it becomes almost completely covered with ice.

The ice originates in eastern Russia

and is pulled south by ocean currents.

In early winter ice around the Shiretoko Peninsula

can reach three kilometers wide

and 50 kilometers long.

At the same time cold currents arrive from the north,

warm currents arrive from the south.

As they collide, the number of plankton explodes.

Huge shoals of fish come here to feed.

These waters become some of the richest

fishing grounds in the world.

And they attract some of nature's most skillful hunters.

A third of the world's population of stellar sea eagles

migrate here from Russia every winter.

Stellar sea eagles are among

the largest eagles in the world.

In full flight, their wingspan reaches 2 1/2 meters.

Slowly circling the ice,

razor-sharp eyes scan the sea for any signs of prey.

A flicker of movement is all it takes.

But catching a fish does not guarantee a meal.

There are jealous eyes everywhere.

Up to 2,000 sea eagles gather here.

And competition is fierce among

these normally solitary birds.

Fights over food are common and can be bloody.

Eventually the hunter prevails.

And after the effort it took to keep hold of its catch,

the eagle seems hungrier than ever.

Stellar sea eagles aren't the only birds of prey

to visit Shiretoko in winter.

White-tailed sea eagles come here too.

In many places,

white-tailed eagles have little competition.

But here, they can play second fiddle.

In fights over food,

stellar sea eagles are often victorious.

For an ancient tribe who live in Hokkaido,

the stellar sea eagle is honored as the god of the eagles.

The Ainu have lived here for thousands of years.

As hunter-gatherers they are totally

in tune with their surroundings.

This ensures that they can survive the harshest of winters.

The Ainu people have a deep reverence for nature.

And there is one creature they regard

as the god of the marshes.

The red-crowned crane.

They are the largest birds in Japan

and are known as tancho, which means "red mountain."

Hokkaido is home to one of the world's two large

breeding groups of red-crowned cranes.

The other lives in northeastern China and Russia.

The Ainu say the cranes are dressed in clothes from Heaven.

And they put their looks to good use

when searching for a mate.

A young male sets his eyes on a potential partner.

And the best way to impress her

is with a dramatic courtship dance.

The female likes what she sees

and shows her acceptance by mirroring his moves.

Red-crowned cranes can live for more than 50 years

and they pair for life.

As more courting couples join the fray,

they reinforce their bonds with loud calls.

Their cries can be heard up to three kilometers away.

More cranes arrive all the time

and the dancing seems to be contagious.

The Ainu celebrate this special event

by performing their own dance,

the haruaki, which imitates the birds' movements.

It's seen as a way of warding off the ill spirits.

As night approaches, the cranes gather in a river.

Grouping together helps deter predators.

And in winter, the water is warmer than the air.

As night draws in, they take it in turn to sleep,

so at least one bird is always on watch.

Savage winter conditions make survival difficult,

even for Hokkaido's hardiest creatures.

Some are forced to come out of hiding to forage,

like one of Japan's most distinctive animals,

the Japanese serow.

Celebrated in ancient stories

for being peaceful creatures that protect the forest.

Some people say they have the legs of a goat,

the body of a deer and the fur of a wolf.

Japanese serow are only found on Honshu

and two other Japanese islands.

They usually live alone and, unlike most animals,

forage for food both night and day.

This loner will try to endure winter

on any leaves and shoots it can find.

As the sun sets, the weak won't survive the cold.

In Hokkaido's winter wilderness,

opportunists are always ready

to take advantage of others' misfortune.

Early morning,

and a northern red fox is on the prowl.

To the Ainu, the red fox is the god of cunning,

and not to be trusted.

If hunters kill one,

it's said they tie its mouth shut

to prevent its spirit escaping.

Loud squawks alert the scavenger to a possible jackpot.

A sika deer has failed to survive the night.

The fox has no trouble in claiming its prize

from a flock of crows.

Razor-sharp teeth make light work of the frozen carcass.

The angry crows are left squabbling for scraps.

It's March in Hokkaido and winter finally draws to a close.

Change is in the air as spring arrives.

Temperatures climb and the pack ice surrounding

the Shiretoko Peninsula begins to break up.

The cracking ice is a signal for

stellar sea eagles to take flight.

After four months of feeding and fighting,

they start the long journey back

to their breeding grounds in eastern Russia.

Melting ice is also the cue for another visitor to leave.

Whooper swans gained their name

from their deep, honking call.

They are the noisiest swans in the world,

especially when they're preparing to migrate.

10,000 have spent winter in Hokkaido

to escape the severe weather in their Siberian home.

Hokkaido's warm volcanic waters bring relief

from the cold and ensure the visitors

a constant supply of food throughout winter.

As the temperatures rise, the swans take to the air.

As they leave for their nesting grounds in Siberia,

some Japanese people say the swans

carry winter on their wings.

Spring's arrival is heralded by a sea of color

as cherry trees burst into life.

The annual cherry blossom, known as sakura,

is one of Japan's most celebrated events.

A pink and white tide sweeps across the country.

It starts in the far southern islands in January

and reaches Hokkaido towards the end of April.

Wherever the blossoms appear,

their beauty is short lived.

Within weeks of blooming,

the flowers vanish.

950 kilometers south of Hokkaido,

are the northern Japanese Alps.

As temperatures climb snowmelt feeds the rivers

flowing down from the mountains.

This is a time of rebirth.

Spawning fish herald a busy time

for one of Japan's hardest working birds.

A custom has been practiced in central Honshu

for over 1,300 years.

It's called usho fishing

and it's an industry like no other.

Early afternoon, an usho fisherman prepares his team.

A flock of highly-trained sea cormorants.

Each bird is carefully examined to make sure it's healthy.

Gently feeling the bird's throat

tests its health and helps keep it calm.

Once all the cormorants have been checked,

they're let outside to relax.

Each bird was captured in the wild

hand reared and taught to fish in fresh water.

They could easily fly away, but don't.

They're looked after so well,

many live twice as long as cormorants in the wild.

But they need to earn their bed and board.

Late afternoon and several birds

are carried downriver in special baskets

by the fishermen who train them.

Each one is given a last careful check.

As the sun starts to set,

soon it will be time for the cormorants to earn their keep.

Before the trip begins in earnest,

different fishing crews gather on the beach.

They discuss which section of the river each boat will fish

and decide on a plan of action for the night ahead.

Routes agreed and plotted, now the hard work can begin.

Each bird is carefully tethered.

Special hemp rope tied around their throats

prevents them from swallowing any fish they catch.

As the usho prepare to leave fires are lit

in iron baskets and hung in front of the boats.

They light the way and make it easier for the cormorants.

The flames draw shoals of trout-like fish

called ayu to the surface.

Now the cormorants go to work.

They dart beneath the surface as the fishermen

fight to keep their tethers untangled.

For expert fishing birds like cormorants,

this is easy work.

Each bird can hold up to six fish in its gullet.

When they're full, they're hauled on board,

and their catch disgorged on deck.

Some can catch up to 60 fish an hour.

In Japan, cormorant-caught fish are a delicacy,

and their beak marks are a hallmark of quality.

As the cormorants work draws to a close,

in Honshu's southern Alps, another night hunter stirs.

A creature which has remained unchanged

for nearly 30 million years.

It's a Japanese giant salamander,

the world's largest amphibian.

They can grow to nearly two meters long.

Giant salamanders don't have gills

and need to live in flowing rivers.

Heavy folds of skin increase their body surface

so they can absorb more oxygen from the water.

A man-made tunnel makes a perfect den for a male.

But it needs to stay alert and on guard.

A rival male wants the den.

It's a big mistake, salamanders are highly territorial.

The tresspasser gets away relatively lightly,

some fights are to the death.

The male has good reason to be extra defensive.

A female has laid a clutch of eggs, which he's fertilized.

Until they hatch, he will protect them at all costs.

But the sudden burst of energy

has seriously sapped his strength.

He needs to feed.

Although they have poor eyesight,

salamanders are skillful hunters.

Special sensors detect minute changes in water pressure.

Like the kind made by a passing fish.

With an explosive burst of energy,

prey is dispatched with a sudden snap.

With no competition from other large predators,

giant salamanders have free reign of the mountain rivers.

But with their habitats being destroyed

as forests are cut down to make way for industry,

they may need to evolve if they're to survive.

Further south, one species has been forced to evolve,

or face the possibility of being

destroyed by a powerful foe.

At these Buddhist temple gardens in southern Honshu,

spring brings a flurry of activity.

A colony of Japanese honeybees

has taken over the garden hives.

Workers scour the gardens for food

to feed the thousands of new arrivals.

The hive bristles with energy

and it's an irresistible target

to the honeybees' ancient rival.

The Japanese hornet.

Hornets also have young to feed

and this scout has found a major source of food,

the honeybees' hive.

The hornet is five times the size of its prey.

And the venom from its sting is so potent,

it can dissolve human flesh.

Just a few hornets could decimate

the colony in a matter of hours.

It's an opportunity too good to miss.

First, the hornet's scent marks his find,

for others to follow.

The honeybees reply in kind

and fan pheromones through the air

to alert the colony to danger.

As the bees retreat, the hornet makes its move.

Seizing the bee in its jaws, it starts to feed.

But all is not what it seems.

As if on cue, the bees strike back.

Japanese honeybees have a unique and grisly defense tactic.

Up to 500 bees form a ball

and their vibrating bodies heat

its core to 47 degrees centigrade.

Slowly, the hornet overheats.

The bees' secret weapon is a greater tolerance

to heat than their enemy.

Just two degrees makes the difference

between life and death.

The invader is roasted alive.

The bees remove the scent mark

so other hornets can't follow the scout's steps.

Soon, there's no trace left of it at all.

For Japanese honeybees, heat is a weapon.

In Japan's extreme south, it's a way of life.

Okinawa is a group of around 160 islands in southern Japan,

including the remote island of Iriomote.

These sun-kissed islands are a world apart

from the rest of the country.

As summer arrives the temperature climbs to over 30 degrees.

Iriomote is the second largest island in Okinawa.

Dubbed the Galapagos of the East,

subtropical forests, waterfalls,

and mangroves dominate the land.

A host of rare animals and plants

live in the lush jungle covering

more than 90% of the island.

And the island's giants tower above them all.

Sakishima sappan trees.

Standing 18 meters tall,

this is the largest sappan tree in Okinawa.

It's huge buttress roots fan out

like tentacles over the forest floor.

They're designed to soak up minerals

from the surface of the soil

and anchor the huge tree in place.

To some of Iriomote's residents,

the island's maze of trees and roots

is vital to everyday life.

The Nakama River is one of several

crossing Iriomote Island on route to the sea.

Fresh water meets salt water

and helps nurture exotic mangrove forests.

The forests thrive thanks to the powerful

Kuroshiro current which ferries warm waters

to Japan's southern islands.

The current keeps the seas at a minimum

of 20 degrees centigrade,

allowing mangroves to flourish

further north than normal.

This is home to a vast array of fish, amphibians and birds.

And one species is especially aptly named.

Mud creepers.

This is one of the largest gatherings

of snails in the world.

Up to 150 can live in one square meter.

Mud creepers can survive without food

for up to four months.

But when they are hungry,

the mangroves provide all they need.

Adults are drawn to the smell released by damaged leaves.

Mealtimes are long and leisurely affairs.

Young mud creepers don't grow the teeth

they need to break down leaves until they're adults,

so slowly sift the sand for leftovers.

The mangroves are fertile hunting grounds

for many creatures.

And a paradise for opportunists.

Hermit crabs need to keep upsizing their shells

as their bodies grow.

When the ideal home comes on the market,

the rush to grab it can be fierce.

Iriomote's mangroves teem with

many different species of crab.

Fiddler crabs try to attract a mate

by frantically waving their oversized claws.

While soldier crabs march en masse,

as they rush to dodge the tide and find food.

Crabs and mud creepers aerate the sand as they feed

and are vital to the lifecycle of the mangroves.

But there's one Japanese creature

whose eating habits set it apart

from the rest of the animal kingdom.

925 kilometers north of Iriomote,

on the tiny island of Koshima,

a scientific discovery has been made.

It involves the animals which can survive

in all but the most extreme of Japan's many environments.

Japanese macaques.

Koshima is home to around 80 macaques

and unlike Hokkaido's snow monkeys,

they don't need thick winter coats.

For this troop, it's staying cool which is the challenge.

Especially at the height of summer

when temperatures climb to 28 degrees.

The macaques visit the beach to enjoy the breeze.

And there's another reason too.

Macaques, like humans,

don't like eating sand with their food.

And the troop on Koshima Island

have come up with a solution.

They wash what they eat first.

Sand free, meals taste a lot better.

They use their human-like hands

to thoroughly clean what they want to eat.

Some even like to season their food with saltwater

and dip between each bite.

It's a straightforward task,

and one which has captivated scientists for decades.

The macaques habit of cleaning their food

has not come through genetics,

but by watching and copying others.

It's one of the greatest examples of

learned behavior ever seen in the animal kingdom.

And scientists feed the troop

so they can study their behavior.

Yong macaques learn the ropes by watching adults

and normally master the technique

by the time they're two and a half.

Until then, infants grab what they can,

although adults always get first refusal.

But such a wealth of food draws other attention too.

An army of bugs on the hunt for scraps.

Sea slaters are king-sized relatives of the woodlouse.

They can grow to three centimeters long

and they perform a useful task.

By gorging on the mess left behind by overzealous macaques,

they help keep the beach clean.

Mealtime over, it's time to relax.

Cheek pouches bloated with food,

grooming is now the order of the day.

No other animal has adapted to Japan's

many environments quite like the macaque.

Not only do they endure freezing cold

by using hot springs,

they pass down special skills

to make the most of any feeding opportunities.

Macaques don't just survive,

they thrive, whatever comes their way.

Stretching over 2,400 kilometers,

the Japanese islands encompass

a vast range of climates and conditions.

And animals have adapted to them all.

Wildlife flourishes in everything from

frozen mountains to sweltering jungles.

This is home to some of the hardiest species on Earth,

many found nowhere else in the world.

And all have found the secret to survival

in Japan's islands of extremes.