Original subtitles

Fresh water is the very essence of Life.

Yet seventy per cent of the earth's supply

is locked up as ice and snow in the Arctic and Antarctic:

frozen for all four seasons,

forever denied to the world's plants and animals that thirst for it.

Most of Asia escapes the Arctic's icy year-round grip.

The fresh water imprisoned in winter is always released in spring.

Over millions of years,

the annual surge of melting ice and snow

has shaped the land and nurtured life.

In North East Japan, some of Asia's cherry salmon

have adapted to cold winters and short warm summers.

Instead of migrating to the ocean to grow,

they spend all their lives in the freshwater rivers

where they were born.

The cranes of Hokkaido also remain throughout the winter,

finding the food they need amid the ice and snow.

The creatures of North East Asia such as cherry salmon and cranes

have adapted to the freshwater habitats created by the melting ice and snow.

They are the CREATURES of the THAW.

Winters in North East Asia are so cold,

fresh water all but disappears.

Most creatures leave.

But some have learned to eke out an existence.

Shika Deer use the ice as a shortcut to the few waterholes

that are not completely frozen over.

To survive, they chew bark, even though it's hard to digest.

The Whooper Swans have flown thousands of miles

to escape an even harsher winter in Siberla.

Where rivers still flow, life can survive the freeze.

The swans look for havens where springs keep water ice free

and where they can feed on aduatic plants.

From December to March,

surface temperatures on the marshes rarely struggle above freezing.

But natural springs ensure that the temperatures

in some ponds are never guite as cold

and this is where the Ezo Brown Frog finds refuge.

Unblinking, the frog looks dead.

İt is dormant, its metabolic rate slowed almost to a standstill

on hold until the spring.

The young cherry salmon spend their first winter

in the headwaters near the mountain slopes,

where the water flows too gulckly to freeze.

They can tolerate temperatures close to freezing and like the frogs,

they shut their systems down for winter-stirring occasionally for food.

The Japanese call the young cherry salmon yamame,

which means Beauty of the Mountains.

They're found only in the rivers of Japan and North East Asia.

Even when air temperatures are

well below freezing natural springs prevent

some rivers from icing over.

The waters much warmer than the surrounding air and it steams.

At night the Japanese cranes roost in midstream,

safe from surprise attacks by its predator, the red fox.

The cranes will stay in the river until the middle of the morning,

waiting for the warming sun.

Upstream, some of the yamame are beginning to stir.

During their first winter, the yamame appear identical.

They have grown up to eight or nine inches long

and their flanks are now beautifully patterned.

But depending on how much food they find in the river,

and on the genetic structure each fish has inherited,

they will grow to maturity in one of two remarkably different ways.

For the moment, all the yamame face a common enemy.

Hunting opportunities for the Crested King Fisher

are limited to the stretches of the river

where the rapid flow or a spring keeps the waters free from ice.

Yamame are a key part of their winter diet.

The pin-point accuracy of the Kingfisher's dive means

that altthough many yamame hatch, many fewer survive the winter.

The cranes wait until the sun is well up before they leave the river.

They will spend the warmest part of the day looking for food,

returning when the temperatures start to fall.

Their favourite winter feeding grounds are the farms near the river,

where they may find beneath the snow stubble

left from the autumn harvest.

Kindliy farmers also leave out food for them.

Japanese Cranes are an endangered species.

There are only seven hundred in northern Japan

and a further thousand in parts of Russia and China.

The people of Japan and China

believe the cranes live for a thousand years.

The birds are icons:

symbols of happiness and long life.

They pair for life and are constantly reaffirming their bonds.

They begin their courtship rituals even

before the breeding season begins

a tender two-step that heralds the coming of spring.

Slowly, winter yields.

İn April, further north in the centre of Siberia,

the world's largest store of freshwater,

Lake Baikal, begins its majestic thaw.

Lake Baikal is almost four hundred miles long

and its surface area is huge almost the size of Switzerland.

The transformation from solid ice three feet deep

to open water starts in the south

and moves north at an average rate of twelve miles a day.

The remarkable Lake Baikal is more than a mile deep

and holds a fifth of the earth's entire supply of liguid fresh water.

The thaw is a trigger of transformation

for the Lake's animals.

Lake Baikal is home to

the only freshwater seals in the world, the Nerpa.

At less than three feet long, they're also one of the smallest.

When mothers give birth in February and March,

the ice acts as a cradle for the pups.

The arrival of the thaw means

they no longer have a safe resting place.

The thaw is the time when the pups are weaned.

First they moult their baby fur,

then they start finding their own food

in the lake's unusually clear waters.

The thaw transforms the marshes of North East Asia.

Warmed by the strengthening sun,

the waters from the melting ice and snow evaporate.

Mists and gentle rain soften buds hardened for winter.

Among the first to open its flowers

is one of the most common plants on the wetlands-the willow.

Over a few short weeks the freshwater

that has been locked up as ice and snow is released.

The melting snow and spring rain fills the rivers to overflowing.

The soil cannot absorb all the snow melt,

and water floods across the marshlands.

The waters help soften the soil and encourage new growth.

Times are now easier for the Shika Deer.

No longer do they have to gnaw on hard bark.

İnstead they dig for roots in the yielding soil,

and they'li feast on the spring growth.

When the flooding rivers recede, they leave waterholes.

Ezo Brown Frogs interrupt their wintering

to spawn in the shallow water.

İt's still too cold for them to find food,

but by laying their eggs now,

the frogs give their tadpoles the best chance of maturing

before winter returns.

The breeding ritual begins with the male frogs calling to attract females.

A successful coupling starts

when the male grabs the female in a tight grip.

A larger male who tries to take over is sharply rebuffed...

but doesn't give up easily.

The firm embrace of the male helps the female

to release her eggs and as they leave her body he fertilises them.

The female has laid about a thousand eggs.

The timing of the spawning is critical.

The frogs need the water to be shallow enough to

allow the eggs to be warmed by the sun,

yet sufficiently deep not to dry out before the eggs hatch

usually in about ten days.

This breeding of the frogs in spring is crucial to other creatures.

At night a formidable predator emerges.

For most of the year the Fish Owl is true to its name.

But in Spring, when frogs are plentiful and easy to catch,

they are its primary food.

While temperatures remain low,

there's not much else for the cranes to eat.

Each bird weighs up to twenty pounds

and needs a large amount of food just to keep going.

The cranes have returned to the marshes to breed,

and the frogs are a precious source of nutrition

for the female before she lays her eggs.

This pair have claimed a corner of the marshlands

and prepared their nest from reeds.

They already have one egg,

and in a day or two may have a second.

The eggs take about thirty days to incubate

and the male and female share the task.

Though, in most ways,

the cranes are supremely adapted to their wetland environment,

their nests are vulnerable to rising water.

To protect their eggs from the chilling floods

that can follow heavy rains,

they constantliy build up the sides of their nests.

The thawing waters of spring are the defining time for the yamame.

There's not enough food in the river to support them all.

The most powerful males occupy the best feeding territorles,

driving off all rivals.

By winning the competition for food,

the strong males have selected themselves

as the yamame most suited to survive in the relative safety of the river.

The best prospects for the other males

and all the female yamame will lie in heading downstream

to the river mouth and growing to maturity at sea.

During the two or three months it takes them to reach the coast,

their physiology is transformed in preparation

for their new life in salt water.

By the time they reach the river mouth

the patterns on their flanks are fading,

their skin has turned to silver,

and the tip of their dorsal fin turns black.

The losers in the battle for survival in fresh water

take their chances in the even more competitive saltwater environment.

The dangers of the ocean will be

much greater than those in the river,

but so too will be the food resources.

At the same time as the departing yamame go to sea,

the salmon who have survived one year at sea

come back to the river to breed.

The Japanese call the returning fish sakura-masu,

or cherry salmon, after the cherry blossom,

which flowers in early spring.

Less than ten per cent of those who go to sea survive.

But because of the plentiful food they've enjoyed in the ocean

they're now twenty to thirty times larger than

the yamame who drove them from the river.

As the female cherry salmon return to freshwater,

the parasite worms that have infested them at sea die,

but battle scars from skirmishes with seals remain.

There's no respite.

For all the cherry salmon,

the three-month journey upstream to

their birthplace will be fraught with dangers.

Their first obstacle is perhaps the easiest.

The brown bears are too clumsy and the cherry salmon far

too nimble to make them an easy catch.

The salmon head instinctively up river,

irresistibly drawn by the scent of the waters where they were born.

As the season turns from spring to summer,

Asia's freshwater rivers, lakes, and marshes really come alive.

When the waters levels recede,

new growth claims the silt-rich riverbanks.

Each spring thaw leaves a legacy of new habitats created from the silt

and gravel swept downstream by the snow melt.

Willows spread their seeds over the riverside like snow.

The rising temperatures and drying air open the hard seed-pods.

A single tree can spawn a million seeds.

Some will take a watery ride to new territories.

Others will be blown as far as thirty miles away.

Most will be lost forever

but some will settle on nearby muddy banks and bars of silt.

The seeds take hold remarkabliy gulckly:

some sending out shoots within hours.

Once they germinate,

the young willows are hardy enough to withstand both flood and drought.

Their speedy germination and toughness allows willows

to secure a foothold where other species can't.

When the pioneering willows

have stabilised the riverbanks other trees follow.

Soon a fringing forest develops:

a leafy illustration of how rapidly the plants of

North East Asia adapt to the seasonal rise and fall of rivers.

The riverside forests provide an important food

source for a wide range of insects associated with the river.

Fallen willow leaves are a favourite food

for the larvae of the Caddis Fly.

Once they decompose,

the leaves will also provide nutrients for the plankton in the river.

The larvae of the caddis fiy and adult insects returning to lay their eggs,

are the main food of the male yamame,

who move to the best feeding stretches of the river as they await the return

from the sea of the female cherry salmon.

The influence of freshwater on the life of cherry salmon is far-reaching.

Much of the freshwater which comes as rain finds its way underground,

where it collects and gathers to emerge years later as springs.

The springs converge to create streams and rivers

which scour the land on their journey to the sea.

Where land still resists the river, there are waterfalls.

These freshwater barriers play a key role

in the natural selection of the salmon.

They're hurdles the returning salmon must cross in order to breed.

They will need to gather all their strength

to make the leap of more than six feet.

Only the strongest and the most-determined

cherry salmon are selected

and continue the journey to the spawning ground.

Summer is the busiest season in the marshlands.

Once the waters recede, the shallows are still.

In this calm, warm environment, plants and animals proliferate,

packing their reproductive energy into the few months

that are free from ice and snow.

Summaer's plenty provides food and shelter for the growing crane family.

Within days of hatching, the chick leaves the nest,

following its parents around the marshes,

and learning what is food and what is not.

ÖOften a second chick hatches within days of the first.

But seldom do both survive.

In daylight, eagles are always a threat.

Parents warn their chicks to stay out of sight in the tall grass.

A fox looking for an easy meal, takes on more than he bargained for.

The crane is one of the top predators on the marshlands

with a kick that can smash a fox's ribs, and a beak that can kill.

A more insidious danger is unseasonable weather.

Even in June, temperatures can plummet.

If the weather's wet as well as cold, the young chick,

whose feathers aren't yet waterproof, is at serious risk from hypothermia.

The safest strategy is to stay close to its parents

For the first month of its life,

the chick will sleep under its parents wings at night,

when temperatures are low.

Japanese cranes lavish extraordinary care on their young:

the survival of every chick counts.

With an abundance of summer food the marshlands are,

for the cranes, a great place to bring up chicks.

In the myriad ponds and bogs,

freshwater plants and fish flourish in a frenzy of growing and breeding.

The stickleback gets its name from its spiky dorsal fin.

The male is the homemaker.

He stakes out a territory and builds

a nest of plant fibre around the stem of a reed.

Building the nest is a days work but he constantliy fusses over İt.

He glues the nest together with mucus.

A female, attracted to the nest, carries out a careful inspection.

Satisfied, she positions herself inside.

The male induces her to lay by prodding around the joint of her tail fin.

As soon as she lays her eggs, he darts through to fertilise them.

If he's lucky,

he will entice several females to his nest during the same breeding season.

He'll look after all of their eggs,

cleaning them and driving a constant flow of oxygen-rich water

through the nest by fanning with his fins.

He chases off anything that approaches.

Among the intruders are tadpoles hatched

from the eggs laid in spring

and who are now running the gauntlet of the marshes.

Of the enormous number born, relatively few will survive.

All around are mouths eager to dine.

The camouflage of the waiting water mantis is almost perfect.

The mouth of the water mantis is like a needle

which it uses to suck out all the tadpole's body fluid.

In the marshes nothing goes to waste,

and the discarded carcass will soon be devoured

by scavengers like the water beetle.

İt carries its air supply

from the surface as a bubble on the rear ofits shell.

But by far the most ferocious tadpole hunters

are the larvae of the large dragon fiy.

Victim number one was lucky to lose only its tail.

The powerful jaws can flick out in a fraction of a second to clutch its prey.

They take less than a minute to consume every scrap of a tadpole's body.

But even the most dangerous insect hunter

is helpless before the Japanese crane.

The dragon fliy larvae are popular snacks for the hungry chick.

Though cranes do eat plants,

in the breeding season they concentrate

on finding animal matter for their chicks,

mainly insects and small fish like goby and sticklebacks.

Freshwater crayfish is another of the chick's favourites.

İt just reguires more preparation.

İn summer, the marshes deliver the cranes everything they need.

Within a hundred days ofits birth

the chick will have grown almost as big as its parents

and will be ready to fly.

Land and water merge in the marshlands of North East Asia.

Marshes are lakes that are in the process of being gradually filled in

by the steady accumulation of silt.

Wherever the silt settles, plants begin to grow.

İtf's a pattern repeated throughout the region.

As season follows season, by a process known as succession,

lakes become marsh-like and marshes in their turn become land.

But in Russia's Lake Baikal subterranean forces are so powerful

they turn all normal assumptions upside down.

This is a lake that shows no sign of disappearing.

Indeed after thirty million years, it is still growing.

Lake Baikal sits astride the junction of two plates of the earths surface

which are continually pulling apart.

Though rivers ands streams pour silt into Baikal

the ever widening lake absorbs it.

Because it has been isolated for so long,

the Lake has an enormous diversity of unigue plants and animals.

Bizarre branching sponges dominate a cliff face in the coastal shallows.

They're green because of tiny algae embedded in their tissue

that capture the sun's rays and help nourish the sponge.

They flourish because of the abundant plankton

in the lake which they filter out.

The sponges in turn are kept clean by herds of grazing amphipods,

which feed off microscopic algae and wastes,

and help maintain the efficiency of the sponge's filtering system.

The lake also claims the world's only freshwater polychaete worm.

All other members of this group of animals are found only in the sea.

There are over three hundred species of amphipod in the lake.

Some of these crustaceans are giants the size of a mouse.

Males often carry females around with them until they're ready to mate.

Of the fifty fish species unigue to Lake Baikal,

more than half belong to the sculpin family.

The stone sculpin has a strategy of wait and pounce.

The priority in summer is to produce offspring before the ice returns.

The yellow-fin sculpin spawn among the rocks of the warmer shallows.

Using his fins in display, and by releasing pheromones,

a single male may attract a procession of females,

each of whom lay more than a thousand eggs.

The male tends the eggs throughout the three weeks they take to hatch.

Like the stickleback,

he uses his fins to fan them clean

and to flush them with fresh oxygenated water.

But many of the lakes creatures must go to the shore to breed.

The pupae of the caddis fly have spent the winter under the ice

and emerge in their millions to drift ashore as waves ofliving protein.

Once they reach the lakeside,

they transform themselves into fully-fledged flies.

As adults they don't eat and may live only a few days.

Their only purpose...

reproduction which begins in a swarming frenzy.

They mate on the ground,

or on patches of snow that have lingered into summer.

Then the females return to the waters edge to lay their eggs...

and become a feast for the waiting gulls.

For the seals of Lake Baikal

summer means laying down fat before the ice returns.

The seals have larger forelimbs than their nearest living relatives

in the Arctic Ocean and the Caspian Sea.

The biggest mystery is how the seals got here.

Some say travelled from the sea up

the Yenisey River half a million years ago.

Others believe they made the journey even earlier,

when the Arctic Ocean and Lake Baikal were much closer to each other.

In the marshlands

early morning mists are a sign the short summer is ending.

Already the leaves of some trees are changing colour.

After three months the cherry salmon

have nearly reached their spawning ground.

And they're beginning to live up the to their name.

When they set out from the river mouth

and swam past the cherry blossoms, they were silver.

Now, as autumn comes their bodies redden.

The males shift into breeding gear.

Their jaws elongate, curving to reveal ferocious teeth.

The cherry salmon are living off their reserves,

propelled by the overwhelming instinct to spawn.

Heedless of all dangers,

they continue their headlong rush day and night.

For some, the journey could end early.

Night is the time many predators prefer.

In this world between the mountains and the sea,

the fish owl reigns supreme.

Now it shows how it earned its name.

As a final test of their endurance,

the salmon who've survived the hazards of the journey

must snake their way through some of the river's shallowest stretches.

Now an extraordinary encounter unfolds.

The tiny yamame who have stayed in the river wait to breed

with the cherry salmon they drove away to sea.

They have returned as giants

and completely ignore the yamame

even the larger ones in their breeding colours of gold and black.

Spawning starts as soon as she scrapes a nest.

Females may attract the attention of more than one large male.

Even though they're exhausted from their long migration,

their mating instincts drive them into a frenzy of combat.

The two are evenly matched and their battle rages

for more than thirty minutes.

Eventually the winner claims his female,

but he must continue defending his right to fertilise her eggs.

A further challenger is soon brushed aside.

As the moment of spawning approaches,

the male stimulates the female by vibrating against her.

Although it seems that the tiny male yamame

have no chance of mating they know otherwise.

When the yamame approach the female,

they're so small that the large male fails to identify them as a threat,

and so doesn't bother to drive them away.

Although the yamame are too small for him to fight,

their sperm are still effective.

The moment to which their whole life has been geared is near.

İmmediately the female releases her eggs,

the yamame rushes to fertilise them.

The little male the yamame

that never went to sea gets its chance to breed.

The female lays more than two thousand eggs,

which she protects by covering them with small stones.

The male cherry salmon who has fertilised

most of the eggs drives off other fish who try to eat them.

Throughout the two weeks of spawning,

the same ritual is played out day after day in hundreds of home streams.

The yamame's sneaky strategy for spawning gives them a chance,

despite their small size, of leaving offspring and passing on their genes.

They fertilise fewer eggs than the cherry salmon,

but their living is easier and they enjoy the same life span.

To return to their home waters,

the larger males and females have had to survive

the dangers of the ocean and the hazardous journey upriver.

Once they arrive, they have only oöne chance to mate,

and once that chance has passed, like other Pacific salmon, they die.

The male yamame who hatched in the same spawning grounds,

never had to leave their home waters.

And next season, some will even get a second chance to spawn.

In death the cherry salmon completes another cycle

delivering the bounty of the sea to the freshwater.

As winter approaches,

life in the marshes again begins to slow down.

During the short summer,

the reeds have grown up to six feet tall.

Now they must spread their seeds before the ground hardens.

A single cat-tail pod can spread tens of thousands of seeds,

which will lie dormant until next spring.

The frogs that have grown from tadpoles are preparing for their first winter.

It will be a further two seasons before they can lay eggs.

The fallen leaves will make a protective shelter.

Falling temperatures and chilling wind

and rain cool the shallow waters of the marsh and insects are now scarce.

The crane chick is now nearly as tall as İts parents, and is eager to fly.

İt is becoming hard to find food on the marshes.

Unless the cranes move soon, the chick won't survive.

İts first flight may be a long one.

The family head for farmland to forage in the stubble.

In the rivers, freshwater is returning to ice.

Yet even as-everywhere-activity

closes down underwater new life is stirring.

The cherry salmon eggs hatched three months ago.

The fry have remailned beneath the stones,

sustained by the nutrients from of their eggs sacs.

Now they emerge to feed.

The cherry salmon cycle is renewed.

As snowflakes begin to fall,

the cranes renew the courtship calls which season after season,

underpin their pairing and strengthen their bond.

Although the harsh freezing winters of North East Asia

challenge all freshwater life,

snow brings the promise of water to come.

Despite the grip of winter,

the Cranes' Dance is a celebration of life and of the certainty

that the abundance of Spring will come again for the Creatures of the Thaw.