Original subtitles

(soft expectant music)

- [Narrator] From the northern ice scapes

of the Arctic Circle, to the southernmost extremes

of Antarctica, winter prowls the Earth from top to bottom,

conjuring up scenes of wondrous beauty and stark severity.

Breathtaking in spectacle,

but often harsh environments to call home.

Those that do live here thrive here

through amazing adaptations and animal cunning.

It's survival of the fittest, the fastest and the fearless.

A cycle of life where being strong, smart, and shrewd,

can mean the difference between life and death.

Because in this extraordinary world of ice and snow,

only the most resilient and resourceful will endure

the "Wild Winter". (bear growling)

(bright thoughtful music)

There are over eight million species

of plants and animals on Earth,

and running through each and every one

is a fundamental biological impulse,

an instinctual drive to reproduce and pass on

their genetic heritage to future generations.

(bright thoughtful music continues)

During winter, the cycle of life in the animal kingdom

is profoundly influenced by extreme cold,

darkness and hunger.

Some animals migrate to warmer regions, other species stay,

well adapted to see the winter through.

Finding mates, forming families,

reproducing to preserve their species,

and teaching their young how to survive

the seasonal cycles of life on Earth.

(soft thoughtful music)

On the vast icy desert surrounding the South Pole,

there are just two seasons,

a freezing summer and a glacial winter.

Antarctica is the coldest place on earth.

For the next six months, temperatures will descend

as low as minus 60 degrees Celsius.

The wind will blow at speeds

of over 300 kilometres an hour.

(wind whooshing)

Only the hardiest animal species

can withstand such challenging winters,

(soft sombre music) (birds cawing)

and for some of them it's a time of new beginnings,

like the orcas that prowl the ocean,

and the emperor penguins waddling across the sea ice.

For these awesome Antarctic beings,

winter is the time to breed and give birth.

Others, like the southern elephant seal,

here on the remote island of South Georgia,

journey back to these wintry waters to give birth,

after mating and moulting further north.

All are astonishing circles of life,

playing out on the coldest continent on the planet.

(soft thoughtful music) (water sloshing)

Orcas live and breed in the Antarctic.

Females start mating at six to 10 years of age,

males at 10 to 13 years.

This mother and her young calf are unaffected

by the excessively chilly waters.

Female orcas can live for up to 50 years,

and with gestation lasting 17 months, they produce no more

than five or six calves in their lifetime.

This cow will give birth every three to 10 years

until she reaches menopause at age 40.

(water sloshing)

So keeping each baby alive is critical.

A mother will nurse her calf for two years,

but they will stay beside their parent for much longer,

cruising together as part of a tight family group.

And even though the younger whales will remain

with the pod as adults, the mothers need to prepare

their progeny for a more independent existence.

Most importantly, they need to know how to hunt.

A growing killer whale has a healthy appetite.

Calves need to consume around 10% of their body weight

each day, eating anything from fish and squid,

to leopard seals and penguins of all persuasions.

(water sloshing) (wind whooshing)

As winter approaches, the emperor penguin

is spending less time in the southern seas,

retreating to the pack ice,

and so will remain safe from their hungry foes,

at least for a short time.

Their focus, breeding.

(wind whooshing) (soft thoughtful music)

In March and April, emperor penguins trek and slide

over the landfast ice to find familiar breeding grounds,

and begin their annual courtship ritual.

Monogamous by nature, they call out

to locate a penguin they've mated with before.

(penguins chirping)

If they're first-timers, the males will be as boisterous

as they can to attract an eligible hen's attention.

(penguins chirping)

Female emperors only produce one egg a year,

so they have to choose a lifelong partner wisely.

Both the male and female's impressive yellow plumage

serves them well when attracting a mate.

This male has successfully wooed his female.

Bowing to each other affirms the bond.

After the commitment ritual is complete, the penguins mate.

(soft thoughtful music)

Two months later in the depths of winter,

the impregnated hen lays her egg.

This is the riskiest time in the lifecycle of the species.

It triggers an extraordinary example of animal co-parenting.

First, the mother must hand over the precious cargo

to the father, which is done very carefully.

Drop the egg and the embryo will freeze immediately,

and the year's breeding season would be wasted.

The transfer is successful.

The father is steady enough to take the egg

and rest it carefully on his feet.

(soft thoughtful music)

While the baby-to-be is safe, mother emperor must now

put her life in jeopardy for the sake of the family.

She's had no food during mating and pregnancy

and has exhausted her nutrition stores,

so heads back to the sea to feed.

She will spend more than two months swimming and foraging

for the seafood that she'll regurgitate

and share with her chick when she returns.

Back on the ice, super dad's taken over as full-time carer.

The adult penguin will incubate the egg

for about 65 days in his brood pOUCh.

This keeps it at approximately 36 degrees Celsius

above zero, while all around the mercury

is more likely to be 36 degrees below.

This male penguin has already hatched his egg.

The fluffy chick is balanced on the insteps

of his father's feet, partially covered by the brood pouch,

the penguin equivalent of a warm hug.

It is vital these two stay close.

The chick can't regulate its own temperature

for the first 50 days of life,

and would freeze to death if left alone.

The doting father feeds his nestling

a curd he's made himself.

Called crop milk, the male emperor penguin can produce

this high-fat substance from his oesophagus

and deliver it directly from his beak,

keeping his chick alive until the female returns.

(soft thoughtful music)

By the time the chicks are three or four months old,

they're forming groups for warmth and safety.

The penguin parents continue to alternate

on the ice and in the ocean.

(soft thoughtful music continues)

They return to regurgitate fish

into the mouths of their growing babes.

Come the end of the cold season, the almost

fully-grown penguins will be ready to go it alone.

They head to the Southern Ocean, teaching themselves

how to feed in the open waters,

and won't return to the colony

for at least another three years,

when they're old enough to breed,

and the cycle of life will start over again.

(soft expectant music)

At the same time as the young emperor penguins

first leave their colonies, southern elephant seals

have already departed on their own journey.

In late winter, they leave the Antarctic and head north,

and come ashore to give birth and to breed.

Here on the remote snow-swept island of South Georgia

near the Falklands, they share their space

with mass gatherings of penguins, fur seals and cormorants.

(wind whooshing) (birds chattering)

And with no permanent human residents,

the animals have the place to themselves.

(seal barking) (water splashing)

Many of the female elephant seals

are already pregnant when they arrive.

After the females deliver and wean their pups,

they'll very quickly be ready to mate again.

(expectant percussion music)

During late winter, these sloping beaches

are home to a dense colony of elephant seals,

where the largest males battle for supremacy.

It's a strict social hierarchy.

Only one will become this breeding season's master,

and gain exclusive rights to a harem of females.

(seals growling)

Fights are common, vicious and costly.

The loser may be too injured or weak to breed at all.

But once the crown is decided, it's usually the older,

strongest bull that commands his cows.

(bright expectant music) (seal barking)

He will mate with a female

that's already weaned her newborn,

which she does just three to four weeks after birth.

Only after that will she be fertile again,

which helps explain why some mothers appear

to reject their young so abruptly.

It's an innate instinct to ensure survival of their species.

(wind whooshing) (soft expectant music)

From June to August, winter in the coldest corners

of the southern hemisphere has a huge impact

on the social hierarchies and survival strategies

of the animal inhabitants.

But winter here is part of a much bigger picture,

because as our world orbits the sun,

earth's changing seasons have a huge influence

on food availability, migrations and breeding patterns

for the entire animal kingdom.

As winter advances north again,

the polar nights in the northern hemisphere

start to get longer, and a wintertime wonder

begins to illuminate the darkening skies.

(bright gentle music)

Derived from two words, Aurora,

the Roman goddess of the dawn,

and Boreus, Greek for north wind,

the Aurora Borealis is a breathtaking natural phenomenon

that materialises as stunning tendrils of colour,

shimmering across high-latitude skies,

best viewed in the depths of winter.

Yet as pretty and peaceful as they look,

they are in fact solar storms,

wild clashes of energised particles from the sun

interacting with our planet's magnetic field

and atmospheric gases, producing dazzling displays

of green and red from oxygen,

and brilliant blues and purples from nitrogen.

Spectacular colours in the celestial sphere.

But as dawn approaches and the sun rises, its brightness

and the ambient natural light overwhelm the aurora,

and their ethereal beauty fades completely.

A new day begins for the animals of the Arctic Circle.

The Canadian Arctic is home

to an increasing population of this cute species.

There are currently more than seven million harp seals

living in the circumpolar region.

(bright gentle music) (seals barking)

Each winter, when the pack ice

of Canada's Gulf of St. Lawrence

is at its thickest and most majestic,

immense stretches of frozen seawater

are home to colonies of harp seals,

all here to breed and give birth.

(bright gentle music continues)

Many of the females are pregnant.

They mated 11 months ago, and like most seals,

have the ability to delay implantation of the embryo,

allowing them to synchronise fertilisation perfectly

for delivery on the late winter pack ice.

(bright gentle music continues)

Pack ice is essential for pupping,

providing a dry, safe haven for the mother and her newborn.

The cow needs to fatten up her pup

to be strong enough to survive and swim on its own.

Each day the baby seal will put on more

than two kilograms of mass and blubber.

(wind whooshing)

Survival of this species requires the baby

to be quickly weaned, so the female can mate again.

The mother feeds her pup for just 12 days,

then she leaves it to fend for itself.

(water sloshing)

The female harp seal takes to the water to find a new mate,

so she can return to the ice to give birth,

Same time next year.

(wind whooshing)

(bright expectant music)

The deserted pup can't quite find its feet,

but it has an astonishing understanding

of what needs to be done to survive alone.

After seven or eight weeks, this young pup is old enough

to teach itself to swim and feed,

and is already heading for the ocean.

A solitary seal determined to make its way in the world,

eventually finding its own mate,

and continuing the cycle of life.

(soft thoughtful music)

Spring may be on its way, but late winter is still a time

of exceptionally cold days and nights

across the Polar North,

particularly in the Norwegian islands,

where snow will fall until June, and in many parts

the temperature rarely passes zero, even during summer.

In Svalbard, two icons of the Arctic

are searching for a mate,

yet their mating rituals are worlds apart.

The Arctic fox always has a familiar female in mind.

Monogamous from season to season,

arctic foxes generally mate for life,

so locating their previous partner

is the most pressing concern.

(soft thoughtful music continues)

A male polar bear, on the other hand,

will take any healthy female he can find.

This boar is tracking a sow and her sub-adult cubs.

Even with older cubs, mother bears remain protective,

and they have good reason.

During mating season adult males can become aggressive,

and have been known to kill and eat cubs

if it means getting closer to his potential mate.

But this mother bear isn't interested.

She usually mates just once every three years,

so the timing is not quite right.

Males outnumber females in heat

by approximately three to one.

The odds aren't good for the big boar,

who will have to continue his search elsewhere.

(soft thoughtful music)

As far as the arctic fox is concerned,

finding a new mate isn't an option.

This male is seeking out his partner.

They will not have seen each other for months.

Around February, the monogamous male foxes

across the tundra and the mountains and the coastlines

are searching for their soulmates.

There is no guarantee they will find each other

after so many months apart, and whether their vixens

have even survived the summer.

The males recognise their females by their scents,

and their barking yowls, used to communicate

only during the winter breeding season.

Some are lucky, reuniting and reacquainting themselves

before reproducing again.

They go on to raise their young in a safe family den.

But others are left wanting,

their vixen nowhere to be found,

like this lone male who may never couple up again.

(soft thoughtful music)

The sun is reappearing slowly,

casting colours across brighter Svalbard skies,

and a couple of newborns are learning

that what goes up must come down.

This mother polar bear birthed her cubs

inside a den during the depths of winter.

For eight months she fasted, relying on her body fat

for the energy needed to get through

the pregnancy and delivery.

Once on the outside, the youngsters

will stay with their mother

until they're at least two years old.

She'll continue to suckle them and teach them how to hunt.

They explore and play together enthusiastically,

and their number one nurturer will keep them safe

until they're able to fend for themselves.

(soft thoughtful music) (wind whooshing)

In the waters of the Beaufort and Bering Seas in Alaska,

sea otters are active breeders,

and several times throughout the year

commence their courtship and mating ritual.

Males indiscriminately search for a receptive female.

Vigorous play leads to copulation.

Sea otters are generally referred to as polygamous,

meaning they have more than one partner,

and need to mate often if their species is to survive.

(soft thoughtful music continues)

60 years ago, these Alaskan waters were empty of sea otters.

But after a successful reintroduction programme,

more than 25,000 now swim and breed here.

To improve her chances of pregnancy,

this female may stay with her bull

for a few days after their union,

resting and recharging while continuing to mate.

During winter and over the course of a year,

all eligible male and female sea otters

mate on numerous occasions,

rarely though with the same partner.

An animal kingdom strategy used by many species,

the males intent on passing their genes

onto future generations.

(bright thoughtful music)

Polygamy though is rare in birds.

(soft thoughtful music)

Many of the world's snow-laden forests

are home to the mostly monogamous woodpecker.

(soft thoughtful music continues)

(birds chirping)

As winter draws to a close,

it's the woodpecker's turn to find a mate.

(beak pounding)

While many birds sing to attract a partner,

the male woodpecker drums.

Using his beak to beat the bark,

the woodpecker declares his territory.

His pecking serves to attract potential mate,

and ward off other suitors,

the rhythmic beat carrying across the forest.

An interested female picks up on the drumming

and answers his call.

Once the woodpeckers pair off, they will stay together

for the breeding season, raising their young chicks

until it leaves the nest.

(birds chirping)

This juvenile woodpecker is a product

of last year's breeding season.

Outside of breeding season, most woodpecker species

prefer to live a solitary life, their omnivorous diet

consisting of whatever food's available,

whether in the trees or on the forest floor.

(birds chirping) (beak pounding)

Having left the safety of the nest,

the juvenile woodpecker must learn to feed itself,

using its jackhammer like beak

to dig out insects or larvae to eat.

Woodpeckers reach sexual maturity at 12 months of age,

meaning come next winter,

it will be this one's turn to mate.

(soft sombre music)

As the calendar year draws to a close,

in the boreal forests of Canada,

temperatures drop to minus 15 degrees Celsius or lower.

(soft thoughtful music)

Snowflakes glisten on conifers,

and the waters of the peat lands

and streams freeze into stylish sculptures.

These harsh conditions can cause the end of life

for already ageing animals.

Older male and female moose that once frolicked

and bred here, now need to conserve energy

in the snow-blanketed forest simply to stay alive.

In poorer physical condition, they must take their time

in the deep snow, and slowly and surely sustain themselves,

eating the vegetation beneath the ice.

But they're not the only inhabitants

that rely on this food source.

(boar grunting)

The plundering and pillaging wild boar share the forest,

trampling food stocks the moose once called its own.

While these hairy hogs may not be

considered conventionally beautiful,

beauty is in the eye of the beholder,

and these animals are prolific breeders.

(boars grunting) (bright gentle music)

If the conditions are right,

wild boar can double their population in a territory.

(bright gentle music continues)

(boar grunting)

December is prime rutting season for most wild boar,

and it's a competition between young and old.

(boar growling)

The sows have spent the year

in an all-female group, or sounder.

The males have come back to stake their claim,

and will fight for the right to mate.

This male and female are testing their chemistry,

a tender moment for the rambunctious wild boar.

Sniffing determines whether the male will pursue the female.

Females are sexually mature

by the time they're 12 months old.

(boar grunting) (birds chirping)

Males mature even earlier.

The older, stronger boars chase the younger males

out of the herd to prevent incestuous relationships,

clearing the way for themselves to couple

with at least five sows each a season.

Once a female's impregnated,

she carries for another four months,

and then a plethora of piglets.

Up to a dozen are delivered, and begin suckling immediately

until they are weaned at approximately 12 weeks.

For the next six months, their stripy coats

will help camouflage them in the forest,

as they follow confidently in their mother's footsteps.

They will stay with their mother

until at least the next litter is born, by which time

these piglets too will be old enough to mate.

(soft thoughtful music)

Further north on the Alaskan tundra,

where the plains are quilted in permafrost all year round,

the somewhat more restrained caribou

still need to find a mate.

(caribou yowling)

A female that strays from the herd,

even with her older calves in tow, is fair game for a male,

as the youngster has already been weaned

and the cow is back in estrous,

so the male is hoping she's ready to breed again.

Females only mate and give birth once a year,

so the bull persists.

It's important that these beasts reproduce,

(gentle thoughtful music)

because caribou numbers are in dramatic decline

through North America, at their lowest in 40 years.

This is believed to be a result

of a decline in female caribou survival rates,

likely impacted by habitat destruction and over harvesting.

Survival ultimately depends

on tens of thousands of these hardy creatures

successfully coupling and raising new generations.

Fortunately, this Alaskan twosome

seemed keen to get to know each other better.

A splendid sign for a vulnerable species.

(water sloshing) (bright soft music)

Although among the most numerous seabird species,

kittiwake populations are quickly declining,

so they too are currently listed as vulnerable.

But with days getting longer and the hint of warmer weather,

this species' need to breed is as strong as ever.

Kittiwakes have spent the winter at sea,

and now flock to the cliffs of Hornoya in Norway.

With an estimated total of 100,000 seabirds here,

kittiwakes are just one of 11 breeding species

that come to this small island.

It's still below zero and the snow's not yet melted

when the first gulls land. (birds cawing)

The male kittiwakes arrive first to claim their territory

and prepare to attract a female.

But nesting colonies can be thousands strong,

so space is at a premium, and turf battles

amongst the competing males.

(uneasy percussive music) (birds cawing)

Once the hens arrive, seduction starts.

The male gulls will feed the females from their own beaks,

and put on noisy displays to show their worth.

The coupled kittiwakes build a nest

from seaweed, feathers and mud, and call to each other.

(birds chattering)

They'll stay together waiting to mate,

then incubate the eggs for hatching,

dedicated parents until their baby seabirds fly the coop.

(birds chattering) (soft thoughtful music)

Kittiwakes are, like most birds in the avian world,

monogamous for a season, sometimes for life.

Not so this showy specimen, the Western capercaillie,

one of the United Kingdom's most endangered birds.

The capercaillie can still be found

in the pine forests of Northern Scotland,

where it was reintroduced

after disappearing completely two centuries ago.

In this remnant of wilderness, late winter temperatures

are low enough that snow still clings to the forest floor.

(gentle thoughtful music)

It's the perfect stage for male capercaillie birds

to strut their stuff, (birds chattering)

attempting to impress potential partners.\

(birds chattering)

Mating success is crucial to this species' future,

(birds chattering)

because despite these large grouse birds being protected,

capercaillie numbers are decreasing.

An increase in predator numbers such as foxes

is contributing to the decline, and more intense summer rain

is harming the survival rate of new hatchlings.

(soft expectant music)

It's early morning, and an elaborate and musical

courtship ritual known as lekking is underway.

The suitors compete for the smaller,

less flamboyant females settled in the trees.

But males outnumber females, so fights occur,

a feud of fierce flapping and biting

until the weaker bird finally backs down.

(bright expectant music)

The victor returns to his courtship routine,

but he must still convince a female

that he's genetically superior.

His enchanting performance could last for hours,

and the clicking and popping sounds he's making,

it's called tooting, and it must also be impressive,

as the hen is attracted to calls

that are longer and more vibrant.

With wings up and tail unfurled,

this older male outperforms his competitor.

The hen has made her decision.

The new couple will roam together,

getting to know each other for a while,

until their bond is strong enough to start breeding

and help save the future of their species.

(soft thoughtful music)

(water rushing)

Winter is finally releasing its tight grip

on the far northern hemisphere.

The hours of daylight are getting longer,

and in the forests and mountains

of Europe, Asia, and North America, brown bears awake.

(soft thoughtful music continues)

Once almost extinct, this imposing species has bounced back,

with around 200,000 now roaming wild across the world.

(soft thoughtful music continues)

A mother bear and her cubs take their first

tentative steps from their winter den.

The cubs were born in that snow-covered hideout.

Like their sister species, the polar bear,

mother brown bears will protect their cubs at all costs,

mostly from other male bears

that would kill her babies to mate with her.

She'll stay by their side for the next two years,

protecting them, teaching them how to find food,

and practising how to play.

It's believed these fighting games

build the youngsters' strength and skills,

and help prepare them for survival in the wild.

(bright gentle music)

But as any child knows, playtime is also fun time.

No harm in making the most of the winter snow

before spring takes it away.

If luck is on their side, these cubs will grow and flourish,

learning to live and breed in the wondrous

but harsh conditions into which they were born.

Mother Nature has gifted them,

and so many other living creatures,

incredible strengths, instincts, and adaptations.

And year after year, generation after generation,

the cycle of life across the wilds of the world continues,

each spring, each summer, and every wild winter.

(bright thoughtful music)

(bright thoughtful music continues)

(water sloshing)