Original subtitles

- [Narrator] Antarctica.

A vast, icy desert.

In terms of rainfall, it's the driest place on earth.

And yet, the Antarctic holds more than two thirds

of the planet's fresh water.

With plunging temperatures and powerful winds,

our southernmost land mass is an unrelenting habitat.

But life persists and thrives.

Once part of a connected southern supercontinent,

Antarctica is now isolated by a current so powerful

it creates undersea highways

back to each and every continent.

Where extraordinary life forms

answer the call of the seasons.

On icy islands and on a land frozen by time.

(dramatic orchestral music)

This is the Wildest Antarctic.

(serene piano music)

Our southernmost continent is the coldest place on earth.

The south pole has just two seasons:

summer and winter.

The warmer months draw a myriad of wondrous animals

to Antarctic waters.

Whales and dolphins stockpile

on abundant schools of fish, squid, and krill.

Seabirds, penguins, and seals arrive on land,

returning to the same areas each year to mate,

raise young, and feed.

Every winter, Antarctica transforms

into a vastly different place.

The extreme weather forces animals

to flee for warmer waters.

The entire continent swells,

doubling in surface size as sea water turns to ice.

Blizzards set in.

Nights lengthen until darkness envelops the land

for weeks on end.

(dramatic orchestral music)

The Antarctic winter exodus reaches every other continent

in the southern hemisphere.

On distant shores, the renewal of life

and the hunt continues.

(dramatic boom)

(serene orchestral music)

South Georgia is a mountainous, barren island

in the south Atlantic ocean.

Some 1,500 kilometers from the Falkland Islands.

And though it's not considered

part of the Antarctic continent,

the climate here is colder than other parts of the world

on the same latitude.

This is because the Antarctic circumpolar current

is at its squeeze point through Drake Passage.

This is the narrowest distance

between the southern continent and South America.

The current emerging on the other side of the passage

funnels icy water around these islands.

It brings a rush of nutrients,

plant and animal-based plankton,

which creates an entire ecosystem just off shore.

As a result, this island is a crowded landing pad

for south polar species.

Especially in breeding seasons.

There are 30 different kinds of birds here,

including one of the world's largest colonies

of king and gentoo penguins.

And four species of the seal family.

(guttural growling)

The weather is highly variable,

but the draw card is the temperature.

In summer, the maximum may reach

as much as eight degrees.

But it rarely dips below minus 10, even in winter.

It stays free of pack ice,

though icebergs carved from the island glaciers

are a common sight in the bays.

The more buoyant become platforms

for the visiting seal colonies.

(serene orchestral music)

Southern elephant seals

spend most of their lives under water.

They are highly accomplished swimmers.

They can deep dive for two hours at a time

and slow their heart rates down

to just one beat per minute.

Moving about on land, however, is another matter.

(bouncy tuba music)

These are the largest of seals.

The males weigh in at nearly four tons,

twice the size of a hippopotamus.

The females are much smaller

and lack the huge nose of the male

that the elephant seals are named for.

(dramatic orchestral music)

The seals haul their large bodies ashore twice a year.

Once to molt, shedding their outer layer of skin.

And once a year to breed and birth.

(seal growls)

Pregnant females return to the beach they were born on.

Within days of giving birth,

they're ready to mate,

which they'll do at the same time

as they raise their young.

It's a big demand,

but these seals have a short window ashore

before they need to return to the ocean to hunt.

The large body of an elephant seal

requires constant feeding.

Young males just a few years old

are already larger than the females,

but are yet to reach the epic proportions

of the big bulls.

They lift up the front half of their huge bodies

and bear down on each other,

taking small bites aimed at the neck.

(guttural growling)

This is just the dress rehearsal.

The juveniles are sparring

in practice for the years ahead.

For one day, one of these young males

will become the beach master.

The beach's alpha male.

(guttural growling)

At summer's onset,

the adult elephant seal bulls

interrupt king penguin colonies

and thunder their way onto the beach first.

They're pumped full of testosterone

and need to stake out the best real estate

for a mating territory.

The bulls corral the females into a harem,

their breeding group.

The strongest bulls will gather 50 or more.

The weight difference between the sexes

is no equal match.

But it's constant work for the males

herding so many wanderers.

(dramatic orchestral music)

Younger bulls carve out smaller harems

and do their best to seduce young females from others.

But there is always one bull that is the most dominant.

This is the beach master.

And he is always being tested.

(guttural growling)

A challenger issues a roar.

The large proboscis, or nose,

is designed as a kind of echo chamber

to amplify the warning.

He charges, and the years of sparring practice

become a real battle.

(dramatic orchestral music)

This young bull, little more than a decade old,

is no match for the beach master.

He retreats back to the safety of the water,

effectively raising a white flag.

(guttural growling)

The beach is lined with bloodied and battle-weary bulls,

and they lose weight every day they are here.

The males are so obsessed with guarding their harems,

some won't eat for the entire three months

of the breeding season.

They survive on the huge fat reserves

they've stored for the summer.

They'll leave the beach

nearly half the weight they were when they arrived.

A female with a baby will also lose weight at this time.

Eight kilograms each day while she's nursing.

Her pup puts on four kilos a day

and quadruples in weight in less than a month.

The elephant seals spend several weeks on this island

before returning to sea

to renew their constant pursuit of fish and squid.

Until then, it's a long summer of fighting,

mating, and finding small havens of space

alongside the thousands of penguins

that share this south Georgia island beach.

(serene orchestral music)

As summer draws to an end,

the resident king penguins of south Georgia island

head back out to sea.

The only penguin that spends its breeding cycle

on the Antarctic continent itself is the emperor.

They're marching to the edge

of the coldest place on earth.

(penguins chirping)

Stretching out into Drake Passage

toward the tip of South America

is the Antarctic peninsula.

75% of the Antarctic's krill,

the smaller larval stages of fish and crustaceans,

is found in the waters around this peninsula.

That brings an astonishing number

of penguins and seals to its shores.

But come winter, they abandon the continent

and head out to sea,

using ice bergs for rest.

All except for the largest of penguins.

These emperors won't be joining the exodus.

They've evolved to survive the harshest winter

on the planet.

(penguin trills)

Emperors stand more than a meter tall.

Compared to other penguins,

they have larger fat reserves.

As winter sets in,

the sea ice freezes into a thick slab

extending from the mainland,

hundreds of kilometers long in some parts,

and more than three meters thick.

The emperor penguins have timed their breeding cycle

to allow the best chance of survival

here for their chicks,

which will hatch toward winter's end.

But first, they must survive the Antarctic's coldest days.

These penguins mate for life.

Each season, the female will produce a single egg.

Her body is depleted from the energy it takes

to create the new life,

so she leaves soon after laying.

She must travel up to 80 kilometers

across the sea ice to the ocean to feed.

There are no materials to build nests here,

so the male emperors become the nest.

The female must transfer the egg to the male quickly,

before the egg freezes.

The male carefully balances the precious egg on his feet

and keeps it in an adapted apron of fat.

It hangs over the egg

and warms it in the subzero temperatures.

The females farewell the fathers

and head off on the arduous trek

to find the point where the ocean

has ceased to freeze over.

The roundtrip will take several weeks.

(wind howling)

The males must endure the coldest depths of winter together.

(penguin trills)

They protect the egg in their brood pouch

and huddle together for warmth.

Antarctic winds are the strongest on earth,

between one and 200 kilometers an hour isn't uncommon.

This adds wind chill to plunging temperatures,

more than 40 degrees below zero.

The penguins take turns bearing the brunt

of the wind and snow on the outside

before moving into the group center.

Here it can reach over 30 degrees Celsius

thanks to the combined body heat.

At the peak of winter,

they'll be in complete darkness

for a fortnight when the sun doesn't rise at all.

(penguins chirping)

Born into the cold and dark,

the new chicks are often hatched

by the time their mothers return weeks later with food.

She regurgitates the meal

she's carried across the ice.

(upbeat chiming orchestral music)

It's still a precarious time for the newborn.

It spends its first days

in the warmth of the brood pouch.

Rolling away for too long will mean freezing to death.

The females take over parenting duty

to allow the males to embark on their own trek

across ice for food.

(penguins chirping)

There aren't many predators

that dare to venture into the mainland

at this time of year.

But good weather brings in seabirds like petrels.

It only takes a moment for the mother to be off guard,

but this one is unyielding.

(penguin caws)

She protects her own and another from the intruder.

(dramatic orchestral music)

(soaring orchestral music)

When the chicks grow large enough,

both parents leave on hunting missions.

The chicks stay behind in creches

with a few adults left to keep watch

over the small groups.

When the adults reach the hunting grounds,

they chase fish, squid, and krill.

Despite their size,

emperors are impressive swimmers.

Their streamlined bodies

have been designed for this underwater environment.

They can stay underwater

for up to 22 minutes

and have logged dives more than 500 meters deep.

Back at the creche,

the older chicks form an orderly queue

for today's important lesson.

Some parts of the sea ice have melted

just enough to form shallow pools.

(bouncy orchestral music)

Once brave chick must be the first

to test the waters.

The group soon follows.

These chicks will spend the days ahead

building up their pectoral wing muscles.

The juveniles' thick downy coats

are designed to keep in heat,

but not to keep out water.

(bouncy orchestral music)

It's a strenuous outing,

but every small puddle is practice.

(splashing)

Each molting sees their feathers

become more tightly packed

and coated with oil.

As the ice melts,

it brings the chance to test deeper waters.

Preparation for the day these emperors

return to the big Southern Ocean

that will soon reclaim these shores.

(splashing)

(bouncy orchestral music)

(dripping)

Melting ice heralds the onset of summer.

It awakens spores of algae,

leaving stains of red and green

on the retreating floes.

As the saltwater softens

and once again becomes liquid,

it allows the arrival of gentoo penguins.

The gentoos ascend from the pebble beaches

and begin a steady trek upwards through the snow.

Their pathways are known

and already worn in by the penguins

that arrived first.

Timing is everything

when it comes to securing the best positions

at the peaks of the hills above.

Gentoos have distinctive red beaks

and white eye patches.

The males arrive at the clifftop first

to work on wooing a female.

After stacking rocks into piles for a nest,

he will then collect more pebbles.

These ones are special.

The male offers them as tokens

to a prospective partner.

She will accept a mate

based on the size and shape.

But the criteria for an impressive pebble offering

is still somewhat of a mystery.

(penguins cawing)

The female gentoo lays her first egg

about five days after mating

and a second three days after that.

The parents share egg-sitting duties

for about a month

before the first signs of emerging life

start stirring from within.

(serene chiming music)

Incredibly, both chicks are born on the same day

despite the eggs being laid days apart.

They're covered in down

and small, just a couple of hundred grams in weight.

They'll need to stay in their makeshift pebble homes

for about 75 days

before they're ready to make their way to the ocean.

(penguin cawing)

The parents, however, have chosen their sites well.

They're close to the sea

and they descend to the shore regularly to hunt.

Gentoos are the fastest underwater swimmers

of the penguin world.

They have to be.

They're one of the favorite prey of these.

Leopard seals.

(dramatic music)

So named for their recognizable spots,

leopard seals have sharp, canine-like teeth.

They also make their way back to the peninsula

as the waters warm.

Some have traveled far.

Leopard seals are sighted

as far north as Tasmania,

on Australia's southern tip.

These marine mammals are fearsome predators

and the only seal that feeds on warm-blooded prey.

They'll even eat other seals.

Leopard seals tend to skew their diet

toward the particular southern region

they return to for summer.

And here it's gentoo.

(dramatic music)

Leopard seals are solitary hunters.

They can match the gentoo for pace in the water.

(serene orchestral music)

When the nesting season comes to an end

some three months after it began,

the gentoo fledglings head to sea.

They do so in their large family flocks.

(splashing)

Safety in numbers is a key survival strategy

for sharing the water with such a ferocious predator.

(serene orchestral music)

Antarctic sea ice peaks in winter

and retreats in the summer months.

The entire continent undergoes

a dramatic transformation

as it shrinks from a 20 million square kilometer surface

down to three million square kilometers.

As the days lengthen,

freshwater ice on the mainland also warms.

(rumbling)

Large chunks break off from glaciers and ice shelves

in a process called carving.

Icebergs are set adrift,

traveling with ocean currents and wind,

often floating into bays

and breaking apart onshore.

Some can be huge.

The largest on record was measured

at nearly 300 kilometers long.

Descriptions vary according to size,

shape, and origin.

Tabular icebergs have a distinct flat top.

Bergs are no larger than five meters above water.

And when they're even smaller again,

under two meters, they're known as growlers.

(serene orchestral music)

As the iceberg slowly melts into the ocean,

it generates a pool of freshwater,

sometimes extending outward

for a full nautical mile.

They also shed the terrestrial material

trapped in the ice.

It's rich in iron

and stimulates the growth of phytoplankton,

the plant-based organisms

that are the building blocks for marine life.

The food chain bursts into action.

Animal plankton and krill,

tiny shrimp-like crustaceans

attract floating organisms like jellyfish.

(bouncy xylophone music)

Small fish hide in holes on the berg's underside.

Fur seals, sea lions, and seals

come to feed and take the opportunity

to rest during the long days offshore.

Seabirds like the Wilson's Storm-Petrel

migrate huge distances from north of the equator

to their summer breeding grounds

around the Antarctic.

They feed around icebergs

by running along the surface of the water,

their foot taps attracting hungry fish

to come within striking distance.

Petrels are not the only ones

returning to home shores

to feast on the exploding krill population.

(deep groaning)

(serene piano music)

At 150 tons and 30 meters long,

blue whales are the largest living animal.

And the largest are found here

in the Antarctic oceans.

These whales sweep up huge amounts of krill

in a single open-mouth lunge,

consuming as much as eight tons a day.

Summer cues a return to these waters for them

and many of their relatives.

(deep groaning)

A southern right whale is easily identifiable.

It's the only large whale

that doesn't have a dorsal fin.

They're returning from breeding grounds

around the southern tips of Africa,

Australia, New Zealand, and South America.

Many have their calves in tow.

The mother's milk is extremely high in fat

and these calves will put on 60 kilograms each day.

They'll wean over the summer

and begin feeding on the polar krill.

Pilot whales are one of the four

toothed-whale species that come here.

Their teeth allow them to catch

and eat larger prey like squid and fish.

Orcas are another toothed-whale species.

More specifically, they're dolphins,

the largest of their kind.

Orcas don't migrate in the way their relatives do,

but will follow the migratory paths

of other animals they hunt.

These are supreme carnivores.

They eat fish, seals, and penguins.

Even other dolphins and whales.

This pack is feasting on the carcass of a minke whale.

(serene orchestral music)

The carcass also feeds a flock of seabirds

making the return journey south.

In these vast, cold oceans,

every floating object from ice to rotting remains

becomes a living ecology for a short time.

(serene chiming music)

Some ocean currents travel for thousands of kilometers,

beginning in one part of the world

and bringing warm or cold water to another entirely.

Just south of the Australian continent

is where currents from the equator

meet those from the south pole.

Eastward, a major current from the tropics

travels the seaboard, rounds Tasmania,

and continues to follow the coastline.

Ocean currents that flow adjacent to coastlines

are called boundary currents.

The Leeuwin is the world's longest.

It arrives from the Indian Ocean in the west.

One area's weather can impact on another.

Monsoon winds hit ferocious speeds

around the equator in the north in summer.

Several weeks later,

the winds have pushed currents to reach peak force

as they arrive into southern Australian waters.

This current flow coincides with a temperature drop.

In the south, Antarctica is being seized by winter.

Here, the water is still cold enough

for the seasonal migrators.

Whales pass by on their way to birthing grounds.

Some species followed

cold current pathways long ago and stayed.

Sea lions, fur seals, and little penguins.

Coastal islands along Australia's south

have become a permanent home

for these cold water specialists.

Kangaroo Island is a large rocky outcrop,

roughly seven times the size of Singapore.

Above the water line,

this island has a number of pristine habitats

from sea caves to sand dunes,

wetlands and dense bush land.

The island is named for its very own kangaroos,

a subspecies separate to the mainland's.

The marine ecosystems are equally diverse.

The sea bed is covered with large gardens

of microalgae, or seaweed.

It's a prime hunting ground that hides small prey

and draws in larger hunters.

This Australian draughtboard shark

cruises the seaweed beds for small fish,

squid, and shellfish.

It's only found in a small range

in these cold southern waters,

and usually at far greater depths,

more than 600 meters below.

The cold water sweeping in from the Antarctic

also cultivates crops of sponges,

a very primitive form of animal

that tends to anchor and grow, much like a plant.

Though more commonly associated with tropical waters,

several species of frog fish

live amid Kangaroo Island's sponge gardens.

These small ambush hunters

are voracious carnivores.

A frog fish's pectoral fins

are fused and splayed,

better suited to crawling than swimming.

Frog fish are also found on the northern fringes

of the Indian Ocean around Indonesia,

connected to the south by the Leeuwin current.

Masterful camouflagers,

frog fish perfectly replicate their habitat,

be it a tropical reef or a cool sponge bed.

(bouncy orchestral music)

This sponge crab goes a step further

in his mimicry act.

It actually takes a piece of the sponge garden

and places it atop its shell.

Not only does the crab blend into the sea floor,

but these sponges are one of nature's

oldest success stories.

They are a live organism

and many produce chemicals that are foul-tasting.

By wearing it like a hat,

the sponge affords the crab

an extra degree of protection.

Close to the island's shore,

an 11-armed sea star stalks the tidal pools.

This is south Australia's largest starfish

and it uses its entire body to catch food.

The arms are covered in tiny jaw-like knobs

called pedicellariae.

They can latch onto small crabs or worms

until an arm or foot can reach

and pass it to the central gut.

Idiomysids are tiny crustaceans,

just millimeters long.

They're also known as sea bees

and it's theorized they help sea grass fields to flourish.

Sea grasses are a marine plant

with roots, flowers, and leaves.

Sea bees have been found

with sea grass pollen in their legs.

The sea grass around Kangaroo Island

harbors two very distant relatives:

the knobby seahorse and the weedy sea dragon.

Both have evolved to have long, plant-like bodies

and elongated mouths designed to suck up

tiny shrimp like the idiomysids.

(serene harp music)

A Shaw's boxfish stalks the sea grass,

blowing jets of air onto the sand.

It's cleverly uncovering any tiny worms,

shrimp, and crabs hiding just below the sea bed.

Like all boxfish, this one grows an exoskeleton

as well as an internal one.

Its body is encased in a bony box

and the skin can release toxins if it gets stressed.

The Shaw's boxfish is considered

to be endemic to the eastern Indian Ocean.

However, it's also found all along

the southern Australian coastline.

The Leeuwin current is thought

to have swept the boxfish from tropical waters to cool.

In some areas of the southern hemisphere,

this process has worked in reverse.

Vast networks of underwater highways

have carried south polar species

to surprisingly warm places.

Like Africa.

(upbeat percussion music)

On South African savannas,

daytime temperatures soar above 30 degrees Celsius.

It's a country renowned for spectacular wildlife:

lions, elephants, and giraffes.

It seems barely imaginable

these animals of the dry, hot plains

could share their home

with the likes of seals and penguins.

Africa's southernmost tip

is a meeting place for roaring trade winds

and a number of oceanic currents.

The Cape Agulhas is a fast-flowing surface current

that transports large volumes

of warm tropical water

along the African coastline to the cape.

It rounds the cape, picking up icy

Antarctic waters from the south,

becoming the Benguela Current heading north.

A current much like this

was a potential pathway for polar travelers

some 30 million years ago: penguins.

African penguins long ago

evolved to cope with the heat.

They have a pink featherless gland above each eye.

The hotter it gets, the pinker it becomes.

The gland sends blood to the area

to help cool the penguin down.

They build nests on land

out of their own excrement, or guano.

Unlike Antarctic emperors that try desperately

to keep their eggs from freezing over,

these penguins have to shield theirs

from the searing African sun.

If they can't find a bush for cover,

they'll use their own bodies for shade

and take the brunt of the heat themselves.

When the chicks have hatched,

parents divide guarding duty.

A fishing trip in the bay

is a well-earned cool respite.

African penguins share the cape beaches

with rock hyrax, a small furry mammal

with feet adapted for rock climbing.

The hyrax looks like a large rodent

but is biologically more closely related to an elephant.

They have a similar skull structure,

including teeth designed to grind

the hard vegetation.

African shores pose a unique problem

for hyrax and penguins alike.

They are hunted by mongoose and leopards.

The penguins at least can escape to the sea.

However, the cold currents of long ago

also brought marine predators.

Fur seals.

(seals grunting)

Roughly two million fur seals

live on the South African cape.

One of the larger colonies is based around

small rocky outcrops near the southern tip.

Dyer and Geyser Islands.

(upbeat percussion music)

Unlike most other fur seal groups,

the cape fur seals live here year-round.

They use these islands as a base for mating,

raising young, and resting.

But spend most of their time fishing at sea.

Like the Antarctic, the island kelp beds

offer up small fish and squid taking cover.

But the cape fur seals' preferred diet

of sardines and anchovies

swim out wider in the deeper ocean.

To reach the open sea,

the fur seals must first pass through the channel

that separates these islands.

This channel is locally known as Shark Alley.

Sharks like bronze whalers are here most of the year

and in bigger numbers for the annual sardine run

that takes place along the coastline each winter.

The cold water also attracts

the largest predatory fish in the ocean:

great white sharks.

In summer, strong southeasterly winds

sweep the current coming from

the south polar region into the bay.

It's also when the cape fur seal pups are born.

By winter, the newly adult seals

are large enough to make their maiden voyages

across the channel.

But they have not yet learned

to swim at their peak speed

and lack open water experience.

The great whites have come to know

this is a regular time and place

that a source of food is on offer.

These are one of the ocean's most skilled hunters.

They can reach over six meters in length

and have large, triangular teeth

designed for securing and ripping into flesh.

Great white sharks prefer to hunt

in cooler waters around the globe,

but they adapt their hunting technique to each area.

At Shark Alley, their weapon is speed.

Despite their huge girth,

these sharks have a pointed nose

and streamlined bodies.

Their tactic: stay deep

and watch overhead for a seal-shaped shadow to pass by.

Then sprint to the surface.

(dramatic boom)

(dramatic orchestral music)

On the South African cape,

great whites launch with such ferocity

they breach the water's surface.

Their entire bodies, all 3,000 kilograms,

clear the water in astonishing aerial leaps.

The young fur seals are learning

the lesson of their lives.

A wrong turn will mean death.

Those lucky enough to escape the first attack

twist and turn, trying to predict

where the shark will strike next

and attempt to sprint to safety.

(dramatic orchestral music)

For many, a misdirection is fatal.

For others, the return swim to shore is a fast one.

A fur seal can learn to outmaneuver

a great white shark.

But the lesson is a costly one.

Only half of the fur seals under attack

in Shark Alley will survive.

Right across the southern hemisphere,

as each season turns,

nature responds with a call to hunt and hide.

To bloom and to birth.

Where the southern wildlife goes

for each stage of their life cycles

is determined by instinct

and handed down through generations.

The clock is reset each year

and emanates from the point of the globe

that is at that part of the year

the farthest from the sun: the Antarctic.

(dramatic orchestral music)