03x06 - Cook Islands

[bunniefuu]

In the huge expanse
of the South Pacific Ocean...

..an archipelago
of tropical islands...

is scattered across
two million square kilometres.

It's a miracle the first seafarers
ever found them...

on their heroic ancient voyage.

(BIRDS SQUAWKING)

Every year...

these islands are the destination
for travellers..

..who undertake one of the longest
migrations on the planet.

Other island residents are also
on a journey.

Slower but just as epic,

which offers a glimpse
into our evolutionary past.

But sometimes even paradise

can be deceptive.

In the southern group
of the Cook Islands...

..Kuki 'Airani.

(CALMING MUSIC)

(WHALES WHISTLES AND CALLS)

(THEME MUSIC)

(BIRDS TWEET)

Anchored in the vast
South Pacific Ocean.

Rarotonga is the mothership
of the Cook Islands group.

Every year from July onwards...

..weary travellers announce
their arrival off these shores.

Humpback whales.

(WHALE CALLING)

They've been gorging on krill
all summer in Antarctica.

When the polar winter closed in...

..the whales began
a 5,000-kilometre migration.

It's taken them three months
to reach this place.

(WHALES EMIT PULSING CALLS)

There's no krill here
for these ocean giants.

But they don't come for the food.

(WHALES CALLING)

3,500 humpback whales

make the journey every year.

To socialise...

mate

and reproduce.

This female gave birth to her calf

just 24 hours ago

in the warm tropical waters
around Rarotonga.

In this island sanctuary,

her daughter can learn
all the life skills she needs.

In between naps.

She can barely hold her breath
for a minute at this age.

So, Mum keeps her
close to the surface.

There's so much for a baby whale

to learn in the first months of life.

She's completely dependent
on her mother.

In around five months' time,

mother and daughter must return
to the whale feeding grounds

in Antarctica.

Already, the female's
fat reserves are dwindling,

and she has to ration her energy.

In contrast,

her calf must fatten up fast.

The Cook Islands are a safe haven

for new humpback whales
in the first months of their lives.

But it's a race against time

for the calves
to grow strong enough

for the arduous journey south.

Rarotonga in
the Southern Cook Islands group..

..is known
as the jewel of the southern seas.

It's a green oasis
in a vast blue sea.

With its rugged mountains

thrust up by the volcano
which created the island

two and a half million years ago.

A shallow tidal lagoon
wraps around the island

like a moat.

Protected from the open ocean

by a massive coral reef.

There are only a handful of entrances
into this turquoise lagoon.

(SOFT MUSIC)

Like arteries...

these channels
carry nutrient-rich water

from the deep ocean...

..into the shallow lagoon.

Constantly refreshed by the tides...

the food chain here is dynamic.

Numerous species use the passageways

to move in...and out.

Eagle rays and reef sharks

feed in the lagoon...

and use them as nurseries
for their young.

And then there's
the endangered green turtles.

Who roam vast expanses
of the Pacific Ocean.

They seek out
the Rarotonga passageways...

..when they need to rest.

But the strong tidal currents

can make the approach hard work.

This big female has done it before.

Every few minutes,
she surfaces to breathe.

And then...lungs full of air...

..she dives...

..to scout the reef
for her favourite resting place.

Once settled,

she wedges her body tight
between the coral outcrops.

And uses her flippers
to hold her in place

to resist the current's pull.

Now she can snooze comfortably

for several hours...

without surfacing for air.

In contrast to this tranquillity...

the shoreline of the Rarotonga lagoon

becomes a w*r zone every day

in synch with the tides.

Predators arrive on the high tide
to hunt the rock-pool residents.

But must time
their departure carefully...

..or be stranded on the low.

On this shoreline
squats a rock fortress.

Home to a local tribe
which has figured out a genius way

to escape this daily drama.

(QUIRKY MUSIC)

Meet the marine blennies.

Fish who are in the process

of leaving the sea.

To become landlubbers.

Fish physiology is not designed

for a terrestrial lifestyle.

Gills are for breathing underwater.

Blennies have gills.

But they also absorb oxygen

through their skin like frogs.

Fish are supposed to swim.

Blennies walk...

sort of...using a unique
tail-twisting action.

In tidal zones,

blennies have always been
at the bottom of the food chain.

So...

in a masterstroke of adaptation...

..Cook Island blennies
began colonising land

to escape predators.

This is not the first time
fish have left the ocean.

Roughly 375 million years ago,

fish with fins
crawled out of the water.

And transitioned to fish with limbs.

Known as tetrapods.

(BIRD CAWING)
All vertebrate life

on Earth as we know it today

evolved from those trailblazers.

Transitioning to land, however,

does not mean blennies have left

all their predators behind.

And they still need salt water
to survive.

So, for now, they remain
tethered to the shoreline.

Around 200 kilometres from Rarotonga,

ancient Atiu

was once an undersea mountain.

And the island is still actively
being thrust up from the seafloor.

It's surrounded
by a living coral reef.

But a fossilised reef,
known as the makatea,

also rises with the island
and currently sits

up to 20 meters above the ocean.

Beyond these elevated shores...

..two more humpback whales

cruise into the Atiu neighbourhood.

They're likely males.

And they know that some
of the Cook Island females

prefer to give birth here

rather than Rarotonga.

Sure enough, close by...

..a female nuzzles
her days-old male calf.

They communicate constantly.

Sound travels over four times faster
in water than in air.

And predators, like sharks and orca,

actually listen out for their calls.

(WHALES CALLING)

So, mum and son
whisper to each other.

(WHALES CALLING SOFTLY)

(CONTINUING TO CALL SOFTLY)

These soft, intimate sounds

are less likely
to be intercepted by K*llers.

But an eavesdropper has picked up
on their conversation.

One of the Atiu males.

Courting females is the reason

all the males flock to this paradise.

He'll play a long game.

Waiting until she's ready to mate.

For now...he keeps
a respectful distance.

Which is just as well...

..because the calf is hungry.

Whales don't have sucking muscles.

So, instead, his milk is injected
straight into his mouth.

Which makes for a messy mealtime.

Over the next few weeks,

he'll slurp around 500 litres of milk
a day.

Which will help him grow
remarkably fast.

Gaining up to 40 kilograms a day.

Lunchtime over...

the male escort ventures closer.

The protective mother
signals immediately...

..that he has crossed a line.

Her calf will always take priority.

(BIRDS SQUAWK)

High above
this whale courtship drama...

a unique aerial mating ritual

is also under way.

(BIRDS SQUAWKING)

Red-tailed tropicbirds

soar over their breeding haven...

Takutea.

The smallest island
in the Southern Cooks group.

(SQUAWKING)

These birds are so graceful
on the wing.

But as they compete to attract
mates...

they reveal
another astonishing skill.

They can fly backwards.

The physics seem inconceivable

for a bird this size.

The only other bird that can do this

is a tiny hummingbird.

As males and females flirt...

..they twitch their long-streaming
tails from side to side.

As an extra stimulus
to capture attention.

(UPLIFTING MUSIC)

Eventually the courting birds

glide back to Takutea

to rest
before the next aerial rendezvous.

Tropicbirds in this region

have a long breeding season.

And many parents
are already hard at work.

Life on this coral cay is so safe

that most nest on the ground.

A female tropicbird
incubates her single egg.

While other nests
already have chicks.

This little marshmallow
is just days old.

(CHICK CHIRPS)

But it's not unusual for his parents

to leave him alone
while they hunt at sea.

Unlike other ground-nesting birds,

tropicbird chicks are born
with their eyes closed.

He's completely helpless

as he waits for a parent

to deliver food...and extra warmth.

(CHICK CHIRPS)

Then...

..a special milestone.

He sees for the first time.

Takutea, as home...

..will be imprinted
on this little bird's brain...

..from now forever.

On the Atiu shoreline...

..the receding tide exposes a shallow
channel in the reef.

These damp, rocky walls...

are home to more blennies.

They're the exact same species

as those found at Black Rock
in Rarotonga...

just over 200 kilometres away.

Like those blennies...

these guys also wriggle in synch

with the tidal flow.

Up and down the rock walls.

They may have escaped the sea.

But technically they're still fish.

And need to stay moist.

To avoid death by drying out,

they have to stay in the splash zone.

But there's a further twist

in the blenny evolutionary tale.

Just meters away
from the channel tribe,

across a stretch of sandy beach...

..the low tide exposes rock pools.

Home to another group of blennies.

But while the first group
is exclusively terrestrial.

These blennies are amphibious.

They spend half their time
in the shallow water

in the rock pools like normal fish.

But when the high tide arrives
with potential predators...

..they can also survive
out of the water,

like their cousins
along the channel.

How these two species,

living in such close proximity
to one another,

became so different

is a marvel of evolution.

A terrestrial blenny
would eventually drown

if it was submerged in water
for long.

But being able to breathe
through their skin...

means they can tuck
into nest holes

above the waterline

and stay safer from predators.

The amphibious blennies

are not as effective as their cousins

at breathing out of the water.

So, their time on land is limited.

These differences were enough

for a reproductive barrier to evolve.

Which means neighbouring blennies
can cross paths...

but they cannot interbreed.

(BIRDS SQUAWKING)

It's late afternoon

on the shores
of the Takutea bird haven.

And on-duty parents

are ready
for the shift change.

This male brown booby,

distinguished by his masculine
blue-gray bill,

has been incubating
his egg all day.

It's his turn to go to sea to hunt.

(CHICK CHIRPS)
A tropicbird chick

urgently requires food.

But the parent has nothing left.

(CHICK CHIRPS)

The cause of the delay

is revealed in the sky
above the shoreline.

(BIRDS SQUAWK)

Pirates lurk.

Great frigatebirds.

They too have demanding mouths

waiting to be fed on Takutea.

These chicks rely on their parents

for up to 18 months.

So, to maximise their bounty...

..frigate parents hunt in a g*ng.

Not for their own prey however.

They live a life of crime.

Stealing food from others.

(BIRDS SQUAWK) All the
returning boobies and tropicbirds

must run this gauntlet

before they can reach their nests.

In the sheltered waters
beyond the Rarotonga lagoon...

..the baby girl humpback

is growing bigger by the day.

Her mother is also being followed
by an escort.

And he shepherds them

as the calf practises
a distinctive whale behaviour.

The breach.

Calves learn
by mimicking their mothers.

And the male escort
also demonstrates how it's done.

Whales breach
to communicate numerous emotions.

Dominance, frustration,

curiosity, and even grief.

With every breach
the youngster nails...

..she's also increasing
her breath-holding capacity.

When lessons are over,

rest is just as important.

The epic journey
back towards Antarctica

will begin in about eight weeks.

So, learning to conserve energy

is also essential.

On the north side of Rarotonga...

just beyond the waves

which break
on the edge of the lagoon...

..grows a landscape like something
out of a fairy tale.

The hard-coral outcrops

resemble terrestrial fungi.

So, it's known
as the Mushroom Forest.

The absence of soft corals here

hints at the ferocity of storms

which blast through
the Cook Islands regularly.

They destroy all the soft corals.

While the more robust hard corals

usually survive.

A maintenance crew of parrotfish

cruise the forest,

working around the clock.

They scrape away dead coral

with their extraordinarily
sharp parrot-like beaks.

To extract nutritious algae
and polyps.

Surgeonfish work alongside them.

Pruning the living algae
like gardeners.

This industrious excavator

has been working so hard,

he's developed an algae moustache.

All that pulverised coral

that the parrotfish ingest...

has to go somewhere.

Parrotfish poop is pure white sand.

And much of it ends up
on the beaches of the Cook Islands.

In the Rarotonga reef passage...

..a big green turtle
wakes from her nap.

Before she leaves the lagoon,

there's something she needs to do.

She's heading
for a specific coral outcrop...

..frequented by a particular species
of fish.

This is what she is looking for.

It's a cleaning station.

She'll have to queue.

She's not the only turtle
who comes here.

Surgeonfish
use their gardening skills

to prune the algae
that grows on turtle shells.

Excessive build-up

can prevent heat absorption
from the sun.

And even cause shells to rot.

Now it's her turn.

Surgeonfish provide the service

in exchange for a free meal
of the algae.

The turtle also treats her underside

to a good scrub while her shell
is being cleaned.

There is another specialist crew
in this neighbourhood.

Bluestreak cleaner wrasse
take on all kinds of clients.

Even the potential K*llers.

They have a mutual understanding

with the moray eel.

The cleaners
devour the eel's parasites.

And in exchange,
the predator won't eat them.

Everybody wins.

At Black Rock...

the terrestrial blennies

also dine on nutritious algae.

Their tent-like mouths
have specialised teeth,

which scrape their greens
off the rock surface.

Lunch is important.

But some of the blennies
have more pressing business.

Attracting a mate.

Males are identified
by a distinctive mohawk.

Which the females don't have.

The bigger the crest...

the more irresistible he is.

A large male
with a yellowback fin...

makes a move on an attractive female.

What he really needs
is to entice her back

to his breeding cave.

The cave he's chosen

has a smallish entrance he can guard.

Close to the waterline.

A male grazes just outside.

So, Yellowfin warns him off.

The female checks out his form.

Now, all he needs is for her to come

and lay her eggs in his cave.

Just as in blenny land...

(WHALE PULSE CALLS)
..male giants assemble offshore

with females on their minds.

(WHALES CALLING)

Socialising is essential
in humpback culture.

And the annual gathering

is the perfect place to mingle.

(WHALE CALLING)

All humpbacks talk to each other...

..like this.
(WHALE CALLING)

(WHALE CALLING)

They have numerous vocalisations,

which all have meanings.

(WHALE EMITS HIGH-PITCHED CALL)

But...it's only the males who sing.

(WHALE EMITS LOW-PITCHED PULSED CALL)

On their travels between the tropics
and Antarctica,

males compose intricate melodies.

(WHALE EMITS LOW-PITCHED CALL)

With phrases and themes.

(WHALE EMITS SHORT CALLS)

They share their songs
with each other.

And they change.
(WHALE EMITS RISING CALL)

But why they sing...
is the bombshell.

This lone male is not singing
a ballad to attract a female.

(WHALE CALLS)

He's advertising his position

and seeking other males
for a competitive alliance.

Possibly to hunt for females.

(WHALE CALLS)

Apparently females are
more likely to choose a mate

from a noisy chorus
of multiple males.

(WHALE CALLS)

Here at the breeding grounds,

the most recent pop songs

from the males' voyages
are performed.

And they all sing along.

(WHALE CALLS)

But what was once a cool song...

might now be out of date.

(WHALES CALLS)

(WHALE EMITS HIGH-PITCHED CALL)

No one has answered
this bachelor yet.

It's possible his song...

..is already so last year.

(WHALE EMITS HIGH-PITCHED CALL)

(BIRDS SQUAWKING)

On tiny Takutea...

..booby...and frigatebird chicks

are growing in their adult feathers.

Little marshmallow, the tropicbird,

has already lost
most of his downy fluff.

But he's still being fed
regularly by his parents.

So, he waits.

(QUIRKY MUSIC)
(CHICK CHIRPS)

A neighbouring chick
has grown impatient.

At just six weeks old,

this intrepid brown booby

is a little shaky
on his land legs.

(CHICK SQUAWKING)

He's looking for his parents.

"Are you my mother?"

"Apparently not."

Offshore, the frigatebird g*ng

prepares its usual ambush.

Unlike other seabirds,

frigates can't land on water

because their feathers
aren't waterproof.

They can snatch food
from the water's surface.

Or from their neighbours.

Marshmallow's mother returns...

fat with fish for her chick.

So, she's a target.

Everyone is fair game.

As long as they have a full belly.

This brown booby can't
outfly the pirate.

Her only option
is to land on the water.

Others aren't as lucky.

(BIRDS SQUAWKING)

The booby is forced
to regurgitate his catch.

But before the pirate can grab it...

an opportunistic giant trevally
claims the prize.

They are familiar
with this daily battle.

Marshmallow's mum
makes a break for it.

And just makes it
through the gauntlet.

Today the precious catch

is delivered
to its rightful recipient.

In a few weeks, this scruffy chick

will have all his adult feathers.

And it will be time for him
to leave home...

and join his parents...

exploring the wild Pacific.

(SOOTHING MUSIC)

Outside the Atiu reef...

..the humpback clan snooze
to conserve energy.

They're not fully asleep,

as humpbacks are conscious breathers.

Even while napping...

..they have to remember to breathe.

So, to stay safe,

they only shut off
part of their brain at a time.

Having a male escort close by
during naptime

can give the female added protection.

As his awake brain
guards his chosen female

and her calf from predators.

Naptime over...

the consort transforms

from protector
back to tenacious suitor.

It's been weeks now,

and despite helping out
with child care...

his attempts to woo her
have fallen flat.

He's growing increasingly frustrated.

The female keeps herself
between him and her calf.

A 30-ton giant can land quite a blow

when he's cranky.

(WHALE CALLS)

Other males hear his frustration

broadcast through the water...

(WHALE CALLS)

And converge in response to his song.

It's a call to action,

an alliance of rivals.

The victor will gain pole position

next to the female.

Each slap...

..and breach...

is full of bravado.

These battles can be boisterous...

but they're rarely fatal.

Mother and calf
seize the chance to sneak away.

There are more peaceful waters

for them to relax in.

But one male follows.

It's their tenacious escort

who has emerged the winner.

He'll stay
at his chosen female's side...

..for as long as he can.

For his chance to mate with her.

Around 24 hours later.

Three whales arrive
at the turquoise waters of the lagoon

surrounding the island of Aitutaki.

The ocean just outside
the coral atoll here

is over five kilometres deep.

So, it's generally
a sheltered pit stop

for whales on their circuit
of the Cook Islands.

The coral atoll
protects a collection of 15 islets

inside the lagoon.

Known as motu.

Coral bommies are sprinkled
throughout the shallow lagoon.

Like oases in a sandy desert.

Numerous species inhabit every nook
and cranny around the bommies.

Giant clams anchor themselves
on the reef.

They can live for 100 years.

And weigh
over 200 kilograms each...

..as they filter-feed
in the pristine lagoon.

Aitutaki looks like
a picture-perfect paradise.

But like all these islands
in the South Pacific cyclone belt.

It's vulnerable
to an approaching storm.

The shallow lagoon has just
one main passageway to the ocean.

So, it can become hazardous

for anyone trapped inside.

(THUNDER BOOMS)

The storm sweeps in.

And one by one, all the islands

in the southern group are impacted.

The locals hunker down.

They're used to this chaos.

The channel and the rock pools
where the blennies live...

..are swamped.

How fully terrestrial blennies

survive storms is a mystery.

But somehow they do.

For those offshore...
there is no shelter.

Reefs, which usually provide
safe haven for the whale calves,

become treacherous in a storm.

Mothers sometimes move
their offspring into deeper water.

But even the most experienced

can lose their way
in the powerful swells.

(THUNDER BOOMS)

(MELLOW MUSIC)

The morning light
reveals calm seas again

around Aitutaki's protective lagoon.

(WHALE CALLS)

But the female humpback whale

cannot find her son.

(WHALE CALLS)

Her desperate calls and tail slaps...

..go unanswered.

(WHALE EMITS SHORT CALL)

(WHALE CALLS AGAIN)

The young calf was no match

for the powerful swells
whipped up by the storm.

He was rolled over
the lagoon's barrier reef.

Slashed by the shallow coral.

And without his mother's guidance...

..he couldn't navigate
a passage out to safety.

Outside the lagoon,
the mother grieves.

Like all highly intelligent
and social animals...

..whales mourn their dead.

These islands are usually a sanctuary

for humpback whales.

But the powerful Pacific Ocean

always has the final say.

All around the Southern Cook Islands,
the residents take stock.

(BIRDS SQUAWKING)

On Takutea...

ground nesters have an advantage
in high winds.

There's plenty of leaf litter
to rebuild with.

And any unhatched eggs

were well protected from the storm

by diligent parents.

At Black Rock, the blennies emerge.

(WATER LAPS) And Yellowfin
is already looking for a female...

..any female.

To entice back to his man cave.

Offshore at Rarotonga...

it's time for the other female
and her daughter

to leave on their long journey
to Antarctica.

They're still accompanied
by their faithful escort.

Who'll hang around as long
as there's any opportunity

of mating with her.

The calf has doubled in size
since she was born.

She's now eight meters long,

and most importantly,

she can hold her breath
for around eight minutes.

She's well equipped

to survive the epic voyage ahead.

For the next three months,

the trio will follow
a precise migratory path

through the Pacific Ocean.

Until eventually they'll reach
the ancestral feeding grounds

in the Southern Ocean.

(WHALE BLOW AIR THROUGH BLOW HOLE)

For the rest of her long life,

the calf will repeat
this ancient journey.

And teach it to her own offspring.

Always returning
to these tropical waters...

here in the middle
of the big Pacific Ocean.