South Pacific

The South Pacific.

The name is familiar,

but 230 years after Captain Cook's epic voyages,

this vast ocean remains little known.

In the endless blue,

isolated islands harbour life that's rarely seen.

And these are some of the most pristine waters of any ocean.

The turquoise seas

and picture-postcard islands look like heaven on Earth.

But all is not what it seems.

The South Pacific also has an unforgiving nature.

Islands born from volcanic seas

erupt with unique and extreme ways of life.

People succeeded here against the odds.

The South Pacific is a tale of the unexpected...

...a forgotten world where isolation has created the bizarre and surprising.

This is the story of life in an ocean of islands.

Out of the blue, a giant emerges from the deep.

Right now, the monster moves silently,

but it's equipped with an awesome force.

Some of the largest waves in the world break on South Pacific islands.

Their birth sums up the scale of this ocean.

The storm swell that made these waves

has travelled 3,000 miles to reach this shallow reef.

These distances proved a great challenge for animal castaways,

but when they found new land, many evolved into new species.

Human colonisers followed similar routes,

and the ocean that isolated them from the rest of the world

became central to their culture.

The big waves were an inspiration,

and riding them has been a tradition here for more than 1, 500 years.

No other ocean has had a greater impact

on the lives of so many different animals and cultures than the South Pacific,

and it's all down to its massive size.

The whole Pacific Ocean is so large,

you could fit the world's continents inside it

with nearly enough room for another Africa.

Ten thousand miles wide, less than one per cent is land.

Best known are the Hawaiian islands.

They sit 1, 500 miles north of the equator,

but their story was shaped by the south.

The South Pacific is made up of thousands of islands

united by cultures and bound together by ocean currents.

Most of the land sits in warm waters,

but travel south and the character of the islands change.

New Zealand is not tropical but temperate.

The ocean currents which cool New Zealand's waters

occasionally bring icebergs.

Starting in the Antarctic, they've drifted for nearly eight months...

...on the way, passing the most southerly outpost in the South Pacific.

Where New Zealand's temperate seas merge

with the icy waters of the Southern Ocean, lies a solitary piece of land...

85 miles of wave-lashed coastline.

It looks desolate, but it's not deserted.

At certain times of year, there's more life here

than on any other island in the Pacific.

In August, after months at sea, elephant seals arrive.

They depend on this island for breeding.

Macquarie will soon be heaving with 60,000 elephant seals,

but they won't have the beaches to themselves.

One month later, another wave of migrants appear in the surf.

These are royal penguins,

and they're about to have their first sighting of land in seven months.

They've spent that time hunting for fish and shrimp in the open ocean.

One last hurdle and they're back on terra firma.

This island is actually the only solid ground

these penguins will ever set foot on.

Macquarie's nearest neighbour is more than 400 miles away,

and in the opposite direction from their favourite feeding grounds.

Within days of the first arrivals, it's standing room only.

Nobody knows exactly how these penguins navigate back to Macquarie,

but with this many adults returning every year to breed, it clearly works.

Out in the open ocean, royal penguins lead solitary lives,

so these cramped conditions take a bit of getting used to.

Disputes settled, it's time to renew old acquaintances.

The elephant seals have also settled down...

even if some still play hard to get.

Though it's not easy turning down the advances

of a suitor six times your size.

A gentle nuzzle, and she appears won over.

And it's not just love that's in the air.

At these southerly latitudes,

ocean winds bring rain six-and-a-half days out of seven.

And when it doesn't rain...

it snows.

It couldn't be more different from the clichéd image of a South Pacific island.

But surprisingly, what makes Macquarie so rich in wildlife

also benefits other islands in the tropical South Pacific,

thousands of miles away.

Macquarie's penguins and seals depend on

a cold, nutrient-rich current... and that doesn't stop here.

Powered by the strongest winds in the world, the current continues east

until it hits the tip of South America, where it's driven northwards.

Over 8,000 miles later, the cold current reaches the equator

and a remote archipelago...

The water has warmed up on the journey north,

but it's still cold and nutrient-rich.

This has allowed some animals to live here which you wouldn't normally find

this close to the equator.

Sea lions.

Isolated on the Galápagos, they've been here so long

they've become a separate species.

When the surf's up,

the sea lions spend hours just messing around in the waves.

Surfing burns a lot of energy, and they can only do it

because these cold seas support vast numbers of fish.

The sea lions share these nutrient-rich waters

with another equatorial misfit.

Penguins -

the only penguins found in the tropics.

Like the sea lions, Galápagos penguins can survive here

because the water keeps them cool and well fed.

But these conditions are not constant.

In EI Niño years, when currents reverse, warm waters replace cold,

fish populations crash

and then, stuck on Galápagos, penguins and sea lions starve.

Their numbers will bounce back,

but it's the price these animals pay for life on these isolated islands.

There are thousands of islands in the South Pacific.

Many are unbelievably remote.

Some are thousands of miles away from the nearest continent

and hundreds of miles from their nearest neighbour.

Imagine each island as a castle,

and the ocean a giant moat stretching to the horizon in every direction,

and you have captured the essence of their isolation.

It's a wonder how any life reached these islands at all.

But no matter how remote or small an island is,

animals have somehow conquered the massive ocean barrier

to reach these specks of land.

For the lucky few that made it,

South Pacific islands provided great opportunities.

Once here, they had the freedom to be different.

Crabs may not seem unusual,

but there's one kind here that's like no other.

On this little island in Vanuatu lives a real oddity.

It's the largest terrestrial invertebrate on Earth...

...the robber crab.

The biggest can weigh up to four kilograms -

the same as a newborn baby -

and have a leg span of one metre.

It's a hermit crab on steroids.

At night, the huge "robbers" really come alive.

Although these crabs are found throughout the Pacific,

it's only on undisturbed islands that you can see them in such numbers.

Exactly why robber crabs have grown so big is a mystery,

but with so few creatures making it to these remote islands,

the giant crustaceans

seem to have filled a niche normally taken by medium-sized mammals.

And with almost no competition from other native animals,

the crabs' huge size allows them to make the most of another great coloniser -

something found here in abundance.

Coconuts are one of their favourite foods -

it's why they're also called "coconut crabs" -

and they've been known to carry them as far as three miles to a favourite den.

Robber crabs are perhaps the only animals in the world able to break into a coconut.

The husk is ripped off by powerful pincers.

Other legs drill through the germinating holes on the seed itself

until the nut finally cracks.

The whole process can take several hours,

but the reward is a meal rich in protein.

Robber crabs may rule the land, but they're no masters of the sea.

An adult crab would drown in a few minutes, which raises the question -

how did these monsters get to so many of the South Pacific's most isolated islands?

This female carries the answer -

thousands of eggs, which will soon be left to the mercy of the ocean currents.

A few shakes of her tail are all that's needed to send them on their way.

The eggs will hatch immediately.

Then the larvae will have just 50 days to find a new home above the water.

For animal castaways,

finding new land in this vast ocean was a chance in a million.

To beat the odds, luck was needed,

sometimes coming from an unlikely source.

Cyclones.

Each year, these powerful, tropical storms form over the huge ocean.

The largest can span more than 600 miles.

Cyclones are one of the most destructive forces in the South Pacific.

Yet surprisingly, they have played a critical role

in spreading life to the loneliest islands.

And few islands are more remote than these.

Two thousand miles from the nearest continent,

Hawaii is the world's most isolated archipelago.

It's so far-flung,

that less than 500 kinds of animal settled here in 30 million years.

Remarkably, many of these colonisers

were carried to Hawaii on the back of cyclones.

For an animal to be sucked up by storm winds, carried across the ocean

and dumped here alive was a matter of extraordinary luck.

Yet that's what happened to the ancestor of this insect.

It's a kind of fruit fly...

but no ordinary one.

Hawaii's fruit flies are the birds of paradise of the insect world.

They attract females with elaborate courtship rituals

and have a sophisticated range of territorial behaviour.

Male hammerhead flies use their heads as battering rams.

A male clavisetae fruit fly fans sex pheromones from his raised abdomen.

His extended tongue is an added attraction.

Since that first coloniser,

they have evolved into nearly 1,000 species,

many with their own unique behaviour.

When it comes to choosing a mate, females are very fussy.