Original subtitles

This is a journey up the coast of South America

following the ocean currents through stormy seas

and some of the richest waters on the planet.

Running over three thousand miles

from almost the Antarctic to the tropics

these shores are truly extraordinary.

They support the greatest concentration of marine mammals

and seabirds on earth.

But what makes these waters so special?

What feeds these teeming millions?

From Antarctic to Equator

one creature above all has unlocked the secret

of life on these bountiful shores

the penguin.

Our journey begins off the tip of South America

where the continent projects into the Southern Ocean.

With little land to break their force

furious winds rage right around the world.

These are some of the most tempestuous waters on the planet.

It's hard to imagine how anything could live in a place like this

But penguins live here in their millions.

The penguins spend months at a time out in the Southern Ocean

but once a year they're forced to return to land.

But getting ashore is not going to be easy.

The dangers of riding massive waves are nothing compared to the perils

of trying to land on slippery rocks

armed with only strong feet

sharp claws and grim determination to get them ashore.

These aren't called rockhopper penguins for nothing.

But why do they take such risks to fight their way ashore?

They've come here to nest.

Few islands break the vastness of the cold southern seas

and those that do are seldom more than barren rock.

But a handful are larger like the Falklands.

When sea levels were lower they were connected to South America

but now they lie three hundred miles off the coast.

They're not just rock

but their interior's hardly more welcoming

a treeless expanse of windblown tussock grass.

For the penguins

this will be home for the next six months.

Three hundred thousand pairs of rockhoppers breed on the Falklands

almost two thirds of the world population.

With good breeding sites so scarce in the Southern Ocean

they jostle for space with all sorts of other seabirds

like black-browed albatross.

It's a rush to rear their young while summer lasts

and the penguins face a tortuous trek every time

they go back to the sea for food.

At least the albatross can fly

but only with help from the elements.

The Falkland's strong winds are just what these huge birds need to take off.

But how do these cold

turbulent seas support such great numbers of birds?

Surprisingly

the cold itself is a key to the oceans' riches.

Cold water holds more oxygen.

That, combined with nutrients

stirred up by rough seas

and the long summer days of sunlight

makes the water very fertile.

It supports huge shoals of krill... shrimp-like crustaceans.

They feed everything from whales to penguins.

Porpoising like this reduces drag

so it uses less energy than normal swimming

and it lets the penguins see where they are going when they come in to land.

These are gentoo penguins.

They're twice the size of rockhoppers

so they're not as good at climbing cliffs.

They nest on the beach or flat ground inland.

The cliffs above are crowded with king cormorants.

All the birds here have their own preferences

and good breeding sites are in short supply.

Gentoos force their chicks to chase them for their food.

It's a race that sorts out the weak from the strong.

Like most penguins they lay two eggs

but sometimes they can only catch enough food to rear one.

When times are hard

the winner takes all... and the weaker chick dies.

And there's competition from another quarter.

Piratical skuas and gulls cash in on the penguins' hard work.

The waters offshore may be prolific

but with so many birds breeding

all have to fight for their share of food...

The Southern Ocean may be a tough place to live

but penguins are great survivors.

Two months after hatching

the chicks make their first acquaintance with the sea...

its riches... and its dangers.

Not a shark, but a killer whale.

If the whale slips under the waves

the penguins can't see it through the surface reflections.

They have no idea where it is.

Pods of killer whales come here every summer to hunt penguins

after their main prey seals have left the islands.

Their technique of stealth in the shallows

is passed on from parents to young

using dead penguins as target practice.

As the frigid waters of the Southern Ocean

surge around the base of the world

only the southern tip of South America interrupts their path.

But it isn't an impenetrable barrier.

It's a maze of channels and islands.

Deep fjords extend far into the interior

letting rich, cold water reach right to the foot of the Andes.

The forces that carved these channels begin high in the mountains.

Huge glaciers grind their way down from the great Patagonian ice-sheet.

When the ice-sheet was even larger than it is today

these glaciers scoured deep trenches in the rock.

The valleys they created filled with the rising waters of the sea.

Some were gouged so deep that only just offshore

the bottom is an incredible hundred and twenty metres down.

This labyrinth of channels is one of the least explored areas on earth.

As the cold water pushes deep into the heart of Patagonia

it brings with it the animals of the southern ocean...

Like fur seals.

Mostly they live on the exposed coast

but wandering young males are drawn into these sheltered fjords

by the rich feeding here.

They can dive as deep as 170 metres to hunt the sea floor

but they feed mostly at night

when the fish come closer to the surface.

Large eyes help them see in the dark

and they may also use echo location

The fjords are often stormy

but they're less exposed than the open ocean

so these fur seals can take advantage of the calm waters to rest.

On the edge of the channels are great forests of kelp.

This giant seaweed is the fastest growing plant in the world.

Its stems can be up to thirty metres long.

Like any jungle the kelp has its predators.

These aren't fur seals but sea-lions.

They prefer to hunt in these shallower waters

searching for animals hiding amongst the weed.

Kelp beds are the rainforests of the sea.

From sunlit canopy to shadowy forest floor

they support a wealth of strange creatures.

It's an ideal hunting ground for sea-lions.

Like the rainforest

this is a world that has yet to be fully explored.

Like birds of prey

the sea-lions fly among the branches of this submarine forest.

There's forest on the land as well.

These deep valleys give a degree of shelter from the relentless wind

and with the heavy rainfall trees flourish.

Deep in the woods, something stirs.

The cold waters of the fjords have even put a penguin in the forest.

These are Magellanic penguins.

Penguins may be elegant in the water

but they're not designed for clambering over branches.

So what are they doing here?

With no broad beaches or broken cliffs to breed on

these adaptable birds actually nest here

scraping a hollow for their eggs among the tree roots.

Nesting in the woods gives them shelter from the elements

and protection against predators...

but when they have chicks to feed

they face a hard trek back to the sea.

Those strange calls gather them into social groups on the shore

before they head out to sea.

It's no surprise that they're often called jackass penguins.

To reach their fishing ground

the penguins have to cross the kelp beds.

But that's where the sea-lions are hiding.

And some sea-lions eat penguins.

Lone males are the most dangerous.

The penguins can't tell if the sea-lion's still there.

They can't see through the water surface and the dense kelp forest

They have to run the gauntlet or their chicks will starve.

The only question is when to go into the water.

It's time to chance it.

There's safety in numbers

but this straggler's missed the group.

His chick needs feeding so he has to take a gamble.

After killing the penguin

the sealion skins it before eating it.

Safely out in the depths of the fjord

the penguins become the hunters not the hunted.

Their prey here aren't krill but fish... sardines.

Flocks of skuas gulls and albatross follow the action.

The penguins hunt as a group

herding the fish into dense shoals.

In their panic to escape

they're driven to the surface

where they're easy prey for the seabirds.

On land, penguins look ungainly even comical...

but underwater they're in their element.

They may be flightless but here they really fly.

The fjords are more than just sheltered feeding places.

They're highways for all sorts of travellers.

One channel cuts all the way through from the Atlantic to the Pacific

the Straits of Magellan.

Peale's dolphins take advantage of this highway between the oceans.

They're small

but strong and agile

perfectly designed for travel through kelp forests

narrow channels and strong currents.

They can reach speeds of over 15 miles an hour.

At the Pacific end of the straits

the waters of the Southern Ocean mingle with the cold Humboldt current.

It's channelled north for two thousand miles

by a deep ocean trench... as deep as the Andes are high.

This current is the key to life on South America's west coast.

The Humboldt is also a highway for sperm whales.

Males feed in the frozen waters of the Antarctic

but the females and young live all year round in the tropics.

So each year

these fifty ton giants swim five thousand miles to find a mate.

The depth of the ocean trench along which it travels is one reason

for the Humboldt current's fertility.

The cold water in the abyss is rich in nutrients

from the remains of dead plants and animals.

It's drawn to the surface

when the upper layers of water are displaced by strong winds.

These enriched upwellings

feeds the most prolific fishing grounds on earth.

The Humboldt current brings the whole coast alive.

As the Humboldt surges up the coast

the rain-soaked forests of the south are left behind.

Trees give way to the driest desert on earth... the Atacama.

It's a strange paradox that the world's driest land

and richest sea are found side by side.

But even with the Humboldt current just offshore

how could anything possibly live here?

Incredibly this desert has penguins...

They're Humboldt penguins... named like the current

after the 19th Century explorer Alexander von Humboldt.

To take advantage of the shoals of fish just offshore

they have to nest in the desert.

This appears to be the ultimate challenge for a penguin.

The woolly chicks, especially

don't look as though they could cope with a hot climate.

And squabbling for food must make it even worse.

Penguins do have to be tough and adaptable to live here

but it's actually not as hot as it appears.

The cold Humboldt current keeps the narrow strip of land

just inshore quite cool.

So long as the penguins keep close to the water, they can survive

The penguins are here because of the fish.

Just a little further up the coast are the richest fishing grounds of all

the richest in the world.

The Humboldt current runs close offshore

and here the vigorous upwellings feed huge shoals of anchovies.

This paradise of surf and seafood is called Paracas.

Paracas is a place of superlatives.

Just one of its sea-lion colonies can have thirty thousand animals.

With so many packed together

it's hard for the bulls to keep control of their harem of females.

Disputes are inevitable.

Paracas has more than sea-lions.

All kinds of bird flock here to take advantage

of the huge shoals of anchovies

whose populations are estimated not in millions, but trillions.

There are thought to be well over five million birds

consuming a thousand tons of anchovies a day.

The cormorant colonies alone contain literally millions of birds.

There are three nests to every square metre

and the colonies cover whole islands

the largest concentrations of birds in the world.

There's standing room only for Peruvian boobies too.

Nesting on islands keeps them safe from four-footed predators

but it's no defence against attack from the air.

Humboldt penguins take full advantage of the rich fishing offshore

but for them, living in Paracas has its own set of challenges.

Knowing how to ski on sand comes in handy if you can't fly.

But at the foot of the slope

they have a much bigger problem to overcome.

Their way to the sea is blocked... by potential penguin eaters.

There are so many sea-lions that there's no way round.

They have to make a dash for it.

In fact

the sea-lions here are so well fed with fish

that the penguins are in more danger of being squashed than eaten.

Thanks to the cold Humboldt current

Paracas is one of the wildlife spectacles of the world.

But what happens if the cold water disappears?

In El Nino years

a change in the prevailing wind brings in warm water from the tropics.

The fertile upwellings are suppressed.

The fish literally vanish.

El Nino spells disaster for almost everything that lives here.

With no fish to feed them

the animals must either leave... or starve.

In El Nino years

only scavengers like the condor grow fat.

The fish move far out into the ocean

but the birds and animals are tied to their breeding colonies on land.

All the young die... and many of their parents starve too.

El Nino's effect on the Atacama coast can be catastrophic.

The only winners are the condors

which come down from the Andes to feast on the fallen.

Yet even they find it hard to survive

once the first glut of food from El Nino's victims has been exhausted.

El Nino is part of a natural cycle.

In time, the cold ocean current is restored

the fish return, and slowly the seabirds and sea-lions increase.

But as the world gets hotter because of global warming

El Nino comes more often.

There's less time for wildlife to recover before the next crash.

The Humboldt penguin is already rare.

Will it survive the next El Nino?

The Humboldt current is the key to life in this barren land

and so far it has always returned after El Nino.

For over two thousand miles

the current hugs the shores of South America.

Now, deflected by the coast of Peru

it turns west... out into the blue.

The bull sperm whales are still following this highway in the sea.

They've swum more than four thousand miles from the frigid waters of the Antarctic

and they still have several hundred miles to go to their rendezvous on the equator.

For the last leg of their journey

they have new companions... bottlenosed dolphins.

Far out into the Pacific the ocean floor is alive.

The bubbles are signs of volcanic activity

that's built mountains four

and a half thousand metres high

so high that their summits now rise above the waves.

Lying six hundred miles west of the coast of South America

these barren cones are the Galapagos islands.

A visit to the Galapagos helped the young Charles Darwin

develop his theory of evolution.

He would have seen all sorts of strange animals

like giant tortoises and the islands' thirteen kinds of finch.

One does the job of a woodpecker... using a cactus spine as a tool.

Another finch has become a bloodsucker an avian vampire bat.

All the finches have their own unique way of life

yet all are descended from a single seed-eating ancestor.

Everywhere you look there's something extraordinary.

A lizard that lives in the sea

A cormorant that can't fly.

Because the islands are so isolated

the few colonists that reached them had the place to themselves.

With no competition

they could develop in all sorts of unlikely ways.

The cormorant may be flightless

but it's an expert swimmer

superb at winkling out prey from submerged lava fields.

The Galapagos lie right at the end of the Humboldt current.

It reaches the islands for only part of the year

and its arrival is erratic and unpredictable.

Birds are constantly testing to see if the rich, cold water has arrived.

When it does

the flush of food triggers an orgy of breeding.

Blue-footed boobies are foot fetishists.

The bluer your feet

the more healthy and fit you're likely to be

a sure turn-on for a potential mate.

These are waved albatross.

Almost the entire world population breeds on one island in the Galapagos

but only when the cold currents make conditions just right.

Flightless cormorants also celebrate the arrival of the cold water.

Like all the birds here

the secret of their success is irregular breeding

nesting only when cold water brings them food.

With limited opportunities to breed

it's even more important to pick the right partner.

Some birds go to extraordinary lengths to impress a potential mate.

Like the boobies blue feet

the male frigate bird's red pouch is a good

if slightly overblown way of showing how fit he is.

The female booby can't spend forever choosing between subtle shades of blue.

The Humboldt current is here.

She must seize the day and pick a mate.

Some boobies have well grown chicks from an earlier time of plenty

when the cold water was last here.

They take full advantage of the new flush of food.

But they're not the only ones looking for a meal.

The Galapagos have their own pirates... frigate birds.

In this land of opportunists

they'll stop at nothing to steal someone else's food.

Down on the shoreline live the most extraordinary

of the islands' many strange inhabitants.

Marine iguanas... the only salt water lizards in the world.

They eat algae... seaweed... growing on rocks between the tides

so they have to wait for the water to go down

before they can feed.

They live only on shores exposed to cold currents

but the arrival of the cold water is a double-edged sword.

Its nutrients stimulate the growth of the algae they eat

but because the lizards are cold-blooded

the cold water slows them down and could even kill them.

The best algae grow close to the low tide mark

so it's a race to eat all they can before the rocks are covered again

and their bodies are chilled to danger point.

Strong claws and a good grip are essential

if you're not to be swept away.

For most iguanas life is ruled by the tides.

But the big males have another option.

Below the low tide mark

the growths of algae are more luxuriant

because the rocks are always covered.

The males use the heat of the tropical sun to exploit them.

They expose the greatest possible surface to its warming rays.

Because their bodies are larger

they can store more heat and don't chill down so quickly.

When they've warmed to an optimum thirty five degrees

they take to the water.

Down here they can take advantage of a food supply

that's out of reach for the smaller iguanas.

They can hold their breath for twenty minutes or more.

But they have to feed fast.

Every minute they spend here

the heat is draining from their body.

If their temperature falls too low

they will be unable to move... and they'll die.

It's time to go.

The cold waters of the Humboldt

bring southern species all the way to the equator.

But when cold currents give way to the warm Equatorial Current

sea temperatures almost double.

A whole new set of fish appears.

This is an ocean crossroads

with an amazing diversity of marine life.

Hammerhead sharks are drawn here in their hundreds.

It's thought they follow electromagnetic 'maps' on the sea floor.

No one knows exactly what attracts them.

There's certainly an abundance of food

but their gathering in huge shoals suggests these mysterious fish

may also come here to socialise and breed.

Hammerheads are not the only ones that come to breed here.

For the bull sperm whales this is journey's end

the culmination of a five thousand mile odyssey

that's brought them all the way from the Antarctic to the equator.

At last, they join the females they've come so far to find.

Head butting and tooth rasping sort out who's dominant.

The winning bulls will mate with several females

For others, the journey will have been in vain

and in just a few weeks

they'll take the long swim back to the Southern Ocean.

This is the end of the road for the sperm whales

and for the Humboldt current too.

But the Humboldt still has one final surprise to spring.

This cold flow has even put a penguin on the equator...

the Galapagos penguin.

They can thrive here in the tropics only because the current brings the rich

cold water on which they depend.

Over the course of our three and a half thousand mile journey

no creatures have proved so adaptable as penguins.

On land, they can deal with everything from forest to desert.

But it's underwater that their true genius is revealed.

These are superb fish catchers.

Penguins have colonised almost the entire west coast of South America...

but they could never have done so without the Humboldt current.

All the way from the Southern Ocean to the equator

that chill river in the sea feeds everything that lives here.

It's the key to life on these penguin shores.