♪♪ ♪♪ -Raw rock and wild water -- Ireland is famous for its stunning scenery and untamed Atlantic coast.

♪♪ But one of its greatest natural treasures is a strange world of gray stone.

♪♪ A rocky wonderland on Ireland's west coast called the Burren.

At first glance, the Burren seems barren and lifeless.

But look a little closer.

♪♪ In this limestone otherworld, some of Ireland's most elusive wild creatures find sanctuary.

In a timeless land, among the castles and tombs of the ancient Irish... ♪♪ ...these sturdy survivors must deal with Atlantic gales and savage storms... ...to carve out a life and make this rocky kingdom on Europe's farthest fringe home.

♪♪ ♪♪ ♪♪ [ Wave crashing ] -2,000 miles of open Atlantic meets its first barrier on the west coast of Ireland.

Walls of water and rain meet ramparts of cliff and rock.

♪♪ ♪♪ Here you find a place unlike anywhere else in Ireland, an ancient kingdom on the edge of the old world, home to warlords and hunters who lived in its vast underworld.

♪♪ 4,000 years ago, it was covered in thick pine and hazel woods until Stone Age farmers cleared the forests, creating this limestone expanse called the Burren.

[ Chirping ] Only tiny scraps of woodland remained.

And in these critical oases, some extraordinary survivors clung to life.

♪♪ On a spring morning near Mullaghmore mountain, a small miracle is taking place.

♪♪ Into the light comes a creature that was all but extinct on these islands.

♪♪ A creature so rare, it was like a phantom of the forest.

This is a pine marten.

Just a handful survived in Britain and Ireland, and one of their very last outposts was here in the Burren.

♪♪ Inside a hollow tree, this pine marten mum has mouths to feed.

Two kits were born in mid-April and they're now almost two weeks old.

Utterly dependent on their mother, they must stay inside their tree house for another month.

♪♪ Until the young pine martens leave home, Mum is their only contact with the outside world.

By day, she grooms and feeds them, and gets some well-earned rest.

Come evening, she leaves for a night hunting in the woods.

♪♪ The kits are left to mind themselves.

And like youngsters of all kinds, keeping quiet is a big challenge.

♪♪ Little do they know but these kits are critical to the future of their kind in Ireland.

Alive thanks to a handful of ancestors who somehow managed to survive in a very hostile world.

[ Insects chirping ] The Burren is built of bones, the skeletons of countless sea creatures compressed over the eons into the rock we see today.

More than 300 million years old, this limestone was born at the bottom of a warm, shallow sea.

Today, the Atlantic waters off this coast are still the realm of prehistoric creatures unchanged in more than 30 million years.

♪♪ Come spring and a warming ocean, these giants move in from deep water.

♪♪ Up to 40 feet long and four tons in weight, basking sharks are the second biggest fish on the planet.

These sharks are hungry and must work hard for their dinner, for they survive on some of the smallest life in the sea, plankton.

Filtering 2,000 tons of water an hour through their giant gills.

Though occasionally seen with a companion or two, the sharks usually turn up alone.

Until recently, when this western edge of Ireland has seen something truly extraordinary.

♪♪ ♪♪ The giants are gathering.

♪♪ ♪♪ No one knows how many there are, or how these sharks find each other... ...or quite why they've come together at all.

♪♪ Their mouths are closed, so food is not the answer.

Scientists think it's some kind of breeding display, a slow-motion dance of desire.

Each shark sizing up suitable partners before slipping away to mate in deep water.

♪♪ We may never know for sure, for these events are incredibly rare to witness.

A brief window into prehistoric times, when the oceans teemed with life.

♪♪ A subtle shift in wind or tide, and they're gone.

[ Water lapping ] [ Animals calling ] 20,000 years ago, Ireland was a blank slate.

♪♪ Almost nothing stirred.

Ice covered most of the island.

Only tiny pockets of life survived.

But as the glaciers retreated, the east winds brought in some pioneers hungry for living space and prey.

♪♪ Today, these early voyagers are still here, living hidden lives unseen by the human world.

♪♪ [ Bat chittering ] Seven different kinds of bats are found in the Burren, and this is one of the most intriguing.

♪♪ A master of the night sky and water.

Daubenton's are often called water bats as they spend much of their lives around rivers and streams, rich hunting grounds home to countless tasty treats.

With their extraordinarily sensitive ears, Daubenton's can detect prey at large distances before homing in for the kill.

So successful are these agile little hunters that on a single night they can consume half their body weight in prey... ...before heading back to their hideaways with the first light of dawn.

[ Animal shrieking ] To the ancient Irish, dawn was the "time between times" when you could break through to the other side.

♪♪ And this Burren otherworld has traveled deep into the human imagination.

Many claim it inspired Middle-earth as J.R.R.

Tolkien often walked these hills while he was writing "The Lord of the Rings."

♪♪ In Burren half-light, the doors to the spirit world do feel wide open.

♪♪ ♪♪ High in the rocky heart of the Burren stands one of the most striking ancient monuments in Ireland, Poulnabrone Dolmen.

♪♪ Built over 5,000 years ago, this large capped tomb marks the burial site of over 30 of Ireland's Stone Age people, the early settlers who began clearing the woods and creating the Burren.

♪♪ All across the region, graves and stone tombs reveal the burial sites of these ancient Irish.

[ Bird cawing ] Alongside the ruins of more recent castles and churches.

But these early Irish left more than monuments and a land of bare stone.

♪♪ By clearing the woods, they'd accidentally created a very different kind of wild world.

A botanical wonderland with a mix of wildflowers and plants found almost nowhere else in Europe.

♪♪ Mountain avens are more at home in the high country of Austria and Switzerland but here flower beside the sea, alongside bloody cranesbill from the Mediterranean.

♪♪ As winter becomes a memory, this gray world explodes with color, supporting whole new worlds of life.

[ Bee buzzing ] Though only a small corner of Ireland, the Burren has the richest insect life on the island.

♪♪ [ Insects buzzing ] But the serenity of this paradise of pollen can be deceiving.

♪♪ Here, the unwary play a dangerous game.

♪♪ Crab spiders are masters of camouflage and one of the only spiders that can change color... ♪♪ ...and they don't use webs to capture their prey.

In this tiny jungle, crab spiders hunt them down.

♪♪ ♪♪ ♪♪ Using powerful front legs, the spider holds onto the prey while paralyzing it with a venomous bite.

Hunt over, the victor retreats to a safe location to enjoy its dinner at leisure.

♪♪ The spring sunshine is finding the Burren's darkest corners and some recent arrivals from Africa.

[ Cuckoo calling ] ♪♪ Alongside the cuckoo, the hazel woods are bursting with new life.

♪♪ ♪♪ ♪♪ For four weeks, the pine marten mum has been feeding milk to her kits, but soon they must make the move to solid food.

[ Bird caws ] For the first time she brings home prey that they will hunt during their future lives in the wild.

At first, the kits don't know quite what to do.

Is it for eating or playing?

They soon figure it out and are hungry for more.

♪♪ ♪♪ Birds, baby rabbits, mice, all are now on the young martens' menu.

♪♪ But for Mum, having two demanding youngsters to look after means even longer hours hunting in the woods.

♪♪ ♪♪ ♪♪ ♪♪ 1,600 years ago, Christianity swept into Ireland and never left.

♪♪ Credit for converting the pagan Irish has long been given to a Welshman, kidnapped and brought to Ireland by pirates.

Alongside the pagans' evil customs, one of St. Patrick's most famous acts was to banish snakes from the island.

The truth is less romantic.

No snakes had ever managed to make the journey to Ireland.

♪♪ Today, this strange creature is as close as it gets.

A legless lizard called a slow worm.

Its round tongue and moving eyelids put it in the lizard camp, as snakes don't blink.

♪♪ ♪♪ Quite how the slow worm reached the Burren no one knows.

A non-native, it's only been discovered here in the last century.

♪♪ A ruthless predator, the Slow worm has mastered the art of hunting... slowly.

♪♪ Beware any creature that comes in range of this speed demon.

♪♪ [ Birds chirping ] The west of Ireland is famous for its rain and the Burren is no exception.

[ Thunder rumbles ] Walls of water march in off the Atlantic, often for weeks on end.

♪♪ ♪♪ ♪♪ But in the Burren, the rain quickly disappears into countless cracks in the limestone.

Underground, a maze of caves and fissures drain it all away... ...creating a dry land with scarcely a stream to quench the thirsty.

But occasionally, so much rain falls that the drains fill up and water floods the surface... ...forming the Burren's remarkable disappearing lakes called turloughs.

[ Birds chirping ] One month the lakes are here, the next month they can be gone.

♪♪ Survival in this changing water world is supremely challenging, but one little creature has carved a life out here.

♪♪ The three-spined stickleback is one of the smallest fish found in the Burren, but also one of the most fascinating.

♪♪ It is the males who do the homemaking in this stickleback world.

On the floor of the lakes that don't dry out, the males build tiny nests to lure in the females, and they must constantly defend both their nest and territory from rival males keen to move in and take over.

♪♪ It's an exhausting business.

The male uses tiny bits of weed and debris to construct his little den, and the better the build, the greater chance of attracting a female to lay her eggs inside.

[ Bird whistling ] ♪♪ ♪♪ In the Burren, every building has a story.

♪♪ A thousand years ago, the early Irish Christians had grown a bit too wild and independent for the liking of the Pope and bishops in Rome.

So they asked some French monks to build monasteries across Ireland and teach the unruly Irish to do exactly what they were told.

♪♪ A thousand years on, the monks are long gone, but Corcomroe Abbey has some new residents.

[ Birds chirping ] A kestrel family has moved into a noisy jackdaw neighborhood.

[ Chirping continues ] Jackdaws don't like to share their living space.

But this kestrel mother set up early and has a perfect nest hole overlooking the church.

It's now late spring.

The chicks are growing fast and need a constant supply of food.

♪♪ Luckily, their mother is a supreme hunter, a master of the air.

♪♪ ♪♪ In the Irish language she's called an pocaire gaoithe, the wind frolicker.

♪♪ ♪♪ [ Baby birds squawking ] For the next month she will keep up this exhausting routine as summer unfolds all across the Burren.

♪♪ ♪♪ Light and heat flows everywhere.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ [ Chirping ] At six weeks, the young martens are getting bored of their tiny home.

There's a big wide world out there to explore.

Brief visits to the den entrance become more frequent as they grow stronger and more confident.

♪♪ ♪♪ ♪♪ Mum decides it's time to move and look for somewhere safer... ...for this is a dangerous time.

If the young marten falls out of the tree, it could be badly injured.

♪♪ One by one, she hauls them off into the woods.

♪♪ It's their very first taste of freedom and a whole new life in the wild.

[ Animals calling ] Lying just six miles offshore are three huge chunks of the Burren trying to escape into the Atlantic, like wayward sons.

Famous for their Gaelic culture, wild beauty and unique sweaters, these limestone reefs are known the world over as the Aran Islands.

5,000 years ago, the first humans reached these outposts on Europe's farthest fringe.

For protection against enemies and Atlantic storms, these prehistoric Irish built great stone fortresses, which still stand on Aran to this day.

♪♪ They also cleared the forests that covered the islands, exposing the raw limestone beneath.

But then, over many generations, they created countless tiny fields with soil made from sand and seaweed dragged up from the shore.

1,500 miles of stone walls surround these handmade fields.

♪♪ In summer they're a blaze of color and life.

♪♪ 21 different kinds of butterflies have been found on Aran.

A warm summer's day can see a butterfly bonanza... ...and all kinds of hidden struggles for survival.

This cluster of tiny jewels is natural treasure of the most precious kind.

These are the eggs of Ireland's rarest butterfly, the only insect on the island with full legal protection, the marsh fritillary.

Across Europe, their numbers are in free fall, but in this part of the world, they do have a fighting chance.

♪♪ After hatching last summer, the caterpillars spent the winter hibernating in a silk nest to keep warm.

Eating all around them, they grow and transform through the Burren spring.

♪♪ Come summer, each one forms a pupa and inside a miraculous transformation unfolds.

♪♪ ♪♪ The adult butterflies emerge to complete their extraordinary life cycle.

♪♪ These precious survivors may live for just two or three more weeks, and in that time they must find a mate and lay the eggs that will sustain their kind for another generation.

♪♪ Nothing stands between these windswept rocks and North America except 2,000 miles of open Atlantic.

To the ancient Irish, this endless ocean was the very edge of the world and teeming with monsters.

♪♪ The second largest animal to have ever lived on planet Earth.

Up to 90 feet long and a hundred tons, fin whales are second only to the blues in size and stature.

Known as the greyhound of the seas, these monsters can slide through the water at extraordinary speed and keep up with some of the fastest ocean liners on Earth.

♪♪ Huge numbers roamed the oceans until centuries of slaughter almost wiped them out.

Saved in the nick of time as whaling bans kicked in.

Fin whales usually stick to deep water on the edge of the continental shelf, But just occasionally they'll venture close to the coast and the human world and remind us of their extraordinary power and majesty.

Midsummer has passed and the sun begins its long journey south.

And often this time brings the calmest weather of the year.

♪♪ ♪♪ At four months, the marten kits make their first expeditions out into the real world.

These carefree weeks of their very first summer are precious, as most martens survive for only five or six years.

Like youngsters of all kinds, the harsh realities of life can seem very distant when there's games to be played.

♪♪ As summer draws to a close, their mother will push them away to live on their own.

These few weeks of play and pleasure will never happen again.

Come early September, the first hints of autumn are in the air.

With hungry months ahead, this is a busy time for the Burren's wild creatures.

♪♪ ♪♪ It's a last chance to build up reserves before food fades away.

♪♪ ♪♪ ♪♪ And it's crucial to keep an eye on neighbors trying to steal your winter store.

♪♪ ♪♪ ♪♪ On the Burren's northern borders, this dark stone tower was once home to one of the world's most famous poets.

In these castle rooms, Nobel Prize winner William Butler Yeats planned and penned some of the most powerful poems in the English language.

Yeats was captivated by the natural world and the changing seasons.

"The trees are in their autumn beauty, the woodland paths are dry.

Under the October twilight the water mirrors a still sky."

As summers faded, Yeats would walk this land, patiently waiting for some white ghosts in the northern sky.

[ Swans whooping ] ♪♪ ♪♪ Whooper swans spend their summers in Iceland, and as the Arctic winter takes hold, deep instincts make them head south on an epic journey.

It takes the swans several days to cross the northeast Atlantic before they finally catch sight of Ireland's shores.

♪♪ ♪♪ Hundreds of whoopers make the Burren their winter home, arriving in October and quickly settling down for the dark months ahead.

[ Swan whoops ] For the poet Yeats, the swans' return marked the passing of another year and the shortness of his own life on Earth.

"I have looked upon those brilliant creatures, and now my heart is sore.

All's changed since I, hearing at twilight, the first time on this shore, the bell-beat of their wings above my head, trod with a lighter tread."

Compared to his own aging bones, the swans seemed immortal, utterly unchanged and serene across the many years Yeats had walked these shores, nature at its most perfect.

[ Thunder rumbles ] Quiet for most of the summer months, the Atlantic is finally losing its patience.

Born in the Caribbean, storms cross the entire ocean to release their fury on the Burren's fractured coast.

[ Waves crashing ] This is not a place for the fainthearted.

[ Birds chirping ] Inland and away from the ocean, life is much calmer.

♪♪ In the highlands, a remarkable tradition connects today's Burren farmers with their Stone Age ancestors who first worked this land more than 5,000 years ago.

♪♪ For generations, Finbar Ryan's family has been raising cattle.

[ Cow moos ] As the days shorten, Finbar takes his cows to winter pastures high in the hills, the opposite to most cattle farmers across the globe who bring their cattle down to the low country or indoors for the winter months.

♪♪ Called transhumance, the Burren is one of the last places on Earth where this seasonal ritual survives.

The key is the limestone itself which has absorbed huge amounts of heat during the summer months and will release it slowly through the winter, allowing the grass to keep growing and the cattle to feed.

But it still takes a tough breed to survive a winter up here.

[ Cow moos ] ♪♪ The warm times become a distant memory, as the Burren enters the season of darkness.

♪♪ ♪♪ For its wild creatures, food grows scarce and hard times descend.

♪♪ As the midday sun creeps lower in the sky, often the only sound is the wind.

[ Wind whistling ] All the summer visitors are gone.

But there are exceptions to every rule.

[ Swans whooping ] Early every morning, the whoopers leave their lake roosting sites and head off in search of a good feed.

♪♪ For a swan born in Iceland, even in winter, the Burren seems like paradise.

♪♪ ♪♪ And all a whooper needs to survive the winter is an endless supply of rich green grass.

♪♪ All through the cold months, the Burren's cattle have been wandering the highlands, following the grass still growing amongst the limestone.

But come spring when most of Ireland's farmers are releasing their cattle into the outdoors, the Burren's cattle herders take their animals down off the pastures.

♪♪ Now free from constant grazing, the meadows and wildflowers explode into life.

♪♪ ♪♪ And as winter fades and the limestone warms under the rising sun, new life stirs in all corners.

♪♪ ♪♪ The marten kits have survived the winter and are all grown up and out on their own.

♪♪ As another year rolls over the Burren, this extraordinary outpost of life on the very edge of the world.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ To learn more about what you've seen on this "Nature" program, visit PBS.org.

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