Original subtitles

In the heart of Southeast Asia is an ancient kingdom...

..with over 3,000km of coastline.

But beyond its golden shores,

there are secret worlds.

Home to mysterious creatures...

..and forest giants...

This is a fast-changing country

where East and West collide.

People and animals must work together to survive...

..forming unique relationships.

A spiritual land,

full of magic and wonder.

This is Thailand.

Southwest Thailand.

A wild paradise of limestone castes,

golden beaches and dense forests.

Along this rugged coast are some close-knit families.

A troupe of 30 long-tailed macaques has made this their home.

This youngster has relied on his mother for the last six months.

But he's now at an age where he needs a more varied diet.

Trouble is, this is one of Thailand's most extreme locations...

..a vertical rock face, 50 metres high.

Up here, good food is scarce.

Bark and leaves provide little energy.

Macaques are the most resourceful and wide-ranging monkeys on earth

and have learned to take advantage of every opportunity.

But this one involved a precarious commute.

It's especially risky for a mother carrying an infant.

For a young macaque still learning the ropes,

having a tail longer than your body gives you the edge.

It can both grip and act as a counterbalance.

This daily descent is well worth the effort.

Across Thailand, there are thousands of Buddhist temples

and families like this get a surprisingly warm welcome.

Thai Buddhists have a unique relationship with nature.

For them, every living thing contributes something to the world

and deserves respect.

This compassionate relationship is the perfect example

of the spiritual connection so special in southern Thailand

where humans are not set apart from nature, but live within it.

There are other welcome benefits for the macaques who visit this temple.

A chance to cool off and have some fun in the heat of the day.

Southern Thailand is a natural paradise

for people and animals alike.

Hidden coves and scattered islands

give it a total of 3,000km of coastline.

Its western shores have been carved and shaped by the Andaman Sea.

Here, astonishing limestone castes have been created -

towering stacks of ancient shell and coral.

This one stands 50 metres tall.

Once part of the seabed,

it was thrust up by extreme geological forces.

The power of the sea and seasonal rains

continue to sculpt this dramatic landscape.

Every year, millions of people are drawn here.

Most come to relax.

Others are here for an adrenaline rush.

Ao Nang Tower stands nearly 100 metres high.

The ultimate challenge for thrill seekers.

People come from all over the world to climb these extraordinary cliffs.

But the locals have been scaling them for centuries.

And it's not thrills they seek.

It's natural treasure.

These men have their sights set on

a cave hundreds of metres up a vertical cliff face.

Inside, there's a hidden prize,

but reaching it is fraught with danger.

There's no hi-tech climbing gear here.

Just old ropes and local knowledge.

They must also navigate a treacherous interior...

..a ten-metre drop into total darkness.

This is what they're after.

Tiny, almost translucent birds nests.

They may not look much, but in Asia,

they're a highly sought-after delicacy.

Eating birds nest soup is thought to boost the immune system,

improve skin complexion and fight ageing.

It's no wonder one kilogram of nests is worth over 2,000.

Wild nest collecting has been going on for over 500 years.

Recently, the safety and sustainability

has been brought into question.

But an unexpected answer was found.

Thousands of loudspeakers in the town of Pak Phanang

play birdsong at full blast.

Tweeting 24 hours a day, seven days a week.

What was once a traditional fishing town is now at the heart

of a brand-new industry -

bird nest farming.

Windows have been sealed up.

The darker inside, the better.

All to accommodate a very particular resident.

The edible nest swiftlet.

During the breeding season, the salivary glands of the swifts expand

and produce extra thick saliva.

Layer upon layer over 40 days,

the birds craft it into a cup-like nest.

These new nesting sites are helping this bird

make a good recovery after years of decline.

Each day, as the swiftlets are out feeding,

farmers like Mr Mu check the nests.

He waits until pairs have bred successfully

and the chicks have fledged

before collecting their precious nests.

The people of Pak Phanang have a risk-free,

sustainable way to harvest the nests

and the swiftlets have a new network of nesting sites.

Across southern Thailand,

people and animals are finding new ways to live together

and that sometimes requires a bit of ingenuity.

Over 50km off the mainland

lie two of the remotest groups of Thai islands,

Similan and Surin.

With crystal clear waters

and golden beaches...

..this place might look like paradise,

but dragons roam these shores.

A giant monitor lizard,

two metres long...

..looking for food.

It tastes and smells the air with its 30-centimetre tongue,

sensing even the slightest hint of a meal.

Hermit crabs protect themselves by hiding their soft bodies

in the abandoned shells of other creatures.

They live up to 30 years, so as they grow,

they need to upsize their homes.

But there's something of a housing crisis on this island.

These idyllic hideaways are a magnet for tourists,

who find it hard to resist taking the occasional souvenir.

Every time a shell is removed, a crab loses a potential new home.

So these canny crabs have found another source of housing.

Each evening, the rangers clear the beaches, piling up the litter.

And now the crabs do something extraordinary.

This hermit has found herself a more modern home...

..in a mackerel tin.

With so few shells around, it's an ingenious solution.

And she's not alone.

This is a fast-growing trend.

An aluminium fizzy drink can makes a lightweight home

that's worth fighting for.

Life in the mackerel tin isn't ideal...

..and the local rangers know it.

So they leave seashells near the rubbish piles

to help the homeless crustaceans.

The crab normally winds its body into the spiral of a shell.

It's far harder to grip a straight and slippery can.

There are plenty of options.

It's all about finding a snug fit.

Well, she can be picky if she wants.

Moving house is an important decision.

At last, the perfect home.

It might look like paradise,

but living along this coastline requires great resourcefulness.

In southern Thailand, long-tailed macaques are sometimes known as

"Ling Thalay" - sea monkeys.

And it's not hard to see why.

But this isn't just about having a good time.

Like their temple-visiting cousins, they've got a clever plan.

They've adapted their lives to the rhythm of the sea.

And twice a day, low tide reveals a feast -

nutritious shellfish.

Trouble is, shells are tough to crack.

But ever resourceful, these macaques have found a smart solution.

They've worked out that rocks make perfect shellfish hammers.

Although clearly some macaques are a little smarter than others.

Either way, low tide provides a seafood bounty.

Stone tool use is a rare skill among monkeys.

But these macaques can only benefit from it by being completely in tune

with the cycles of nature...

..something many of Thailand's human residents aspire to.

The south of the country is rich in Buddhist temples and shrines.

Sacred places where monks seek to understand themselves and the world

in which they live.

Buddhist principles place human life in the context of a series of cycles

like those in the natural world.

For more than 2,000 years,

the full moon has been celebrated as an embodiment of this idea.

This celebration of the full moon is embraced by visitors to Thailand,

but their version is rather more exuberant.

Koh Phangan's famous beach party is a rite of passage for backpackers

passing through southern Thailand.

Partygoers are bathed in ultraviolet light

and their fluorescent body paint glows.

But hidden from view, just below the water's surface,

there's an equally vibrant display.

By shining the same ultraviolet light underwater,

an unexpected wonder is revealed.

These tropical waters are home to an abundance of coral reefs.

A protein within them absorbs the ultraviolet light,

emitting back a whole new spectrum.

These corals are all fluorescing.

First discovered in the 1930s,

scientists are still debating why this happens.

One theory is that fluorescent proteins

might act as a type of sunblock...

..protecting the coral from the sun's intense rays.

But it isn't just corals that glow under ultraviolet.

It's possible that other creatures are able to see this show, too,

and use it to their advantage.

One reef resident's behaviour seems to support this theory.

The scorpion fish is an ambush predator

so camouflage is key.

Passing fish need to beware.

Come too close and his cavernous mouth will suck them up

in a split second.

For this scorpion fish,

red fluorescing algae appears to be the perfect disguise.

Southern Thailand's secret worlds go far beyond its dazzling coastline.

In the very centre of the peninsula is a freshwater lake called

Cheow Lan, surrounded by great mountains.

Limestone peaks intercept moisture-laden clouds,

producing much-needed water for this rainforest.

3,000 square kilometres of it.

It is home to an exceptional diversity of plants and animals.

For 12 million years, the forest has

echoed to strange and haunting sounds.

The wing beats of a giant.

The great hornbill.

For this male, it's an important time of year.

Inside this nest hole is his lifelong partner.

There's a slit just wide enough for a bill.

But she's sealed in and won't come out until her chicks fledge

in four months' time.

For now, she's completely reliant on him to find food for them all.

A long bill makes fruit easier to reach.

It's tossed to the back of the throat and stored in a pouch.

Remarkably, hornbills can carry

over 250 berries at a time.

Delicately regurgitating one at a time,

he eases his beak through the narrow hole.

This devoted couple have raised

chicks in this tree for over a decade.

And because they might live to the age of 40,

they should be back here for many more years to come.

On the east coast of Southern Thailand,

there is another secret world far from

the tourist trails, teeming with wildlife.

Flat coastal plains are home to four expansive lagoons,

covering over 8,000 square kilometres.

In Thailand's largest lake,

local people are finding unique ways to make a living.

Somjai is a farmer.

He's raising the only large animals to be found here.

Somewhere amongst this expanse is his herd of water buffalo.

Although their wild ancestors are native to Thailand,

these are domesticated buffalo.

Somjai lets them live a mostly wild life.

But in the evening, he tracks them down.

In the shallowest parts of the lake, punting is the only option.

The buffalo spend the day feeding on the rich aquatic plants.

In the 40 degree heat,

a mud bath cools them off and repels insects.

The buffaloes' splayed hooves stop them sinking into the soft ground.

But the constant exposure to water can be damaging.

So he must round them up and steer them into a dry pen for the night.

For Somjai, this work is about much

more than making a living.

The dry pen not only protects their feet,

but gives them a chance to rest for the night.

This free range partnership also has

unexpected benefits for the wider ecosystem.

Ploughing their way through the wetlands,

spreading seeds as they go,

the buffalo help important plants to regenerate.

Carpets of lotus flowers create a haven for over a million birds...

..making this a wetland of global importance.

It's the perfect place for specialists,

those with a light step...

..and fast reactions.

This purple swamp hen may look ungainly,

but he's got a secret weapon.

Huge feet to spread his body weight over the floating foliage.

This helps a lot when stealth is not your style.

He also has a particular taste in food,

unwittingly helping to protect his habitat.

Golden apple snails aren't native to Thailand and can harm natural

habitats when numbers boom.

Luckily, swamp hens love them.

If they can find them.

A secure footing is vital when you're trying to haul in your catch.

Long toes mean a foot can act as a hand.

Purple swamp hens are perfectly adapted to this environment,

and in a small way,

these accidental conservationists are helping to preserve it.

These aren't the only animals

helping to conserve the natural beauty of Southern Thailand.

This is Kui Buri National Park.

Formerly thick forest,

it was cleared for farmland and the wildlife forced out.

In the 1990s,

public support for Buddhist-inspired

environmental principles started to grow.

Respecting the natural world was not simply a spiritual notion.

It had to become a reality.

In 1999, the government gave this area back to nature.

These native elephants reclaimed land

and have had a remarkable impact on the ecosystem.

Asian elephants need to eat 150kg of food each day.

They eat over 50 different plant types,

spreading seeds far and wide in their dung,

replanting Kui Buri's forest.

And by pushing through the undergrowth,

they create pathways for smaller animals like sambar deer.

They also give birds an opportunity to pick off scattering insects.

Elephants were allowed to rebuild the ecosystem

and they have done just that,

creating a wild paradise.

Turning this habitat back over to

the animals has restored the balance.

But in other habitats,

sometimes only human intervention will do.

Although these boards are being used for a bit of fun,

the Thai people invented them long before the wake board.

And when used in the traditional way,

they are a vital form of transport,

and the best way to get safely around a mangrove swamp at low tide.

These men are here on urgent business.

Mangroves once covered much of Thailand's coastline...

..but since the 1960s,

half have been uprooted to make way for shrimp farms.

When people began to realise the devastating impact

of shrimp farming on the landscape,

they started looking more closely at this vitally important ecosystem.

Decomposing leaves provide valuable nutrients

which support a rich biodiversity.

Mangroves also act as a barrier between the land and the sea,

protecting low-lying communities from storms and coastal flooding.

They produce seeds that are buoyant,

floating away and germinating in far away places.

As their roots grow outwards,

they trap sediment,

and are one of the few habitats

that can actually build up the coastline.

Cutting down the trees is now illegal,

and over the last 30 years,

volunteers from all over the south

have been replanting the mangrove forests.

Little by little, this crucial habitat is reclaiming the land.

And mud skippers are moving in -

a tangible sign of recovery.

Seeing them here means there is a healthy supply of food.

And a good tidal flow creating lots of fresh puddles

to keep their skin wet.

For ecologists,

seeing them living in a new forest

is a sign the ecosystem is functioning once again.

And this mangrove restoration has far-reaching effects.

The coral reef owes its clear waters to the mangroves' natural filtering

of silt and pollutants.

South-east Asia has more coral reef

than any other region of the world.

Lying at the heart of this area,

Thai waters are home to more than 2,000 types of fish...

..such as the moray eel,

clownfish,

and cuttlefish.

When the reef is in balance,

every individual plays a crucial role.

The crown of thorns starfish grazes on the fastest-growing coral,

giving the slower-growing corals a chance to catch up.

Long-spined sea urchins feed on algae,

clearing the way for coral growth.

But the reef is a delicate ecosystem

that can easily be knocked out of balance.

Pollution and a loss of natural predators

can cause starfish and urchin numbers to explode.

Both are covered in venomous spines.

But there is one renowned reef resident able to take them on.

The titan triggerfish.

They've got a fearsome reputation...

..aggressively defending their patch of reef.

A sea urchin's spines are no

protection against teeth like these.

Although the crown of thorns is well protected on top,

it has a soft underside.

Titan triggerfish play an important role

in keeping numbers at healthy levels.

And with this much food around,

it's a great place to start a family.

This couple have a little bundle of eggs to care for.

While the female blows water over the eggs to oxygenate them,

the male is on guard patrol.

This sort of parental care might be surprising,

but it's vitally important they protect

the next generation of reef helpers.

All the creatures here play their part.

And this has a direct influence on the open ocean.

When the coral and other reef animals spawn,

it helps to feed the plankton.

Some of this is swept up by large filter feeding animals...

..like the manta ray...

..and whale shark.

The rest can drift far away,

forming a floating food supply.

This not only supports life under the sea,

but also above it.

Fish is the most important source of protein in Southern Thailand.

Almost two million Thai people keep

the country supplied with this staple.

In this village on the east coast of Thailand,

Bang, his wife Patima,

and their son Thongchai rely on a good daily catch.

Early every morning, they head out to sea.

Before they cast their nets,

there's a sign from nature they always hope to see...

..something that helps guide them to the biggest shoals of fish.

This is the Indo-Pacific humpback dolphin,

a species found in coastal waters from India to Australia.

It's sometimes called the pink dolphin.

Grey in their juvenile years,

they slowly lose this colour in blotches,

turning bright pink when they fully mature.

These unusual-looking dolphins

scour the coastline in search of the

small fish that feed on plankton.

Anchovies are a favourite for dolphin and fishermen alike.

And today it's a good haul.

There's one more thing they want to do before heading back to shore.

Across their range,

pink dolphins often forge special relationships with people.

Southern Thailand is a natural paradise

where people and nature are deeply connected.

For many Thai people,

their existence is no more important than those creatures

with whom they share their world.

Habitat to habitat,

surprising connections and partnerships run deep.

This is a place that draws people from all over the world

to enjoy its beauty.

It's a wild wonderland

full of unexpected surprises.

The coral reefs of southern Thailand are world-renowned.

But there's an animal that lives on

the reef that strikes fear in all who enter the water.

It's definitely the fish that everyone is scared of.

Like, we have some sharks, no problem.

I don't want to get on the wrong side of them.

This woman got bitten or rammed on her head or something.

And there was just blood pouring down her head.

The titan triggerfish.

It may be only 60 centimetres long,

but its huge teeth are built to bite

through coral and shell.

During the breeding season, they're particularly aggressive

when caring for their eggs.

And this is what the BBC crew were here to film.

Producer Lara Bickerton has just one week to get what she needs.

Seeing a triggerfish at all would be a start on this shoot.

But cameramen Johnny Rogers and Simon Enderby are highly skilled

underwater cinematographers.

The waters surrounding Thailand are famous for their incredible clarity.

But not today.

No triggers. No titans.

No titans. Visibility about no more than five metres.

Apparently the visibility is better on the other side of the island,

so shall we go and give that a go?

Yeah.

It's a good plan, but the crew don't get far.

We're just on our way to another dive site and found out our boat's

broken down. The ironic result is the boat that is now towing us is

actually towing us faster than what this boat

was doing under its own power.

At last Simon gets a second dive in.

Got it?

Although the visibility is still poor,

he captures the odd glimpse of a titan.

They are certainly around.

They're there, but we just can't see them.

Visibility is too bad.

The crew are told normal weather patterns

are running three weeks late,

and that could be what's reducing the visibility.

Things only get worse.

Lara is increasingly concerned.

High winds, heavy rain and rough seas.

The team need their luck to change.

Three days later, the storm passes.

The crew hope the water visibility has improved, too.

The challenge now is not finding more triggerfish,

but filming a complete behavioural sequence.

So the crew focus their attention at a site where the triggerfish's prey,

the crown of thorns starfish, is most abundant.

It's a place that marine biologist Spencer Arnold knows well.

Sometimes starfish numbers can explode and damage the reef.

So Spencer and the volunteers from New Heaven Dive School

work hard to remove them.

But there are still plenty left for the triggerfish.

The titan triggerfish will eat a crown of thorns sea star.

So obviously very,

very important keystone species on the island of Koh Tao in terms of

controlling these, these pest species.

The challenge for the crew now is finding and filming the triggerfish.

With so little time left,

Lara decides to form a tag team, with both Johnny and Simon working

back-to-back, maximising their time underwater.

Johnny Rogers is also using a re-breather diving system,

allowing him to spend over two hours at a time underwater.

And as soon as Simon comes out,

Johnny gets in.

This allows them eight hours a day of uninterrupted filming.

With the visibility much better, the team make progress.

Johnny captures footage of a triggerfish

attacking the soft underside of a crown of thorns starfish.

It's a great start to the sequence.

We got her on a crown of thorns.

- Did you? - Yeah. - Awesome. - Great news.

And Johnny's seen a triggerfish.

Well, I've seen one before, but not on this trip.

It's only taken four days.

The team are soon back underwater,

making the most of the time they have left.

And Johnny gets a remarkable bit of behaviour no one expected.

The triggerfish bites each individual spine off the sea urchin

before devouring the whole thing.

Finally we're actually getting somewhere.

Simon captures the final bit of the puzzle.

It's when the titans are guarding

their nests they get most aggressive.

But this couple are surprisingly chilled,

letting Simon get an intimate view of the female aerating her eggs.

Well, patience finally paid off.

That's the closest I've ever come to a nesting

titan triggerfish in my entire life.

Male and female. Male, we found the male first, defending his territory.

Thought, OK. Actually swam over the female looking at the male,

didn't notice that. I went, "Oh, hello."

So I was basically this much from her, puffing away on her eggs.

Sunshine, blue water,

target animals.

Amazing, amazing news.

I am so chuffed at that.

Today has paid off.

The team finally had the conclusion they needed.

And along the way learned that if you catch

this notorious fish on a good day, they're remarkably easy-going.

Next time, we head to Thailand's bustling capital.

Here, spirituality can be found in human and animal relationships.

Both likely and unlikely.

This is the very heart of Thailand.

Home to mysterious giants and striking beauty.