Original subtitles

(INTREPID MUSIC)

(VO) NARRATOR: Off the southern coast of India,

Sri Lanka,

an abundant oasis in a tropical ocean.

Over 2,000 years,

humans have changed the face of the island...

..creating both opportunities

and obstacles... (HORN HONKS)

..for its wildlife.

It's a delicate balance that needs protection...

(TRUMPETS)

..to survive. (GROWLS)

(MAJESTIC MUSIC)

From the Arctic... (BEAR GROWLS)

..to the tropics... (ELEPHANT TRUMPETS)

..islands are wild laboratories...

..where unique rules apply... (BIRD SQUAWKS)

..and nature puts life...

(SNAKE HISSES) (BABOONS CHATTER)

..to the ultimate test.

(HYENA LAUGHS) (BEAR GROWLS)

(BIRDS TWITTERING)

A huge variety of animals live on Sri Lanka,

side by side with 20 million humans,

on an island of many diverse realms.

Central Highlands,

cloud forests, scrubland...

..coast.

And nowhere do they live closer

than on a forested, rocky outcrop to the north.

An ancient civilization began to reshape this landscape

with the arrival of Buddhism...

..and the establishment of the first wildlife sanctuary...

..in the world,

where animals were granted equal rights to the sacred site.

(MONKEYS SCREECHING)

One species has thrived here ever since.

(MONKEYS CHATTERING)

Toque macaques,

intelligent monkeys, found only in Sri Lanka.

And this is the first time they've been filmed in the temple.

This family has over 75 members.

The island provides them with plentiful food...

..but a troop of this size is only possible

because of the freedom they get in the temple.

Elsewhere, they are considered pests.

(SQUEAKS, THUDS)

This home has allowed one mum to raise twins...

..something so tough,

it's extremely rare in the wild.

But these eight-month-olds

must now start to find their place in the family.

And brother and sister will take very different paths.

(CHATTERING)

(PLAYFUL MUSIC)

The male twin has to learn to fight.

(SCREECHING)

He plays with the other male infants...

..to learn when he's in charge...

..and when he's not.

He will eventually leave the troop

and fight for his place in a new family.

His sister will stay and inherit her rank from Mum.

But she will need her own social network,

to have a better chance of survival into adulthood.

Mum shows her how it's done.

Macaques groom to build relationships.

(CHATTERING SOFTLY)

But she's resistant to the lesson.

The macaques' outcrop may be a protected pocket...

..but on a crowded island,

shared with her family and humans,

she has a lot to learn.

(DYNAMIC MUSIC)

Sri Lanka wasn't always an island.

More than two billion years ago,

it sat at the heart of super continent Gondwana.

(RUMBLING, CRACKING)

Tectonic shifts split the continents apart

and forced the new island into the tropics.

But a relic of this old world still remains.

At two and a half thousand metres above sea level,

the Central Highlands are colder and more exposed

than the rest of the island.

(BIRDS CHIRPING)

Humans no longer settle here,

leaving valuable space for wildlife.

(BIRDS CAWING)

Elsewhere on the island,

sambar are endangered due to habitat loss.

(GRUNTING)

But on a grassy plateau hidden amongst the peaks...

..these resilient deer can thrive.

But it doesn't mean life on the plains...

..is without danger. (SAMBAR SNORTS)

(BIRDS CHIRPING)

(HIGH-PITCHED BARKING)

(DRAMATIC MUSIC)

(LEOPARD GROWLS)

Sri Lankan highland leopards.

(HIGH-PITCHED SQUEAL)

So elusive, they've never been filmed before.

These two cubs are almost fully grown.

And with Mum away hunting,

now is the perfect time to practise their own skills.

(OMINOUS MUSIC)

The female leaves her brother for the first time.

As the deadliest animal in the highlands,

she radiates confidence.

But to succeed,

she must also master... stealth. (TWIG SNAPS)

And out from the trees,

she's finding it hard to remain unseen.

Only a few days old,

this sambar calf is the perfect target.

(FAWN GRUNTING)

Ambush hunters... must learn patience.

(SUSPENSEFUL MUSIC)

(MUSIC STOPS)

(CRIES PIERCINGLY)

(PIERCING CRIES CONTINUE)

The sambar wins this round.

She could take six months to get this right.

But it's the price highland leopards pay

to live on the open plains...

(LOW GROWLING)

..away from humans...

..on a crowded island.

(DAWN CHORUS CHIRPING)

A world engineered by humans has some advantages.

Up in the temple...

..a pool built to contain water for the monks is full...

(MONKEYS CHATTERING)

..of monkeys, trying to cool off.

(RELAXING MUSIC)

Even the twins join in.

(BELLS CLANGING IN DISTANCE)

But the peace is broken when sounds from the temple...

(EXCITED CHATTERING) ..signal the arrival of worshippers.

Thousands can visit each day.

They bring meals and snacks with them.

And for the macaques, this means high-energy leftovers.

The male twin, now foraging for himself,

can see this is a calorie jackpot.

He tries to learn from the other family members...

..but even they don't know what's safe to eat.

(ARGUMENTATIVE CHATTER)

The female twin still lacks confidence,

but this means she doesn't yet need to face this challenge.

Lots of leftover food

supports a growing number of infant macaques...

..and it also leads to a fierce rivalry

with other troops living in the temple.

(FRENZIED CHATTER)

(MONKEYS SCREECHING)

Another macaque family decides it's their time to feed...

..and that this food is worth fighting for.

The twins could be killed if caught by a rival male.

Males bare their teeth to show they're fierce...

(FIERCE SCREECHING)

..and try and scare the others without risk of injury.

(ANGRY CHATTERING)

The alpha and his gang prove more powerful...

..and head to check the border.

But for some, success is not without sacrifice.

The arrival of this convenience food

disrupts the delicate balance.

(WORRIED CHATTERING)

And when confined to an island,

heightened competition can leave the residents in turmoil.

(DYNAMIC DRUMMING)

Sri Lanka sits on the very edge of the continent.

Its coastlines are exposed to powerful ocean forces

that reshape the land.

Just 500 years ago, a land bridge

still connected the island with the subcontinent.

It was even possible to cross to India on foot.

But when a storm destroyed what was left,

the island was cut off.

But the ocean brings more than storms to these coasts.

Cool deep-water currents,

unusual in the tropics,

meet the island's edge

and well up.

These currents provide food...

..for the biggest animal on Earth.

(SEAGULLS CALLING)

(GRACEFUL, SERENE MUSIC)

Blue whales can eat four tonnes of krill each day,

a small crustacean that prefers cold water.

Usually, blue whales must leave tropical water to feed...

..but thanks to Sri Lanka's chilly depths,

krill thrive here.

The island provides enough food

for blue whales to feed here all year.

There's even enough...

..to support a growing family.

(DYNAMIC DRUMMING)

In the southwest of the island,

the shores are protected by a fortress of trees.

As the tide meets the wetland...

..it creates a cocktail of fresh and salty water.

This world between river and sea is the domain of specialists,

who can deal with the ever-changing levels of water,

salt, and oxygen.

(INSECTS CHIRPING)

Here, the river is slow,

and the island lays down deposits of sediment,

to create sandbanks and inlets.

The ideal spot for mangrove trees to make their home.

But these monsoon-battered coasts

are not an obvious place to put down your roots.

Salty water, low oxygen,

and poor-quality soil

mean many plants can't survive here.

But mangroves are not like other trees.

Adapted glands sweat out the salt from the water...

..and specialised roots absorb oxygen from the air,

to be totally at home on the coast.

Mangroves also have to be devoted parent plants.

Unlike other plants that shed their vulnerable seeds,

mother mangroves keep their saplings protected

amongst their branches.

They will feed them until they are strong enough

to be released...

..into the tidal waters.

While the sapling's roots dig down

and secure the sediment below...

..its leaves stretch out.

As the roots and branches knit together,

the mangroves create a barricade of vegetation

that will protect the banks from stormy weather...

..and create prime real estate

for the coastal animals seeking a more sheltered lifestyle.

(PLAYFUL MUSIC)

The barred mudskipper is a committed homemaker...

..but building with the island's sediment

requires particular skills.

He excavates the mud from below to create a fortress

that will protect his burrow from the returning tide.

The barrier stops the tunnel from flooding.

And below, a private underground pool

will be a safe place to raise a future family.

Also expert at using the mangrove's sediment

to its advantage is an army of fiddler crabs...

..named after the male's single, oversized claw.

Like the mudskipper, they build their underground homes here.

But for the male fiddler crab,

it's how it looks on the outside that's important.

They work quickly, racing the tide.

Each boulder is excavated and reshaped...

..and carefully positioned nearby.

These structures are walls that mark out their territory...

..warning neighbours to keep out.

But when another strays into their patch...

..skill is quickly out-weighed by size...

..and the cumbersome claw comes into its own.

(TENSE, DRAMATIC MUSIC)

But attentions switch...

..when a female comes by.

And for her...

..size really matters.

They wave their big claw to get her attention.

She makes her choice...

..and enters the suitor's burrow.

And with his rival still nearby...

..he follows quickly behind.

(PLAYFUL MUSIC)

The return of the tide has brought a love interest

for the mudskippers too.

And she is approached by a male

doing a courtship display of his own.

But he... fails to impress.

(HIGH-PITCHED CAWING)

She heads up the bank to see what else is on offer...

..and approaches the homemaker's completed burrow.

It's worth a closer inspection.

She seems satisfied.

And he seals the deal.

For a family living in this island's ever-changing mangroves...

..there's nothing more important

than a safe and stable home.

(BIRD CAWING)

(DYNAMIC DRUMMING)

(VO) The scrubland in Sri Lanka's northeast

is the island's driest region.

It hasn't seen decent rain for nine months...

..and the animals here must adapt

to the island's seasonal extremes.

But the scrubland is about to be transformed...

..by a wonder of nature.

(THUNDER RUMBLES)

The monsoon.

Sri Lanka is uniquely positioned in the path of two great monsoons

that drive the seasons on the island.

The southwest monsoon doesn't reach the scrubland,

but when the northeast monsoon arrives,

it can rain for 16 hours a day,

for three months.

(CHATTERING)

(DYNAMIC MUSIC)

The dense bedrock here means

water isn't easily absorbed into the ground.

It sits on the surface and creates mud.

(ELEPHANT GROWLS)

A welcome relief... (ELEPHANT SNORTS)

..for the island's biggest land mammal.

(TRUMPETS)

Asian elephants use their trunks

to flick the cool, wet earth onto their backs.

(SNORTS)

But it's their youngest member's first monsoon...

..and it will take her a year

to master her 40,000 trunk muscles.

(TRUMPETS)

(SNORTING) But she sees some of the herd...

..are using an easier technique.

(SNORTING)

(TRUMPETING) And learns a mud bath...

..is just as effective.

(ELEPHANTS SNORTING, TRUMPETING)

Elephants' intelligence helps them adapt to seasonal changes.

(BIRDSONG)

But one island resident has taken ingenuity even further.

Vast bodies of monsoon water

now cover the hard bedrock valleys...

..revealing an immense water storage system,

engineered by humans.

Over 2,000 years ago,

dams were built in the valleys to collect monsoon rainwater.

(WATER RUSHING)

Only when the sluice gates open

does the water run into the farmland below.

This vast network of floodplains and channels

creates the highest density of reservoirs in the world...

..harnessing water that helps wildlife live here year-round...

..and providing resources

to meet the scrubland's growing human demand.

(DYNAMIC DRUMMING)

Sri Lanka is small,

but supports a huge variety of wildlife.

This is down to an intimate relationship

between island, climate, and fresh water.

Away from human settlements,

the island has a water collection system of its own.

In these high altitude forests,

the humid air settles over the trees.

And the dense canopy acts as a net,

collecting water droplets from the atmosphere...

..to drip down to the roots below.

(SERENE MUSIC)

As the plants drink, they grow...

..and slowly breathe water vapour

back into the atmosphere.

This clever cycle keeps the cloud forests' humidity

in perfect balance.

For one tiny resident,

this system is vital to family life.

(CROAKING)

This Taruga tree frog is new to Science.

And he is on a mission to find a mate.

His soft, wet body is well adapted

to a life in the humid forest.

But it leaves him vulnerable to predators.

Better to chance this expedition

under the cover of darkness.

(NOCTURNAL BIRD CALLS)

As the temperature drops at night,

sound travels further through the forest.

He uses his best mating call...

(CHIRPING CROAK)

..to sing into the dark.

(CHIRPING CROAK)

But it seems he is not the only one on a night-time mission.

Sri Lanka is home to one third of the planet's snake species.

This rat snake is a precision hunter

that stalks the trees...

(TENSE MUSIC)

..and will sense the sound vibrations

of a potential meal...

(CROAKS)

..from a call, or even the slightest move.

(TENSE, OMINOUS MUSIC)

A narrow escape.

But there's no time to waste.

(CROAKING)

(CHIRPING CROAKS CONTINUE)

At last, the call he's been waiting for.

A female. (HIGH-PITCHED CROAK)

(CHIRPING CROAK)

(FEMALE FROG CROAKS)

Twice his size,

she carries him with ease...

..until they find the perfect spot...

..to create a nest built from foam.

They whisk it up by rubbing their legs together

over secretions of proteins.

The outside of their bubblewrap pod

will harden and protect their fertilised eggs.

The island's humidity prevents the nest from drying out.

Suspended below a leaf, the eggs are safe

from the predators in the forest streams below.

(BIRDS TWITTERING)

After just a week...

..the Taruga tadpoles are restless.

They are now strong enough to face the next stage of life...

..in the island's cascading waterways.

(WATER RUSHING)

Mountain streams gather into freshwater pools.

An oasis for some.

Crowded and unforgiving for others.

Here, a battle breaks out

every time something hits the water.

But this pack of hunters is about to become the hunted.

This Sri Lankan keelback is an expert freshwater predator.

(OMINOUS MUSIC)

It is endemic to the island,

and found nowhere else on Earth.

Its fishy prey is constantly distracted by falling seeds.

An opportunity too good to miss.

(TENSE, OMINOUS MUSIC)

Back-facing teeth hook its slippery meal.

Sri Lanka's hidden freshwater worlds

provide unique opportunities

for its extraordinary island specialists.

Space is always at a premium on a crowded island.

It takes skill to adapt to a life alongside humans...

..and their free-roaming pets.

(CAT PURRING) (MONKEY CHATTERS)

(CAT MEOWS)

(CHATTERING)

The twins are about to get the family masterclass...

..on how to benefit from the worshippers...

(PEOPLE CHATTERING)

..by stealing their flower offerings.

Macaques are notorious thieves.

And here on these sacred steps...

..they've learnt the visitors will be tolerant.

The twins watch

as the robbers grow in confidence...

..and win the sweet flowery treat.

(PLAYFUL MUSIC)

The relationship between macaques and humans is delicate.

If the twins get it wrong, they could get hurt.

For now, they practise stealing dropped petals

from a safe distance.

(PARROTS SCREECHING)

The twins are learning skills they will need

to build family relationships...

..and share their temple world with humans.

(MONKEYS CHATTERING)

These are lifelong lessons

that should provide security into adulthood.

(GROWLING, CHATTERING)

For millennia, Sri Lanka has sustained a delicate balance,

where people and wildlife could live in close proximity.

(DYNAMIC DRUMMING)

Today, modern changes threaten this relationship,

leaving a tough journey ahead for some.

(ELEPHANT ROARS) This single island

is home to one tenth of the world's Asian elephants,

the highest density on Earth.

(ELEPHANTS GROWLING)

Safe spaces with food and water are limited...

..so they call on generation's old knowledge

to start their annual pilgrimage...

(ELEPHANT TRUMPETS)

..to a food source

that only appears in the dry season.

(ELEPHANTS GROWLING)

A phenomenon born out of human innovation.

Every year, Kaudulla Reservoir is drained

into farmland irrigation channels.

When the water level drops,

bare ground is exposed

and fresh protein-rich grass shoots grow;

vital food for the elephants.

But in recent years,

human pressures have delayed the drop in the water level.

So, the elephants can't be sure there will be food when they arrive.

But before they can find out,

they must face another challenge.

(MOTORBIKE REVVING)

(ELEPHANT TRUMPETS)

A human highway cuts across their ancestral path.

(HORNS HONKING)

(ENGINES RUMBLING) (TRUMPETING)

These daily confrontations

leave the drivers and the elephants in great danger.

(ENGINES REVVING)

Travelling with a baby,

this family needs to minimise the risk.

They will wait for a gap in the traffic.

(VEHICLE WHIZZES)

(SNORTS)

(TRUMPETS)

(MATRIARCH TRUMPETS)

(TRUMPETING)

But was their journey worth the risk?

(MAJESTIC MUSIC)

They're in luck.

The water has started to drop,

and lush grass is growing.

And they are not alone.

(ELEPHANTS TRUMPETING)

This is the biggest gathering of Asian elephants on Earth.

(TRUMPETING)

This is an island society,

built over generations.

(ELEPHANTS GROWLING)

And it is the baby's first gathering.

She's not used to so many different elephants...

(SQUEAKS)

..and has lost her family.

She can only tell them all apart by their scent.

(TRUMPETING)

This one smells like her sister.

And she's safely escorted back to Mum.

The gathering is fundamental to elephant society.

It's where adults look for mates...

..and the baby can form relationships with other herds.

(SQUEAKING, SNORTING)

It used to number over 400 elephants.

Today that figure has halved.

The elephants rely on the island's rhythms staying the same...

..and when humans are in control,

sudden changes leave them vulnerable.

If humans reset the balance with nature on the island

before it's too late...

..perhaps the ancient ritual of the gathering

will continue here for generations to come.

(BABY TRUMPETS)

(UPLIFTING MUSIC)

From the highlands to the coast...

..the temples to the scrubland...

..Sri Lanka is a treasure trove,

a world shaped by those who call it home.

Through skill and strategy,

diversity and adaptability,

each plays their part

to create an island bursting with life.

(CHATTERING)

(UPLIFTING MUSIC CONTINUES)

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