Far away, cut off by vast oceans...
..lie Earth's tropical islands.
Home to remarkable animal castaways...
..that have evolved in isolation.
And human cultures that have adapted in extraordinary ways.
From the jungles of Borneo, with their staggering wild diversity...
..to Hawaii, the most remote island chain,
colonised by only the hardiest pioneers.
And Madagascar, the oldest island of all...
..where time has given rise to thousands of unique species.
These tropical islands
have developed into astonishing and unique worlds.
Cradling precious life found nowhere else on Earth.
In the tropical waters of the Indian Ocean...
..lies the oldest island on Earth.
Madagascar.
Isolated for longer than any other island,
life has had time to evolve in the most surprising ways.
With over 15,000 species found nowhere else...
..Madagascar boasts more unique plants and animals
than any other island on the planet.
Madagascar was formed nearly 90 million years ago.
Giant landmass, known as Gondwana, broke apart.
As India split from Africa,
Madagascar was cast adrift.
It's a vast island, almost the size of France...
..and home to an astonishing array of ancient habitats.
At its heart lie the Highlands,
an immense mountainous spine that determines the island's climate.
Warm, wet air blows in off the Indian Ocean,
drenching the east of Madagascar with rain.
But the mountains block this rain from reaching the west,
creating a great expanse of desert.
This arid landscape stretches halfway up the west coast.
It was here, around 55 million years ago,
that a few animal castaways washed ashore...
..having somehow survived the 300-mile crossing from Africa.
One of the very first mammals to arrive
was an ancient species of primate.
And their direct descendants still live here in the desert today.
Ring-tailed lemurs.
It's dawn,
and a family of nine soak up the warmth of the early morning sun,
preserving vital energy for the day ahead.
This young lemur is just six months old...
..and born into the harshest habitat on the island...
..known as the Spiny Forest.
Tiny leathery leaves provide little nourishment.
The troop spends up to eight hours a day
scouring the desert for food,
tackling even the most hostile vegetation.
The sticky sap that oozes out of Euphorbia plants
can be caustic, and burn human flesh...
..yet ringtails are resistant to their corrosive powers.
Euphorbia sap is also rich in fats,
much-needed fuel that will help this young lemur survive
this inhospitable desert.
Ringtails are just one of the many species of lemur.
These primates are found only on Madagascar.
Their ancient ancestors gradually spread east across the island...
..adapting to each of Madagascar's varied habitats.
They now number more than 100 different species.
Humans are thought to have arrived on this island
just a few thousand years ago.
First from Asia, and then from Africa,
they settled on the coast.
Pushing inland, those in the west faced the hostile desert.
Just 20 miles from the coastline lies the village of Ampotaka.
It's the dry season.
Temperatures often reach 40 degrees Celsius.
It hasn't rained for ten months now.
With their nearest water supply over 40 miles away,
life is a daily struggle.
The remains of this year's melon harvest
provide just enough water to cook with.
At 62, Adolphe has lived through the driest of years.
Today, Adolphe is joined by his son Leris...
..to visit the secret to their survival.
The baobab.
Known as "The Tree Of Life."
They can live for over 1,000 years.
Growing up to 30 metres high,
baobabs can hold vast quantities of water in their immense trunks...
..and can survive for years without a single drop of rain.
For Adolphe, this baobab provides a lifeline.
By hollowing out the soft trunk, they created a tank,
which they could fill with water during the brief rainy season.
This living reservoir can store thousands of litres of water.
But this dry season has lasted so long that the tree is already empty.
Still, it's an important opportunity to trim back the growing bark,
maintaining the tank's size ready for the rain
they hope will come soon.
This tank may have run dry...
..but Adolphe inherited seven of these wells from his father.
Only one still holds any water.
With only enough water to last a few more weeks,
it's a worrying time for Adolphe and his family.
Survival in this desert depends on the arrival of the rains.
On the forest floor, there are signs that the weather is changing.
Tiny Labord's chameleons, only three centimetres long, begin to hatch.
They live for only four months...
..the shortest lifespan of any land vertebrate.
For this young male,
it's a race against time.
In the dry season, there is little food.
But his hatching is perfectly timed.
THUNDER RUMBLES
It's the start of the rainy season.
The parched landscape is transformed
into a flush of green.
Just what this growing chameleon needs.
As his eyes can move independently...
..he can spot a meal in any direction...
..and, by locking both eyes onto a target, judge distance...
..with deadly accuracy.
With so much food on offer,
the male Labord's chameleon can grow five times his size
in just two months...
..transforming into an adult male with an eye-catching horn.
A female approaches.
But the male has a rival.
With such short lives,
there's fierce competition for a chance to mate.
HE HISSES
HISSING
With his rival out of the way,
he hasn't got long to take this opportunity.
After just four months,
this male has succeeded in securing the next generation.
The female will lay her fertilised eggs underground before she dies.
And as the dry season returns,
not a single adult Labord's chameleon...
..will be left alive.
Arid regions cover more than half of western Madagascar...
..including one of its most extreme habitats.
The Grand Tsingy.
More than 500 square miles of sharp limestone pinnacles.
Eroded by rainfall over millions of years.
Its deep, shaded ravines retain moisture...
..allowing small pockets of forest to grow...
..and providing an oasis...
..for an extraordinary lemur.
Decken's sifaka.
This youngster is three months old...
..and already practising the vital skill of leaping.
No one cluster of trees is large enough
to sustain a whole family of hungry sifakas.
This mother and son need to seek out another pocket of vegetation,
possibly hundreds of metres away.
They must run a deadly gauntlet.
These limestone shards stand more than 100 metres tall...
..and are sharp enough to shred human skin.
But sifakas have thick, rubbery footpads,
and spring-like legs that can leap nine metres in a single bound.
These lemurs have evolved into blade runners.
Safely across, mother and son claim their reward.
The fresh, juicy leaves they need to survive.
Over millions of years of evolution,
the Decken's sifaka has overcome the extreme conditions
of the Grand Tsingy.
But as Madagascar's lemurs continued to spread east across the island,
they eventually encountered an immense barrier.
Over 100 miles inland, the Highlands.
It's these towering peaks that divide Madagascar's climate.
Rising over 2,000 metres, they capture the full force
of the seasonal rain blowing in from the east.
Millions of years of rainfall have carved out fertile valleys,
perfect for growing rice,
a staple food of Madagascar's people.
Just a few thousand years ago,
settlers from Asia brought the skills to turn even
the steepest mountains into terraced rice paddies.
Today, subsistence farmers produce more than one million tonnes
of rice here every year.
INDISTINCT CHATTER
Marivelo owns four paddy fields...
..providing just enough rice for her family of ten.
It's January, the height of the rainy season,
and the most important time for any rice farmer.
Each kilogram of rice needs more than 2,000 litres of water to grow.
With rainwater flooding the rice paddies,
Marivelo must prepare them for planting.
But instead of using a plough, she uses her most prized possession.
Originally from Asia, these are zebu cattle.
The stampeding hooves churn up the soil.
It may be dangerous work,
but it's an ancient practice, unique to Madagascar...
..and brings the whole community together.
With the soil prepared, it's time to get planting.
To make the most of the peak rains,
Marivelo and her daughters need to work fast.
THEY CHEER
They're precision planters.
Every blade is 20 cm apart,
ensuring maximum yield.
THEY CHEER
In three months' time, the rice crop should be ready for harvest,
providing Marivelo and her family with plenty of food
for the year ahead...
..Unless the crop is struck by one
of the most destructive creatures on the planet.
Locusts.
They're normally solitary insects,
but when there's an abundance of crops,
their numbers can reach plague proportions.
These flightless hoppers can form armies over half a mile long.
But they have only just begun on their path of destruction.
At five weeks old,
they morph into fully-fledged adults...
..and can take to the air in their billions.
A swarm this size may only appear once in a decade in Madagascar.
Travelling over 50 miles a day,
they can devour 40,000 tonnes of vegetation...
..including the farmers' precious rice crops.
On reaching the Highlands, a plague is finally stopped
by the heavy mountain rains.
Wet wings prevent the locusts from flying,
until, eventually, the swarm runs out of food,
and dies.
To the east of the Highlands lies a completely different world.
With warm, humid air blowing in off the Indian Ocean,
it receives ten times the rainfall of the west,
creating lush rainforests.
When Madagascar's ancient castaways eventually reached
these eastern forests, they flourished.
Over time, creatures evolved in extraordinary ways...
..colonising every corner of the jungle.
Today, two thirds of the island's plants and animals are found here.
The forest floor is home to another ancient castaway,
originally from Africa.
It may look like a hedgehog, but this is a tenrec,
found only on Madagascar.
They give birth to more babies than any other mammal.
As many as 32 in a single litter.
Like lemurs, they've evolved into a wide variety of species...
..each adapting in remarkable ways to their forest home.
At just four weeks old,
these streaked tenrecs are almost fully grown...
..eagerly sniffing out a meal with their flexible snouts.
To fuel their high metabolism, they can eat over 30 worms a day.
And they quickly disperse.
A deadly Madagascan ground boa.
The mother tenrec senses danger
and quickly sounds the alarm...
..by rubbing together modified spines on her back.
The high pitched sounds cut through the clamour of the forest
and the youngsters scurry back to her.
This is a unique form of communication
used by no other mammal on the planet,
a bizarre adaptation to survive in these crowded forests.
At night, an even stranger cast of creatures emerges.
The aptly-named pelican spider.
No larger than a grain of rice, he has a formidable set of jaws.
This male is on the hunt for his next meal.
Using his extra-long front legs, he searches for signs of life.
A silk thread...
..is the perfect lead.
A female orb web spider.
But she's protected by her sticky web.
What to do?
Fortunately, the pelican spider
has had millions of years to fine-tune its technique.
Mimicking the movements of a fly caught in her web,
he lures her towards him.
He uses his massive jaws to keep her at a distance
and avoid her lethal bite,
then paralyses her with his own powerful venom,
before tucking in.
The intense competition for food in Madagascar's crowded rainforest
has pushed its inhabitants to evolve in the most extreme ways...
..and the lemurs are no exception.
This is an aye-aye,
filmed in a special enclosure.
Her favourite food is insect larvae,
which can only be found deep inside the branches of trees.
But the aye-aye has perfected a truly remarkable
way of getting to them.
It's a technique that's thought to take four years to master.
Using her nine centimetre-long middle finger,
she taps to hear where the branch is hollow.
Then she gnaws away at the protective bark...
..before deploying her super-sized finger
to fish out any juicy grubs.
Madagascar's unique wildlife has had millions of years to slowly evolve.
But in the last few thousand years, the pace of life
has increased rapidly,
with deadly consequences...
..as revealed by a recent discovery in Madagascar's most remote desert.
This pool is a portal to a previously unexplored world.
In 2015, divers first ventured into this network of flooded passages.
50 metres below the surface,
they entered a truly magical underworld...
..discovering more than 11 km of connected tunnels...
..and some of the largest underwater chambers in the world.
But what they found inside these caves
was even more remarkable...
..a vast graveyard...
..the preserved remains of mysterious creatures...
..four metre-long horned crocodiles...
..puma-like predators, and ancient pygmy hippos.
But perhaps most impressive of all...
..the skulls of giant lemurs that grew to the size of a gorilla.
All long gone.
Their extinction coincided with the most disruptive change
in Madagascar's long history...
..the arrival of people.
And today, our impact on the island is greater than ever before.
Madagascar's forests are disappearing faster
than any other tropical country,
cleared largely for subsistence farming.
As little as 20% of the island's original forest remains.
And the impact on Madagascar's unique wildlife
has been devastating.
95% of lemurs are now threatened with extinction...
..making them the most vulnerable group of mammals in the world.
One of the most endangered is found in the east of the island...
..the greater bamboo lemur.
Like all lemurs, they're highly-specialised.
Bamboo makes up nearly 95% of their diet,
despite being packed with deadly cyanide.
Every day, a single lemur
can eat enough poison to kill five humans.
They have evolved to withstand its toxic effects,
keeping these thickets all to themselves.
But now, their unique adaptation has left them trapped here...
..unable to live anywhere else.
As their bamboo forests are cleared for agriculture,
these lemurs are left with nowhere to live,
and little to eat.
The greater bamboo lemur was once thought to have gone extinct...
..but thanks to a recent concerted effort to protect them,
there is now a glimmer of hope.
In the last year, this group
had a record number of babies,
adding 72 to their total population of 400.
The island of Madagascar has reached a critical point.
And only with intensive conservation efforts will its remarkable
and unique wildlife
survive into the future.
Filming the critically endangered greater bamboo lemur
took the crew to one of the most remote regions
of eastern Madagascar,
only accessible by a challenging two-day drive.
The road is deteriorating.
The wooden bridges are getting narrower.
The roads are worse than everyone expected.
We appear to have already got one of our vehicles stuck.
Finally, they reach Vohitrarivo,
a village close to one of the last known refuges of this rare lemur.
Over the next two weeks, the crew will be led by primatologist
Delphine Roullet, who came here ten years ago on an urgent mission
to save the bamboo lemurs.
With the help of her organisation, around 400 lemurs now live
in these pockets of bamboo forest, but they're spread over a vast area.
Hopefully, we're nearly there and can stop climbing up the hills.
To help narrow their search,
they head into the bush to meet local lemur researcher Noret.
Ahead of the shoot, he sets up camera traps
to hopefully establish the lemurs' whereabouts. Let's see.
Oh, what's that?
There is one!
It's a good sign.
A troupe of bamboo lemurs were in the area just a few days ago.
Oh, look, just here. Yeah, completely dark.
But the lemurs can travel through these thickets with ease,
so it will take all of Noret and Delphine's skills
to track them down.
I think Noret can see them.
I can't see them.
You can see a dark spot, just straight.
They may have spotted them in the distance,
but the lemurs are leading the crew into even thicker vegetation.
I'm getting entangled in sticky grass, and it's dense here.
No way this is going to work.
After nearly a week of tracking,
cameraman Justin is finally getting closer.
But getting a clear shot of them remains a significant challenge.
Yeah, right now there's two just below us, but we can't film it.
There's too much vegetation.
Their wild lemur chase
eventually takes them to the edge of the bamboo forest
and into the farmland beyond.
Noret and the crew check in with the locals
to get the latest information on any lemur sightings...
THEY SPEAK OWN LANGUAGE
..only to stumble upon the lemurs right in front of them.
So, we've just turned up to find them crossing this section
of rice paddy, between one part of bamboo forest and another.
With much of their bamboo forest cleared for agriculture,
the lemurs are forced to venture into the open.
Sort of surprising to find them here, because they really don't
like dogs, and the villagers keep dogs, but so far they seem relaxed.
Although bamboo is their preferred diet,
the lemurs will sometimes resort to raiding rice crops.
In the past, this has led to conflict with the locals,
but Delphine's project has changed all that.
Villagers like Noret are trained as lemur guardians.
They help study the troupes and marshal them
off farming land before any damage is caused.
Justin is still trying to get his shot...
..when conditions take a turn for the worse.
THUNDERCLAP
The rain makes filming quite difficult, and it makes it
really hard to keep everything and everybody dry, and not muddy.
So, at the moment the lemurs are keeping their heads down,
so we're doing the same.
The lemurs may be close by,
but the rain continues for four whole days.
We're just having to sit it out
and hope they start moving somewhere we can see them.
That frustration of having what you want, but not being able to see it.
But all this rain brings about a surprising change to their fortunes.
The rain triggers a flush of growth in the bamboo shoots,
the lemurs' favourite food, and draws them out into the open.
So, it's been raining nonstop for five days now,
and I feel pretty wet from top to bottom.
We can see six of them
stuffing their faces with bamboo, which is a lovely sight to see.
I'm really happy to be here, despite the rain.
It's amazing.
And there is an added bonus.
The mother bamboo lemurs have timed their births
to coincide with the arrival of fresh bamboo,
and the crew can film one of the first newborns of the season.
Oh, it's so good to see the babies! Cute!
Took a long time to get to this point of actually having them
in front of us, so we can film them.
It's just great to have moments like this.
These rare and intimate portraits of baby lemurs
is the start of a record breeding year.
Over the following two months, 72 babies are born.
It's a huge boost to this endangered population.
But their future rests in the hands of the next generation
of lemur guardians.
A vital part of Noret and Delphine's work
is sharing their knowledge with those living side by side
with the lemurs.
Thanks to Delphine, Noret, and their dedicated team,
one of Madagascar's rarest lemurs is now back
from the brink of extinction.
Next time, Borneo...
..home to a staggering variety of habitats.
From its bustling coral reefs
and ancient rainforests,
to its mountainous heart...
..Borneo holds possibly the greatest diversity of life...
..of any island.