Original subtitles

Deep in the heart of the Amazon rainforest

lies the largest collection of river islands in the world.

Thousands of kilometers from the nearest ocean,

these are some of the most unusual habitats on Earth.

Stranded on the mighty Rio Negro,

the islands are engulfed by seasonal floods,

changing their landscape completely.

Everything living here is forced to adapt

or die.

This is life on the floating forests of the Amazon.

The Amazon Rain Forest

covers 4,000,000 square kilometers of our planet.

Sprawling across almost half

of the South American continent,

it is fed by the might Amazon River.

And at its heart are a group of islands

knows as the Anavilhanas

and Mariua Archipelagos.

More than a thousand islands stretch along

the Rio Negro branch of the Amazon River

and together make up the largest collection

of river islands in the world.

Thousands of kilometers from the nearest ocean,

these river islands are unique.

Surrounded not by coral reefs

and crystal clear waters,

but by flooded forests

and hidden dangers.

This is home to some of the most unusual creatures

in the world.

Flooded for six months of the year,

the islands are a mass of submerged trees

and wandering vines.

This is a world like no other.

The forest floor becomes the river bed.

Fish feed from the treetops.

And canopy dwellers are stalked

by creatures that lurk beneath.

It's May and the flood waters are starting to rise.

The lives of the animals that call the islands home

take a dramatic turn.

Only two primates live here,

red howler monkeys

and the more common squirrel monkeys,

who have the run of the canopy.

Because they spend much of the year

cut off from the mainland,

they've learned to adapt to life above the water.

It's early morning and a large group

is heading out on a foraging expedition.

The monkeys make the most of the daylight hours

as they move through the canopy.

They're on the lookout for fruits, flowers,

and insects that make up their diet.

Long tails provide them with excellent balance.

And aided by nimble hands and feet,

they're able to investigate any opportunity.

But the canopy offers slim pickings.

Surrounded by water, the archipelagos

do not support the abundance of food

that is available to monkeys elsewhere in the Amazon.

Some of the young males aren't impressed

with what's on offer.

So they decide to venture down,

deeper inside the flooded forest.

The rewards are worth it.

Young monkeys have incredibly good eyesight

and they're able to spot food

amongst the dense vegetation with ease.

They found a favorite.

The Clitoria flower's sweet nectar is irresistible.

After a frantic morning foraging,

one of the youngsters is desperate for a drink.

But it's a risky business.

Black caiman lurk below.

An alarm call alerts him to the danger,

but he's not out of trouble yet.

The slightest slip could be fatal for the plucky primate.

Finally, he makes it back to the canopy,

where he's safe for now.

Giant reptiles are not the only predators

patrolling these waterways.

None has a more fearsome reputation

than the piranha.

Blood in the water will whip them

into a feeding frenzy.

These red-bellied piranhas

could strip a monkey to the bone

in a matter of seconds.

Jaws filled with razor-sharp teeth

are designed to slice off bite-sized pieces of flesh.

As the waters continue to rise,

many animals become cut off.

A three-toed sloth is forced to brave

the treacherous waters in search of a new home.

Despite the dangers, it has no choice.

Built for life in the treetops,

sloths are surprisingly good swimmers.

They paddle efficiently with their long arms

and are able to move much faster

than they do on land.

But not quickly enough to go unnoticed.

Green anaconda are always on the lookout

for an easy meal.

This is an opportunity too good to be missed

for one of the forest's deadliest predators.

Chemoreceptors on the snake's tongue

help it track its prey's movements through the water.

Finally, the sloth makes it to a suitable tree,

but it's a long way to the top

and time is against it.

Once caught, the sloth stands no chance of escape.

After such a big meal,

the giant reptile will last for weeks

or even months until it has to hunt again.

Life on the river islands is ever-changing

as water levels continue to rise.

The flood waters originate hundreds of kilometers away,

high up in the Andean peaks.

In December, as temperatures begin to rise,

melt water from the mountains starts to pour down

the Amazon's many tributaries.

They flow east and gather forces.

These are joined by rainwater

as the wet season begins in earnest.

On the Rio Negro, rainfall is measured

not in centimeters but in meters.

The river bursts its banks and overflows,

flooding the river islands.

Amazingly, the rainforest creates almost half

of the yearly rainfall itself.

While the other half blows in from the Atlantic Ocean.

The islands of the Anavilhanas

and Mariua Archipelagos are transformed.

Water penetrates for a distance of up to 20 kilometers

on either side of the main channels.

Whole islands disappear underwater,

and in places, only the treetops remain.

By June, the floodwaters have risen

by up to 10 meters

but there's still more to come.

Curtains of green hide the islands'

mysterious inner world.

Trees and plants have developed

a number of techniques for surviving

their months underwater.

Some choose to hibernate.

Some lose all their leaves.

And some even continue to photosynthesize

while submerged.

Throughout the river islands,

animals are adapting to the new challenges

the waters bring.

Over two hundred species of birds

live on the islands of the Anavilhanas Archipelago.

While some are looking for food,

others are looking for love.

Living out of reach of the flood waters,

birds are able to put all their energy

into courtship.

A male streak-throated hummingbird

uses its enchanting song and simple display

to attract potential mates.

Although the flash of tail feathers is impressive,

it's usually the best song that wins the female's heart.

Deeper in the forest, another bird

goes to even greater extremes to find a mate.

The wire-tailed manakin.

There are over 50 species of manakin in the world

and the majority of these are found

in the forests of South America.

Stiff tail feathers give the birds their name.

A male surveys the forest

from his private display perch.

He's ready to strut his stuff

at the first sign of a female.

It doesn't take long for one to arrive.

But unlike most manakins, who display on their own,

wire-tailed manakins dance in pairs

as they attempt to win the female's affections.

The pair take to the stage.

It's a dance off

and both are desperate to impress.

The female sizes up her suitors from a distance.

Keeping a close eye on proceedings.

The dance comes to an end

with a show of dominance

and the female makes her choice.

All the loser can do is look on

as she leads the victor away.

Manakins are not the only island inhabitants

preoccupied with passing on their genes.

Throughout the islands,

the larger and more established trees

have been waiting all year

for the flood waters to arrive.

Now, finally, they get what they've been waiting for.

The trees use the waters to distribute their seeds

far and wide.

The pods of a munguba tree

have spent the dry season maturing.

Now they burst open in spectacular style,

revealing seeds hidden

amongst the giant balls of fluff.

The seeds are scattered in the wind.

Each is attached to a parachute to carry it on its way.

The seeds will be transported throughout the islands,

hopefully, germinating where they land

and helping to maintain the forest.

But the munguba trees need to be quick.

Fresh food doesn't go unnoticed for long

on these islands.

Tui parakeets make the most

of the freshly opened seed pods.

The munguba tree is a favorite.

They use their beaks to pry the seeds

from their fluffy cocoons.

It doesn't take long for the hungry birds

to strip a pod.

At this time of the year, there's more food

than they could wish for.

And they quickly move on to the next tree.

Parakeets are not the only animals

to take advantage of the fruit in trees.

Some seeds make a break for freedom

and float down into the forest

where more hungry mouths lie in wait.

While trees adapt to life in the water,

fish adapt to life among the trees.

South American trout, or brycon,

leap from the water to be first to the falling seeds.

They can jump up to four times their body length

in their quest for food.

Each mouthful is a priceless source of protein

for the hungry fish.

Even though the seeds of the munguba tree

don't last long, some trees have learned

to use the fish to their advantage.

Amazonian flooded forests

are the only place in the world where fish

act as the major seed disbursers.

Trees can rely on more than 200 species of fish

to distribute their seeds.

Many eat the fleshy fruit

before spitting out the unpalatable seed.

And by doing so, they help the trees

to deposit their seeds throughout the archipelagos.

The flooded islands are inundated

with aquatic visitors of all different shapes and sizes.

But despite the wealth of food,

the islands are not always the easiest place

for fish to live.

The quantity of decaying leaves in the water

means that oxygen levels are low.

Bacteria and other microorganisms

use up supplies as they break down the leaves.

As more and more of the river's oxygen is used up,

very little is left for the animals that live here.

The electric eel is a deadly predator.

But without a regular supply of oxygen,

it will not be able to hunt.

Like many fish in the black waters,

it's forced to the surface to gulp air.

Its mouth acts like a lung,

absorbing oxygen from the world above.

Another air-breather is the gigantic,

pike-like, pirarucu.

One of the largest known freshwater fish in the world,

fully grown adults can weigh up to 200 kilograms.

The three-meter-long monsters rise to the surface

every 10 to 15 minutes to breathe.

This armor-plated giant

has survived for nearly 100 million years.

The Anavilhanas and Mariua Archipelagos

still provide a safe haven for them

and many other creatures.

These ancient islands were formed

during a time of change in the Amazon

over 1500 years ago.

Then, the black waters of the Rio Negro

did not flow so freely into the mighty Amazon River.

Conditions were much calmer.

Sediment arriving from the Rio Branco to the north

started to settle.

Joined by waters from the Rio Negro's upper reaches,

pockets of forest started to form.

They developed into the islands we see today.

Over time, the Rio Negro once again picked up pace

and started to flow back into the Amazon.

The islands were left and survive to this day.

But they wouldn't exist at all

if weren't for the white waters of the Rio Branco.

Where, even to this day,

life doesn't just survive,

it flourishes.

One of the Rio Branco's most charismatic creatures

is the giant river otter.

The otters spend most of their time hunting.

Moving as a pack,

they're able to corral fish

before picking them off one by one.

Fresh fish make a fine breakfast.

Otters need to fuel their energetic lifestyle

and can crunch through up to four kilograms

of fish a day.

Catching the fish with their mouths,

they then hold them with their forepaws

as they devour their prey, scales and all.

But these deadly predators have a softer side

and when breakfast is over,

it's time to play.

Giant river otters live in large family groups

and it will be some time before last year's cubs

head off to form families of their own.

Family life revolves around the den.

The mother remains hidden

while she raises the next generation.

With several dens dotted around their territory,

the family move regularly in the search for fish

and to avoid unwanted attention from predators.

Just a few months old,

the cubs must be carried

as they're still too young to swim.

The family head off up river.

Arriving at their next den,

the first priority is to get the cubs inside

where it's safe.

The father keeps watch

while his family settles into their new home.

The males scent mark the entrance

to warn others that they are now in residence.

It's a pungent concoction that will keep

even the nosiest neighbors away.

All along the Rio Branco,

life flourishes on the sediment-rich waters.

The river banks are dotted with wildlife.

Including the largest rodents in the world.

Closely related to the guinea pig,

capybaras are equally at home in or out of the water.

But the wealth of animals attracts unwanted attention.

A jaguar stalks the river bank.

Capybaras make a tasty meal.

The Amazon's apex predator

is rarely found far from the river,

and the abundance of food on the Rio Branco

makes it an ideal hunting ground.

When escaping dangers, the giant rodents can dive

and remain underwater for up to five minutes.

The jaguar stalks off silently

to continue its search for food.

Back on the river islands,

the mid-morning peace is shattered.

Red howler monkeys can be heard

throughout the islands.

These secretive primates don't only use

their roaring calls to deter predators,

they also use them to mark their territory.

Unlike their island neighbors, the squirrel monkeys,

they tend to travel in smaller groups

and stick to the top of the canopy.

Excellent acrobats, the monkeys

rarely come down to the ground,

and during the floods, they're even more reluctant,

all too aware of the dangers that lurk beneath.

It's now late July and water levels are at their peak.

The forest floor has sunk under 15 meters of water.

The flood waters bring about a change

in everyone's lives.

A colony of fire ants has been forced out

of their underground home

by the rising water levels,

providing an easy meal, despite their painful sting.

This tree will provide a safe haven

until the waters fall

and they can return to the forest floor.

The resilient ants quickly move

into a vacant crack in the bark.

Some animals don't just survive,

they thrive in the new conditions.

Leaf cutter ants swarm through the trees.

Able to carry pieces of leaf

weighing 20 times their body weight,

they're born to work.

These are no ordinary ants.

It's believed their a separate species

to the ones who nest underground,

and they've developed a unique behavior.

They've swapped the forest floor for the treetops.

By building their nests in the canopy,

they avoid the annual floods,

so, despite the rising waters,

they continue undisturbed.

Colonies can contain up to 8,000,000 individuals,

making it one of the most dominant creatures

in South America.

And one of the river islands' most resilient residents.

Worker ants are sent out to collect supplies.

Foraging far and wide,

they're able to find their way home

by laying out a thermal trail.

The pheromone is so powerful, one gram of the scent

would be enough to lay an ant trail

all the way around the world.

Only the freshest and juiciest leaves are selected.

Powerful jaws slice through the cellulose with ease.

Once loaded up, the ants then begin their journey

back to the nest.

Leaf cutter ants cultivate a special fungus garden

deep within the nest.

And are almost entirely dependent on the fungus for food.

Maintaining the garden is crucial

to the survival of the colony.

Only the queen is able to produce offspring.

She's capable of laying thousands of eggs per day,

most of which are destined to become workers.

The ants are true forest specialists,

and, out of the reach of the flood waters,

they continue to dominate.

Other insects have not adapted

to their new aquatic home quite so well.

Some are forced to venture across the water's surface

in search of dry land.

It's a crossing fraught with danger.

Arowana lurk beneath.

The fish patrol close to the surface,

scanning for prey.

No insect is safe.

As the flood waters rise,

more and more get washed into reach.

It's a time for the arowana to fatten up

before the long dry season returns.

Some of the waterways' more unusual creatures

are also taking advantage of the new food available.

Needlefish lie just beneath surface.

Their slim profile helps them to avoid detection.

They hunt by sight and are ready

to take advantage of any stragglers.

Unlucky spiders are picked off with ease.

Carnivorous fish are not the only underwater animals

enjoying a glut of food.

One of South America's largest animals

lurks in these waters.

The Amazonian manatee is an iconic symbol

of the Anavilhanas and Mariua Archipelagos.

Hiding out in the quiet backwaters,

they gorge on the food that arrives

with the flood waters.

For the manatee, this is a time of plenty.

And also a time to rear their young.

These shy mammals give birth to a single calf

once every two years.

The mother will spend time teaching the youngster

the best routes through the maze of river channels.

The calf will need all its mothers knowledge and support

with the dry season fast approaching.

It's now August

and the rainy season is coming to an end.

Water levels are finally starting to fall.

The animals and plants that have survived the floods

can look forward to drier times ahead.

Eking out a living on the ever-changing islands

can be a challenge,

but there are always ways and means of doing so.

As the flood waters start to fall,

spectacular fish begin to appear

in the shallows of the forest.

Cardinal tetras are found deep in the heart

of palm forests along the black waters

of the Rio Negro.

This family makes the eight-hour round trip

from their village each day

in order to gather the tiny fish.

Their catch is destined for exotic fish tanks

around the world

and provides the family with a vital source of income.

Come midday, it's time to head back to the village.

On their return, the fish are quickly sorted.

The highly prized cardinal tetras

are separated and piled into boxes.

A thousand fish sells for around five dollars.

A decent income, but the family supplements

by hunting and fishing.

Once the morning's work is done,

the pace of village life slows.

By the end of September, the heavy rains cease

and the water engulfing the river islands

has fallen by almost a third.

As the levels drop, beaches reappear.

For many, life starts to become easier.

Butterflies feed on freshly exposed land.

Migrant birds return to nest.

Newly exposed plants burst back into life

with a flush of green.

Squirrel monkeys are less fearful

of the world below as the retreating flood waters

lead the dangers away.

Which is also good news for the sloths.

But for the islands' wet season visitors,

it's time to move out.

The manatee mother and calf

have feasted for the past four months.

They must now prepare to return to the main channels

and begin their dry season fast.

And fish are also forced to leave

the islands' flooded forest

and return to the deeper river channels.

The Anivilhanas and Mariua Archipelagos

spread along a 1,000 kilometer stretch of the Rio Negro.

They provide a home for some of the hardiest animals

in the world.

As flood waters engulf the islands each year,

those that live here are forced to endure

incredible extremes.

But animals have developed ways of coping

and have learned to master their ever-changing environment.

It's either sink or swim

here in the floating forests of the Amazon.