Original subtitles

Deep in the heart of South America

lies one of the most spectacular secrets of the natural world

Iguacu

one of the planet's largest waterfalls

It's a fearsome display of the raw power of water

but it also has a gentler side

A vast and continuous cloud of fine spray

rises up over the surrounding trees

This refreshing moisture nurtures a very special section of rainforest

a biological hotspot for some of South America's most amazing animals

But Iguacu National Park is a refuge fighting for survival

Dedicated teams work tirelessly to guard it from poachers and illegal loggers

Drastic action is needed

but this is a hard place to police

In the wet season

Iguacu can have up to 300 individual falls

draining from the hundreds of kilometers of surrounding forest

Can this magical place be saved?

Around 120 million years ago

the rupture of the supercontinent of Pangea

led to the creation of Africa and South America

Lava bursting through

hardened into giant blocks of fine-grained basalt

This is the rock from which the Iguacu waterfalls have been sculpted grain by grain

Basalt is such a hard rock that it erodes very slowly

leaving behind a line of cliffs up to 82 metres tall

At one point 7 miles long

Iguacu's horseshoe-shaped falls are nearly 3 times the size of Niagara

In the wet season

enough water flows over the edges every day

to supply the city of London for more than a year

The torrent could drag you to your death

but Great Dusky Swifts fly right through it

Behind the wall of water

they are safe from predators

Most other animals have to make do with the spray-drenched forest

which surrounds the falls

Tucked away, some 15 metres up in the canopy

lives one of Iguacu's most successful mammals

the ring-tailed coati

a relative of the raccoon

Every year they produce a litter of up to six cubs

It's risky place to raise young

but it's a lot safer than on the ground

Jaguars

the mightiest cats of the Western Hemisphere, still roam here

But they're in steep decline

Good news for the coatis perhaps

but bad news for Iguacu National Park

These forests used to stretch back from most of Brazil's Atlantic coast-line

Now only 7% of this unique Atlantic rainforest is left

Iguacu

straddling the border between Brazil and Argentina

is one of the last refuges for the outstandingly rich and endemic wildlife of the area

known locally as the 'Mata Atlantica'

In the eighties

Iguacu was given World Heritage status

but it was steeped in folklore long before this

A native legend tells of Naipi

daughter of a tribal chief

a girl so beautiful that the Iguacu River would stop to admire her

Tarob�� a brave young warrior

fell in love with Naipi, and won her heart

With each passing day

their feelings grew stronger

But the chief had already chosen Naipi to be sacrificed

to honour their ruling serpent god, M'boi

The night before the sacrifice

the couple made their escape

Little did they know that the god M'boi was watching in fury

The waters raged with the Gods wrath

and a gigantic gorge opened before them

Thus the demise of Naipi and Tarob��

was the creation of the Falls of Iguacu

In what is now called the Devil's Gorge

it is said their spirits remain forever

Each Spring

new life emerges from this bewitching place

Flocks of up to three thousand swifts come here to breed

The birds clamber over each other

as they attempt to show themselves off to best advantage

On these precipitous cliffs

the ability to Hang On might be the most attractive trait of all

Despite their numbers at the falls they have been little studied

and their courtship behaviours are not fully understood

The acrobatics continue for several days on both sides of the cascade

Until eventually the birds pair off

But nothing about life on the falls is easy

the female allows the male to court her

but often rejects him over and over

He offers her some useful nesting material for her hard basalt hollow

but even that doesn't do the job

The flirting eventually pays off

and it's time for the flying circus to begin family life

While the swifts are just starting to build their nests

the baby coatis are growing too boisterous to stay inside theirs

They're three and a half weeks old

and getting a taste for adventure

The mother has two more weeks teaching them the ropes on her own

Like their mother

the babies need to become excellent climbers

it's vital for finding food

but also for escaping from predators

For now, though

it's one step at a time

Despite the occasional mishap

the youngsters quickly cotton on

Long tails help to balance

while strong, sharp claws grasp the bark

as they literally hang on for their lives

And, if they ever lose their nerve

help and encouragement is at hand

After about 6 weeks isolated with their young

mother coatis reassemble into large social groups

that can number more than 60 individuals

Even after short periods apart

coatis engage in excitable greetings and groom each other

At last, relief from looking after the kids

mothers take turns running a cr��che

Some go off looking for food

while others watch over the unruly cubs

Iguacu appears idyllic

but scientists in the park fear that many treasures have already been lost

There is little knowledge of life in the forest beyond the falls

Both Brazilian and Argentine scientists are working hard to put that right

Ricardo Melzew is part of a special Jaguar project

funded by several government departments

They've discovered that in the last 15 years

Iguacu's jaguar population may have suffered an 8 fold decrease in numbers

Researchers use cameras to spy on these elusive predators

An infrared sensor is tripped by passing animals

producing snapshots of jaguars' secret lives

These can tell Ricardo and the team a good deal:

We use a camera trunk to track the cats

especially the spotted ones like the jaguar

Each jaguar has unique spot patterns

like fingerprint

so based on those we can tell exactly how many individuals there are

Back at the lab

the researchers face the challenge of interpreting all their data

Do Iguacu's most powerful feline predators stand any chance of survival?

Iiaria Agostini thinks the evidence

from photos, feces and footprint casts all points one way

Jaguars are disappearing

first and foremost, because of hunting

There are many records of jaguars killed by poachers who shoot them

in order to sell their skin

or just for the thrill of killing a jaguar

But the most recent snaps offer some encouragement

They've identified a male-female pair

Extremely good news

as the park population is estimated at a mere twelve individuals

Maybe this pair will breed

But it's not just jaguars that scientists want to protect

This is a special bird

in its element at Iguacu

The snail kite depends on water to supply its main food source

juicy amphibious apple snails

The kite may eat as many as 70 snails a day

so it regularly patrols the fast-flowing water

Some rapids are too powerful for fishing

though the kite seems able to cope with the strong currents at the edge of the falls

Few birds of prey are this specialized

The ultra-rounded beak is perfectly shaped for scooping out

and lacerating the muscle tissue that binds snail to shell

With the rainy season is underway

activity around the falls is hotting up

Red-rumped caciques are well into a huge nest-building programme

The males do the hard graft

and the females keep tabs on them

An elaborate series of knots

secures the long tear drop shaped nests to the tree

With dozens of couples living in a single tree

the occasional dispute is unavoidable

Desperate to finish in time

a cacique may steal a neighbor's supplies to get ahead

But community life has its advantages

Large colonies mean better protection

when the nests host precious offspring

After the clamour from the cacique colony subsides

yet another of Iguacu's residents joins the wait for a new generation

A mother caiman listens carefully

Nearby, her nesting mound contains up to sixty eggs

This is the sound she's been waiting for

The babies synchronize their emergence by calling to each other

while still inside the egg

The mother caiman has protected this mound for 90 days

Now, by hatching all at once

her babies have further reduced each individual's chances

of being picked off by monkeys, lizards or birds

The hatchlings head directly towards water

where they will remain under their mother's guard for several months

But tonight, they've been spotted

Fortunately they're being hunted by park biologists

carrying out their annual caiman census

Just as jaguars can tell scientists about the overall health of the forests

broad-snouted caiman numbers are a good indicator of water quality in the park

Caiman are very vulnerable to pollution

The main threat to them, however, comes from people

Many caiman are hunted for meat

but the broad-snouted caiman is especially targeted for its unique skin

used to make fine leather goods

When Justo Herrera and the Argentine National Park team began the study ten years ago

the caiman population was alarmingly low

"The drop in the Caiman population was due to heavy poaching in the area

Now, there are more park rangers on patrol

This seems to have deterred hunters

letting the population begin to recover"

These are small but hopeful signs for Iguacu's future

The swifts are also doing well

If the sun is shining the swifts will be on the wing

It's summer and temperatures have risen by around 10 degrees Celsius

The mist cloud creates a super-humid micro-climate around the falls

but the swifts have the ultimate antidote for the oppressive heat

The high-pressure showers are not only cooling

they help rid the birds of parasites

Feathers need to be in top condition for their aerial stunts

and long hours on the wing

The swifts compete for the nooks and crannies under the falls

which will make the best nest sites

Nest-building is soon under way

Materials include plants, feathers and moss from all around the falls

But it's their own saliva that will help glue the nest to the slippery rock

In the carefully prepared crevice

the swift lays just a single egg, guarded with utmost care

Virtually no nest predator can get up here

so the swifts have no need to reproduce in great quantity

The eggs take an unusually long time to hatch

possibly because of the chilly conditions in the dank hollows

Nearby, the 3-month-old coati cubs have become intrepid explorers

They're nimble climbers now, and growing fast

which means they're in constant search of food

But their playful antics can also put them into grave danger

it's not wise to annoy some of the jungle neighbours

The South American rattlesnake is one of the most poisonous of the rattlers

its venom can easily kill a human

let alone a young coati

But when hot on a scent

the cubs often take little notice of other creatures around them

The bone-chilling rattle should be enough to send anyone running

But young coatis are both naive and curious

The rattle is the warning

Provoking it is a deadly game to play for the youngsters

Its neuro-toxic venom invades and disrupts the victim's nervous system

The coati cubs survive another day

but the fate of Iguacu as a whole remains less certain

Iguacu is a large island of rainforest

surrounded by a huge sea of farmland

The long term impact of the encroaching areas remains to be seen

In a pioneering expedition to find out more

scientists are penetrating deep into the little-known heart of Iguacu

and the pristine Floriano River

This is as far as the chopper will take them

The team is led by National Park biologist Alcides Rinaldi

and visiting specialist Carolina Ribas

They hope to find traces of the giant river otter

a species native to the area whose current status is unknown

They're accompanied by Adaildo Policeno

who once made his living as poacher

For team-leader, Rinaldi

this is unknown territory

"This expedition is a rare chance to explore an area

where very few people have ever set foot

It's totally remote

closed off to visitors

So it can give us a look at how this whole region must have been long ago"

Some of the local inhabitants are agitated by the group's arrival

These are so-called 'killer bees'

a dangerous hybrid descended from escaped African bees

originally brought to Brazil for honey production

Their aggressive nature and the number of stings sustained by the team

threatens to end the expedition before it's even started

The river offers an escape from the harmful bees

and the oppressive summer heat

The group heads off as quickly as possible

The biologists are looking out for any signs of the 1.8m long giant otter

But expert, Caroline Ribas

believes this part of the river isn't quite right

"I think there's too much current here to be giant otter habitat

The water is very clear and there aren't many large fish

So far we've seen a lot of common river otter marks

but no sign of any giant otter

I'm hopeful though!"

It's so remote here that it's possible to see very rare animals

even the fugitive jaguar can prowl here in relative safety

The name jaguar comes from the indigenous word "yaguara"

meaning "the beast that kills his prey in one leap"

So even large mammals must remain vigilant in this dense forest

Excellent hearing and a keen sense of smell

will help keep this tapir out of trouble

The Brazilian or lowland tapir has a unique crest along the back of its neck

thought by some scientists to be a protection from jaguar attacks

Its ancestry links it to the primitive horse and the rhino

Despite appearances

tapirs are good runners and have extremely tough skin

If frightened or attacked

they will rush into water to escape

A 200kg tapir would be several days' worth of food

But only an experienced jaguar would succeed in bringing one down

Most jaguars don't get that far

Along the rivers in the Iguacu heartland

are some of the greatest concentrations of butterflies on earth

rivaling the spectacle of the Amazon rainforest

Scientists reckon that there may be over 800 different species in the park

but so far only 257 have been identified

They gather in huge numbers on damp ground

because these are the best places to absorb essential salts and minerals

Unfurling their straw-like tongues

they suck up huge amounts of water

Inside their bodies the necessary minerals are filtered out

and the surplus river water is steadily flushed out at the other end

These gatherings are almost exclusively male

And it's competitive

The males pass their mineral strength to the female when they mate

So filtering more water now will increase the chances of passing on his genes

Along the nearby Floriano River

the search for the giant otter continues

The team has paddled and hacked its way through a 40km obstacle course

Finally they reach the place where ex-hunter, Adaildo Plicenoa

remembers seeing a giant otter six years ago

"Here, between the first and second waterfalls

I saw a giant otter sitting on this rock

He was looking up in that direction

The water was high and he was sitting right here eating a fish"

"It caught my attention because it had a white mark here

"Was it near its mouth, or on the chest?"

"More on the chest

Historically giant otters were easier to find in the rivers of Iguacu

Social and gregarious

they live and hunt in packs

earning them the nickname of 'water wolves'

But in recent decades

sightings became fewer and fewer until, in the late 1980's

the otters seemed to disappear altogether

Along the banks

Carolina Ribas and the team find only traces of the smaller, common otter

"Right here we've found some common otter mucous

they use it to mark their territory

Look at this here

Here on the bank

you can see really clearly where the otters have left claw marks"

There's an otter's holt

but it also belongs to a common otter

The whereabouts of its elusive giant cousin remain a mystery

The Floriano River starts and ends on protected land

making it one of the purest waterways in Iguacu

If the giant otter is to be found anywhere it should be here

They check each stretch of the river for likely spots

"We've reached a part of the Floriano river

that's deeper and calmer any of the sections we've encountered so far

It's around 4 and a half feet deep

That means there are probably more fish here

which would make it a more likely place to find giant otters

Unfortunately we haven't found any traces of them yet"

"Not finding a single sign is a disheartening end to the expedition

Giant otters are very sensitive to pollution

Could contaminants from the surrounding farmland have already seeped into the park?

It's a reminder of how easily the balance of nature

in this island of rainforest can be upset

The arrival of the annual rains can be quite disruptive too

Some animals benefit from the extra food on offer

But a violent rainy season raises river levels at an alarming rate

Recently, Iguacu experienced intense rainfall

The flow over the falls reached a staggering 17,000 cubic meters per second

one of the highest since records began

Normally, the falls provide unparalleled protection for the great dusky swifts

Now the waters threaten to destroy this year's brood

and take down the adults too

Life becomes both a matter of endurance and luck

Here, the river has risen an incredible 20 metres

nearly swallowing some of the falls

The swifts are resilient

and within days they are back in action, re-building their lives

The coatis take the rainy season in their stride

Their life is spent high and dry

The coati diet is very varied

and much of what they need can be found in the trees

But they do get their feet on the ground

to find protein-rich invertebrates

and their elongated up-turned snout is ideal for rooting them out

For digging into the best bug hideaways

their climbing claws come into their own

This year's cubs are discovering that Iguacu's forests

offer a fantastic variety of fruit

No wonder coatis are doing well here

They can get around quickly

thanks to a reversible ankle joint which gets them down trees head-first

and they are learning fast

both from each other and their adult chaperones

For now the pack travels as a group

But before the youngsters reach their third year

things will change

The females will stay with their mothers

but the males will have to peel off on their own

Young male coatis need to make the most of the precious time

spent under their mother's wing

At sundown, when the coatis are tucked up

different characters emerge around the falls

On the forest floor

one of the true terrors of the night

Already the size of a human hand

the tarantula can take on prey even larger than itself

Hairs on the tarantula's body

form an array of sensory hunting equipment

They allow it to detect heat

chemicals and vibrations in the air

A perfect predator

Just one of the helpless, blind mice would be a perfect meal

enough to satisfy the tarantula for several days

Babies everywhere are under threat

The nests at the cacique colony are now full of chicks

Adults are on full alert

even before the first rays light up the forest

Red-rumped caciques have plumage to match their noisy nature

As the chicks begin to stir

their parents begin the daily grind to feed them

Some of the caciques have already lost chicks to predators

but many nests still contain one, two or even three hungry mouths

desperate for an insect breakfast

But they always keep an eye out for danger

Their enemy, the Toco toucan, doesn't need camouflage

It's big, and it's pushy

The combined efforts of the cacique colony are no real match

A cacique chick is just a protein supplement in the toucan's fruity diet

But in mere seconds

a cacique's season of labour is lost

The Park authorities can also find their hard work undermined

Poachers are at work in Iguacu

and Brazilian and Argentine rangers join forces to root them out

Apol?nio Rodrigues, Vice-President of the Brazilian park

scans the riverbank for any tell tale signs of infiltration

Argentine head ranger, Jorge Cieslik, shares command

There's no telling what they might find

poachers can be heavily armed

Rodrigues and Cieslik are sure they're on the right track

"Clearly there is a camp nearby."

"There is a path cleared that splits off

We know there's nothing in one direction

but in the other direction it's likely we'll find the camp

"When we first got here��"

"We heard firecrackers when we got here

That's their accomplices warning them

So now we know they are in there

But taking the suspects by surprise will not be easy

The rangers advance cautiously

in this remote patch of forest there's no back-up

The ambush is successful

but the rangers know these are the little guys

Local people are poor

Hunting, although illegal

can bring in many times the minimum wage

The rangers collect up evidence

which includes some dangerous, primitive weapons

and the remains of a rare white-lipped peccary

"This is a homemade canon, old-fashioned style

Our friends here set them up all around the park"

"This one's been well-used already

They set up a wire, and when an animal trips it"

"��it pulls this trigger here"

"Hunting has always been a problem in the park

It has increased because it's so lucrative

People no longer hunt just for themselves;

they sell kills to dealers

or sometimes they work on special order for people in the area"

Now the park rangers themselves have to use increasingly radical

and sometimes violent tactics

In this tranquil place

it seems to be the only way to give Iguacu's wildlife a fighting chance

Around the falls the coatis numbers have become more concentrated

maybe taking advantage of the decline in big cats such as the jaguar

The ground has become a much safer place for the young males to spar

This is practice, perhaps

for when they need to fight for the right to mate with females

Soon the young males will have to leave

already they are testing their independence

They've already started to build their own sleeping nests near the group

It's time to reaffirm group bonds

and settle in to replenish their energy for the adventures ahead

The worst of the rainy season is over

and the falls at Iguacu are back to normal

The swifts have recovered from the raging flood

and the single chicks are growing strongly

They're demanding little things

hungry for insects that the parents catch in mid-air

For weeks the chick has observed his parents' fearless flight path

But that won't make its maiden plunge any less harrowing

Mum and dad form a safety net while the chick tests its wings

Then comes the day of reckoning

The falls are a formidable place to live;

a gated fortress to which only the swifts have the key

The grand falls of Iguacu are a world monument

That status has helped to protect

the remnant of Atlantic rainforest that lies behind

It is sobering to think that without this fantastic spectacle

an entire wild community might already have disappeared

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