All language subtitles for 01z

A remote Colombian island...

...feared for its
deadly wildlife...

...and home to
a notorious prison.

A natural fortress,

surrounded by
dangerous reefs

and shark-infested seas.

Covered with
impenetrable forest,

teeming with venomous snakes.

For convicts,
escape was futile.

But following
in the footsteps

- of the few who tried...
- [Screeching]

...we reveal another side
to the island -

a wildlife haven.

A sanctuary where creatures
thrive in remote isolation.

[Screeches]

Theirs is the real story
of life on Gorgona:

the snake prison island.

Remote and isolated,

Gorgona is a tiny lump
of volcanic rock

rising from
the Pacific Ocean.

It lies 35 kilometers
off the coast of Colombia.

Overrun by dense jungle,

it conceals a multitude
of deadly animals.

[Rustling]

It was the stuff
of nightmares

for early explorers

and has resulted in the
island's sinister history.

Because of its isolation,

Gorgona was chosen by
the Colombian government

as a site for a prison -

the country's own version
of Alcatraz.

In 1959 it began housing
the nation's

most notorious criminals.

Modeled on Nazi
concentration camps,

claims of human rights
abuse were rife.

Murders within its walls
were common.

25 years it was a living hell

for the 2,500 inmates
who did time here.

[Bird calls]

If the prison's
thick concrete walls

weren't enough
to prevent escape,

the jungle outside
harbored a deadly deterrent.

There are 18 species of snake
on the island,

from the skinny -
but fast - sipo...

...to the powerful giant boa.

Of those 18,
three carry deadly venom.

When Spanish conquistadors
sailed to the island

in the 1500s and claimed it,

they learned the hard way

about the island's
natural dangers.

87 sailors died
from snake bites:

more than half the crew.

That snake legacy
continues today.

The last prisoners
left Gorgona in 1984.

30 years on, the island's
natural inhabitants

have reclaimed the
penitentiary for themselves.

Bats hang like the lightbulbs

that once lit
the prison corridors.

Bees build cells to house
their own colonies.

The island's rats now have
the run of the prison.

[Chattering]

And the once imposing walls

have become a playground
for monkeys.

Some of the prison's
first inmates

were violent gang members...

...locked up for killing
rivals in vicious turf wars.

Today, Gorgona still sees
boundary disputes.

But they involve
a very different primate.

White-faced capuchin monkeys

live in small troops
led by an alpha male.

They watch each other's backs

and defend
precious resources.

Females stay with the troop
they are born into

for their entire lives.

But males must leave
to find new families.

They seek out new groups
every four years or so

to avoid inbreeding.

When they set out
to find new troops,

they often band together.

There's safety in numbers.

But these roaming
all-male gangs

can be bad news
for a family troop.

[Chattering]

A gang has breached
the prison perimeter -

climbing the walls
and scaling the roof.

They're on the lookout
for females to breed with.

The troop's resident alpha
knows he's under threat.

When a new male
takes over a group,

it will typically kill
existing babies.

This brings the females
into estrus more quickly,

allowing them to replace

the outgoing males' offspring
with their own.

The alpha male
calls his troop to arms.

[Screeching]

He and the subordinate males
in his group

present a united front.

This is how
the lower-ranking males

earn their place
in the troop's hierarchy.

Providing back-up
to the alpha

also earns them
the chance to breed.

The invading males on the
roof are visibly outnumbered.

It's not worth the risk
of tackling this group.

[Screeches]

The male gang retreats.

With their patch defended,

the troop breaks out
in search of food.

In its heyday,
the prison was like a zoo.

But the people
were behind bars,

while the animals ran free.

It must have been torturous
for the inmates

to watch monkeys
scaling the walls,

enjoying the freedom of
the forest.

The monkeys
may even have inspired

a few escape plans.

But if a convict
did manage to break out,

it would have just been
the start of his problems.

The fer-de-lance:

one of South America's
most deadly snakes.

This two-meter pit viper

is capable of moving
at lightning speed.

Highly aggressive,
they're quick to strike.

[Hisses]

Its venom is so fast-acting,

it kills more people than
any other poisonous animal

in South America.

One bite
contains enough venom

to kill more than 30 people.

An escaped prisoner
wouldn't have stood a chance,

suffering excruciating pain

as the venom destroys
his body tissues

from the inside out.

The threat of
a fer-de-lance bite alone

was enough to prevent
most convicts

from attempting to escape.

[Chirruping]

But if a jail-breaker managed to
avoid the deadly snakes, he'd
soon be swallowed by the
island's dense jungle.

Gorgona is two and a half
kilometers across

and nine kilometers long -

about half the size
of Manhattan.

For once, nature might help.

The thick forest
could conceal a prisoner,

if he could stay alive.

He'd need to find food.

Following
the island's primates

might give him clues.

The capuchins snack on buds,

seeds,
and even small animals.

But the bulk
of their diet is fruit.

Foraging keeps them
constantly on the move,

seeking out trees
with the ripest treats.

They have an unusual way of
making group decisions,

more like the behavior
of bees and ants

than other social mammals.

[Monkey chatters]

Although they have an alpha,

anyone in the troop -
male or female -

can have their say.

A monkey sets out
in one direction.

It's his suggestion
to the others.

But the troop
won't blindly follow.

They carefully
consider his proposal.

If they think he's likely
to find food,

they'll follow him.

If not, he'll be forced
to return to the group.

In the future,
his suggestions

won't carry much weight.

But this capuchin male
sticks to his guns,

hoping he can find
two or three others

to share his vision.

So far,
they aren't buying it.

Finally,
a few decide to join him.

It's enough
to tip the balance

and the rest of the troop
is persuaded to follow.

But it could be
a short-lived triumph.

Their movements are being
closely monitored from below.

A giant boa constrictor
is lying in wait.

Female boas
are bigger than males.

And this one's a whopper,
nearly four meters long.

Her powerful body's about
30 centimeters in diameter.

She's a formidable predator.

She may not mate every year,

and will only reproduce
if she's in prime condition.

So, her priority
is fattening herself up.

She'll eat anything
she can swallow.

With her expandable jaws,
a capuchin monkey,

about the size of
a domestic cat,

would be an easy mouthful.

She doesn't have fangs,

but she does have
more than 70 teeth

to lock into
and anchor her prey.

Like alligators and sharks,

damaged or lost teeth
are constantly replaced,

keeping them needle-sharp.

She can't hear the
approaching capuchins.

Instead,
she follows their movement

via vibrations
through her jaw bone.

But as soon as she makes
her move, her cover's blown.

[Low screeching]

[Low screeching]

The capuchins screech
their alarm calls.

[Screeching]

The monkeys mob her,
hoping to scare her away.

- [Screeches]
- It doesn't work.

The capuchins have only
one option: retreat.

They must start the decision
making process from scratch.

The monkeys' movements
are dictated by

the fruiting trees throughout
their home range.

For Gorgona's convicts,
forced to eat basic rations,

the fruit was a tantalizing
but forbidden luxury.

The monkeys are picky,

looking for
the ripest fruits.

As they browse, they dislodge
fruit and leaves

that fall to
the forest floor.

For escaped prisoners,
the monkeys' leftovers

could have been
a life-saving free meal.

The fallen fruit is manna
from heaven for insects

and other creatures
in the undergrowth.

One animal cashing in
on the castoffs

is the millipede.

This species is toxic,
releasing a chemical defense

through glands
along the sides of its body.

In some species, the toxins,
known as Benzoquinones,

are powerful enough to
dissolve the bodies of ants

and other insects.

A wise prisoner on the run

would give millipedes
a wide berth.

Even just touching them

can cause irritation of
the eyes and skin.

But the capuchin alpha is
actively trying to find one.

He isn't going
to eat the millipede.

He wants it for protection.

The millipede's toxic
chemicals keep pests at bay.

Wiping the insect
over his fur

provides an excellent
monkey mosquito repellent.

Despite being
a walking chemistry set,

the millipede
is a friend of the forest.

It breaks down
decaying leaf litter,

returning nutrients
to the soil.

Millipedes were among
the first land animals

to appear on Earth,
around 400 million years ago.

While they've evolved
to survive

in almost any habitat,

they thrive in humid tropical
forests like Gorgona's.

The island's location
close to the equator

means there's an average
temperature of 27 degrees.

Humidity rarely drops below
95 per cent.

Molds and fungi thrive
in these conditions.

While leaves, bark and
fallen fruits quickly rot.

This would have made it challenging

for any prison escapee.

The high levels of humidity

added to
the tough conditions

for those imprisoned
on the island.

A prisoner on the run
wouldn't get much relief

from any sea breezes.

Here, trade winds
laden with moisture

from the ocean's surface
add to the humidity.

Moisture in the air
has a snowballing effect,

acting like a magnet,
attracting yet more humidity.

But there's only so much
water the air can hold.

Eventually,
the inevitable happens.

[Storm rumbles,
wind whistles]

[Rain pattering]

For most of the year,

torrential downpours
are a daily event.

The combination of heavy rain
and high temperatures

would have added to
the misery of the prisoners.

But for an escaped convict
hiding out in the forest,

it could prove deadly.

The moist, warm environment

is the perfect breeding
ground for infection.

Even the smallest wound
quickly festers.

[Rain gently splashing]

When the day's torrential
downpour stops,

a brown-throated
three-toed sloth emerges

to take advantage
of the sun's warming rays.

Gorgona's sloths are unique.

The island used to be
attached to the mainland.

At the end
of the last Ice Age,

sea levels rose
and cut it off,

leaving the sloths behind.

They have been isolated
from mainland Colombia

for so long, they have become
a distinct sub-species.

Just like the convicts, they
are now marooned prisoners,

cut off from
the outside world.

After the heavy rain,

the sloth hangs
himself out to dry.

In most mammals,
hair parts along the spine

and flows down the back
to the belly.

But because of his
upside-down life in the trees

the sloth's fur
grows the other way,

belly to back,
allowing him to drip-dry.

He's in no rush, and might
hang here for hours.

The leaves of the rainforest
don't offer great nutrition,

but he gets by
thanks to a slow metabolism.

And to save energy,
he spends a lot of time

just hanging around.

He keeps still for so long,

that his fur has developed
its own mini-ecosystem.

Algae is the first organism

to colonize
his hollow hair follicles.

The simple
single-celled organisms

give his fur
a greenish tinge,

perfect camouflage
in the canopy.

The algae promote
the growth of a fungus

that has scientists excited.

For sloths, the fungus
seems to inhibit infections

and keeps parasites at bay.

For humans, scientists
think it may have disease-

and even cancer-resistant
properties.

The algae also feeds
a species of moth

unique to the sloth.

When the sloth climbs
to the ground to defecate,

the moth lays its eggs
on the droppings.

Their larvae
then feed on the dung.

Every member of this
community benefits the other.

The moths fertilize
the sloth's fur

with their nutrient-rich
droppings.

That, in turn, encourages
more algae to grow,

which helps to protect the
sloth through camouflage.

It's an amazing,
self-contained ecosystem,

all on the sloth's back.

As the sloth
and his lodgers dry out,

other forest-dwellers

are making the most
of the moisture.

It rains all year round
on the island.

But the heavy downpours
of the rainy season

trigger a male
marbled poison frog

to spring into action.

His mate is an absent mother.

She laid her eggs directly
onto the forest floor,

then left them.

Once the eggs hatch,

it's Dad who does
all the heavy lifting.

Like all tadpoles,

his offspring
breathe through gills.

They need water to survive.

So it's down to the male

to find them
a more permanent pool.

He piggy-backs his tadpoles
across the forest floor.

A layer of sticky mucous

makes sure
his precious cargo is safe.

The hunt for
a suitable nursery

is fraught with danger.

Even tiny ants could make
a meal of his tadpoles,

so he needs to find
somewhere secure.

Eventually he spots
the ideal location -

a prison sink.

The bathrooms here
were once a terrifying place.

There were so many murderous
attacks on the inmates,

the bathroom walls
had to be lowered

to allow
constant monitoring.

Now the bathroom's
a sanctuary,

an old basin creating
the perfect nursery

for the young tadpoles.

It's sheltered, secluded,

and a breeding ground
for the insect larvae

the tadpoles can feed on.

His precious load delivered,

the male's parental
contribution is done.

Now his tadpoles
must go it alone.

[Birds chirruping]

As the skies clear,
the warmth of the sun

tempts other prison residents
from their cells.

Stingless bees.

[Buzzing]

There could be up
to 10,000 of them

living in this cavity
in the wall.

Worker bees are
strengthening the entrance.

They use their jaws
to pulp wood,

using sticky saliva
to cement it into place.

The hive is their fortress,

their honey store and
a nursery for their young.

This is teamwork at its best.

Every individual
has a specific role...

...from bringing back pollen,
to construction,

to taking out the trash.

Because stingless bees
don't pack the punch

of their well-armed cousins,
they need to be careful.

Insects are low
on the food chain.

[Bird cries]

As the sun begins to set
over the island,

the bees' nemesis stirs.

Little big-eared bats.

Nocturnal hunters.

They use echolocation
to home in on prey,

their large ears picking up
the returning echoes

of their high-pitched
squeaks.

[Squeaking]

Like a security camera,

they scan the room
for signs of prey.

They have a special fondness
for crunchy food,

especially beetles,
crickets and cockroaches.

They're not the only bats
in the ruins

but there's no
competition for food.

The lesser long-tongued bats

are their vegetarian cousins.

At night they visit flowers,
lapping up pollen and nectar,

and pollinating
the forest's plants.

Their tongue is half
the length of their body.

So long,
it permanently protrudes

through a gap
in their front teeth.

It's four centimeters long,

tipped with bristles to help
gather up their sugary diet.

As the bats prepare
to head out on the hunt,

other nocturnal inmates emerge.

[Chirruping]

Rats were a permanent fixture
of prison life,

adding to the misery
and squalor

of the living conditions.

The people may have gone,

but the prison's ruins

still offer
hiding places to rodents.

Under the cover of darkness,

spiny rats vacuum up
any fallen fruit.

Their teeth
never stop growing.

They rub against each other,
wearing down the edges,

forming chisel-sharp blades

that can cut through
the toughest nut shells.

The rodents perform
an important role

in the island's ecology.

Many of the forest's trees

rely on the spiny rats
for propagation.

Cracking the shells allows
the seeds to germinate.

And, by caching their finds,

the rodents help
to distribute the seeds

around the forest.

But these gardeners
are themselves

on the forest menu.

They're prey for pretty much
every large predator

on the island.

Having failed to snare
a capuchin,

the female boa
is on the hunt again.

Like many snakes,
she has a sixth sense

when it comes to hunting.

She's able to detect
the warmth of her prey

even if
she can't see them.

And with every flick
of her tongue,

the boa picks up
scent molecules

from the surrounding environment.

Guided by heat and scent,

she can track her quarry
even on the darkest night.

She's locked on to
her target.

A master of
stealthy stalking,

she's got the perfect
camouflage for an ambush.

She lies in wait for the rat
to get within striking range.

Her sharp teeth
lock into the rat.

Before it has the chance
to fight back,

she throws her coils
around it.

She kills by crushing,

squeezing the rat so hard
it stops the blood flow.

Death comes quickly.

The rat is swallowed whole.

[Soft squelching]

It will now take her
at least a week

to digest her meal.

Gorgona's forest at night

would have been
a terrifying place

for an escaped convict.

Dawn would have brought
immense relief.

[Birdsong]

The early morning sun
lures a ten-centimeter-long

female blue anole
from the shadows.

Today, she's on a mission.

But she's not going anywhere
until she warms up.

Blue anoles
only exist on Gorgona.

Once she's absorbed
the sun's energy,

she heads down to
the forest floor.

She's going to lay her eggs.

Her forest home
wasn't always like this.

Before the jail
first opened its doors,

Gorgona suffered
mass clearance of its trees

for shipping and farming.

Although the building
of the prison

allowed the forest to grow
back, the damage was done.

The blue anole was left
critically endangered.

The female's precious
cargo - her eggs-

are vital for the future
of her species.

But going to the ground
is a risky business.

Today the biggest threat

to the survival of
this endangered species

is a non-indigenous
invader...

[Clicking]

...the Western basilisk.

Introduced from the mainland,

the meter-long lizard is
wreaking havoc on Gorgona.

It eats anything
from insects to fruit

but is especially fond
of other lizards.

This crested male has
the pregnant female anole

in its sights.

Just when it looks like
the end of the road

for the anole,

the hunter
becomes the hunted.

A Boddaert's racer.

Three-quarters of its diet
is made up of lizards.

And the basilisk looks like
a convenient meal.

Despite being no bigger
than the basilisk,

the racer snake is more
than up for the challenge.

But the basilisk has
a clever trick up its sleeve.

Named the Jesus Christ lizard,

the basilisk
is a master of escape.

It uses its long,
broad, scaly toes

to trap air pockets
under its feet

and walk or run
on water.

It can cover one-and-a-half
meters a second.

But eventually
gravity catches up,

and the lizard sinks.

It's still been enough
to escape the snake.

Just to be sure, the basilisk
stays submerged.

It's capable of hiding under
water for up to half an hour.

But this time he might have
jumped out of the frying pan,

and into the fire.

Spectacled caiman can reach

two-and-a-half meters
in length.

At just a meter long,
this is a youngster.

But it still has dagger-sharp
teeth and powerful jaws...

...more than enough to make
short work of the basilisk.

Time for another miracle.

Gorgona's waterways are full
of dangerous predators,

but to a prisoner on the run,

they'd be a useful
navigational tool.

Walking in the water
wouldn't leave footprints

for the guards to track.

Following the rivers downstream

would lead the escapee
to the coast.

But the island
wouldn't release

its captive inhabitants
quite so easily.

Before reaching
the coastline,

an escapee would be faced

with the island's
mangrove swamps.

The soft mud
would act like quicksand,

while the tangle of roots
presents a labyrinth:

a spider's web
of living plants...

...so dense it's almost
impossible to penetrate.

Mangrove trees
are specialists,

adapted to cope
with brackish water.

They're vital to the island,

protecting its coastline
from storm surges.

The mangroves' aerial roots

are an adaptation
to their soggy lifestyle.

They act like snorkels,
taking in oxygen from the air

when the rest of the roots
are submerged.

The forest's dropped leaves
feed mangrove fiddler crabs.

Which, in turn, aerate the
waterlogged, anaerobic soil.

The crabs may be adept
at maneuvering

through the thick
sticky mud of the swamps.

But it would slow down
any prison break.

By following the rivers
through the swamp,

the exhausted prisoner
would finally break free

of the mangroves.

Only to come to
the ultimate dead end...

the Pacific Ocean.

Remote and isolated,

the nearest coastline
is over 30 kilometers away.

Marooned on the beach,

the prisoner
could have done little

but watch the receding tide.

As the water retreats,

painted ghost crabs
emerge to feed.

For a fugitive,
the crabs might have become

a life-saving meal.

Left to their own devices,

the aggressive crustaceans
scavenge for treasure

washed up by the sea.

Each fiercely defends
its patch of sand.

In the crab world,

trespassing's
a risky business.

They take no prisoners, often
cannibalizing intruders.

But right now, this male
has other things on his mind.

He's busy excavating
his burrow.

Each crab digs a burrow
above the waterline.

It needs constant maintenance

and every crab
has its own technique.

Some crabs just kick
the sand to one side.

But this male
is piling up a spoil heap.

This isn't just
good housekeeping.

The mound of sand
serves another purpose.

Female ghost crabs
release their eggs

under the new moon,

when tides are higher
and the darker nights

make it harder for predators
to spot their offspring.

To get the timing right,

they need to breed
two weeks earlier,

signaled by the full moon,

which brings the males
out to perform.

[Tapping]

They bang their drums

pounding the mounds
with their pincers.

They're serenading
potential mates.

A colony of drumming crabs

might have been
a wondrous sight

to a convict camping out
on the beach.

But it would not
have helped his escape.

[Squawking]

The birds flying overhead

might have offered inspiration.

[Squawking]

Every morning,
blue-footed boobies

preen their feathers,

coating them in oil
to waterproof them

before setting out to feed.

Studying the way
the seabirds used the waves

might have helped him
to understand

the currents offshore,
and formulate a plan.

In the island's entire
history as a penitentiary,

only three prisoners
ever got past the beach,

making the ultimate prison
break by building rafts.

They may have used
the large Cecropia trees

that are common
on the island.

Its bark can be twisted
to make excellent rope

that could have strung
a raft together.

Even if a convict
got this far,

he was far from home free.

Dragging the raft out
through the shallows

would have possibly been
the most dangerous part

of this prison break.

Huge tiger sharks
patrol the beach.

They're one of the most
dangerous sharks

in the world.

More than half a tonne
of muscle,

with teeth shaped to slice
through flesh and bone.

The tiger shark is a
highly effective predator,

hunting in shallow water.

Isolated from the mainland,

filled with venomous snakes,

enclosed by a web
of mangroves,

and patrolled by sharks...

...it's obvious
why Gorgona was chosen

for a maximum security jail.

But even if a prisoner
managed to safely launch

a raft into the water,

the island still has one more
natural barrier to breach -

a coral reef surrounding
the whole island.

The seabed is littered
with the wrecks of ships

the reef's claimed
over the years.

Reefs have always represented
a threat to mariners.

The vast structures funnel
water into eddies and rifts

that can drive boats

against the hull-destroying
jagged edges.

The razor-edged coral

can tear through rafts
and human flesh alike.

Passengers thrown overboard

would be churned
in the breakers

and dashed against the rocks.

If they didn't drown
right away,

they'd face marine predators

or be swept out
into the Pacific Ocean.

The reef is the final barrier

to escape from
the natural fortress -

a prison with no escape.

Just like the prison ruins,

today the shipwrecks
scattered around Gorgona

provide a sanctuary
for wildlife.

During its operation,

the prison took
a heavy toll on the reef.

Fish were harvested
to feed the inmates.

Goliath grouper
was heavily hunted.

This species has now
been pushed to the brink.

It's one of the top ten most
endangered fish on Earth.

But, ironically,
the island that once led

to the grouper's downfall
might now be its savior.

Gorgona's prison
ran from 1959 to 1984.

But in the same year that
its doors finally closed,

the island was declared
a national park.

The goliath grouper,

the blue anole,

the brown-throated
sloth -

all the wildlife
that has evolved here

and lives nowhere else on
Earth is now fully protected.

And at its heart,
the prison itself -

a reminder of the island's
brutal past -

is slowly returning
to the jungle.

A once impregnable fortress,
Gorgona has become a refuge.

Snake Prison Island

is a prison no more.