All language subtitles for Secrets.of.Wild.Australia.Series.1.3of7.The.Crocodile.1080p.HDTV.x264.AAC.MVGroup.org.eng

(Hisses)

They've been on Earth
for millions of years.

Crocodiles...

..the largest
of all living reptiles...

..and among
the most dangerous animals

in Australia.

Superbly adapted
to aquatic life,

crocodiles
are formidable predators...

..with skull-crushing jaws
and lightning speed.

They're skilled hunters:

fishermen,

scavengers,

and even cannibals.

And they're survivors.

Once rare and in decline...

..these powerful carnivores

are in the ascendant
once more.

They dominate
the waterways and wetlands

of far North Australia...

..a vast island continent,

home to
some of the planet's

most unusual
and fascinating animals.

These are the Secrets
of the Crocodile.

Far North Australia.

The climate is tropical...

..and features some of
the most exotic landscapes

in the country.

The coastline is fractured
by multiple river systems

that snake their way
towards the sea.

In these brackish waters and
along these wooded riverbanks

lurks
an awe-inspiring creature...

..the saltwater
or estuarine crocodile.

Known locally as "salties,"

these are the country's
largest land-based predators.

Freshwater crocs
also live here.

They have narrower snouts,

better suited to catching
the aquatic life they eat.

They often live
alongside the salties,

in fresher waters
further upstream.

These amphibious reptiles
are everywhere.

Whether they're visible
or not,

if there's water
in this part of Australia,

crocs are there...

..solitary
and extremely aggressive...

..in rivers and creeks...

..mangrove swamps...

..waterholes...

..even the open sea.

This is Boris,

one of the crocodiles
on this stretch of river

named by researchers
studying crocodile behavior.

He's a large saltie,

at around
16 and a half feet long

and weighing
over 1,500 pounds.

At this time of year,
he spends time

soaking up the sun
at the water's edge.

It's October, and the dry
season is drawing to a close.

Up here in the far north,

there are just
two main seasons:

the wet and the dry.

When the rains come,
everything will change,

and it will be time to mate.

Boris is already moving in

on Amber.

At just under ten feet,

she's one of
the largest females around.

But there's a problem.

Amber's in the territory
of Ted,

the dominant male
of the area.

Crocodiles have a
fierce dominance hierarchy,

and, as top croc,

one of Ted's privileges is
to hold on to mating rights

with any females
on his patch.

If Boris wants Amber,

he'll have to get past Ted.

Dominance
is partially based on size,

and - at 17 feet long

and weighing
nearly 1,800 pounds -

Ted is the largest croc
on this stretch of river.

Most males are
between ten and 16 feet,

but salties
have been known to grow

as long as 21 feet

and weigh in
at over 2,800 pounds.

Size is also
a marker of age -

and Ted is thought to be
an impressive 100 years old.

Ted's gnarled
and deformed head

are evidence of years
of battling with rival males.

He's also blind, and
has lost many of his teeth.

These fall out and grow
again up to 45 times

as the crocodile
increases in size.

But Ted's run out
of replacements.

Crocs swallow their prey
whole,

so he can still eat,

but his hold on power
may be starting to wane.

When breeding season begins,

Boris could challenge Ted
for mating rights with Amber.

In the meantime, Boris
and the other crocodiles

must get on with the everyday
business of surviving.

It's something they're
perfectly adapted to do.

Crocodiles were here
long before the dinosaurs,

and have outlived them
by millions of years.

Crocodile fossils have been
found dating as far back

as 200 million years...

..and they appear in
ancient Aboriginal rock art.

Salties are found
in parts of southeast Asia
and New Guinea too.

In other parts of the world,
their numbers are threatened.

But they've been protected
in Australia since the 1970s,

which has led to a huge
surge in their numbers.

It's thought that
the saltwater crocodile
population now stands

at between
150,000 and 200,000.

It's been dry season now
for over five months.

There hasn't been rain
in a long time.

Waterholes are developing
thick mud at their edges.

Rivers are low.

And animals coming down
to the water's edge to drink

can be excellent quarry
for the stealthy crocodile.

Salties are hyper-carnivores,

meaning their diet is more
than 70 per cent meat.

They'll eat just about
any animal
they can catch and overpower,

including
fish, birds, small animals...

..even humans.

Like all
estuarine crocodiles,

Boris is mostly nocturnal...

..but will hunt during the
day, when he gets a chance.

He gets into position
along the riverbank,

to watch for anything

that comes
within striking distance.

Sweeps of his powerful tail

propel him silently
through the water.

His short limbs
with clawed, webbed feet...

..are ideal for swimming.

His eyes, ears, and nostrils

are located
on top of his head,

allowing him to lie low,

while keeping an eye
on his prey.

As well as
a good sense of smell,

he has sensory pits
along his entire body,

which detect vibrations.

Boris senses movement.

He dives, keeping
any exposure to the minimum.

When Boris is underwater,
his scales -

known as osteoderms -

create a low-pressure system
around him,

resulting in a counter
current around his body.

The water surface
won't ripple,

as he swims up to his prey.

He's invisible.

The little moorhen
in the reed beds

is oblivious
to his presence.

But Boris is after
a bigger prize.

He moves on silently.

An unsuspecting wallaby has
come to the water to drink...

..unaware of
what may lurk nearby.

A crocodile
can lunge incredibly fast,

using both feet and tail

to propel himself
from the water.

Boris clamps the wallaby
with his long, powerful jaws.

A special valve
at the back of his throat

allows him to open his mouth
to catch and hold prey

under the water, without
any entering his throat.

But to eat the wallaby, his
head needs to be above water.

A crocodile can eat

an incredible 23 per cent
of its body weight in one go.

He can secrete gastric acid
faster than any other animal,

liquefying bone matter
in just a few hours.

The only thing Boris
can't digest is keratin,

so he'll cough up the fur
later.

Anything he can't
manage now,

he'll conceal, and return
for snacks when he's hungry.

While crocodiles
are opportunistic hunters...

..it's harder for them
to move around

to other waterways
during the dry season.

This can limit
their feeding options.

But the drier,
less humid weather

allows the crocs to stock up
on energy in other ways.

From the sun.

Saltwater and freshwater
crocodiles are ectotherms,

meaning they're
cold-blooded.

Unlike humans and other
mammals, they're unable

to internally regulate
their body temperature.

To keep warm,
they need to sunbathe.

They stay very still,

and their metabolism
shuts right down

to conserve energy,

whilst they absorb
the sun's warmth.

The scales
on a crocodile's back

act rather like
their own solar panels.

Tiny blood vessels
carry blood

right to the surface
of the scales,

where it's quickly
warmed by the sun's rays.

As the blood circulates,

the heat is transferred
to the rest of the body.

This regular need for warmth
explains why crocodiles

are only suited
to living in the tropics.

Crocodiles don't need
to expend any energy

generating body heat,
which is why they can go

for long stretches
without feeding.

Basking to absorb heat

takes up at least
a few hours of each day,

depending on the weather.

Now, at the end of
the dry season,

there's still
plenty of sunshine.

Crocodiles
often like to sunbathe

with their mouths open.

It may show off this croc's
superbly sharp teeth,

but it's actually
a way of helping him

regulate
his body temperature

when it gets hotter.

The Australian sun
is fierce,

and temperatures
may rise still further

when the wet season arrives.

Like a panting dog, the
crocodile produces saliva,

which will cool him
as it evaporates.

But if his temperature rises
above 95 degrees Fahrenheit,

he'll shoot back
into the cool of the water.

While Amber
basks on the banks,

she may look asleep...

..but she's actually
always half awake.

Crocodiles
are able to shut down

one side of their brains
at a time,

while keeping one eye open.

This is known as
unihemispheric sleep.

Scientists have discovered
that crocodiles can deploy

unilateral eye closure
while dozing...

..enabling them
to keep one eye out

for potential threats or prey

at all times.

Crocodiles
also have three eyelids:

two ordinary ones,
made of keratin,

and a third underneath, which
covers the eye sideways,

called
the nictitating membrane.

This acts as a protective
layer against detritus

while underwater.

As the dry season
draws to a close...

..many crocodiles
take to the water

to make the most of an
unusual feeding opportunity.

The East Alligator River
in the Northern Territory.

It's 99 miles long,

and, despite its name,
is full of crocodiles.

50 miles
from the river's mouth

is a causeway
known as Cahills Crossing.

It's in
Kakadu National Park,

a popular
tourist destination.

Cars can only cross here

when the river's lower
in dry season.

But at the end of
the season, that changes.

This year,
the change of season

coincides with
the highest tide in weeks.

And the crocodiles seem to
know exactly when it's due.

As the waters start rising,

Boris...

..Amber

and numerous other crocodiles
begin to appear.

They converge on the area

from all over
the river system.

It's not known precisely
what triggers the crocs

to arrive at the same time.

They may have deeper
communication abilities

than are currently
understood.

Crocodiles have extraordinary
powers of hearing.

Their middle ear
can detect sounds

that are inaudible
to the human ear.

In between either side of
their cranial plate and ears

is a small muscular flap,

which allows them to navigate
magnetically, like birds.

It's also known
that crocs can track

the migratory routes of their
prey, as the seasons change.

The causeway usually prevents
fish from migrating upstream.

But as the spring tides

boost the water levels
in the river,

they bring mullet,
barramundi

and even turtles
from downstream,

attracted by
the weed beds and nutrients

of the fresher water.

The arrival of the tide
means that the river's flow

switches direction
to upstream,

making movement
easier for the fish,

as they travel
towards the source.

As the water levels
steadily rise,

the crossing is still used
by road traffic.

The big males
are first in line

for the migrating
fish feast, and take up

the best positions
just over the causeway.

One of the
largest crocodiles here,

a 14-foot male named Nigel,

has been fitted
with a GPS tracking device

by scientists
following his movements.

Studies of
crocodile navigation

have found that,
when they're on the move,

salties can travel
great distances,

up and down the river
systems and out to sea.

Males of between
ten to 12 feet

have been observed
traveling furthest.

They aren't big enough to
have their own territories,

but are large enough
to defend themselves

from sharks
and other crocodiles.

Nigel has been tracked
traveling 75 miles

down
the East Alligator River,

into the sea,
and back up another river.

Another study
tracked a crocodile

covering nearly 370 miles
in less than a month.

As the waters begin
to engulf the causeway,

motorists -
keen to make the crossing -

take greater risks.

The crocodiles use the surge
created by the cars

to give them
extra propulsion.

Local police advise drivers

to always give way
to crocodiles.

Salties may not
actively hunt humans,

but -
if one crosses their path -

they're more than happy
to take the opportunity.

During the 1980s,

a crocodile knocked a car off
the crossing with its tail.

And a fisherman was also
taken by a crocodile here,

when he fell into the water.

Over the past 45 years
in Australia,

there have been
99 crocodile attacks -

27 of them fatal.

The fish are jumping.

The crocodiles
wait with open mouths...

..and their front limbs
stretched out wide.

It's a technique known
as cross-posture fishing.

The crocs have sensory
receptors in their scales,

called ISOs,

which are more sensitive
than a human fingertip.

Scientists believe that,
by holding their arms wide,

the crocodiles create an arc

with the receptors
located around their jaws.

This increases their ability

to determine any movement
around them.

And as more and more fish
cross the causeway,

the better the opportunities
for feasting.

There are
as many as 40 crocodiles

at the crossing now.

What makes this event
so extraordinary

is that
it's the only time of year

when big males like Boris
will tolerate one another

in such close proximity.

Some experts believe

the crocodiles
may be cooperating:

working together
in close line formations

to herd schools of fish,
so they can all feed.

The blockade effect
of the crocodiles

makes it harder
for the fish to get through.

Further upstream,

any fish that have
made it past the big males

come up against
a second line of hungry jaws.

Females like Amber -

and the smaller males -
wait at a slight distance

from the front-line feeders.

When crocs are able
to feast like this,

they make the most of it.

This meal
can last them some time,

and they may even store fish
under rocks to eat later.

The salties
swallow the fish whole.

The crocodiles' tongues
don't move easily,

so they manipulate the food
into position for swallowing.

But if a fish
isn't pointing head first,

the scales can get stuck
in their throats.

So this croc flips his fish
like a pancake

to get it the right way up.

But sometimes
a misjudged throw

lets the fish
make a lucky escape.

After just two hours, the
tidal waters start to recede.

As quickly as they arrived,

the crocodiles
silently disappear...

..and drift apart once again

to return to their
more solitary existences...

..well stocked up
for the season ahead.

(Thunder rumbles)

The wet season
finally arrives.

Humidity goes up...

..storms erupt...

..and heavy rain
falls in blasting showers.

90 per cent of
the entire annual rainfall

will occur
in the next four months.

Away from
the unusual feeding event,

the crocs are back to
their more typical hierarchy.

Crocodile society is run

on highly combative
domination tactics.

Head clashes will establish
and reinforce dominance,

and can even happen
between females.

Wet season means that
the time is approaching

for the crocodiles to mate.

Ted may be old,

but he's still
the dominant crocodile here.

Keeping his grip
on the top spot is vital,

as it means
more chances to breed.

As temperatures rise,
intense courtship begins...

..a challenge for Boris, who
has his sights set on Amber.

Boris needs to broach
Ted's territorial dominance

to get her.

For crocodiles,

body posture is a
key means of communication.

Boris approaches Amber.

She raises her head:

a sign of submission.

These are the first overtures
in crocodile courtship.

Amber starts blowing bubbles
in the water.

This indicates
that she's receptive.

(Rasping breaths)

She makes
encouraging noises,

with chirpy rasps
from her nostrils.

Boris starts to circle her -

the next move in the ritual.

But just as things
are hotting up...

..Ted moves in,

and Boris
is forced to retreat.

But Boris hasn't given up.

Later that night,

he uses the cover of darkness
to continue wooing Amber...

..giving out deep
rasping noises of his own.

(Rasping breaths)

They swim around together
for hours,

before they eventually mate.

Copulation can last
up to 15 minutes,

and takes place
while fully submerged.

Ted's reign as the dominant
male has been challenged.

Amber's behavior
is not unusual.

Females will often allow
subordinate males

to mate with them
on the sly,

to ensure all of their eggs
are fertilized.

Researchers analyzing
crocodile eggs

have found that,
in some cases,

only a few belonged
to the dominant male.

The next day, Ted's regime
is threatened once more,

when large male Chopper makes
his way into his territory.

Saltwater crocodiles
are keen ambush predators,

but - if a chance arises -
they'll also scavenge.

And the wet season
presents new opportunities.

As water levels
fluctuate with the rain,

the riverbanks
become littered
with all sorts of debris,

including carrion.

Domestic livestock
can end up here,

as well as wild animals,

like this large feral pig.

It may be in
Ted's territory,

but whoever
gets to the carcass first

will consider it theirs.

When there's a ready
food source like this,

Chopper doesn't hold back.

Salties don't mind whether
food is fresh or rotting.

The carcass quickly
attracts other crocodiles.

Soon Ted, Boris
and several females

are fighting it out
for the free meal.

Chopper keeps trying
to oust Boris and Ted...

..by smashing down
onto their snouts.

Chopper
continues to dominate.

He fights off the others...

..and sticks close
to the carcass, hissing.

(Hisses)

Crocodiles
have no vocal chords.

He makes these sounds

by forcing air
out of his nostrils.

A study of the saltie's bite
found that theirs

is the strongest of
any creature in the world.

With a maximum bite force

of 4,000 pounds
per square inch,

their muscles are ranged
for clamping down tightly.

Once Chopper
gets close enough

to get his teeth around
part of the pig,

he needs to find a way
of taking bites from it.

His teeth interlock,

so, when they bite
into an animal,

it creates a serration,

better for gripping prey,
rather than for chewing.

To shear meat off,
he needs to shake.

So to do that,

he grips, rolls, and rips.

This behavior
is often referred to

as the death roll.

A dominant male
will let the females feed

and chase away
the smaller males.

But Ted doesn't manage
to see off Chopper.

Chopper manages to drag
most of the carcass away.

Now it's clear that Ted's
rule is on the decline.

It's December...

..and Amber has produced
a small clutch

of 16 hard-shelled eggs.

Females can lay
up to 80 eggs in a season.

She's scratched a nest
almost three feet high,

using vegetation and mud.

The eggs will be incubated
both by heat

generated
from the rotting leaves

and by solar radiation.

Her nest
is close to the water.

She's placed it carefully.

Too close,

and rising waters
could flood the nest,

and kill the embryos.

Amber will stay here
day and night

for the three months it
takes for the eggs to hatch.

She's fiercely protective.

She'll react aggressively

to defend her eggs
against would-be predators,

like wild dogs, lizards,

or feral pigs,

as well as other crocodiles.

For Amber's babies,

the struggle for survival
has begun.

The exact timing of hatching

will depend on
an optimal temperature

of 87 to 89 degrees.

Any higher or lower

and the hatchlings
could be deformed or die.

It's estimated that
up to 75 per cent of eggs

laid in a season
won't hatch at all.

When Amber's hatchlings
emerge,

they're highly vulnerable.

Baby crocodiles
are only ten to 12 inches
long at hatching,

an easily edible snack
for many predators.

Carnivorous fish,
like barramundi,

will eat
a young crocodile...

..while on the land, goanna
lizards may prey on them.

From the air, birds of prey,

like the white-bellied
sea eagle, can attack.

Crocodile mothers
protect their young

during the first months of life.

But as the young saltie grows,

an even greater threat will
come from his own species.

Big males,
like Ted or Boris,

will do anything they can
to get rid of young rivals.

And that extends
to cannibalism.

They'll eat both hatchlings
and young juveniles,

if they get a chance.

A dominant male
can pick up the scent

of smaller males
in his territory...

..and get rid of them.

Young females
can also be eaten,

but have a better chance

of being saved
for future breeding.

It's thought
that only one per cent
of male hatchlings

make it to adulthood.

So the odds are that only one
or two of Amber's hatchlings

may reach maturity.

If they do, there's a chance

that they could still be
alive 100 years from now...

..long after
their likely father -

Ted or Boris - has departed.

They could become
the next alpha crocodiles,

aiding the survival of
their extraordinary species

for many more generations
to come.