Original subtitles

Off the south coast of Australia

lies an ocean fortress...

...cut off by wild seas 10,000 years ago.

An enchanted refuge where some of the mainland's wildlife have

made a last stand.

[Birds chirping in distance]

A world apart, it's moulded both its residence

and its visitors, and made them its own.

[Squawking]

A place full of the amazing, the endearing,

the endangered, and the dangerous.

Battles rage on land, in the trees, on the beaches,

and under the waves.

Life here marches and kicks to the beat

of its own drum.

[Birds chirping in distance]

This is life on a spectacular living arc.

[Squawking]

Kangaroo Island.

[♪]

[♪]

It's autumn, and the dry summer heat

has given way to mellow, cooling breezes.

A welcome relief to the island's Australian sea lions.

Wedged between rocky ramparts with its own surf beach,

and rich hunting and fishing grounds just beyond

the breakers,

this is Seal Bay.

As close as you get for paradise for a seal.

But it's not just a seaside resort for sunbathing

and fine dining...

[Barking]

It's an important breeding destination

for about 1,000 Australian sea lions,

one of the most endangered pinnipeds in the world.

[Barking]

But even here, life isn't always as idyllic as it seems.

Sea lions aren't big on romance and breeding can be a brutal

and dangerous affair, especially if you happen to be

a young and lonely male sea lion.

Towering between him and the possibility

of mating is the beach master,

a 300-kilogram testosterone-fuelled beach bully

who wants all the females to himself.

[Barking]

But the call to reproduce is strong.

Body surfing nonchalantly in the shallows,

the young male keeps a sharp eye out for any windows

of opportunity.

[♪]

[Barking]

And there she is, a lone female up in the dunes,

and the beach master is snoozing.

The young male slips out of the surf as surreptitiously

as he can, holding his 180-kilo bulk.

But the beach master is a light sleeper.

[Grunting]

He has to be with juvenile delinquents about.

[Grunting]

Honking disapproval, he dashes the young male's hopes.

[Grunting]

The youngster will just have to bide his time.

The tail end of autumn sees the start

of the rainy season.

Kangaroo Island is at the convergence

of seasonal ocean currents that create cool wet winters

and hot dry summers.

Over aeons, these rains have seeped into

the soft porous limestone bedrock and dissolve the rock

to form massive subterranean caves,

caves that hold secrets to the island's past.

Over hundreds of thousands of years,

the Kelly Hill Caves have been pitfall traps to unwary animals

that have fallen to their deaths.

The bones of ancient long-extinct species

speak to a time when strange large marsupial predators

hungrily roamed this landscape.

The Australian coastline today is the result

of great sea level changes over millennia.

Once, Kangaroo Island was part of the continent.

When the last Ice Age ended, sea levels rose almost 120

metres and predators were cut off

from the newly-formed island.

Kangaroo Island has since remained virtually free

of large predators, a situation prey species have

taken advantage of in fascinating ways.

These are some of the most iconic

and beloved beneficiaries of the island's safe haven.

[Birds chirping in distance]

No ordinary hoppers,

they are Kangaroo Island kangaroos,

a subspecies of western grey roos that evolved

in isolation since the island

was separated from the mainland.

[Birds chirping in distance]

[♪]

With no predators, they have become shorter,

slower, furrier, chubbier,

[Birds chirping in distance]

and apparently lazier.

Kangaroos are marsupials, a group of mammals that

have been wildly successful in the isolation of Australia.

Their defining characteristic of course, the famous pouch.

[Birds chirping in distance]

On Kangaroo Island, joeys have little to fear inside

or outside the pouch.

[Birds chirping in distance]

The adults have no one to fear but each other.

[Birds chirping in distance]

The autumn rains are a perfect time

for males to establish their pecking order.

[Birds chirping in distance]

Rains stimulate grass growth and triggers breeding activity.

[Birds chirping in distance]

Young males spar with each other constantly play fighting.

They're not strong enough yet to do any real damage.

[Birds chirping in distance]

But the fully-grown males called "boomers" fight in earnest.

[Birds chirping in distance]

There are breeding rights at stake.

[♪]

With sharp claws, they scotch and gouge.

More dangerous is the kick from their powerful hind legs.

They rock back supporting their entire body weight

on their tails and aim violent blows to the belly.

[Birds chirping in distance]

A well-end kick can be fatal.

[Birds chirping in distance]

[♪]

The winner will have all the females in the mob to himself.

[Birds chirping in distance]

Nearby, dropping she-oak trees seem to be

raining shredded seeds.

[Birds chirping in distance]

This natural confetti celebrates one of the great stories

of the living arc that is Kangaroo Island.

[Birds squawking in distance]

The source of the raining seeds

is a South-Australian glossy black cockatoo.

[Birds squawking and chirping in distance]

This little island is the only place in the world

where the subspecies of the bird exists.

[Birds squawking in distance]

They're picky eaters surviving solely

on the equally are drooping she-oak.

The she-oak disappeared from South Australia where it

was clear-cut to make way for farming

and expanding urban areas, and with it went the glossy

black cockatoo.

[Birds squawking in distance]

This is now the last remaining home for both bird and tree.

The cockatoo spends hours twisting the seeds

from the branches.

[Birds squawking in distance]

[Birds chirping in distance]

Curiously like all parrots, they're almost all lefties,

standing on their right leg and manipulating the seeds

with their left.

[Birds squawking and chirping in distance]

There may as few as 100 of these glorious birds left

and the subspecies is considered critically endangered.

[Squawks]

[♪]

The females lay only one egg per breeding season,

which is tightly synchronized with the seasonal fruiting

of the drooping she-oak.

[Birds squawking in distance]

With such a low reproductive rate,

their population recovery will be a slow

and precarious journey.

[Birds squawking in distance]

Some animals on Kangaroo Island have no such problems.

This unlikely-looking creature is extremely adaptable

and thrives in a variety of habitats across the island.

It's the strange and endearing Kangaroo Island echidna.

Like the glossy black cockatoo here on the arc,

it become a subspecies of the mainland variety.

Its protective spines are actually specialized hairs.

[Birds chirping in distance]

The echidna is not your average mammal.

It belongs to an extremely small and incredibly ancient lineage

of mammals called "monotremes".

[Insect chirping in distance]

Usually solitary, this female is about to find

herself quite popular.

[Birds chirping in distance]

The shorter days and cooler temperatures

of autumn have brought her into oestrous,

and now her dance card is full.

[Birds chirping in distance]

Trains of up to 10 males frequently

fall in behind a receptive female.

[Birds chirping in distance]

Their long noses entranced by the pheromones wafting behind

her as she waddles along.

[Birds chirping in distance]

But she's not too picky.

She may mate with all of them.

[Birds chirping in distance]

Echidna trains can last for up to six weeks

and the mating period can lumber from late autumn

into the winter months.

Back at Seal Bay, testosterone fuels more chaos

for the females.

One weary female emerges from the surf.

[Grunting]

Only to find herself squarely on the young male's radar.

[Barking]

And the beach master is nowhere in sight.

[Grunting]

She wants no part of him.

She is already pregnant and won't come into oestrous

again till immediately after she pups.

[Grunting]

[Growling]

The inexperienced male doesn't know any better.

Aggressively, he cuts her off from the harem

and chases her up the dunes.

[Barking]

[Growling]

[Grunting]

And he's not the only randy juvenile around.

[Barking and growling]

She could be in serious danger with these

awkward violent teenagers bent on mating.

[Grunting]

Fortunately, they get caught up in their own testosterone drama

and she makes a getaway.

[Grunting]

Now that she's eating for two, she needs to feed

as often as possible.

She slips into the sea, headed for rich feeding grounds

where there's an all-you-can-eat buffet.

But to get there, she'll have to make sure

she doesn't land on someone else's dinner plate.

[♪]

Off the coast lurks one of the most fearsome predators

on the planet.

The great white sharks of Kangaroo Island are among

the largest in the world with unconfirmed

reports of some up to 7 metres long.

They're here for the bountiful menu

of marine mammals.

[Bleating]

Kangaroo Island and the surrounding are supports

the largest populations of both Australian sea lions

and fur seals.

[Birds chirping in distance]

It's not just the big hungry adult sharks that mammals have

to contend with.

There's also an influx of younger sharks

this time of year.

Juveniles return here in autumn, after their communal

gathering in the warmer waters in the north.

[♪]

And they know where the seal's feeding grounds are.

[♪]

These sharks are actually warm-blooded, equipped to hunt

in the chilliest of waters,

Their fast-contracting white muscle can propel them at speeds

up to 50 kilometres per hour in an instant.

And with 300 teeth, every inch of them is built for the strike

and a kill.

[♪]

But sea lions aren't without their won defences.

The pregnant female has highly light-sensitive eyes that enable

her to see in poor visibility under water.

She's also more agile than a great white.

She frequently huddles with other sea lions in the water,

so a multiple set of eyes can be on the lookout for predators.

She keeps a low profile looking out for sharks and waiting

for the right moment to bolt for the feeding grounds.

In deeper water, sea lions have an ingenious

method to counter the shark's deadly ways.

Sharks almost always ambush their prey from below,

shooting out of the depths at high speed.

So while she's at the surface, she swims with her head tipped,

so that one eye is looking up and one is always scanning

for an attack from below.

This way she can flip around to make sure she's not in front

of the business end of a shark, but instead trailing behind it.

[♪]

After a quick feed on cuttlefish and octopus,

she heads back to the beach.

As autumn comes to an end, it seems as though romance is

in the air everywhere.

[Birds chirping in distance]

The plentiful pastures on the island's grassy norms

bring another rare species to the island for the winter.

[Squawking]

Cape Barren geese pair for life and return here

each year to breed.

[Birds chirping in distance]

These geese originally inhabited only isolated islands further

east, but their numbers were falling.

They were introduced to Kangaroo Island

in the 1930s to safeguard the species.

[Birds chirping in distance]

Those that were subsequently born here,

then returned here to breed as do their chicks.

[Birds chirping in distance]

Today, there are over 200 here with migrants

from other islands arriving

regularly each breeding season of their own accord.

Their recovery has been such a success that the colony is now

one of the healthiest in world

[Birds chirping in distance]

This couple has arrived early

and found some prime real estate.

[Birds chirping in distance]

As grazers, they lay claim to the richest

patches of open grassland and defend their chosen

territory vigorously.

[Squawking]

[♪]

When the business of courting is done,

she lays her clutch in a nest that he's built

and lined with his own down feathers.

While she does all the incubating,

he'll be her bodyguard for the next 35 days.

[♪]

These hooded plover eggs seem to be

in a much more precarious position,

exposed to sudden winds that batter the coastal sand dunes

and predatory gulls.

The plovers live life sandwiched between the dunes

and the Southern Ocean as they scour the shoreline

for molluscs, insects, and crustaceans.

The survival of their eggs depends

on a clever deception by their parents.

When an inquisitive hungry gull arrives on the scene,

the plovers quickly create a diversion.

They move down the beach and huddle as though

they're on a nest.

The diversion tactic draws the seagull away from the edge

of the dunes and away from their real nest.

[Squawking]

It seems to be working.

[Squawking]

But there's a greater threat looming on the horizon.

The weather.

On Kangaroo Island winter is marked by the arrival

of cold winds of the vast Southern Ocean.

[Birds chirping in distance]

[Squawking]

Four weeks after they've laid their eggs,

the Cape Barren geese have a family.

[♪]

[Squawking] On the sanctuary of the island, this pair has successfully

raised four out of their five chicks,

a fat greater survival rate than they could achieve elsewhere.

[Squawking in distance]

The couple shares parental duties,

keeping a close eye on their precious charges.

[Squawking in distance]

Since the day after hatching, the chicks have been grazing

alongside their parents, rapidly putting on weight.

[Squawking]

But it will be another month before they get their flight

feathers and can head back to the mainland with their parents.

[Squawking in distance]

Although, Kangaroo Island is an ideal arc

for threatened animals,

it can fall victim to its own successes.

[Birds chirping in distance]

Even an adorable icon can become a problem.

[Birds chirping in distance]

In 1920, when koala numbers were

plummeting on the mainland, 18 koalas were introduced to

Kangaroo Island.

Today, there are thousands of them grazing

in the island's eucalypt forests.

[Distant cawing]

Eucalypts are actually evergreens

producing leaves year round.

But since the leaves don't provide much nutrition or fuel,

the koalas have to eat, and eat, and eat.

[Birds chirping in distance]

Koalas can be impressively strong and agile,

allowing them to move freely throughout the forest.

[Birds chirping in distance]

No eucalypt tree is safe from these voracious creatures,

and on Kangaroo Island that's a problem.

[Birds chirping in distance]

Without predators to keep them in check,

the koalas are slowly eating themselves

out of house and home.

The constant grazing gives the eucalypt forest

little chance to recover.

Wildlife managers are now working to manage the

populations through a process of sterilization

and relocating animals to eucalypt forests

on the mainland where their numbers have continued to fall.

Back in the water, reproductive urges are luring

fantastic creatures form the deep.

In winter, giant cuttlefish leave the deeper waters

of their preferred feeding grounds

and migrate to the island's sheltered shallow bays to breed.

This is the largest species of cuttlefish in the world.

Males can grow 1 metre long

and weigh more than 10 kilograms.

Cousins to squids and octopus, they're shape-shifters

and masters of camouflage.

Specialized organs in their skin change colour

and texture.

The body and arms almost magically assume

postures that make them indistinguishable

from the algae around them.

Males gather in arenas to challenge each other

in battles for dominance and perform dazzling fan dances

for the females.

These are not always well received.

[♪]

Once a large male has found a willing female,

he shadows her smaller body waiting until she's ready.

Until then he'll have to spend a lot of time

repelling rivals trying to steal her away.

Sometimes when the male is locked in battle

with another large male,

a smaller male will disguise himself as a female

and try to sneak up on the object of their desire

and quickly mate with her.

This male is having none of it and chases the sneaker male off.

[♪]

If a female is agreeable, the male approaches her

face-to-face grasping each other with their arms.

The male then uses a specialized tentacle to deposit a small

sperm sac near a sperm-storage organ

next to the female's mouth.

But the chaos in conflict of breeding takes its toll

and for many, the fan dance is their last dance.

By the end of winter, when all the females have

deposited their fertilized eggs on the reef,

much of the adult population dies.

[Birds squawking in distance]

[♪]

Little penguins make their way up the beach after a day spent

foraging at sea.

[Squawking]

They're also known as "fairy penguins".

At only 30 centimetres tall and 11⁄2 kilos,

they're vulnerable to dogs and feral cats found

in other places and their numbers are

diminishing throughout Southern Australia.

Even here, on the relative safety

of the island, the little penguins

seem to be disappearing.

No one understands exactly why, but you wouldn't know it

from the deafening sound of their colonies.

[Squawking]

They're monogamous and dedicated parents during

their breeding season.

Clearly, this chick has been well looked-after.

The pudgy little thing is losing its downy coat

and will soon leave the nest.

[Squawking in distance]

As dawn approaches, the parents all set off together

to find food, heading out to fishing grounds

where they'll eat around 25% of their own body weight

in fish and squid.

It's the start of spring.

Nearly half of the island's annual rainfall

has fallen in the last three winter months

and the island's inhabitants are enjoying a time of plenty.

Spring is the cue for another underwater

inhabitant to start breeding.

In the calm waters of a kelp-covered reef,

a fascinating and cryptic creature makes its home.

Nearly invisible and looking for love, a leafy sea dragon,

a close relative of the seahorse

hides in plain sight.

[♪]

With alga-like protrusions all along his body,

he seems like just another floating piece of seaweed.

[♪]

The way the leafy sea dragon swims, reinforces this illusion.

[♪]

His seaweed-like protrusions are of little use to propel him

through the water.

Instead, two small transparent fan-like fins

waft him gently along with the current in search

of a female.

[♪]

He's not just a master of camouflage,

he's also a devoted dad.

When he does find a mate, he'll carry the eggs

on his tail throughout their incubation.

[♪]

The sheltered bay on the north coast of the island

will provide protection

and a stable water temperature for his young.

Strong southerly winds drive cold deep waters to the surface

and the sea temperature here will remain cool right through

the early spring months.

Kangaroo Island is awash with currents and upwellings.

It has a varied coastline, both sheltered and exposed,

which ensures rich pickings of one sort

or another all year round.

[Birds chirping in distance]

For fish-eating raptors like ospreys,

these are perfect conditions to raise a family.

[Birds chirping in distance]

This pair has constructed an impressive nest,

but they are only responsible for the top storey.

[Birds chirping in distance]

Its foundation were laid by their ancestors.

A nest this size would have been used by several generations

of ospreys.

And with a lifespan of around 10 years,

that means this nest has been constructed

over several decades.

[Birds chirping in distance]

Its continued use is a testament to what the island's waters

can provide, season after season.

[Birds chirping in distance]

At Seal Bay, breeding season is in full swing.

[Barking]

Unlike all other seals and sea lions,

the Australian sea lion has an 18-month breeding cycle.

So the Seal Bay mums have both newborns

and last season's 18-month-old pups.

Each sea lion colony breeds at a different time

to its neighbouring colonies.

[Barking]

This asynchronous breeding means that there are always females to

mate with somewhere.

[Squawking]

This male has been island-hopping in search

of a receptive mate.

His timing has to be spot on as females only come into

oestrous for a few days after giving birth.

[Grunting]

And he doesn't always have the young mothers to himself.

[Barking and grunting]

The beach master will guard the pregnant females

due to give birth,

blocking their path to the ocean.

[Birds chirping in distance]

During this critical period, he doesn't dare leave the

fertile females to feed himself at sea.

He will gradually lose weight and strength.

[Grunting]

Milk production is energy-demanding

and females need to make more regular fishing trips

to nourish their young.

This increases the risk of shark attack.

[Sea lions barking in distance]

Horrific wounds testify to the dangers sea lions face

simply to feed

and mothers are particularly vulnerable.

[Barking]

This mother, having given birth four weeks ago,

carefully keeps herself and her baby out of the fray

and up in the dunes.

But she can't protect him from one thing,

her need to feed,

sometimes leaving him for five days at a time.

Without a backward glance, she slips into the surf

intent on finding enough fish and octopus

to keep herself healthy

and lactating the rich fatty milk he'll need to grow.

He's packing on weight at the rate

of 100 grams per day.

Tucked into the dunes away from chaos on the beach,

he should be safe enough.

But his mother is far less secure.

She'll have to run the gauntlet sharks both going out to

and coming back from the feeding grounds.

Many mothers don't make it and third pups soon starve.

This 18-month-old pup from last season,

still suckling, is desperately searching

for its mother and is in need of a feed.

[Bleating]

In its desperation, it seeks out other lactating

mothers on the beach.

[Barking and bleating]

With their own young to feed, he's rejected repeatedly.

Having lost so much weight already,

it's likely his mother fell victim to the sharks

many days ago.

All this pup can do is wait.

Spring prompts new leaf growth in the eucalypt forests.

[Grunting] And an outbreak of violence

among the densely-crowded koalas.

[Grunting]

The females are going into heat and the males viciously fight

for the opportunity to mate.

[Grunting]

The winner claims his prize.

[Grunting] Tender seduction is the last thing on his mind.

Luckily for the females, they only need to mate

once a season.

That's more than enough on the living arc

of Kangaroo Island.

[Grunting]

Abundant food and a lack of predators mean the koalas

have bred like rabbits.

They're now such a plentiful fixture that birds,

like this white-necked honey eater, use their fur

for a ready supply of nesting material.

The eucalypt forests are overburdened.

But recent wildlife surveys are a source of hope.

Their sterilization and relocation programs

seem to be working.

Koala numbers are down and the forests are showing

signs of recovery.

[Birds chirping in distance]

Unlike the destructive koalas, the island's echidnas are busy

if oblivious caretakers of the arc's ecology.

[Birds chirping in distance]

As the forage, they constantly excavate the

leaf litter and rip up rioting logs.

[Birds chirping in distance]

Their foraging inadvertently helps condition the soil,

spreading nutrients, helping moisture

and air to penetrate, promoting the healthy growth

of plants on the island.

[Birds chirping in distance]

[♪]

After his successful autumn mating,

the female echidna holds up in a log.

[Birds chirping in distance]

An unusual birth is eminent.

[Birds chirping in distance]

As a monotreme, she displays some distinctly

reptilian features:

A lower body temperature and a very unmammal-like way

of giving birth.

[Birds chirping in distance]

Remarkably, she produces a leathery egg,

out of which wriggles a tiny newborn called a "puggle".

It crawls around inside her pouch until it finds

her milk patch.

With no nipples, the mother simply sweats milk

for her puggle to lap up.

Milk production is demanding and the female needs to eat.

[Birds chirping in distance]

She spends 18 hours a day searching for food.

[Birds chirping in distance]

For 45 days, the puggle will remain

in her pouch growing quickly.

Then she'll stash her baby in a nursery burrow,

returning every five days to suckle it.

By the end of spring, she'll simply stop returning

and this puggle will be on its own, hiding in the burrow

from the island's larger reptiles.

The Rosenberg's goanna is a species of monitor lizard,

a throwback to the age of the dinosaurs.

These monitors, Kangaroo Island's largest native

predators, can grow to 11⁄2 metres and weigh over 3 kilograms.

This female goanna has a remarkable albeit one-sided

relationship with the island's termites.

[Birds chirping in distance]

At the end of last summer, she excavated into this termite

mount and deposited 13 eggs.

The industrialist termites then went to work,

sealing up the damage inadvertently creating a prefect

goanna nursery.

For eight months, her eggs incubated

in ideal humidity and temperature

within the protected mount safe from predators

and the winter rains.

When daytime spring temperatures outside,

reach the temperatures inside the mount,

the young begin to hatch.

They have a ready supply of food,

the poor termites who have unwittingly been their hosts

for this whole time.

Once they're around four months old,

the youngsters scratch their way out of the mount.

[Birds chirping in distance]

They bask in the sun before setting off on their own

to forage on insects and spiders.

It's a dangerous business.

They're face intense predation from birds and only 1

in 12 will make it through the first year of their life.

[Distant cawing]

Even so, Kangaroo Island is an arc

for these creatures, too.

The species has nearly disappeared from the mainland

and the island is their last stronghold.

On the beach, other youngsters are making

their spring debut.

The hooded plovers have remarkable managed not only to

survive the winter, but also to protect their eggs

from predation.

They now have two healthy chicks.

But they aren't out of danger yet.

The chicks are incredibly vulnerable to gulls and birds

of prey, and need constant supervision.

At least, here on the beach, they're safe from perhaps one

of the greatest threats on the island, fire.

As summer approaches, hot dry winds whip in

from the mainland deserts and the eucalypts drop their

leaves, creating a build up of dry leaf litter.

[Birds chirping in distance]

In the canopy, tall mallee trees hold

on to their drying leaves, making the situation worse.

From top to bottom, the forest becomes a tinderbox.

[Crackling]

Every few years, lightning or a carelessly-thrown

strikes this tinder.

[Crackling]

Fed by constant winds off the ocean,

massive bushfires sweep through the forests...

...leaping from tree to tree with

breathtaking speed, driving before it the

inhabitants of the living arc.

[Crackling]

Sometimes hundreds of square kilometres burn.

[Crackling]

The echidna can't tap around the flames.

So she quickly burrows into the ground,

her keratin spine shielding her from the heat above.

The eucalypts may be highly flammable,

but they're fire-adapted and recover quickly.

Some even depend on fire for their seeds to germinate.

The ash bed that blankets the forest when the flames burn out,

makes ideal compost.

When the echidna senses the all-clear, she surfaces

and resumes her foraging as though nothing had happened.

[♪]

As she tills the new ground, she helps speed the recovery

of the forest.

[♪]

Down at the beach, the lonely pup has been spared

from the fires of the interior, but is stalked by a greater

danger, hunger.

He's been waiting for his mother to return

from the sea for almost a week.

[Pup bleating]

Chances are she's fallen victim

to one of the great whites patrolling the island.

[Calling]

Finally, the pup hears a familiar sound.

[Bleats] [Sea lion calling]

[Bleats]

It's his mother.

Mum and pup identify each other first by sound.

[Calling]

Then confirm their identity by scent.

This mum may not breed again for another 18 months,

but instead she will devout her time to nurse

and protect her pup.

Australian sea lions are the most devoted mothers

of any species of seal.

And on Kangaroo Island, they have found a sanctuary.

Here, on this remarkable island,

cut off from a rapidly-changing world,

rare and endangered creatures have found a place

to make a last stand

and native wildlife thrives unmolested

by the threats of the modern world.

The ancient battles of survival remain to drive off

rivals, to find a mate, to bear and raise young,

and to escape the worst that nature can throw at them.

But here, where time stands still,

nature can catch a breath and her creatures can thrive

on the living arc that is Kangaroo Island.