Original subtitles

(HOOTING AND PIPING)

(HONKING)

DAVID ATTENBOROUGH: The natural world is filled with sound.

(CLICKING, THUNDER CRASHING)

(CLUCKING)

(BRAYING)

(GROWLING)

But, so far, we've been hearing only part of it.

Some animals call even before they enter the world.

(SQUEAKING, SOFT HONKING)

(RATTLING SOUND)

Others use sound to communicate with their siblings.

(CHATTERING)

Or call to their parents.

(GROUP SQUAWKING)

Using the most advanced audio technology,

we can listen to them all... (DRAWN-OUT WHINE)

..to reveal how baby animals use sound to stay alive...

(WHINES)

..in a world where the odds are stacked against them.

(HOWLING)

(ANIMATED BIRDSONG)

The most perilous time in an animal's life

is at its very beginning.

(CHUCKLES)

These little cygnets are just three days old.

And at this stage of their lives, and for some months to come,

they are unable to fly.

As a consequence, they are easy prey for a gull or a fox.

But there's just one thing that is of extreme importance

to their survival.

And that...is sound.

(CHIRPING)

The Kalahari Desert in southern Africa.

(CHIRRUPING)

This is the home of a kind of burrowing mongoose...

Meerkats.

(HIGH-PITCHED CHIRPING AND GRUNTING)

This season's pups are taking their first steps in the world

outside their family's home.

(CHATTERS)

(SHORT SCREECHES)

(SQUAWKS)

In time, they will get to know the sounds of everything

that's going on around them.

(FLIES BUZZING)

(SNORTS)

But just now, what they want is breakfast.

And to get it, they must make themselves heard.

(SQUEAKS)

The smallest pup has an injured foot

and keeping up with the rest is a struggle.

(HIGH-PITCHED GRUNTS)

Once they emerge, meerkat pups need more food

than their own parents can provide,

so they must persuade other adults to feed them.

(PURRS)

But in this harsh country,

food isn't easy to find.

Temperatures can reach over 45C,

and most food is hidden underground.

So a meerkat's life is dominated by digging.

They may have to shift their entire body weight in sand

to find just one mouthful to eat.

After all this hard work, the helpers can be more interested

in feeding themselves than the pups.

(RAPID PURRING)

So the youngsters beg continuously.

(SQUEAKING AND PURRING)

The moment food is found,

each pup switches to a high-pitched begging call

in an attempt to ensure that it, and not its siblings,

gets the mouthful.

(ALL CHATTERING AND SQUEAKING)

And those who make this begging call more intensely

get the food.

The biggest pup is successful, and the smallest misses out again...

..and again.

Staying close to an adult increases the chances of being heard

and being fed.

But this brings its own hazards.

(PUP SQUEAKS)

Finally, the small one does get a mouthful.

But he takes a long time to eat it...

..and when he looks up, everyone else has gone.

(SOFT SQUEAK)

If there's one thing more important to a meerkat than food,

it's family.

Without their guidance, he wouldn't last for long in this intense heat.

(CHIRPS)

He calls for help.

(CHIRPS)

(LONG CHIRP)

Making such a noise, however, has risks.

(CHIRPS)

(DISTANT CHIRP)

At last an adult hears him.

(SQUEAKING)

But the heat and exhaustion have taken their toll.

It may be too late.

His sister encourages him to get back on his feet.

(CHEEPING)

Once again, the little meerkat has been saved...by sound.

(URGENT BARKING)

As the pups grow, they will face many new challenges...

..including predators.

Sound will be invaluable to help them navigate these dangers.

(CROAKING)

But some baby animals use sound before they even enter the world.

(BIRDS HOOT AND PIPE)

The swamps of South America.

There is danger everywhere.

(SNORTING)

One vigilant mother here is on guard.

A caiman.

Over two metres long and weighing around 60 kilograms,

she lives by ambushing prey in these murky waters.

On the bank, close to the river,

there is a great mound.

It's her nest.

And inside, there are her eggs,

30 or so of them.

Her nest-guarding duties, however, are coming to an end.

The young, still within the eggs,

are approaching one of the most dangerous moments

they will ever face.

And they are squeaking.

(PULSING SQUEAKS)

Their chances of survival will depend on these noises.

We have a special camera with 60 super-sensitive microphones

which can show us which squeak is coming from which egg.

(SQUEAKING)

(SQUEAKING)

The first starts to hatch.

(SQUEAKING)

But the youngsters would stand a much better chance of survival

if they all hatched simultaneously.

(VARIOUS TONES OF SQUEAKING)

So they call to one another

to indicate how close they are to emerging.

(SHORT GRUNTS AND SQUEAKS)

It succeeds in struggling free from the egg.

But it has a problem.

(BIRDS CHIRPING)

The nest that once kept them all safe...

..now keeps them trapped.

(GULPING SQUEAKS AND HONKS)

The calls of the emerged now encourage the others

to break out of their eggs.

(HONKS)

But they still can't get out of the nest without help.

Individually, they can barely be heard.

(HONKS)

But together they become loud enough for their mother to hear them.

(MANY HONKING SIMULTANEOUSLY)

(CHORUS OF HONKS)

She has been waiting for these sounds for nearly 70 days.

(ANIMATED HONKING)

(HONKING)

And she goes into action.

(HATCHLINGS HONK AND CHITTER)

One by one, she picks her hatchlings up

and takes them down to the water.

The last to hatch are sometimes forgotten.

But with the nest fully opened, they can now get out.

But they have no idea where their mother is.

(HONK AND CHITTER) Once again, they are saved by sound.

They can recognise the voices of their siblings

and follow the sound to the water...

where their mother will guard them all.

(CHITTERING)

Sound has guided them on the first and most hazardous journey

of their lives.

(CHITTERING)

(CUCKOO CALLS)

(SHEEP BLEATS, WOODPECKER TAPS, WOOD PIGEON COOS)

(BLACKBIRDS SING, BEES BUZZING)

The sounds of an English spring.

(BIRDSONG AND BUZZING)

For many of the animals that live here,

they carry important messages.

(BEE BUZZING)

This bee has discovered that the flowers are now producing nectar.

She gathers all she can...

and then flies back with the good news.

(BUZZES)

Her colony has been inactive during the colder months.

But now the time has come for action.

(HIVE BUZZES)

(AMPLIFIED BEATING SOUND)

The forager conveys her news

by repeatedly thumping her abdomen on the comb.

Bees, like many insects, don't have ears,

so they can't hear airborne sounds.

(BEATING SOUNDS)

(BUZZING)

But they can feel the vibrations she makes on the comb...

(RAPID TAPPING)

..detecting it with the sense organs in their legs.

(ECHOEY TAPS)

And those that are still asleep

are alerted by her signal that drums directly into their body.

(CONSTANT TAPPING)

Eventually, the workers are roused into action.

Within days, the hive's depleted stores

are restocked with nectar and pollen...

..food that will fuel the production of the next generation of bees.

When a colony has grown so much

that it contains around 40,000 individuals,

it prepares to swarm.

But a new swarm will need a queen, and the old queen has already left.

There are several contenders for the role

who are developing in particularly large cells.

Tiny super-sensitive microphones

enable us to hear an extraordinary call,

like the quacking of a duck.

(REPEATED QUACKS)

The unhatched queens are signalling

that they're ready to emerge.

(QUACK-LIKE CHORUS)

The workers detect the vibrations of these calls

and in response they start to release the first queen.

(QUACKING)

If two queens are released at the same time,

they will fight one another to the death.

So, she does her best to make sure

that her rivals remain in their cells.

(WHINING SOUND)

She does that by making a sound beekeepers call a toot.

(WHINY TOOT)

(DEEPER HUM)

Slowed down a thousand times

and using new software that converts vibration to colour,

we can see how she creates this call.

(HUM)

The vibrations travel down her legs,

across the comb, and are detected by the legs of the workers.

(TOOTING)

As she toots, the whole colony, for a few seconds,

stops moving... (RUSTLING STOPS)

..in recognition that a new queen has ascended the throne.

Each toot is answered by a chorus of quacks

from the rival queens who are still within their cells

and eager to emerge.

But as long as the new queen continues tooting,

the workers will not release her rivals.

The crowned queen toots repeatedly until, after a few days,

she prepares to depart with half of the workers in a swarm.

(HUGE SQUEAKS AND RUSTLING)

The sounds in the hive become increasingly intense,

until finally the swarm leaves the nest.

(UPLIFTING MUSIC)

They re-assemble on a nearby branch...

..and a new colony will soon be established.

(CHORUS OF CROAKS AND HONKS)

Many animals, when they first appear,

rely on their parents for everything they need

and use sound to keep in touch with them.

(CROAKING AND HONKING)

20,00 flamingos breeding off the Yucatan coast in Mexico.

The noise here is deafening.

(CHORUS OF GRUNTS AND HONKS)

The chicks, nonetheless, are able to exchange intimate sounds

with their parents.

(CROAKS)

This one has only just hatched.

The colony provides protection for its members.

But living in such a huge crowd is nonetheless hazardous.

the chick's very survival depends on its ability

to recognise the voices of its parents.

So it must learn to do so quickly,

because within ten days of hatching,

it and its parents will leave the nest.

(CROAKS, CHICK CHIRRUPS)

The call of each flamingo is unique.

It's a kind of vocal fingerprint.

(CROAKS) How the chick manages in such a din

to memorise and pick out the calls of its parents is unimaginable.

But it does so.

(CROAKS)

(CHIRRUPING)

(HONKING)

(SOFT MUSIC)

This one is taking its first steps out of the nest.

But it's not really ready for the wider world.

Eventually it becomes a little braver.

but now it has a new problem.

It's growing fast and both it and its parents need food.

To get it, the adults must leave the colony and their chick.

The chick cannot fly and will be unable to do so

for another three months.

So, until then, it's very vulnerable.

There are hundreds of youngsters with the same problem.

The young gather together in an enormous creche.

There's safety in numbers.

A few adults have stayed behind to keep the creche together.

The others eventually return.

But now each must recognise its own chick

among the densely packed flock of thousands.

(CACOPHONY OF CLUCKING AND CHITTERING)

Amazingly, each family trio — male, female and chick —

are able to recognise one another's voices.

(CROAKING)

Distinguishing individual calls among this deafening chorus

must be difficult.

And this male can't find his chick.

(CROAKING)

Adults aren't the only ones who are searching.

A crocodile is lurking nearby.

(CALLS) The chick calls...

(CROAKS)

But it can't hear its father's reply.

The crocodile attacks.

(ANXIOUS CHITTER)

(HUGE CHORUS OF CALLS AND CROAKS)

It's failed to grab a chick,

but it did create dangerous confusion in the flock.

The chick has become separated from the others

and seems to be lost.

(CHITTERS)

It begs for food from any individual that passes.

(CHITTERS)

Its father, in another part of the flock, keeps calling.

(CROAKS)

But the chick is too far away to hear him.

And this is how many chicks meet their end.

But not this one.

(HIGH-PITCHED CHIRRUP) It keeps calling.

And from across the lagoon... (CROAKS)

..its father replies.

(CHITTERING AND CROAKING)

The unique sound of the chick's voice has been recognised

by its father, and the two at last are re-united.

As young animals grow,

they learn to recognise oncoming dangers and become big enough

for their voices to sound an alarm.

(CHORUS OF HOWLS)

A wolf pack, in Ontario, Canada.

(EERIE HOWLING)

This communal howl binds the pack together

and registers their ownership of a territory.

(WOLVES HOWLING)

With only around 500 of these Eastern wolves left,

this heart-stopping sound is now extremely rare.

(ALL HOWLING)

But this chorus has some new voices.

(HOWLING AND BARKING)

It's August and the pups are joining in.

These youngsters, however, create a problem...

..one that could endanger them all.

(BIRDSONG)

(DRONE OF BUZZING)

(CHIRPS)

Now, in summer, the days are over 14 hours long.

So the wolves have to hunt in the light.

(WHINES)

The pups are too big to stay in the den,

but too inexperienced to join in the hunt.

So the adults leave them in an open area - a rendezvous site.

Its very openness makes it a great place for play.

But this is a particularly dangerous time in their lives.

Half of them won't live beyond their first year.

What happens here and now will determine whether these will do so.

Two of the youngsters know exactly where they are supposed to stay.

But their sister can't resist exploring.

(HIGH-PITCHED TWEET)

Distracted, she doesn't notice that a black bear is approaching.

This is one of the few animals that will kill a wolf pup.

The wandering youngster seems unaware of the danger.

But her brothers are.

(DISTANT HOWLING)

They sound the alarm. (BOTH HOWL)

Alerted, the wandering pup spots the bear.

(HOWLING)

(BARKS)

(BARKING AND HOWLING)

Now the lives of all three pups are at risk.

But, as the bear moves in, she hears a different call.

It's her own cub.

And he needs his mother.

(GROANS)

(GROANS)

(HOWLS)

It's been a lucky escape for the pups...

(HOWLING)

..but they are not yet in the clear.

The pups' howls are shorter and higher-pitched

than those of the adults...

..but they can still be heard many miles away.

(DEEPER HOWL) And they are answered.

(HOWLS)

The sound has alerted an adult wolf.

(PURPOSEFUL MUSIC)

(HOWLS)

It's their father.

(PUPS WHIMPER)

He's returned with food for the pups.

(EXCITED YELPS)

As dusk falls, the pack celebrates with a reunion chorus.

(DISTANT CHORUS OF HOWLS)

Their voices have been crucial in keeping the pack together.

(DISTANT EERIE HOWLS)

But many animals issue warning calls

that contain far more complex information.

(WHIMPERING)

The meerkats, as they grow, learn how to find their own meals.

And they are discovering how to avoid becoming someone else's.

The desert is full of hungry mouths...

..and meerkats are small and obviously edible.

Their defence is neither armour nor weapon.

Instead, they use sound -

a complicated system of alarms.

These calls are not just generalised alerts.

(SHORT WHOOPS)

This one warns of a flying predator...

(SHORT WHOOPS CONTINUE)

..and those hearing it look up and scan the sky.

(WHOOPING)

Danger on the ground is indicated by a different call.

(HIGHER-PITCHED HOOTS)

Best to look around.

(GRUNTING)

Snakes are identified by a third signal.

(GRUNTS)

A call from the look-out summons others

to come and help drive it away.

(COBRA HISSES, MEERKATS GROWL)

Meerkat warnings are so detailed

that they can be a bit confusing for youngsters.

So the best thing is to do what everybody else is doing.

(SQUEAKS)

The calls also carry other information,

such as how fast a predator is approaching.

And there is one call which should never be ignored.

(SHORT GRUNTS)

This is the high-urgency call, a warning of immediate danger.

(SERIES OF SHORT GRUNTS)

Not to react to this could be disastrous.

So when you hear this call... (GRUNTING)

..run for your life!

(GRUNTS)

(BIRDSONG AND CACKLING)

Sounds in the open air are important for many animals.

But there is another world of sound with which we are far less familiar.

We can't hear very well underwater,

because our ears are shaped to work in the air.

But there is a way in which we can eavesdrop on this underwater world,

by using a special kind of underwater microphone

called a hydrophone.

(PULSING CHIRP-LIKE SOUNDS)

I don't know exactly what's making those noises,

it's probably some small invertebrates or maybe a small fish.

We've known for some time that quite a lot of fish produce sounds.

It's only recently, however, that scientists have discovered

just how widespread that ability is.

The ocean covers around 70% of our planet's surface.

And sound also plays a crucial role

in the lives of many of the animals that live in it.

(CROAKING AND CREAKING SOUNDS)

Coral reefs are surprisingly noisy places.

(DEEP CROAKS)

Many of these sounds are made by fish.

(GRUNTING AND CROAKING)

Here too, sound can be important

from the very beginning of an animal's life.

Without it, one of the most strikingly coloured fish on the reef

would never find its way home.

It's just days before a full moon

and this female clownfish is about to lay her eggs.

Clownfish live in small communities,

each based around a particularly large anemone.

In this busy colony, only two adults will reproduce -

the largest, the dominant female...

..and her partner, the next in size, the dominant male.

There's a strict hierarchy, one that's based on size,

but policed by sound.

(CROAKY GRUNTS)

Her larger body enables her to make the deepest sound

by snapping her teeth together to produce pops and pulses.

(PULSING GRUNTS)

(SHORT GRUNTS)

The male signals his subordinate status

by quivering his head

and producing a purring noise.

And everyone around the anemone knows that she is the boss.

At full moon, she will be ready to lay eggs.

So the group needs to find a firm surface for them.

A coconut shell, brought in by the currents,

would be ideal.

But it needs to be moved into the right position.

She indicates her needs with a low-pitched grunt,

and the juveniles in the colony comply by shaking their heads.

(MYSTERIOUS MUSIC)

Working together, they manoeuvre the coconut shell into position.

Team work takes a lot of co-ordination,

and a lot of grunting and jaw-grinding.

Next, the stage needs to be prepared.

And at last, the moment arrives.

She lays her eggs in neat lines.

The male then makes HIS contribution - fertilising the eggs.

Now he takes charge.

For the next seven days, he will fan and clean the eggs as they develop.

Three more days and the embryos begin to respond

to the sounds around them.

(GRUNTING)

The sounds that they hear now could play a critical role

in the next stage of their lives.

But a different sort of noise is already threatening their survival.

The male reacts to the noise of a boat as he would to a predator.

If there is constant motor traffic,

he spends more time hiding and less tending the eggs...

so they are more vulnerable to predators and disease.

(THRUM OF MOTOR BOAT)

The noise around these reefs has increased dramatically

in recent decades, and that has affected the lives of the fish here.

But the clownfish father has managed to keep his young healthy,

and a week later, they begin to change.

The plankton-sized fry wriggle free

and are then swept away from the reef by ocean currents.

(UPLIFTING CELLO MUSIC)

For ten days, the larval fish drift out in the open ocean.

(BIRDS CRY)

By the time that each is about the size of a grain of rice,

they are strong enough to swim against the current.

And they need to find their way back to a reef.

The key to their homecoming is sound.

Underwater, the sounds of a reef can be heard for many miles around.

The tiny young clownfish can hear this noise and swim towards it.

They can even judge the health of a reef by its sound.

The noisier it is, the more vigorous it is.

(CLACKING AND BUBBLING)

The anemone will provide him with shelter and sanctuary

for the rest of his life.

Sound has brought him home.

(UPLIFTING MUSIC)

For these fish, and for many other baby animals,

sound is crucial for launching themselves into the world

and learning what they need to stay safe and to thrive.

For them, sound is survival.

(GENTLE MUSIC)

What's one of the close ones over here...

Biologist Mark Meekan became fascinated by coral reefs

more than 30 years ago.

'Coral reefs are these incredible habitats

and I've always been struck by their diversity

and just incredible beauty.'

Today he is fighting to save these reefs

from the ravages of climate change.

This is Australia's Ningaloo Reef

that stretches along the country's western coast.

But over decades of research,

Mark discovered something else —

that coral reefs are full of sound.

A hunch about the significance of this inspired him

to try and find a way to use this sound to save coral reefs.

'If we could hear underwater,

we would hear this cacophony of hoots and yowls,

really strange screams made by fish.

And these little fish may actually be helping the coral to grow.

Basically, by sheltering in the coral, pooping in the coral,

fertilising the coral.

A healthy reef is really very noisy.'

This sound is key.

After hatching, reef fish are swept out to sea.

When they return, they use these healthy sounds

to choose the reef that will be their home.

And this was just a wow moment.

We suddenly thought, "We can actually use this to help the reef."

The result is a multi-million-dollar project with one goal —

to discover if sound can also help save a dying reef.

The first step is to collect three and a half tons of coral debris.

It's alive and extremely vulnerable.

Mark's team build 60 experimental reefs.

Underwater speakers are guided to some of these and turned on.

It's their job to attract fish

by playing the sounds of a healthy reef.

The results will be compared to experimental reefs

without speakers.

At Ningaloo, it's a new moon.

Tonight, the reef fish are coming home.

(BUBBLING AND POPPING SOUNDS)

At the experimental sites, speakers are on,

broadcasting the sounds of a healthy reef.

OK, get ready, Daphne.

They are laying out light traps

and assessing if the speakers are attracting fish

to the experimental reefs with sound

versus ones without.

And they are!

'We actually got the fish to come.

They arrived in big numbers on the reefs.'

Mark's team have been photographing these reefs for 12 months.

Now they're going to see if the fish have helped the coral to grow again.

So, on the left here, we've got our patch reef model from one year ago.

And on the right-hand side, our reef model from a couple of days ago.

You can see fairly obviously already

there's been a fair bit of growth over the year.

Wow! This one's roughly 20cm across,

maximum diameter,

and the same colony a year later, it's almost 40.

So we've doubled in size. Fantastic, man.

(LAUGHS)

Wow.

(SOUNDS OF PIPS AND POPS)

oral reefs today are in such a state

that we're beyond shouting to everybody that it's bad.

We have to move into doing something about it.

The sound made by fish might just be a vital tool

to help scientists save coral reefs around the globe.

(SPRINGTIME BIRDSONG)

(CUCKOO CALLS)

(BLACKBIRD SINGS)

(SHEEP BLEATS)

(WOOD PIGEON COOING)

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