01x03 - Finding a Voice

[bunniefuu]

The natural

world is filled with sound.

But, so far, we've been hearing

only part of it.

Some animals call

even before they enter the world.

Others use sound to communicate

with their siblings.

Or call to their parents.

Using the most advanced

audio technology,

we can listen to them all

..to reveal how baby animals

use sound to stay alive

..in a world where the odds

are stacked against them.

The most perilous time

in an animal's life

is at its very beginning.

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 thatis sound.

The Kalahari Desert

in southern Africa.

This is the home of a kind of

burrowing mongoose

Meerkats.

This season's pups are taking

their first steps in the world

outside their family's home.

In time, they will get to know

the sounds of everything

that's going on around them.

But just now, what they want

is breakfast.

And to get it,

they must make themselves heard.

The smallest pup has an injured foot

and keeping up with the rest is

a struggle.

Once they emerge, meerkat pups

need more food

than their own parents

can provide,

so they must persuade other adults

to feed them.

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.

So the youngsters beg continuously.

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.

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.

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.

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.

He calls for help.

Making such a noise, however,

has risks.

At last an adult hears him.

But the heat and exhaustion

have taken their toll.

It may be too late.

His sister encourages him

to get back on his feet.

Once again, the little meerkat

has been savedby sound.

As the pups grow, they will face

many new challenges

..including predators.

Sound will be invaluable to help

them navigate these dangers.

But some baby animals use sound

before they even enter the world.

The swamps of South America.

There is danger everywhere.

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.

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.

The first starts to hatch.

But the youngsters would stand

a much better chance of survival

if they all hatched simultaneously.

So they call to one another

to indicate how close they are

to emerging.

It succeeds in struggling free

from the egg.

But it has a problem.

The nest that once kept them

all safe

..now keeps them trapped.

The calls of the emerged

now encourage the others

to break out of their eggs.

But they still can't get out of

the nest without help.

Individually,

they can barely be heard.

But together they become loud enough

for their mother to hear them.

She has been waiting for these

sounds for nearly 70 days.

And she goes into action.

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.

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.

Sound has guided them on the first

and most hazardous journey

of their lives.

The sounds of an English spring.

For many of the animals

that live here,

they carry important messages.

This bee has discovered that the

flowers are now producing nectar.

She gathers all she can

and then flies back

with the good news.

Her colony has been inactive

during the colder months.

But now the time has come

for action.

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.

But they can feel the vibrations

she makes on the comb

..detecting it with the sense organs

in their legs.

And those that are still asleep

are alerted by her signal that drums

directly into their body.

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.

The unhatched queens are signalling

that they're ready to emerge.

The workers detect the vibrations

of these calls

and in response they start

to release the first queen.

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.

She does that by making a sound

beekeepers call a toot.

Slowed down a thousand times

and using new software that converts

vibration to colour,

we can see

how she creates this call.

The vibrations travel down her legs,

across the comb, and are detected

by the legs of the workers.

As she toots, the whole colony,

for a few seconds,

stops moving

..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.

The sounds in the hive become

increasingly intense,

until finally the swarm leaves

the nest.

They re-assemble

on a nearby branch

..and a new colony

will soon be established.

Many animals,

when they first appear,

rely on their parents

for everything they need

and use sound to keep in touch

with them.

20,00 flamingos breeding

off the Yucatan coast in Mexico.

The noise here is deafening.

The chicks, nonetheless, are able

to exchange intimate sounds

with their parents.

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.

The call of each flamingo is unique.

It's a kind of vocal fingerprint.

How the chick manages in such a din

to memorise and pick out the calls

of its parents is unimaginable.

But it does so.

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.

Amazingly, each family trio —

male, female and chick —

are able to recognise

one another's voices.

Distinguishing individual calls

among this deafening chorus

must be difficult.

And this male can't find his chick.

Adults aren't the only ones

who are searching.

A crocodile is lurking nearby.

The chick calls

But it can't hear

its father's reply.

The crocodile attacks.

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.

It begs for food from any individual

that passes.

Its father, in another part of

the flock, keeps calling.

But the chick is too far away

to hear him.

And this is how many chicks

meet their end.

But not this one.

It keeps calling.

And from across the lagoon

..its father replies.

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.

A wolf pack, in Ontario, Canada.

This communal howl binds the pack

together

and registers their ownership

of a territory.

With only around 500

of these Eastern wolves left,

this heart-stopping sound is now

extremely rare.

But this chorus has some new voices.

It's August and the pups

are joining in.

These youngsters, however,

create a problem

..one that could endanger them all.

Now, in summer,

the days are over 14 hours long.

So the wolves have to hunt

in the light.

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.

Distracted, she doesn't notice that

a black bear is approaching.

This is one of the few animals

that will k*ll a wolf pup.

The wandering youngster seems

unaware of the danger.

But her brothers are.

They sound the alarm.

Alerted, the wandering pup spots

the bear.

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.

It's been a lucky escape

for the pups

..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.

And they are answered.

The sound has alerted an adult wolf.

It's their father.

He's returned with food

for the pups.

As dusk falls, the pack celebrates

with a reunion chorus.

Their voices have been crucial

in keeping the pack together.

But many animals issue

warning calls

that contain

far more complex information.

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.

This one warns of

a flying predator

..and those hearing it look up

and scan the sky.

Danger on the ground is indicated

by a different call.

Best to look around.

Snakes are identified by

a third signal.

A call from the look-out

summons others

to come and help drive it away.

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.

The calls also carry

other information,

such as how fast a predator

is approaching.

And there is one call

which should never be ignored.

This is the high-urgency call,

a warning of immediate danger.

Not to react to this

could be disastrous.

So when you hear this call

..run for your life!

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.

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.

Coral reefs are surprisingly

noisy places.

Many of these sounds are made

by fish.

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.

Her larger body enables her

to make the deepest sound

by snapping her teeth together

to produce pops and pulses.

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.

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.

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.

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.

For ten days, the larval fish drift

out in the open ocean.

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.

The anemone will provide him with

shelter and sanctuary

for the rest of his life.

Sound has brought him home.

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.

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.

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.

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.

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.