Secret World of Sound with David Attenborough (2024) s01e03 Episode Script

1
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 kill 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.