Original subtitles

(CHIRRUPING AND ANIMAL CALLS)

(SQUAWKING AND CHIRPING)

DAVID ATTENBOROUGH: The natural world is filled with sound.

(THUNDERCLAP)

(CLUCKING)

(BELLOWS AND SCREECHES)

(ROARS HOARSELY)

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

(CHIRRUPS AND CLICKS)

(PULSATING SQUEAKS)

The most advanced audio technology

can now record sounds that we can't even hear.

(DEEP VIBRATING HUM)

(RATTLING)

(WHOOPING CALL)

(SOFT CLICKING)

(CHIRPS)

For some animals, sound is the key to survival.

(BUZZING)

(CLICKS AND SQUEAKS)

They use sound to hunt...

(FRANTIC SCREECHING)

(DEEP GROWLING)

..and escape.

(PADDING AND RUSTLING)

(SOFT THUDDING)

Sound can make the difference between life and death.

(SCUFFING)

(SCUFFING AND PATTERING)

(HISSES)

It's time to open your ears

to life as you've never heard it before.

(GRUMBLING AND TRUMPETING)

(CHIRRUPING AND TWITTERING)

(SQUAWKING AND SCREECHING)

(DEEP RUMBLING GROWL)

(CHIRRUPING)

(SQUAWKING AND SCREECHING)

(GRUNTING)

(CHITTERING AND CROAKING)

(CACOPHONY OF ANIMAL CALLS)

(SOFT MOANING)

(CHIRPS)

Dawn on the African savanna.

(GRUNTING)

(BELLOWING)

(GRUNTING AND BELLOWING)

It's the best time of the day

for lions to broadcast their message.

(GRUNTS)

(BELLOWS HOARSELY)

(BELLOWS HOARSELY)

(BELLOWING CONTINUES)

As the sun rises, cold air is trapped near the ground.

Because it's denser than warm air,

it allows sound to travel further before dissipating.

(GRUNTING ECHOES)

(GRUNTS)

It's a declaration to other prides

of his ownership of these hunting grounds...

..and the key to his and his pride's survival.

(RUMBLING GROWL)

(BELLOWS)

It's one of the greatest acoustic displays of power in nature.

(HIGH-PITCHED BELLOW)

(DEEP RUMBLING ROAR)

(GRUNTS AND ROARS)

(GRUNTS AND ROARS)

(GRUNTS)

He can be heard up to five miles away.

(RUMBLING ROAR)

(DEEP GRUNTING)

But even this isn't far enough

to reach the boundaries of their territory.

It spans over 150 square miles.

To defend an area as immense as this,

the pride must roam and roar.

(SONOROUS RUMBLING ROAR)

But some members are too small to get very far.

(YOWLS)

This pride is protected by three brothers.

Together, they head off on patrol.

A lion's roar sends a clear message to other prides.

But sound can also be used in more subtle ways.

(CHIRRUPING)

(TWITTERING AND CHIRPING)

(LOW BUZZING)

(BUZZING CONTINUES)

(BUZZING AND HUMMING)

(INTENSE BUZZING)

This garden is filled with the sound of the buzzing of bees.

It's a sign that the plants have been successful in attracting pollinators

with their brightly-coloured flowers

and seductive smells.

(INTENSE BUZZING)

The buzzing sound we associate with bees

is a by-product created by the beating wings as they fly.

(BUZZING)

(BUZZING)

But some bees take advantage of their buzz,

and use it, in a surprisingly sophisticated way,

to get to a supply of food that others can't reach.

(BUZZING)

One such bee lives underground.

(BUZZING THRUM)

These are buff-tailed bumblebees.

For the colony to survive,

each worker must collect as much pollen as she can

with which to feed their young.

(CONTINUOUS BUZZING THRUM)

Searching for it is a constant preoccupation.

(SOFT RUSTLING)

(INTREPID MUSIC)

(BUZZING)

It's spring in England...

(BUZZING)

(SOFT FLUTTERING)

(FLUTTERING AND CLICKING)

(GENTLE BUZZING)

..and she is not the only one in search of food.

Competition for pollen and nectar is high.

And poppies are putting on a show.

Packed full of pollen,

they flaunt it at the top of long filaments called anthers.

(BUZZING)

These flowers are a free-for-all...

..and everyone is seeking a share of the bounty.

(BUZZING)

(HARMONIOUS BUZZING)

But she doesn't need to compete with other species

if she can find a particular kind of flower.

(SOFT FLUTTERING)

She's found what she's been looking for...

(SOFT BUZZING AND FLUTTERING)

..a type of nightshade.

(BUZZING)

Its flowers are less striking

and, unlike poppies,

its pollen is locked up inside long yellow anthers.

The only way for it to escape is through tiny holes.

The bumblebee holds the key

that unlocks this treasury of pollen.

Sound.

Locking in her wings,

she uses her flight muscles to vibrate her whole body,

buzzing up to 370 times a second.

(INTENSE BUZZING)

This sonic assault blasts the pollen loose.

(BUZZING CONTINUES)

She then grooms the pollen down into sticky sacs on her legs

and flies off to the next flower.

(INTENSE BUZZING)

Very few species can buzz-pollinate in this way,

so bumblebees have nearly exclusive access to the nightshades' pollen.

(INTENSE BUZZING)

The bee's pollination buzz is higher pitched

than that made during flight.

It's the same frequency as the musical note D.

(HIGH-PITCHED BUZZING)

She's like a living tuning fork.

Some buzz pollinators can vary their pitch,

fine-tuning it to suit different flowers.

So pollen is released in the most efficient way.

Fully loaded, she returns to the hive.

She has successfully used sound

to help secure the pollen her colony needs.

(CONTINUOUS HUMMING)

We tend to take bees for granted...

but it's not just plants that depend on them, we do too.

Many of our crops rely on pollinators

like bees and other insects.

Worryingly, bee populations,

together with those of many other insect pollinators,

are in serious decline around the world.

And with their numbers plummeting,

both the natural world and our own food supplies are in danger.

(CONTINUOUS BUZZING)

Bees need our help

and without them and the sound of their buzz,

the future for us all would look bleak.

(INTENSE BUZZING)

Sound provides the key to this partnership

between bumble bees and plants.

But not all relationships in nature are as harmonious.

(BIRDSONG)

(DISTANT BIRD CALLS)

The Bahama Islands in the Caribbean.

The sand flats here are the home

of garden eels and razorfish.

(WATER BURBLES GENTLY)

(FAINT SQUEAKING)

But there is trouble in paradise.

(ECHOEY CLICKING AND SQUEAKING)

The sound of approaching danger.

(ECHOEY RHYTHMIC SQUEAKING)

It's a cue to hide.

(ECHOEY WHISTLING AND SQUEAKING)

(SQUEAKING AND CLICKING)

A mixed groups of spotted and bottlenose dolphins.

(SQUEAKING AND WHISTLING)

Their whistles and squeaks are part of their continuous conversations...

(CLICKING)

..with a range of frequencies seven times greater than ours.

(HIGH-PITCHED SQUEAKING)

(CLICKING AND SQUEAKING)

To hunt for food, they must split up.

(CLICKING AND WHISTLING)

Each dolphin needs 15 kilograms of fish a day.

(CHIRRUPING)

But, thanks to their rowdy arrival,

there isn't a morsel in sight.

The hunt is on.

(LOW GRUMBLING)

(LOW GRUMBLING)

(CLICKING AND CHIRRUPING)

The bottlenose dolphins now switch from whistles

to bursts of fast clicks,

up to 200 per second.

(RAPID CLICKING)

(INTENSE HIGH-FREQUENCY CLICKING)

These high-frequency clicks are sent out like a sonar beam

through an organ in the forehead called a melon,

with which they can scan the ocean floor.

(RAPID CLICKING)

When the beam of sound hits a fish hiding beneath the sand,

it's reflected back, revealing its location.

(CLICKING)

Using echolocation,

the dolphins are able to create a visual map

of what is hidden under the sea floor.

(RAPID CLICKING)

Some of these clicks are ten times higher

than the sounds our ears can detect.

(HIGH-PITCHED CLICKING)

(SILENCE)

High-frequency sounds are most effective at close range,

enabling the dolphins to pinpoint their prey with great precision.

But there is more to these pirouettes than meets the eye.

(CLICKING)

Scientists have recently discovered that bottlenose dolphins

favour their right side when scanning the seabed.

The right side of the head usually produces the sonar clicks.

And the right side is also better at detecting the returning echo.

(CLICKING)

(MELLIFLUOUS MUSIC)

The only evidence that there has been a sonar search here

are small craters in the sand.

Dolphins use sound with great effect

to find their food.

But in other places, a quieter approach

is the key to a successful hunt.

(DISTANT SQUAWKING)

(DISTANT CHIRRUPING)

(SQUAWKING)

(SOFT RUSTLING)

In the forests of Manitoba in Canada,

the great grey owl is a master of silence.

Specially-adapted flight feathers

allow him to approach silently.

(WIND GUSTS GENTLY)

His prey is hidden under a blanket of snow.

(SOFT SNUFFLING)

Voles.

Finding them in this vast, snow-covered landscape

seems an impossible task.

To combat the extreme cold,

he must catch seven voles a day.

His ears will be his most effective weapon.

(SNUFFLES AND SQUEAKS)

Voles need to feed continuously

or they will freeze to death.

(HIGH-PITCHED SQUEAKING)

(PATTERING FOOTSTEPS)

They constantly dig tunnels to find new food supplies...

..unaware of the danger above.

(SNUFFLING AND SCUFFLING)

Hidden under a face covered by feathers,

the owl's ears are positioned

at slightly different levels on either side of his head.

Sound will hit one ear before the other,

allowing him to pinpoint his prey with great accuracy.

His acoustic arsenal doesn't stop there.

The large facial ruff,

formed from feathers that are particularly stiff and dense,

help to amplify sound and funnel it towards the ears.

(RUSTLING AND SQUEAKING)

Through half a metre of snow,

the sound of scampering feet is inaudible to us.

But it's loud enough for him.

With the help of a specialist camera

equipped with 60 highly-sensitive microphones,

we can reveal what the owl is hearing.

(FAINT SCUFFLING)

The camera visualises where the vole is beneath the snow.

(SNUFFLES)

And he's off.

(SCUFFLES AND SNIFFS)

(CRUNCHING)

This time he's missed.

(RUSTLING)

Despite his acute hearing, hunting in snow is a challenge.

The snow not only muffles sound,

it bends it too.

While it appears as if the vole is here,

it's actually over there.

The only way to defeat this acoustic illusion,

is for the owl to get directly above the vole,

where sound is no longer distorted by the snow.

(WIND GUSTS SOFTLY)

As he flies, he tracks the sound as it changes.

(SUSPENSEFUL MUSIC)

The closer he gets, the less the sound is bent.

Directly above the vole, he can pinpoint his target.

(VOLE SQUEAKS)

The great grey owl's hearing

is its key to securing a meal.

For others, it's crucial to avoid being eaten.

(CHIRRUPING)

In the Arizona desert, it's the height of summer.

Daytime temperatures are over 40 degrees Celsius.

So it's best to be active at night.

Filming under infra-red lights with a specialist camera...

..we can see everything.

(WIND GUSTS SOFTLY)

But to a kangaroo rat,

it's nearly pitch black.

In the dark, her most valuable ally is sound.

(WIND GUSTS AND PLANTS RUSTLE)

(SNIFFS)

Her mission tonight is to collect as many seeds as she can.

But food is scarce...

..and competition fierce.

(SNIFFS)

And, in the dark, it's hard to spot danger.

(SCUFFLING)

(FOREBODING MUSIC)

(SOFT RUSTLING)

Her ears are 90 times more sensitive than ours...

and hollow spaces in her skull

act like an echo chamber,

amplifying the faintest of sounds.

(RUSTLING)

(RUSTLING)

But she has another problem tonight.

(WIND HOWLS)

(WIND GUSTS AND SAND RUSTLES)

Wind.

(WIND HOWLS)

(SAND RUSTLES)

She might not hear a predator until it's too late.

This time, it's just a stick.

But, in the darkness, she's right to be cautious.

Snakes can pick up the sounds of scampering feet

through their lower jaw.

(SOFT RUSTLING)

(SNIFFS)

She's made it to her favourite feeding spot.

But she's not alone for long.

She warns him to stay away by drumming her foot on the ground.

(TAPPING)

(TAPPING ECHOES) He can decipher her size and strength

from her signal.

(TAPPING)

He drums back.

(TAPPING)

It's a battle of beats.

(TAPPING ECHOES)

(TAPPING CONTINUES)

Stalemate.

There's only one way to resolve this.

(DRAMATIC ORCHESTRAL MUSIC)

(MUSIC FADES)

Dinner time at last.

She hears something.

(OMINOUS MUSIC)

Just out of striking range, she drums again...

(TAPPING)

..this time to alert the snake it's been spotted.

But just to be sure...

(SCUFFING AND RUSTLING)

(RUSTLING)

(HISSES)

Message received.

While kangaroo rats use the ground as a drum

to drive their enemies away...

others are summoned by seismic sounds.

(LOW GRUMBLING)

(LOW GRUMBLING)

(WIND WHISTLES)

(WHOOSHING)

Amboseli National Park in Kenya.

It hasn't rained here in nearly a year...

(DEEP GRUMBLING)

..and the dry season has turned into a severe drought.

(CACOPHONY OF SCREECHING AND SQUAWKING)

For elephants, the situation is desperate.

(LOW GRUMBLING)

With no food or water for miles around,

the matriarch must wait for a message...

..a sound that will travel through the ground.

(LOW GRUMBLING)

(HUFFING)

If it arrives, it will guide them from disaster.

The young calves are especially vulnerable.

(GRUNTING)

Their mother's milk will dry up if rain doesn't arrive soon.

(WIND WHISTLES)

(LOW GRUMBLING)

(RUMBLING AND GUSTING)

A hundred miles away, a storm has broken...

(THUNDERCLAP)

..and the elephants have heard.

(THUNDER RUMBLES)

(LIGHTNING CRACKLES)

Not with their ears...

..but with their feet.

(RAIN SPLATTERS)

The sound of the storm sends low-frequency vibrations

through the ground.

(AMPLIFIED RUMBLING)

The herd picks up the vibrations

through a network of nerves in the fatty pads of their feet.

(AMPLIFIED RUMBLING)

(HEAVY SPLASHING)

By lifting one foot,

they can make better contact on the ground with the other.

(STEADY PATTERING)

It's the message the matriarch has been waiting for.

(LOW GRUMBLING)

She gives a low "let's go" rumble.

(LOW GRUMBLING)

It's echoed by her sisters.

(GRUNTING AND GRUMBLING)

The journey ahead is treacherous...

..but the sound of the storm will be their guide.

(TRUMPETING)

(GRUNTS AND SCREECHES)

(LOW GRUMBLING)

(WIND WHOOSHES)

Finally, after two days on the move...

..they've made it.

Their ability to detect sound a hundred miles away

has saved the herd.

(THUNDER RUMBLES)

Elephants aren't the only ones who respond to the sound of rain.

But sometimes sounds can be deceptive.

In Vancouver, in Canada, it's also raining.

(HISSING AND PATTERING)

(STEADY PATTERING)

Underground the soil is teeming with earthworms.

Some rise to the surface in search of food or mates.

But if the ground isn't wet enough, they risk drying out.

Sound helps them pick the opportune moment.

(SPLASHING)

As the rain hits the ground,

it creates vibrations that travel down into the soil.

They are picked up by sensitive nerve cells in the worm's skin.

As they rise, the tumultuous pitter-patter

is music to their senses.

(STEADY PATTERING)

But it is also a sound that can seal their fate.

Worms aren't the only ones on the move.

(GULLS SQUAWKING)

Outside the city, a flock of gulls

are co-ordinating their morning departure from the roost.

(CACOPHONY OF SQUAWKING AND SCREECHING)

Thanks to the rain, they've got a special meal on the menu today.

Worms!

But by the time they arrive,

the downpour is over...

..and the worms are already retreating.

Dining options look scarce...

..but the gulls have a crafty trick.

For it to work, they must find their rhythm.

(SOFT RHYTHMIC TAPPING)

Paddling creates vibrations that likely mimics the sound of rain.

It's a dance of deception.

(MUFFLED TAPPING) The worms rise once again.

(MUFFLED TAPPING)

They can't resist the rhythmic rain dance.

(RHYTHMIC TAPPING)

(STEADY PATTERING)

Another shower brings an acoustic climax.

(RHYTHMIC TAPPING)

The rainy season will last all winter,

so worms are on the menu until spring.

For these gulls, the cunning use of sound

helps them win an easy meal.

But in other parts of the world,

the stakes are higher for both predator and prey.

(LOW GRUMBLING)

(LOW GRUMBLING)

(INSECTS CHIRRUPING)

(LION GRUNTS)

As night falls on the African savanna,

the air is filled with sounds of a formidable hunter.

(LIONS BELLOW)

(BELLOWING CONTINUES)

(BELLOWING)

(DEEP RUMBLING GROWL)

On the other side of the territory,

the females of the pride are preparing to hunt.

Over 30 strong, they must make a kill every night.

(SOFT GROWLING)

Close by, a hyena den.

(SOFT SQUEAKING)

The adults must also head out to find their next meal.

Hyenas will often steal if the opportunity arises...

..even from their deadliest foes.

But separated from the males, this pride is vulnerable.

For a successful heist, the hyenas rely on sound.

First, the lionesses need to make a kill.

(GROWLING AND GRUNTING)

With a noisy family in tow, that can be tricky.

(YOWLING)

(MOOING AND GRUNTING)

Wildebeest have gathered together for safety.

(MOOING AND GRUNTING)

In the darkness, they have to rely on their hearing.

(DISTANT MOOING AND GRUNTING)

The lioness makes a stealthy approach...

..but there is a problem

(SNUFFLING AND RATTLING)

A porcupine is a playful distraction for the youngsters.

(QUILLS RATTLE)

The sound of shaking quills is a warning...

(QUILLS RATTLE)

(SNARLING)

(YOWLING)

..and the wildebeest have heard the commotion.

(THUNDERING HOOVES)

They have blown it for her.

(GRUNTING AND GROWLING)

They will take the rattle of shaking quills more seriously next time.

(MOOING AND GRUNTING)

The pride have detected another opportunity.

A warthog burrow.

(GROWLING)

(WARTHOG SCREECHES)

(SNARLING)

(WARTHOG SCREECHES)

(SLURPING AND CRUNCHING)

The sound of their feast carries far in the cool night air...

..and the hyenas have heard.

(CRUNCHING AND SLURPING)

But there are too many lions here to steal this meal alone.

She will need the full force of her clan.

(LOW WHOOPING CALL)

She sends a message to rally her troops.

(WHOOPING CALL)

(WHOOPING CALL)

Directed at the ground, her message resonates further and faster

than it would through air.

(CHITTERING AND SQUEAKING)

(CHITTERING)

(HIGH-PITCHING SQUEAKING)

(CHITTERING)

Even with numbers now on their side,

sound is critical if they're to steal this meal.

(WHOOPING AND CHITTERING)

(SNARLING)

Calling unites the clan.

They must approach as a tight-knit group,

making as much noise as they can.

(CACOPHONY OF WHOOPING AND CHITTERING)

(LOW GROWL)

(HYENAS SCREECH)

(HYENA SCREECHES)

(LION SNARLS)

(YELPING AND WHIMPERING)

(SNARLS)

(SCREECHING AND ROARING)

The noise of the battle has alerted more lions.

(SNARLING)

(FRANTIC SCREECHING)

(YOWLING)

(YELPING)

(LOW GROWL)

It's game over for the hyenas.

(HIGH-PITCHED SCREECHING)

The brothers have returned.

(YELPING)

(BIRDS TWITTERING)

After a successful night, the pride is well fed.

Some will spend the day dozing.

But for others, it's time to reaffirm

the prides' ownership of their territory.

(GROWLS HOARSELY)

(GRUNTS)

We are only just beginning to understand

the many ways that animals use sound.

For us, the sound of the natural world

is a source of peace and tranquillity.

For other animals, it's a tool they have to master

in order to hunt and survive.

MAN: Yep. WOMAN: It is so cold out here.

MAN: I think just over here to the left looks pretty good.

OK. We have picture.

Our film crew have come to Manitoba in Canada

in search of the great grey owl.

Yeh, that looks like a promising spot.Oh, OK.

I think there were some owls here last week.

But, like many of our shoots,

we rely on the work of others who've come before us.

For years, scientists have wondered

exactly how the owl penetrates the layers of snow that conceal its prey.

Biologists Chris Clark and Jim Duncan are on a mission.

This is excellent. There's a plunge hole right here

where the great grey hit the snow.

They are armed with a special tool.

I'll grab the battery. OK.

An acoustic camera.

This version has 40 sensitive microphones

that pinpoint sound, while a tiny camera films its exact location.

It should allow them to see exactly what the owl is hearing.

(RUSTLING)

This camera is wonderful because it visualises

where the sound is coming from.

So I'm able to look and see,

how does the environment affect the sound.

(MUFFLED RUSTLING)

Snow is a formidable barrier.

For the vole, it's a cloak of invisibility.

(SNUFFLING)

To the owl, it's an obstacle that must be overcome by hearing alone.

52cm? Yeah.

The researchers bury a speaker under the snow

which will play the sound of a foraging vole.

(HIGH-PITCHED SQUEAKING)

They will bury it at different depths

and use the acoustic camera to see how the snow affects the sound.

The speaker is now visible in the camera view.

This black thing right here, that's the speaker.

And the acoustic camera, that blob of colour,

is localising the sound coming from the speaker.

But the playback from the snow-covered speaker

reveals a surprise

- the snow dramatically alters the location of the sound.

(MUFFLED SQUEAKING)That metre stick is above the speaker

and there's a blob of colour where the acoustic camera

perceives the sound to be coming out of the snow.

It's amazing. The snow is bending the path that the sound is taking.

As a result, if an owl were to try to localise the sound of the vole,

from where it hears the sound, it would miss and hit the wrong spot.

But Chris realises there is a way for the owl to overcome this problem.

As the owl is coming in,

it's listening to pinpoint the location of the vole.

Because of the snow, it sounds like the vole is here...

..when it's actually there.

But as the owl gets closer,

it starts to overcome the effect that snow has on the sound.

For the first time Chris realises why, at this point in its attack,

the great grey owl hovers.

The acoustic camera reveals that it's now in the perfect position.

The sweet spot for the owl is when it's right above the prey.

Directly above the vole, the snow doesn't bend the sound

so the owl can pinpoint exactly where the vole is.

(SQUEAKING)

Only then does the owl plunge.

(VOLE SQUEAKS)

Wow!

It's completely amazing that these owls can localise their prey

just by listening.

I love doing this kind of research and, through that,

understand the natural world and the amazing things

that species like the great grey owl are doing.

For decades, researchers had believed

that there was more to discover about the great grey owl's acute hearing.

Now they've finally uncovered the complex ways

it uses sound to hunt its prey in snow.

Alrighty.

(THUNDERCLAP) (CROAKS)

As the story of sound continues...

(DEEP HUMMING)

..we reveal how animals use sound to fight off competition...

(WHOOPING)

(RAPID THUDDING)

..and use songs in their quest to win a mate.

(STRIDENT SQUAWKS)

(INSECTS CHIRRUPING)

(SOFT RUMBLING ROAR)

(SQUAWKING AND CHIRRUPING)

(WHOOPING CALL)

(ANIMAL SOUNDS CONTINUE)

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