01x01 - Hunters and Hunted

[bunniefuu]

The natural world

is filled with sound.

But so far,

we've been hearing only part of it.

The most advanced audio technology

can now record sounds

that we can't even hear.

For some animals,

sound is the key to survival.

They use sound to hunt

..and escape.

Sound can make the difference

between life and death.

It's time to open your ears

to life

as you've never heard it before.

Dawn on the African savanna.

It's the best time of the day

for lions to broadcast their message.

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.

It's a declaration to other prides

of his ownership

of these hunting grounds

..and the key to his

and his pride's survival.

It's one of the greatest

acoustic displays of power in nature.

He can be heard

up to five miles away.

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.

But some members are too small

to get very far.

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.

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.

The buzzing sound

we associate with bees

is a by-product created by

the beating wings as they fly.

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.

One such bee lives underground.

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.

Searching for it

is a constant preoccupation.

It's spring in England

..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.

These flowers are a free-for-all

..and everyone

is seeking a share of the bounty.

But she doesn't need to compete

with other species

if she can find

a particular kind of flower.

She's found

what she's been looking for

..a type of nightshade.

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.

This sonic as*ault

blasts the pollen loose.

She then grooms the pollen

down into sticky sacs on her legs

and flies off to the next flower.

Very few species

can buzz-pollinate in this way,

so bumblebees have nearly exclusive

access to the nightshades' pollen.

The bee's pollination buzz

is higher pitched

than that made during flight.

It's the same frequency

as the musical note D.

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.

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.

Bees need our help

and without them

and the sound of their buzz,

the future for us all

would look bleak.

Sound provides the key

to this partnership

between bumble bees and plants.

But not all relationships in nature

are as harmonious.

The Bahama Islands in the Caribbean.

The sand flats here are the home

of garden eels and razorfish.

But there is trouble in paradise.

The sound of approaching danger.

It's a cue to hide.

A mixed groups

of spotted and bottlenose dolphins.

Their whistles and squeaks are part

of their continuous conversations

..with a range of frequencies

seven times greater than ours.

To hunt for food, they must split up.

Each dolphin

needs 15 kilograms of fish a day.

But, thanks to their rowdy arrival,

there isn't a morsel in sight.

The hunt is on.

The bottlenose dolphins

now switch from whistles

to bursts of fast clicks,

up to 200 per second.

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.

When the beam of sound

hits a fish hiding beneath the sand,

it's reflected back,

revealing its location.

Using echolocation,

the dolphins are able

to create a visual map

of what is hidden

under the sea floor.

Some of these clicks

are ten times higher

than the sounds our ears can detect.

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.

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.

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.

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.

His prey is hidden

under a blanket of snow.

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.

Voles need to feed continuously

or they will freeze to death.

They constantly dig tunnels

to find new food supplies

..unaware of the danger above.

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.

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.

The camera visualises

where the vole is beneath the snow.

And he's off.

This time he's missed.

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.

As he flies,

he tracks the sound as it changes.

The closer he gets,

the less the sound is bent.

Directly above the vole,

he can pinpoint his target.

The great grey owl's hearing

is its key to securing a meal.

For others,

it's crucial to avoid being eaten.

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.

But to a kangaroo rat,

it's nearly pitch black.

In the dark,

her most valuable ally is sound.

Her mission tonight is to collect

as many seeds as she can.

But food is scarce

..and competition fierce.

And, in the dark,

it's hard to spot danger.

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.

But she has

another problem tonight.

Wind.

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.

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.

He can decipher her size and strength

from her signal.

He drums back.

It's a battle of beats.

Stalemate.

There's only one

way to resolve this.

Dinner time at last.

She hears something.

Just out of striking range,

she drums again

..this time to alert the snake

it's been spotted.

But just to be sure

Message received.

While kangaroo rats

use the ground as a drum

to drive their enemies away

others are summoned

by seismic sounds.

Amboseli National Park in Kenya.

It hasn't rained here

in nearly a year

..and the dry season

has turned into a severe drought.

For elephants,

the situation is desperate.

With no food or water

for miles around,

the matriarch

must wait for a message

..a sound that will travel

through the ground.

If it arrives,

it will guide them from disaster.

The young calves

are especially vulnerable.

Their mother's milk will dry up

if rain doesn't arrive soon.

A hundred miles away,

a storm has broken

..and the elephants have heard.

Not with their ears

..but with their feet.

The sound of the storm

sends low-frequency vibrations

through the ground.

The herd picks up the vibrations

through a network of nerves

in the fatty pads of their feet.

By lifting one foot,

they can make better contact

on the ground with the other.

It's the message the matriarch

has been waiting for.

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

It's echoed by her sisters.

The journey ahead is treacherous

..but the sound of the storm

will be their guide.

Finally,

after two days on the move

..they've made it.

Their ability to detect sound

a hundred miles away

has saved the herd.

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.

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.

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.

But it is also a sound

that can seal their fate.

Worms aren't the only ones

on the move.

Outside the city, a flock of gulls

are co-ordinating their

morning departure from the roost.

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.

Paddling creates vibrations that

likely mimics the sound of rain.

It's a dance of deception.

The worms rise once again.

They can't resist

the rhythmic rain dance.

Another shower

brings an acoustic cl*max.

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.

As night falls

on the African savanna,

the air is filled

with sounds of a formidable hunter.

On the other side of the territory,

the females of the pride

are preparing to hunt.

Over 30 strong,

they must make a k*ll every night.

Close by, a hyena den.

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 k*ll.

With a noisy family in tow,

that can be tricky.

Wildebeest have gathered

together for safety.

In the darkness,

they have to rely on their hearing.

The lioness

makes a stealthy approach

..but there is a problem

A porcupine is a playful distraction

for the youngsters.

The sound of shaking quills

is a warning

..and the wildebeest

have heard the commotion.

They have blown it for her.

They will take the rattle of shaking

quills more seriously next time.

The pride

have detected another opportunity.

A warthog burrow.

The sound of their feast

carries far in the cool night air

..and the hyenas have heard.

But there are too many lions here

to steal this meal alone.

She will need the full force

of her clan.

She sends a message

to rally her troops.

Directed at the ground, her message

resonates further and faster

than it would through air.

Even with numbers now on their side,

sound is critical

if they're to steal this meal.

Calling unites the clan.

They must approach

as a tight-knit group,

making as much noise as they can.

The noise of the battle

has alerted more lions.

It's game over for the hyenas.

The brothers have returned.

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.

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.

- Yep.

- It is so cold out here.

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.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.

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.

Snow is a formidable barrier.

For the vole,

it's a cloak of invisibility.

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.

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.

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.

Only then does the owl plunge.

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.

As the story of sound continues

..we reveal how animals use sound

to fight off competition

..and use songs

in their quest to win a mate.