All language subtitles for Earthsounds.S01E07.ATVP.WEB-DL.DDP5.1.H.264-NTb.en[cc]

[Tom Hiddleston]
The deserts of Southern Africa.

This is a world where silence is golden.

[insects buzzing]

But listen carefully...

and these hushed lands are alive
with secret conversations

we're only beginning to understand.

And for one little desert dweller,

hidden messages are key
to keeping their family safe.

Meerkats.

These chatty creatures
spend most of their waking hours

digging for insects and grubs.

- Some more carefully than others.
- [chitters]

But with their heads buried in the sand,
it's impossible to spot danger.

- So meerkats have evolved...
- [squeaking]

...an ingenious alarm system.

Their squeaks may sound simple,
but slowing them down...

[distorted squeaking]

...reveals different chirps
made without moving their mouths.

[distorted squeaking continues]

They combine these
to build 30 distinct phrases.

[distorted squeaking]

[squeaking]

This sophisticated language,
more complex than that of many primates,

allows them to alert each other
to specific predators.

A martial eagle.

Africa's largest bird of prey,

and just one of the perils meerkats
come across every day.

- This young male is on lookout duty.
- [Meerkat chirping]

[meerkats chirping continues]

He's spent six months
learning meerkat language,

and must now use it to let his family know
what's going on around them.

[chirping]

This is the all-clear call.

[chirping continues]

It means, "Keep digging.
Nothing to worry about."

But when you're just one foot tall,

danger doesn't only come from above.

A Cape cobra.
Its venom could kill a meerkat.

- The lookout barks the snake warning,
- [grunting]

but surprisingly, the family doesn't
run away from the threat.

[grunting continues]

They run towards it.

- [hissing]
- [growling]

- [grunting]
- By continuing to call,

more and more join the assault.

[Meerkats grunting]

Safely seen off...

[Meerkat chirps]

...and once again,
the lookout gives the all-clear.

[chirping]

But scientists
are discovering meerkat language

is far more complex
than just identifying different predators.

[squawks]

Amazingly, they can also communicate
the urgency of a threat.

The martial eagle is on the hunt.

It's still a long way off,
and may just pass them by.

[whimpering]

The lookout sounds
the low-urgency aerial alarm.

But the eagle is edging closer.

Time to shift things up a gear.

[grunting]

A medium-urgency alarm.

No need to panic,
but everyone in earshot now stops.

[grunting continues]

And puts eyes on the eagle.

- Finally, the high-alert call.
- [squealing]

Everyone makes a dash for the burrow.

[squealing continues]

Today,
the whole family lives to tell the tale.

And it's all thanks
to our young lookout's mastery

of meerkat language.

Far more sophisticated
than we ever realized.

[chirps]

Bordering the meerkat's home

in the arid Kalahari...

lies the oldest desert on the planet.

The Namib.

A vast sea of dunes,
some a thousand feet tall.

A stage where the faintest footsteps...

can give you away.

But out here, it's not
only animals that make secretive sounds.

[wind whistling]

When the desert winds
blow over the crests of the dunes...

they trigger an avalanche of sand.

[rumbling]

- Microphones capture the tiny sounds...
- [crackling]

...as the grains tumble over each other...

and start to vibrate.

Trillions of sand particles
vibrating together

cause the surface of the dune to resonate
like a giant speaker.

[humming]

Known as the singing dunes of the Namib,

this planetary hum has been buzzing
for more than a million years.

[humming continues]

But there are some noises out here
that are beyond our hearing.

[insects buzzing]

[bellows]

Secret channels of sound
that animals use to keep in touch

over vast distances.

[rumbles, trumpeting]

The African elephant...

- [trumpeting continues]
- ...as loud as a jumbo jet.

Their bellowing trumpets
reach 120 decibels.

[rumbling]

But they also use low-pitched rumbles

to keep in touch with distant herds.

[rumbling continues]

Deeper sounds travel further,

but we only hear a fraction
of what they're saying.

Using cutting-edge technology,

we can tune in to the very lowest rumbles
of elephants like never before.

[distorted rumbling]

Known as infrasound...

we're now hearing the parts
of their calls usually inaudible to us.

[distorted rumbling continues]

They create these lowest of sounds

by blowing air across giant vocal cords

eight times larger than ours.

[distorted rumbling]

These can broadcast
for over 100 square miles.

It allows herds to keep
in touch across these vast plains.

[trumpeting]

And more importantly,
to join forces when they sense danger.

[breathes heavily]

This is lion country.

[groaning, sniffs]

The largest prides
can take down young elephants.

In the desert,
Africa's biggest predators gather close

to the few water holes...

where they know
all prey must eventually come to drink.

[trumpeting]

To get to water, the herd must figure out

how many lions there are,

and whether they pose a risk
to their calves.

- They can do this simply by listening.
- [lion roaring]

Elephants eavesdrop
on lions' territorial calls.

[roaring continues]

And have even learned to count.

Huddling around youngsters
if they feel threatened...

the wisest and oldest elephants
over 60 years of age

can also distinguish
between the calls of lionesses...

[roaring]

...and the deeper,
louder roars of more dangerous males.

[roaring continues]

If there are too many lions,
the elephants will avoid the water hole.

But when they outnumber the predators,

they're not afraid
to show them who's boss.

- [rumbling]
- [lion growling]

[trumpeting]

[trumpeting]

[rumbling]

With the lions sent packing,
the herd gets to drink.

By dialing into a world of sound that
we're only just beginning to understand,

elephants keep their families safe
across these vast planes.

[rumbling]

[birds chirping]

For other desert inhabitants,
success comes not from listening

to distant sounds...

but to minuscule murmurs
just beneath their feet.

The bat-eared fox.

No prizes for guessing
how they got their name.

Their outer ears, known as "pinna,"
are five inches tall

and act like satellite dishes

making these dainty little foxes
the desert's ultimate acoustic predators.

In the last light of day,
this family is getting ready to hunt.

And that means
tuning into the desert's quietest sounds.

Harvester termites,
the fox's favorite snack.

No bigger than an ant,

strangely, a termite's footsteps
are 100 times quieter.

They may seem impossible to detect.

But the bat-eared fox
has a sonic superpower

and uses its oversized ears
to amplify the tiniest sounds.

[amplified footsteps]

Ultra-sensitive microphones give
an insight into how a fox hears its prey.

[amplified footsteps continue]

Listening for termites in the day
is hard enough.

But bat-eared foxes are largely nocturnal.

And when the sun goes down,
they face a deafening problem.

[insects buzzing, chirping]

As they patrol,

the desert's amazing night chorus
turns up to full volume

downing out
the tiny sounds of termite footsteps.

[buzzing, chirping continues]

The cacophony is created
by amorous bush crickets

that belt out
their 90-decibel mating calls

by rubbing modified wings together.

But the clever fox
can filter out their din.

[crickets chirping fades]

They cock their heads

and aim their satellite dish ears
to the ground

blocking out the background noise...

[rustling]

...and just listening in to their quarry.

Their hearing is so acute

a single fox can eat 3,000 termites
a night.

As the sun rises,
the nocturnal chorus fades.

[birds chirping]

And the fleeting burst
of life fills the airwaves.

[thudding]

But of all Africa's desert dwellers,

there's one that's pushed secret sounds
to a whole new level.

The ostrich.

This young couple
are expecting their first chicks.

Thirteen of them.

But to bring their family
safely into the world,

they'll have to listen out

for the faintest of messages
from their unhatched offspring.

The eggs appear dormant,

but there's a world of sound
inside the shells.

[bubbling]

At around ten days old, the developing
chicks' tiny hearts start beating.

[hearts beating]

After 40 days we can hear them
take their first gasps of air...

- [breathing, gasping]
- ...through pores in the eggshell.

The parents-to-be take it in turns
to incubate the eggs

all the while listening out
for another secret sound

using ears at the back of their heads.

And after 42 days on the nest...

Mum hears what she's been waiting for.

[cheeping]

A gentle cheeping from within the eggs.

[cheeping continues]

It's a sign the chicks are just hours away
from hatching.

And for the parents,
it's a cue to get ready for action.

[cheeping]

They now stay close together
guarding the nest

and won't leave
until every egg has hatched.

[cheeping continues]

[cheeping]

And before long...

the proud parents
welcome their first baby into the world.

But this is a dangerous time.

The smell of freshly hatched egg
will soon attract desert predators.

Black-backed jackals.

- The parents need to get the others out...
- [chirping]

...and leave the nest site
as quickly as possible.

Now Mum starts making a sound of her own.

[beak clapping]

She beak claps to her eggs...

as if she's telling them to get cracking.

[chirping]

And incredibly, the first hatchling
also helps speed things along.

Every time he calls,

it triggers a burst of energy
from his siblings...

helping them to break out of their shells.

[chirping]

One by one,
others join in the hatching chorus.

[chirping]

Soon,
the family is complete and ready to roll.

Just in time.

[chirping]

Ostriches make a noisy entrance
into the world.

But it won't be long
before the chicks stop chirping

and tranquility returns to the deserts
of Southern Africa.

[chirping continues]

To capture the secret conversations
of elephants like never before,

the Earthsounds team ventured
to the northern reaches of the Kalahari.

[elephant trumpets]

Sound recordist Sebastian Dunn
is tasked with an unusual challenge.

To record the infrasonic rumbles

of elephants completely undetectable
to human ears.

[rumbles, bellows]

So, inside this little ball of fluff
are two microphones.

The one microphone is a stereo microphone

that will record the sounds
that us humans can hear.

- But the other microphone in there...
- [elephant trumpets]

...is able to record sounds
that we cannot hear.

[Hiddleston] His first recordings
aren't quite what he was hoping for.

[flatulence]

Little bit of flatulence, but, um,

it's pretty much all that I'm getting
so far.

[Hiddleston] But it's not long
before he starts capturing

the elephants' deepest vocalizations.

[rumbling]

That is amazing.

[rumbling continues]

And I can hear that rumble, but I know
there's so much more that I can't hear.

[whispers] Wow.

[Hiddleston] Almost 90% of elephant calls
contain sounds below our hearing.

[rumbling, trumpeting]

But listening to his recordings,
Sebastian discovers that elephants

aren't the only ones
producing low-frequency sounds.

[Dunn] I can hear vehicles.

The low-level rumbling of a car
really travels far on the ground.

[Hiddleston]
Even in the middle of the desert,

the distant drones from car engines
can travel over a mile.

[engine whirs]

Scientists are discovering
that low-frequency noise pollution

from human activity
can disrupt elephant behavior

and may affect their ability
to hear each other over long distances.

To capture clean elephant rumbles
without the background noise of vehicles,

Sebastian sets his microphones
to record overnight.

But come morning,
the elephants have a surprise for him.

[rumbling]

Oh, no. [chuckles] Oh, no. Guys.

[elephant trumpets]

This used to be one long cable.

[Hiddleston] This is a small price to pay
if Sebastian has managed

to record the infrasonic sounds
of the nighttime raiders.

[elephants rumbling]

Ooh, that's a lovely rumble.

- [rumbling continues]
- [Dunn] Oh.

Wow, that is amazing.
I've never heard that. That's fantastic.

[Hiddleston]
These recordings reveal a whole new side

to elephant communication
we're only beginning to understand.

[rumbling]