Original subtitles

[animals bellowing]

[Hiddleston] The great grasslands of Africa.

A vast landscape.

Buzzing with life.

[bellowing]

This is a world dominated by the loudest voices.

[bellows]

[rumbles]

But if you listen carefully...

[insects buzzing]

...there are secret sounds hidden in the grass.

Welcome to Earth's weirdest acoustic contest.

[animal chattering]

[hisses]

[squawking]

A serval. An elusive African wildcat.

And the grasslands ultimate sonic spy.

These hunters search for prey

using their oversized ears to tune in to every sound.

[rumbles]

[buzzing]

In a landscape where it's impossible to see far...

[animal shrieks]

...relative to its size, the serval has the largest ears of any cat.

Allowing them to map their world through sound.

[rustling]

And there's one tiny noise deep beneath the grass

that they're tuned in to above all others.

[sniffing]

The footsteps of striped mice.

[rustling]

Their satellite-dish ears can move independently,

thanks to ten muscles in each.

Giving perfect surround sound.

But to really dial in to their prey, rather surprisingly,

the serval sits down.

While most cats stalk, their hearing is so good...

[insect buzzing]

...they can hunt with their eyes closed.

They can detect the footsteps of a mouse from more than ten feet away.

And may remain motionless for up to 15 minutes.

Patiently waiting for their prey...

to make the slightest noise.

[chewing, rustling]

[sniffing]

[footsteps approaching]

[rustling]

[scampering, rustling]

Once locked on, the serval faces one more challenge.

How to make a move without being heard.

And to do this... they get airborne.

Leaping up to six feet high,

they can strike with pinpoint accuracy.

Servals have one of the highest hit rates of any cat.

Twenty percent more successful than lions.

And it's all thanks to their amazing ability

to hear the tiniest sounds on the savanna.

From the quietest to the loudest.

Across Africa's vast grasslands, there's one sound...

[thunderclaps]

...that transforms this landscape like no other.

Thunder is the starting gun for Africa's Great Migration...

[trumpets]

...detected from over 90 miles away.

Thirsty, growing grasses pop as they suck up water

and tiny air bubbles from their roots.

The lush vegetation brings together

the greatest gathering of large mammals anywhere on earth.

[rumbling]

[breathing heavily, rumbling]

It's a cacophony of life.

[bellowing]

Set in motion by the simple sound of thunder.

In such a packed arena,

Africa's acoustic contest hits a whole new level.

And perhaps the most astonishing trick is performed by tiny insects...

who use sound to help protect their home from giants.

Cocktail ants. Less than half an inch long.

And named after the habit of cocking their tail-like abdomens.

They live in a certain species of acacia tree

that have evolved hard, thorny growths which house the ants.

The tree also provides food.

Secreting a sugary sap for the benefit of the hungry insects.

For the ants, life on their tree would be perfect

were it not for one rather large problem.

[elephant rumbles]

Ants are not the only animals that adore acacia.

Eating over 200 pounds of food a day...

[rumbling continues]

...an elephant can destroy a tree in minutes.

So the insects have come up with a remarkable way of using sound

to keep their acacia safe.

New science suggests the ants have learned to burrow entrance holes,

largely on the windward side of their nests.

As the wind picks up, the tree begins to whistle.

[whistling]

The ants have turned their tree into a giant woodwind instrument.

[whistling continues]

And these whistles are carried on the breeze.

It seems elephants have learned this is a warning call.

A whistling acacia is infested with biting ants,

and one best avoid it.

But the ants' system isn't foolproof.

When the wind drops, the warning fades.

[whistling stops]

And the tree can quickly find itself on the menu.

From an ant's perspective...

[rumbles]

...an elephant grazing is a disaster.

But the insects have another acoustic trick.

[elephant rumbling continues]

When alarmed, they rattle their abdomens.

Producing vibrations known as stridulation.

Now new technology allows us to eavesdrop

on this strange insect chatter for the first time.

[rattling]

The vibrations travel along the branches,

mobilizing the colony in less than a second.

[rattling continues]

This secret call to arms allows the ants to coordinate their attack.

[rumbling]

Biting the elephant's eyes, and sensitive trunk.

Faced with 25,000 angry insects,

even the largest of all land mammals turns tail.

[elephant rumbles]

It seems impossible,

but by teaming up to create one of nature's weirdest warning calls,

cocktail ants can see off an animal one billion times their size.

Insects aren't the only animals to strike unlikely partnerships

with their neighbors.

[bellows]

Cape buffalo.

These animals have formed a quirky alliance with a noisy wingman.

[twitters]

Yellow-billed oxpeckers spend most of their lives perched on their host,

picking off parasites.

No respecters of personal space,

the birds will go anywhere for a tidbit.

[buffalo bellows]

Intimate cleaning isn't the only service they provide.

Nicknamed "the watch bird,"

they've evolved a highly effective alarm system.

- [squawks] - [bellows]

- [squawks] - [rumbles]

[squawking]

[bellows]

The buffalo have learned the oxpeckers' shrill calls mean trouble.

Lions.

Africa's top predators.

For these big cats,

sound can hold the secret to a successful hunt.

With the buffalo spooked...

[animal grunts]

...a warthog could be an easier target.

To avoid alerting her prey,

this 300-pound lioness must tread carefully.

[grunts]

For stalking requires absolute silence.

[twig snaps]

[grunting]

Over 80% of lone lion hunts end in failure.

Today it seems she and her family will go hungry.

[chattering, rumbling]

However, during the wet season there's a dramatic change

in the acoustics of the savanna.

[thunderclaps]

And it's this, along with the background din of wind and rain,

- that turns the odds in the lion's favor. - [rumbling]

This chaotic new soundscape...

[thunderclaps]

...drowns out the footsteps of the pride.

It's a phenomenon ecologists call acoustic masking.

Allowing the lions to fan out across the plains.

[bellows]

Undetected by prey.

The perfect conditions for getting closer than ever.

[grunts]

[snarls]

[grunts]

[bellows]

But of all the animals in the grasslands' great acoustic contest,

there's one star performer

that's taken finding a mate to flamboyant new heights.

A Jackson's widowbird.

This young male is new to the mating game.

And to attract a female

he needs to master one the grasslands' most complicated chat-up lines.

For the last two days, he's been busy.

Constructing a three-feet wide amphitheater,

complete with a strange central tuft.

Now, to draw in a female, he begins his courtship call.

[twitters]

But this little bird faces a big problem.

From down in the grass, his efforts go unheard.

[rustling]

Deadened by dense vegetation.

[twittering]

But the widowbird is a specialist at hitting the high notes.

[twittering]

Jumping up to three feet, he clears the undergrowth.

Broadcasting his distinctive trill at the peak of each leap.

[twittering]

He calls nonstop for up to 20 minutes,

until he catches the ear of a female.

But he's not the only bachelor out to impress.

There are other males.

[twittering]

Lots of them.

All trying to attract the female by outjumping

and out-calling him.

[twittering]

To entice her over, he must give it everything he's got.

[clicking]

[clicking continues]

Now he takes his performance to next level.

Shaking his magnificent tail feathers like a giant rattle,

he creates a stream of rapid-fire clicks.

[clicking, twittering]

But then things get even stranger.

Circling around his giant tuft,

he hides from his date.

When the female moves, he counters...

[clicking, twittering]

...because he wants to impress her purely through sound.

[clicking]

It's known as a peekaboo display.

Only when he believes she's been wooed,

does he bring out the final chat-up line.

[clicking, twittering]

A make-or-break gurgle.

[gurgling, clicking]

Has he done enough?

Sadly, no.

This time, his bid ends in frustration.

[twittering]

[shrieking]

In Africa's grasslands,

even the most flamboyant performance doesn't guarantee success.

The widowbird will have to sing again tomorrow.

To capture the sounds of the African plains

in more detail than ever before,

sound recordist, Sebastian Dunn, traveled deep into Kenya's Maasai Mara.

[Dunn] I'm in the most beautiful place.

It's an absolute treasure trove of sounds that I didn't even know existed.

[twittering]

[chittering]

[Hiddleston] One of the many recordings Sebastian wants to capture

is the intimate calls of Africa's biggest predators.

And to do that, he has to get creative.

[Dunn] To get a microphone really close to the action, I thought,

"Let me design a sound buggy to take the microphone to the animals."

The sounds I'm hoping to pick up

are hopefully the... the little micro communications.

They're really difficult to get when you're quite far away.

Right. Here we go.

[Hiddleston] But early tests don't go according to plan.

[sniffing]

[growls]

[Dunn] Yeah, it's holding it.

She's got it in her claws.

That's not what I really want to happen.

I'm gonna just move it backwards a little bit,

just to... hopefully, she'll move away.

[Hiddleston] It isn't long before the lions accept the buggy.

And Sebastian begins to capture the sounds he's after.

[groaning]

[chattering]

The subtle vocalizations of cubs asking for milk.

And the unique play calls they use to build bonds

that will be crucial for their survival.

[rumbling, groaning]

As well as more intimate sounds,

Sebastian also wants to record the most iconic sound of the African plains.

The lion's roar.

To do that, he teams up with lion conservationist, Nic Elliot,

who knows of a dominant male that is particularly vocal.

[lion rumbles]

[roars]

From this close, a lion's roar is over 100 decibels.

[roars]

As loud as a motorcycle.

[roars]

- Wow. That was amazing. - [chuckling]

Did you... Di... Did you feel that?

I felt it in my chest. That is so impressive.

[Hiddleston] But it's only when Sebastian compares different recordings of roars,

that he notices something remarkable.

[Dunn] Here's the sonic signature of the male's roars.

A beautiful signature.

Okay. So, that's... that's one individual, so...

That's one individual. Another individual is that one.

The actual sonic signature looks completely different.

- Yeah. - [Dunn] It makes me think

that each individual has its own sonic footprint.

So that's really interesting.

[Hiddleston] These tiny differences in lion vocalizations

could transform the way conservationists track lions in the wild.

If you can identify different individuals, then that...

yeah, that starts to become incredibly useful

and exciting for monitoring.

[Hiddleston] It's brand-new science.

In the future, the lion's roar could play an important role

in tracking and conserving this African icon.

[rumbles]