All language subtitles for Earthsounds.S01E01.ATVP.WEB-DL.DDP5.1.H.264-NTb.en[cc]

[animals chattering]

[Hiddleston]
The ancient eucalypt forests of Australia.

[chattering continues]

A prehistoric world teeming with bizarre
and captivating sounds.

[animal rumbles]

[Hiddleston]
Isolated for over 35 million years...

the animals here have evolved weird
and wonderful ways to communicate.

[animals chattering]

Especially when it comes
to finding a mate.

[bird singing]

The superb lyrebird, one of the world's
oldest surviving songbirds.

[twittering, singing]

Each winter to attract a mate,

males take part
in the ultimate avian talent show.

[twittering]

At 15 years old, this experienced male
is something of a star.

[twittering, chirping]

But with younger rivals jostling
for the airwaves,

this season he will have to put on
the performance of a lifetime.

First, he clears his arena.

[chattering]

Everything has to be just right.

Then his show begins.

[singing, squawking]

Lyrebirds are master mimics.

[twittering]

- First, a whipbird.
- [impersonating whipbird, singing]

[singing]

[singing, chirping]

It's a convincing start.

And it's caught the attention of a female.

She will choose a partner
who does the most accurate impressions.

So next,
he pulls out an Australian classic.

[twittering, chirping]

The Kookaburra.

[twittering, chirping]

Not bad.

The female seems interested.
So he continues with a cockatoo.

[impersonating cockatoo]

Seventy percent of his repertoire
is mimicry,

learned from listening to older lyrebirds
and copying them.

[twittering continues]

To sing such complex and varied songs,

lyrebirds are able to produce
multiple notes at the same time.

[twittering, chirping]

Slowing their song down
reveals the secret.

[twittering slows]

They have the avian equivalent
of two voice boxes.

One produces lower tones.

[low, slowed singing]

The other higher ones.

[high-pitched singing]

Allowing them
to switch notes effortlessly.

[singing, chirping]

Barely stopping for breath.

Drawn in by his song...

[twittering]

...the female approaches.

And this is when he reveals
his showstopper.

[twittering, chirping]

A perfectly choreographed song
and dance routine.

[twittering, chirping continues]

But only when she gets close,
does he reveal his grand finale.

[twittering, impersonating laser]

The laser gun.

[twittering, singing continues]

For a female, it's irresistible.

[singing continues]

Lyrebirds may be the star performers
in Australia's forests...

but across the year,
the sound of the forest builds

as different animals take turns
to broadcast their courtship calls.

[animals chattering]

We can hear this change on
an acoustic journey through the seasons.

In spring, the airwaves
are filled with the love songs

of more than 300 bird species.

[birds chattering, singing]

In the sweltering summers,
insects buzz to attract a female.

[buzzing]

And at the start of the wet season...

[water splashing]

...the patter of rain builds.

Ninety percent of the annual rainfall
occurs in just six months,

turning rain forest rivers
into thundering waterfalls.

Now, animals must shout to be heard.

[animals chattering]

And it's some of the forest's smallest
inhabitants that have the biggest voices.

[frogs chirping]

Australia has over 200 frog species.

[croaking]

Each with a unique mating call.

[chirping]

This female orange-thighed tree frog
may only lay eggs once a year.

So tonight she's listening out
for Mr. Right.

[chirping]

But there's so many species calling,
it's hard to pick out who's who.

[frogs croaking, chirping]

Luckily,
frogs have a special way of hearing

that's totally unique
in the animal kingdom.

Their lungs are connected
to their ear drums.

[croaking, chirping continues]

And when inflated, it's believed
they dampen out background sound.

Rather like noise canceling headphones.

It allows this female
to filter out the hubbub...

[croaking]

...singling out the perfect partner.

[frogs chirping, croaking]

Amidst the cacophony of the frog chorus.

[chirping, croaking continues]

The wet season triggers other
strange sounds in the Australian forests.

More subtle calls that are used not
to attract a mate...

but to protect precious young.

Along the rivers
of the northern territory...

lurks Australia's most fearsome predator.

The saltwater crocodile.

Up to 20 feet long,
these giants can live for 70 years.

But to survive the first day
of their lives, sound is key.

This female is soon to be a mother.

Three months ago,
she laid a clutch of 30 eggs

and buried them deep inside a nest
of sticks and mud...

to incubate and protect them.

But as soon as the eggs hatch,
they'll face dangers.

Pied herons scour this riverbank

and could easily pick off
a croc hatchling.

To keep guard,

mum has stuck close
by her nest for the last 90 days.

[insects buzzing]

She's been listening out
for one particular sound.

[murmuring]

A low-pitched murmur
from inside one of the eggs.

[murmuring continues]

Soon another egg joins in.

Then another.

The baby crocs are talking to each other.

[murmuring continues]

And they're hatching a plan
to all break out at the same time.

Mum is able to hear these faint chirps
from over 30 feet away

through ear slits just behind her eyes.

[crocodiles murmuring]

She heads to the nest to check it out.

[growls]

[huffs]

Crocs don't just hear through their ears.

Placing her head on the nest,
she uses receptors along her jaw...

- [murmuring]
- ...to pick up vibrations from below.

When she knows the time is right,
she starts to dig.

[murmuring continues]

Surprisingly, scientists have discovered

that the sound of digging
encourages the eggs to hatch.

[huffs]

As the first youngsters emerge
into the world...

their mother leads the way to the river...

[chirping]

...and waits.

Chirping to keep in touch,

the young crocodiles
scramble towards the water

and the safety of mum.

[crocodile chirping]

But all this noise hasn't gone unnoticed.

[grunting]

- [grunting continues]
- Herons start to gather.

[chirping]

[chirping]

One last hatchling remains.

Alone, the odds are against him.

[chirping continues]

But female crocodiles
are fiercely protective.

[roars, growls]

With all the youngsters in the river,
the immediate danger is over.

Continuing to chirp to each other,

the hatchlings will use these calls
for the next five weeks...

to stick together in a crocodile crèche.

[birds chirping, twittering]

Whilst many animals
in the Australian forests

produce sounds that are audible
to the human ear,

some creatures detect sound
in a completely different way.

A female orb weaver spider...

the size of a human hand.

Spiders don't have ears.

Instead, they pick up vibrations
through receptors in their legs.

Feeling sound rather than hearing it.

Now, using laser technology
that transforms vibrations into sound...

[thudding]

...we can tune in to the spider's web
and enter an alien world.

[thudding continues]

Virtually blind,
her web acts as a giant acoustic sensor,

allowing her to listen in
to the world around her.

[bird squawks]

She's waiting for one sound
above all others.

- [buzzing]
- [thuds]

The impact sends ripples
up each silk string,

allowing her to pinpoint her prey...

[chewing]

...and devour it.

For the miniscule male...

just a tenth of her size,
this makes courtship dangerous.

He must tread carefully,

or she may mistake him for pray
and eat him.

So he turns the web
into a musical instrument...

[strumming]

...and serenades her.

[strumming continues]

Plucking the silk strings,

he reassures the female
he's friend, not foe.

Next, he shakes his abdomen to produce
a pulsing vibration across the web.

[pulsating]

Known as tremulation.

[thuds]

It puts the female into a docile trance.

These sound signals allow the male
orb weaver to edge closer to the female.

And if he's lucky, to mate with her.

This time,
music really is the food of love.

[birds twittering, chirping]

But there's one love song
in the Australian forests

that is so deep and resonant,
it defies the rules of physics.

[animal chattering]

And it's produced by
the most unlikely of animals.

The koala.

[yawns]

Famous for not doing very much at all,

these eucalyptus-munching marsupials
are quiet for much of the year.

But each spring, for just a few weeks,
all that changes.

This big male is searching for a mate.

High in the canopy,
it's hard to see potential partners,

so the best way to make yourself known
is to do this.

[bellowing]

[bellowing continues]

A call this low should only be possible
in an animal 20 times the size of a koala.

But scientists have discovered
their secret.

Males have an extra set of vocal cords
that are 15 times wider than normal...

[bellowing]

...allowing the koala to make a sound
as deep as an elephant's rumble.

[bellowing]

His deep bellows can be heard
from half a mile away...

[bellowing continues]

...and catch the attention of a female.

But there are other male suitors here
eager to impress...

and soon they join the battle
for the airwaves.

[koalas bellowing]

Smaller males can't call as low.

And unfortunately for them,

females prefer males
with the lowest voices.

[bellowing]

Because deep bellows are a sign of size
and strength.

Eventually,
the big male silences the competition...

and can now approach the female
without being challenged.

But first, he must track her down.

Koalas only come to the ground to move
between trees, but are surprisingly agile.

He spots the female and approaches.

[bellowing]

Has she been impressed?

[shrieking]

This isn't the response he was hoping for.

[shrieking continues]

A rejection call.

Today, even the deepest bellow
isn't enough to win her over.

[grunting]

For a moment, things are quiet.

But it won't be long

before another captivating song
fills the airwaves

of Australia's ancient forests.

[animals chattering]

To capture the enchanting chorus
of Australian tree frogs,

the Earthsounds team traveled
into the rain forest

of northern Queensland
to record a particular species

that only calls one or two nights
of the year.

To help, they're joined
by renowned frog scientist, Jodi Rowley.

I'm really hoping that we hear a species
that we haven't heard in quite some time,

which is the orange-thighed tree frog.

[Hiddleston] These rarely seen
little frogs live high up in the canopy,

only coming down to breed after rain
forms puddles on the forest floor.

And tonight, conditions are perfect.

[Rowley]
It's rained really, really heavily today.

So I'm hoping that we'll find
some orange-thighed tree frogs

because they love it when it pours
with rain.

[Hiddleston] In the thick bush,

these tiny frogs
are incredibly hard to spot.

So while I'm actually looking
for frogs here with these torches,

the best way to actually find frogs
is just to listen.

[Hiddleston] The tree frogs aren't
the only ones out in this wet weather.

[chirping]

Up to 40 species of frog are calling,

bringing the forest to life
with their ribbits...

[chirps]

- ...barks...
- [barks]

- ...and honks.
- [frog honks]

Okay. I can hear a barred frog
somewhere in this leaf litter.

I have no idea where it is now.

[frog honks]

Ah, there it is.

So, look at how camouflaged
this beautiful frog is.

If he hadn't called out,
I would never have found him.

Oh, I love these guys.

[Hiddleston] But time is of the essence.

If Jodi is going to hear
the elusive tree frogs in this cacophony,

she will need to keep moving.

[croaking]

Oh, I can hear them.

This is really, really exciting.
I can hear the orange-thighed tree frogs.

You know, I haven't actually seen them
or heard them for 20 years.

Think we're getting closer.

Very close.

Ah. There. Look at that.

Look at the beautiful frogs.

You can see one over there.
Oh, one there, one there.

[stammers] Oh, my gosh.
There's a lot more of them than I thought.

There is just so many male frogs calling
right now

that I can barely hear myself talk.

[frogs croaking]

Listen to them all.

[Hiddleston] This cacophony is a sign
of a balanced ecosystem.

Frogs are incredibly sensitive
to environmental change

and their calls can be used
to monitor the health of the rain forest.

But for Jodi, it's also a magical moment.

[Rowley] I feel like I've hit the jackpot.

Uh, this is something that you don't get
to see very often.

And for me being in a frog chorus
and a... a chorus of this species,

which is pretty hard to get in chorus,
is... uh, is heaven.

I'm in heaven right now.
This is really, really awesome.

[Hiddleston] Having so little time,
the team moves quickly...

recording the sounds of the chorus
and the unique calls of individual frogs.

[frogs chattering, croaking]

[Rowley] We could come a 100 times
to this stream,

to this spot, and not see them.

But we've hit the night.

[Hiddleston] With Jodi's expertise
and a bit of luck,

the team manages to record
the rarely heard chorus

of one of the smallest but loudest
inhabitants of Australia's forests.