Original subtitles

[waves crashing]

[Tom Hiddleston] The wild Atlantic coast, where land and sea collide.

In this cauldron of noise,

animals have found astonishing ways to cut through the chaos.

Especially when it comes to finding a mate.

[calling]

Rockhopper penguins.

Each spring,

around 1,000 gather on this remote island in the southern Atlantic to breed.

And finding their long-term partners in this bustling colony

all comes down to sound.

This busy male hasn't seen his mate for over half a year.

Hoping she'll arrive soon...

[squawks]

...he diligently prepares their nest.

It might not look like much, but to him, it's perfect.

When he's done, he lets out what's known as an ecstatic call...

[calling]

...telling others this is his patch.

Far below, more penguins are arriving...

and his partner is among them.

But to get to the colony,

these flightless birds must somehow scale cliffs that are 100 feet high.

Timing is everything.

Go too soon and they're hurled against the rocks.

Too late, and they risk being swept back into the water.

Even when timed perfectly, they land on slippery slopes.

Gripping tight, they claw away from the crashing waves.

Then, they hop.

[honking]

Finally at the top, they set about trying to find their mates.

On his nest, the male calls eagerly for his companion.

[calling]

But somehow

she must hear him over the boisterous cries of almost a thousand noisy birds.

[calling]

To our ears, all these calls sound the same,

but she can detect tiny differences in each penguin's song.

We can hear what she's tuning into

by slowing his call to a quarter of its normal speed.

[slowed calling]

She homes in on the tone of his voice

and, importantly, his unique rhythm.

A beat only he uses.

This is what allows her to pick him out of the crowd.

[calling]

Guided by his call, at last they're reunited.

[squawking]

For rockhoppers,

the secret to their long and successful relationship

is all in the rhythm of their song.

From the wild southern seas,

the Atlantic coast stretches north for over 60,000 miles.

It's a world dominated by the crash...

[waves crashing]

...of white water.

As waves hit the shore, their familiar sounds rip through the air.

But the ocean's roar is actually created underwater.

Rolling waves trap air, forming a sea of bubbles.

Each one vibrates, ringing like a tiny bell.

[bubbles ringing]

Billions of bubbles chiming together

create the signature sound of the Atlantic.

[waves crashing]

Yet, even in the world's wildest ocean...

there are pockets of calm,

where hunters use stealth to catch their quarry.

[blows]

Orca.

In winter, more than a thousand gather in the deep fjords of Norway.

They're here to hunt, and they do that entirely through sound.

[whistling]

Close-range microphones

record their contact whistles and calls in extraordinary detail.

[whistling, calling]

Family groups, or pods,

use these alien sounds to stay together as they move through the deep fjords.

But to find prey, the pod uses a sonic superpower.

They produce a series of high-pitched clicks.

[clicking]

Known as echolocation,

orca listen as the clicks rebound from objects around them...

building up an acoustic map.

[whistling, clicking]

Using this sixth sense, they search for their favorite food:

herring.

The pod can locate a shoal from 500 feet away.

They switch to hunting mode.

The orca fan out.

But they face a challenge.

Herring can detect the clicking orca and will retreat when under attack.

So, these intelligent hunters switch to a quieter form of echolocation...

[softly clicking]

...clicking at half the volume.

From above,

the herring look like a dark, shifting cloud...

tantalizingly out of reach.

To catch them, the orca use an ingenious trick.

They lash their tails at speeds of 30 miles per hour...

sending out a wave of sound and turbulence.

The herring closest are stunned.

[whistling, calling]

Using this acoustic attack...

the pod can eat over half a ton of fish every hour.

And it's all down to their mastery of sound.

Away from the northern fjords,

the soundscape of the Atlantic is constantly changing...

driven by the ebb and flow of the tide.

And as the waves retreat,

hidden acoustic worlds come to life.

Rock pools.

They may seem silent,

but every animal has its own minuscule signature sound.

Limpets scrape as they feed.

[scraping]

Whilst hermit crabs unfurl.

[unfurling]

And territorial corkwing wrasse pop at any intruder that comes close.

[popping]

We can even hear the footsteps of predatory spiny starfish

as they creep by on thousands of tube feet.

[footsteps tapping]

This scallop senses the danger...

and makes its escape.

The cuttlefish is the rock pool's silent assassin

and strikes with pinpoint accuracy.

But perhaps the most surprising sound

is the satisfying burp of a strawberry anemone...

[burps]

...as it digests its prey.

[burps]

This secret world is soon drowned out by the rising tide.

[waves crashing]

And as the rumble of waves return,

the animals of the Atlantic coast turn up the volume.

[grunting]

Elephant seals.

Over 2,000 come to the beaches of the Falklands each spring to breed.

To us, they may sound unsavory...

[grunting]

...but new science shows

that these brutes use sound in a surprisingly sophisticated way.

[bellowing]

The beach is ruled by one colossal male,

and he fiercely defends more than 40 females.

If his immense four-ton bulk isn't enough to keep rival males away,

then this should scare them off.

[roaring]

[honking]

Reaching 120 decibels, it's as loud as a thunderclap.

Usually enough to keep the competition away.

[roaring]

But not always.

A young interloper.

To land a space on the beach,

he'll have to challenge this huge resident male.

[bellowing]

And he starts not with a bellow, but a ground-shaking approach.

[thuds]

As he moves onto the beach, his massive body creates vibrations

and underground microphones capture this for the very first time.

It's known as seismic sound.

[vibrating]

His rival can detect these reverberations through receptors in his skin

from over 60 feet away.

Alerted to the challenger,

the resident responds with a deafening roar...

[roaring]

...setting off the Atlantic coast's ultimate shouting match.

[roaring]

The larger the male, the lower and louder the voice.

And when neither backs down, there's only one option.

It's time to fight.

[thuds]

These heavyweight battles can last up to 30 minutes.

[grunting]

And they're a test of sheer strength and stamina.

Today the young interloper is outmuscled and outbellowed...

[bellowing]

...in the Atlantic's ultimate shouting match.

[bellowing]

[honking]

All along the Atlantic coast,

animals fight to be heard in this turbulent world.

But there is one that has learned to use the noise of the ocean itself

in a truly astonishing way.

The albatross.

The Atlantic's greatest travelers.

They can fly around the world in less than 50 days...

and cover over 70,000 miles a year.

How albatross navigate across the endless blue has long been a mystery.

But it is now thought they use the sound of the sea to help guide them.

This female is searching for a rocky outcrop

where she returns each year to breed.

Finding the right one is a challenge,

but the acoustics of the coast offer a clue.

As waves crash against the shore,

they create low-frequency sounds unique to that stretch of coastline...

[waves crashing]

...meaning each island sounds slightly different.

Amazingly, scientists now believe

that albatross are tuning in to these subtle differences

and using them like a road map to find their way home.

[squawking]

After nearly a year at sea,

she touches down for the first time.

And now she must find her mate.

[squawking]

Unlike the rockhoppers, who use calls to locate each other,

she knows exactly where her partner is.

They meet on the same nest every year.

[braying]

Finally reunited...

[braying]

...they perform an intricate love song.

[braying]

Clacking beaks and softly calling.

Albatross form lifelong pairs.

This couple could stay together for more than 40 years.

The ocean's long-distance travelers,

brought together by the sound of the wild Atlantic coast.

[braying]

To capture the booming vocals of elephant seals,

sound recordist Ellie Williams traveled over 7,000 miles to the Falklands.

[Ellie Williams] I don't think I've ever been anywhere quite this remote.

We're on this tiny island called Sea Lion Island

in the m-middle of the Atlantic.

[grunting]

I can't get over how big that male is.

- [chuckles] - He is like Jabba the Hutt.

[Hiddleston] Joining Ellie is cinematographer Sue Gibson.

[both chuckling]

[grunting]

[Hiddleston] When Sue starts filming,

Ellie's first challenge is to record the elephant seal calls.

But with the constant roar of white water, that means moving in close.

[grunting]

With her boom microphone attracting too much attention,

Ellie gets creative

using a stick to push a small microphone into the middle of the colony.

But things don't quite go to plan.

[Williams grunts] There it is.

[gasps] He snapped the stick.

[chuckles] Oh. [chuckles]

He's on it. [chuckles]

It's literally under his body and it's stopped working.

- [crew member speaks indistinctly] - No, it's stopped working.

[Hiddleston] But she perseveres.

And finally manages to record the earsplitting calls of the males.

[roaring]

[Hiddleston] It's a promising start.

But scientists believe there is a secret side to elephant seal communication,

and recording that is Ellie's next challenge.

[Williams] There's a theory that they produce such low, deep frequencies

that their sounds travel through the surface of the Earth,

which is quite extraordinary.

[bellowing]

[Hiddleston] This part of their call is so low it is inaudible to the human ear.

So Ellie tries using a microphone originally designed to record earthquakes.

So I've got something a bit different with me.

Um, this is called a geophone,

uh, and it's got this probe,

and I have to dig it not too deep but just under the top of the sand.

And hopefully, I'll be able to hear vibrations coming from the elephant seals.

But I'm also potentially gonna record a sound that has never been recorded before.

So it's something very new both for me and science.

[Hiddleston] With the geophone in position,

Ellie can hopefully listen in to the world of underground sound.

[elephant seals bellowing]

[grunting]

That is the deepest sound I think I've ever heard in my life.

[sniffs] Like, it was... it was really amazing just to...

- [elephant seals grunting] - [chuckles]

[elephant seals grunting]

[bellowing]

The sound waves passing aboveground were kind of impressive enough,

but hearing the... [sniffs] the ground move at the same time, that was extraordinary.

[Hiddleston] By using cutting-edge technology,

Ellie has captured the seismic calls of elephant seals for the very first time.

[Williams] I've managed to prove and get recordings

of this whole seismic world

that there were only theories about before we came here.

[Hiddleston] How elephant seals use seismic communication

is still relatively unknown,

but Ellie's recordings will help scientists better understand

the earthshaking sounds that have been hiding beneath our feet.