Original subtitles

NARRATOR: Sir David Attenborough is the unstoppable champion

NARRATOR: Sir David Attenborough of the natural world.

of the natural world.

His pioneering ideas about life on our planet

His pioneering ideas opened our eyes to new worlds.

opened our eyes to new worlds.

These have been called nature's greatest experiment.

In his mid-80s, many thought he had retired.

However, over the next seven years,

he launched a new era However, over the next seven years,

he launched a new era of natural-history filmmaking.

(SQUAWKS) Ooh!

(LAUGHS)

He revisited iconic locations across the globe.

I'm here surrounded by one of nature's greatest wonders.

Embracing advanced technologies,

his mission was to show us the world from a different perspective.

Ow!

That's a very powerful beak!

This is a journey from that very special time of global adventures.

Oceans cover almost three-quarters of our planet.

It's a world which reveals an astonishing diversity of life.

In the shallow seas off the north-east coast of Australia

lies the world's largest coral-reef system.

I'm here surrounded by one of nature's greatest wonders,

a living structure so enormous it can be seen from space...

..the Great Barrier Reef.

I've been fascinated by it for almost 60 years.

It's an ecosystem like no other.

And, for me,

it's truly one of the most extraordinary places on the planet.

Coral reefs are surprisingly noisy places.

Fish and invertebrates

produce a whole range of clicks and grunts and snaps.

produce a whole range The healthier the reef

The healthier the reef

the more varied and numerous The healthier the reef

the more varied and numerous its inhabitants

the more varied and numerous and the louder this chorus is.

and the louder this chorus is.

We now know that fish, just like birds,

vocalise most at dawn and dusk.

(SNAPPING)

Damselfish call to defend their territory.

(SNAPPING)

Seahorses click to attract a mate.

(CLICKING)

(GRUNTING)

Others create a very different soundscape

simply by carrying out their daily duties.

(CRUNCHING)

Parrotfish crunching through the hard coral

Parrotfish are a constant on the reef.

are a constant on the reef.

(CRUNCHING)

Fish perceive sound (CRUNCHING)

Fish perceive sound in two different ways.

Fish perceive sound Many have internal ears,

Many have internal ears,

but underwater they can also feel sound as a vibration.

The noise is a key indication that the community is in good shape.

In fact, the louder the noise on a reef

the more inviting it is to newcomers,

newcomers like the young clownfish.

This little male is no bigger than a button,

but the time has come for him to find his place in the big city.

At this stage, his swimming abilities leave something to be desired.

But his hearing is so sensitive,

he can tell over hundreds of metres if a reef is suitable.

His journey can last days.

The final approach is usually made at night to avoid predators.

In the case of the clownfish,

juveniles have been known to travel 250 miles before they find a reef. In the case of the clownfish,

juveniles have been known to travel 250 miles before they find a reef.

Fortunately, for the majority,

it's usually a much shorter journey.

While they rarely return to the particular anemone

While they rarely return beside which they hatched,

beside which they hatched,

60% find a new home on the same reef.

The clownfish keeps the anemone in good health

by removing unwanted parasites, keeps the anemone in good health

by removing unwanted parasites,

and, in return, the anemone offers security.

Its stinging cells ward off the sort of creatures

which would otherwise threaten the clownfish.

Cooperation is the key to success in this extremely crowded environment.

Other residents, however, take a very different approach.

Rather than share their home,

Rather than share their home, their territories.

they fiercely defend their territories.

This is a mantis shrimp.

There are many different species of mantis shrimp,

but they all have one thing in common...

..superb vision.

The 400-million-year-old visual system of the mantis shrimp

is the most complex in the entire animal kingdom.

is the most complex in the entire animal kingdom. Its eyes are mounted on two stalks,

Its eyes are mounted on two stalks,

giving it independent vision.

But, whereas our eyes produce binocular vision,

each one of theirs produces three different images.

each one of theirs Not only that -

Not only that -

whereas we have three photo receptors in our eyes,

the mantis shrimp has up to 16,

giving it access to parts of the spectrum

that we can't even see, let alone imagine.

And they can use their amazing vision

to devastating effect.

While some are armed with spears,

others carry clubs.

Many are champion boxers.

They can deliver a punch

that accelerates faster than a .22 calibre bullet.

These powerful blows are used to stun their prey

and defend their burrows. are used to stun their prey

and defend their burrows.