Night on Earth (2020) s01e04 Episode Script

Dark Seas

The sea at night can be a terrifying place.
Many fear what lies beneath.
But now, using cutting-edge filming techniques, we can dive into the inky depths and discover an extraordinary world full of bizarre creatures strange phenomena and astonishing behavior.
Where the moon and tides determine the rhythm of life.
And the blacker the night, the more wonders these waters reveal.
Our dark seas are the stage for the most magical nights on Earth.
It's the middle of the night on Australia's Great Barrier Reef.
But just bright enough for ultra-sensitive cameras to see into the darkness.
With the full moon, the tide is at its highest.
Just what female turtles have been waiting for.
It helps them to get over the reef and high up the shore.
Thirty years after hatching here, a green turtle has returned to lay eggs of her own.
With fewer predators around, night is the safest time to nest.
She's a latecomer.
The first nests were laid almost two months ago, and now they are beginning to hatch.
The odds are stacked against each tiny hatchling.
Only one in a thousand will make it to adulthood.
Drawn by moonlight reflecting off the water, they head for the ocean.
This short journey should be relatively safe.
But silver gulls can hunt by the bright light of the full moon.
Being one of the last to emerge can be a blessing.
The gulls are getting full.
She's almost there.
But high tide has drawn even greater dangers to the shore.
They'll take a third of the hatchlings that make it to the sea.
Past the danger zone.
Many more challenges lie ahead on her journey to adulthood.
But this young turtle has already survived one of the toughest nights of her life.
As she swims out into the East Australian Current, she'll become deeply connected to the rhythm of the ocean that fluctuates with the phases of the moon.
Even from over 380,000 kilometers away, the moon's gravitational force is strong enough to pull our oceans towards it.
It creates the tides that have ebbed and flowed over billions of years.
The tidal waters that pass through Indonesia's Lembeh Straits stir up rich nutrients from the deep that fuel some of the most bountiful waters on the planet.
Much of the life here is active at night.
This 15-kilometer stretch is home to some truly bizarre creatures of the night.
With thousands of different species all vying for food and space, competition is intense.
Predators must evolve ever more sophisticated ways to outwit their prey.
There's danger at every turn.
Lembeh is home to the ultimate ambush hunter.
The tiger mantis shrimp.
A monster over 30 centimeters long.
It's been lurking in these shallow seas since before the dinosaurs.
And in that time, it's evolved the most complex eyesight in the animal kingdom.
Each eye gauges distance independently, allowing it to pinpoint its prey with deadly accuracy.
But on darker nights a sixth sense takes over.
Specialized scales on its body detect pressure waves from passing fish.
Once locked on it strikes.
Harpooning its prey on razor-sharp hooks.
As the moon waxes and wanes, it changes the size and strength of the tides.
Which in turn dictate key events in many marine creatures' lives.
In the Pacific Ocean, the remote archipelago of Palau.
It's three days before the new moon.
The darkest phase in the lunar cycle.
Tides are growing stronger creating perfect conditions for bumphead parrotfish to breed.
Up to a meter long, thousands of these giants have gathered together.
This five-year-old male is joining them for the first time.
He has stiff competition.
Some of his rivals have been coming here for over 30 years.
As they wait for the tide to turn, cleaner fish remove dead skin and parasites.
Preparing the youngster for his big night.
It's still a few hours before conditions will be right.
He must save his energy.
At last, the tide is turning.
Hormones surge.
His face flushes white to show that he's ready.
Sensing the outgoing current, a female makes her move.
Males race to keep up, jostling for position.
The youngster tries to get close to the female.
But more experienced males block his way.
Another female.
As soon as she expels her eggs, the males release plumes of sperm.
The youngster tries again.
Forcing his way to the front.
Doing all he can to pass on his genes.
Their dramatic display is perfectly timed.
The tide sweeps the fertilized eggs away from the reef's hungry mouths.
And out into deep water.
In the open ocean, they join a blizzard of life.
A remarkable array of tiny creatures.
The larvae of fish, crabs, lobsters, jellyfish the next generation.
During the day, these zooplankton stay deep, away from most predators.
But under cover of night, they rise hundreds of meters to feed on algae at the surface.
The human equivalent of a 400-kilometer round trip every night.
Trillions of creatures all across the planet.
It's the largest migration in the world.
And the main source of food for countless marine creatures.
From small fry to ocean giants.
But even five-meter manta rays are dwarfed by the biggest fish in the sea.
The whale shark.
This female could grow over ten meters long.
And live for up to a hundred years.
She barely uses her eyes, but smells her way through the darkness.
Swimming vast distances in search of food.
She'll filter over four million liters of water and swallow 20 kilos of plankton every 24 hours.
The whale shark's life is mainly a solitary one.
Apart from the entourage of remoras that tag along as she journeys through the dark.
At the coast, tidal changes can be immense.
Twice a month, the sun, moon, and Earth align.
Their combined gravitational force creates spring tides that can rise and fall by up to 16 meters.
As tides recede, they leave rock pools behind.
By day, they look benign.
But at night, they are surprisingly hostile.
On the British coast, a prawn, just four centimeters long, is trapped.
Until the tide returns, he has a tough night ahead.
Without sunlight, seaweed stops producing oxygen.
The prawn must find food before the oxygen runs out completely.
Stinging anemones stand in his way.
Thanks to his protective shell, he makes it through.
But his troubles have only just begun.
In these first hours of night, whilst there's still oxygen, the pool comes alive.
The prawn must beware.
His eyes, made of thousands of tiny lenses, collect every last bit of available light.
Just as well.
You never know who's lurking in the shadows.
The rock pool's cast of characters changes with every tide.
A starfish.
One of tonight's most voracious visitors.
It prizes limpets from the rocks with brute force.
And leaves a trail of destruction in its wake.
Rich pickings for a hungry prawn.
But there are other, bigger scavengers here.
Protected by its shell, a hermit crab can afford to be bolder.
He's a less intimidating prospect.
But still not willing to share.
Another hermit crab creates a distraction.
Just what the prawn needs.
Oxygen levels are now dangerously low.
The prawn's life is at risk.
He must act.
With a modified limb, he beats the surface.
Drawing oxygen-rich water over his gills, an extraordinary behavior new to science.
But he can't keep it up for long.
He hauls out so he can absorb oxygen directly from the air.
Finally, the sun returns.
Seaweed starts producing oxygen once again.
But the stranded prawn is in danger of drying out.
Saved by the tide, he survived a hazardous night.
Over millions of years, the moon and tides have shaped the lives of marine creatures.
But now, our influence on the oceans is leading to new nocturnal behaviors.
This tiny Island in Mossel Bay, South Africa, is home to 4,000 Cape fur seals.
It's May, and the pups are now four months old.
Time for them to learn to swim and catch fish.
But seals are not the only hunters here.
Great white sharks.
Every year, they travel thousands of kilometers to get here.
And they've timed their arrival to perfection.
Inexperienced seal pups are soft targets.
As the sun sets, the fish that the seals feed on rise up from the depths.
To reach the fish on the far side of the bay, they must cross a deep channel.
The perfect hideout for hungry sharks.
Great whites hunt using an array of senses.
Vision is key.
Light levels have to be just right.
Too bright, and they're easily spotted.
Too dark, and they can't see their prey.
Driven by hunger, the first seals take the plunge.
Below them, the sharks can cruise just out of sight.
But the low sun reveals the seal's silhouette.
Once night falls, the seals should have a better chance of sneaking past.
But in Mossel Bay, even on moonless nights, complete darkness never arrives.
Light from the town spills out over the sea illuminating the surface waters.
It's all the great whites need.
By exploiting artificial light, the sharks here can hunt long into the night.
But at some point, the rest of the seals must feed.
The young pups seek safety in numbers.
Predator and prey are evenly matched.
Both see well in the artificial light.
Sharks have the element of surprise.
Seals are more agile.
Once beyond the city lights in the dark open ocean, the fur seals are safer.
But they'll face the same danger night after night until the sharks leave town.
Mossel Bay is the only place in the world where great whites are known to hunt seals using artificial light.
But the moon and cities aren't the only things that illuminate our seas.
Coral reefs grow in tropical seas where it's shallow enough for sunlight to penetrate.
During the day, algae that live inside the corals turn the sun's energy into food.
But too much sun can kill.
So corals have an intriguing defense.
It only becomes apparent after dark.
Bathing the reef in blue light reveals what's going on.
The corals glow.
It's a psychedelic sunblock.
Their pigments are absorbing harmful ultraviolet light, converting it into less dangerous wavelengths.
And it's not just corals that glow.
All sorts of reef creatures fluoresce.
But we are only beginning to understand why.
Perhaps it's to lure in prey.
Or warn off predators.
By night, even corals show a dark side.
They can no longer use the sun to produce food.
But they can keep feeding.
Speeding up time reveals their deadly secret.
Stinging tentacles that catch minuscule creatures floating by.
Every square centimeter of the reef is hotly contested.
This fast-growing branching coral is threatening to smother its neighbor.
An orange doughnut coral.
The doughnut can't escape, but it can fight back with chemical weapons.
Remarkably it pushes out its guts dissolving its enemy with digestive enzymes.
A successful counter-attack.
The doughnut coral stands its ground tonight.
But the turf war will never end.
The lunar cycle determines the rhythm of the many dramas in the sea at night.
And it's during the moon's darkest phase that the ocean puts on its most magical displays.
New moon in Japan's Toyama Bay.
Fishermen are setting out their nets in deep water.
They can only attempt this catch on a few nights in spring.
This female firefly squid is migrating hundreds of meters up from the abyss.
She's not alone.
Helped by the new moon's tidal surge, many thousands of her kind are rising to the surface.
Firefly squid make their own light, using special cells called photophores.
It's how they communicate in the deep.
And how she may have found a mate.
Only females make this one-way trip.
They're bringing their fertilized eggs up into the shallows to be dispersed by strong currents at the surface.
It's the final act of their short lives.
The Japanese consider firefly squid a delicacy.
By collecting them after they've released their eggs, they make little impact on their population.
Every year, hundreds of people come to harvest these treasures from the deep.
A tradition generations-old.
These nocturnal displays are surprisingly common.
Three quarters of all marine animals create bioluminescence, making their own light and illuminating the seas.
Sometimes, the sea puts on a particularly special show.
Luminous tides.
They've puzzled people for centuries.
But we now know they're caused by billions of single-celled creatures.
When disturbed, they produce light via a chemical reaction.
Each generating a flash to warn off predators.
But any agitation will trigger a response.
Dolphins glowing in the dark.
Seldom seen, and never before filmed underwater.
Dolphin eyes are highly sensitive to blue light.
They can clearly see the bioluminescence.
They may even use the light to help them hunt.
Or perhaps they're just enjoying the show.
Armed with the latest technology, we are venturing further into these dark waters.
But there's still an ocean of discovery to be explored in the depths of the night.
All around the planet, night presents animals with extraordinary challenges and opportunities.
Our understanding of some of the most iconic creatures is already being redefined.
Who knows what more surprises are hiding in the dark of a night on Earth?
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