Original subtitles

For centuries we've fantasized

about alien life on other planets.

And because life as we know it needs water,

we imagined seas on the moon,

rivers on Mars,

and lakes beneath Europa's icy surface.

So far, we've discovered only dust

except on this watery blue marble,

where inner space hides creatures

as weird as anything extraterrestrial.

There are oceans of oddballs...

with strange shapes,

strange rituals, and strange bedfellows...

right here in Earth's own

"Alien Abyss."

Sci-Fi writers have come up

with some pretty strange rituals

for their alien characters.

Turn off that tickle ray!

But science fiction

doesn't even scratch the surface

of what goes on right under our noses.

The ocean is full of alien lovers

of free-love love-ins...

swashbuckling sex shifters...

And works of erotic alien art.

Every animal faces two fundamental challenges.

There's transferring your genetic material...

And making sure some of your offspring survive

to carry on your own peculiar genes.

As long as you meet those simple criteria,

anything goes.

And there's some pretty strange ways

to get your DNA into the next generation.

Let's start with the Big Bang.

In the beginning, darkness was over the face of the deep...

because it was night

at the bottom of the sea.

And then there was light.

It was the moon,

and verily did the squid answer the moon's call.

They had a massive orgy, and everybody died.

Wait, what?

Let's back this up a bit.

This is the opalescent squid.

It lives along North America's Pacific Coast

over the continental shelf.

It's an unremarkable squid in most respects...

medium-sized, short-lived.

Seriously, six to nine months of feeding on krill,

and that's it.

But at least it ends with a bang.

That really is the scientific term--

big bang mating.

And so here we are,

one moonlit night half a year or so after these guys hatched.

All the local squid of breeding age

have moved into shallow inshore water...

so everyone can check each other out.

Then the pairing up begins.

Males take willing females in a tender embrace.

They've prepared for this moment

by storing up packets of sperm

called spermatophores under their mantles.

That's the part that looks like a long pointy hat.

Mating is as simple as handing one of these packets over

and hanging on.

Most males use the guard strategy.

They try to hold on to their partner

to the bitter end.

Their plan is to make sure she doesn't mate with anyone else.

This is, after all, their one shot

at staying in the gene pool.

The guards flash angry red at any males

that try to muscle in.

And plenty do.

Sneaky little guys called sneakers.

Their game plan is to sneak up on as many females as possible

and sneakily sneak their sperm under her mantle...

even if she's already attached.

Once the frenzy has died down, the females lay eggs.

These they attach to the sandy bottom with a sticky cement.

And that's it.

Males and females have saved up all their energy

for this one night of synchronized mating.

And then everybody dies.

By morning, scavengers have already eaten

most of the adults.

The eggs, with their tough protective protein sheaths

are not that appealing.

Although the parents pay a high price,

squid babies are cheap to produce.

Each mom and dad pair can make 4,000 potential replacements

for themselves and leave the rest to chance.

Octopuses, close relatives of squid,

are easily the most alien creatures in the ocean...

so, of course, they do once-in-a-lifetime mating

their own peculiar way.

They do it slowly.

In preparation, males and females

begin digesting their own muscle tissue

to make sperm and eggs.

There is one problem, though.

Mating requires meeting.

And if there's one thing an octopus hates,

it's another octopus.

Encounters usually lead to violence...

Sometimes even...

cannibalism!

Hence this male day octopus approaches a female with care.

He has one thing going for him, though.

Because they don't meet many of their own kind,

the female is not fussy.

He'll do.

Not that she's going to stop hunting fish

just because some guy puts his hectocotylus inside her.

He doesn't mind.

He's literally thinking with his reproductive organ.

His hectocotylus is one of his arms

adapted for sperm delivery,

and like all his arms, it has its own brain cells.

Being able to keep his reproductive partner

at arm's length is quite handy

for an octo-dad because, you know...

cannibalism.

But inseminating is a delicate operation.

A male must snake his hectocotylus

into his partner's siphon.

That's the tube she also uses

for breathing and jet propulsion.

If he succeeds, he'll leave a packet of sperm

in a holding area below her ovaries

ready for her to use.

If she doesn't eat him first,

he'll die in a matter of months.

A female octopus may keep her packet of sperm tucked away

for several weeks before she's ready to use it.

When she does,

she signs her own death warrant.

This blue-ringed octopus

is looking for her final resting place.

Sorry, I mean nesting place.

Barely 20 centimetres long, all she needs is a nice rock.

Whereas a female giant Pacific octopus

needs a full-sized cave.

She strings her eggs up from the ceiling,

tens of thousands of them.

She tends every one of them for six months,

grooming and blowing oxygen-rich water over them.

She doesn't eat.

Food scraps could attract predators

or be a source of infection.

Her final, most alien act

is to starve herself to death for her children.

With her last remaining strength,

she blows the hatching eggs out into the water.

Despite all her care,

only one in a hundred of these newborn orphans will survive.

The rest are insurance.

Taken to extremes,

this strategy of making a lot of extra babies

is something of a dark art.

It's called predator swamping...

A brutally practical way to win at reproduction.

Out there in the abyss,

an alien army lurches unseen towards the shore...

ready to take on any predators

that might threaten their babies.

Their strategy-- overfeed the enemy.

The well-armored American horseshoe crab

looks like a spaceship

but, really, it's more of a time traveler.

They have changed very little

for 450 million years.

They're not crabs or even crustaceans,

but relatives of now-extinct sea scorpions.

Their tail has no sting.

It helps the crabs right themselves

if they tip over on their long spawning journey.

Some have walked for 100 kilometres

from the continental shelf

to be at the love-in in Delaware Bay.

It's business time.

They are guided by the phases of the moon

to spawn at extra-high tides,

laying their eggs on the beach.

The larger females release pheromones

that drive the smaller males wild.

The lucky ones get a ride up the beach with a partner.

As she lays her eggs in the sand,

he fertilizes them.

It's an orgy of confusion.

They haven't spent those 450 million years

working on their choreography.

Lesser males trail behind,

scattering sperm as they go.

On the beach,

the fertilized eggs are safe from marine predators.

Unfortunately, they're easy pickings

for land predators.

The eggs are an important food source

for hordes of migrating seabirds

that time their stopover with this bonanza.

It looks like slaughter,

but across the bay,

hundreds of thousands of females

lay billions of eggs.

There is no way the birds can eat them all.

That's predator swamping.

In a fortnight's time,

the survivors will hatch and be washed into the sea.

Clearly, there are some strange goings-on

down there in the abyss...

but so far, there's been at least one familiar thing

to hold on to.

It takes a female and a male to make a baby,

doesn't it?

Well, not quite.

Coral reefs are fascinating, colourful places...

full of fascinating, colourful creatures.

Some of the parents here

look like they come from outer space--

all bulging eyes and weird appendages.

But strangeness is in the eye of the beholder.

Take the traditional division of male and female genders.

Those fall apart on the reef,

where gender can flow as freely as the currents.

Ribbon eels, for instance,

are small morays with colourful bodies

and even more colourful sex lives.

Like other morays, they spend much of their time in burrows,

picking off passing fish.

The males are blue.

The females, yellow.

Nothing weird about that,

except that they are all born

as males and black.

Within a few years, juvenile males turn blue,

signalling they're ready to mate.

But who with if they're all born male?

Older versions of themselves is who.

When they reach about a meter in length,

the males turn yellow and female.

Ribbon eels are sequential hermaphrodites--

first one gender, then the other.

There are also fish that swing the other way.

Parrotfish, for example.

They start life as females

and only become colourful males when they reach a certain size.

Some gobies can change sex repeatedly in either direction.

They can go from producing eggs

to producing sperm in a matter of days,

depending on what the local population needs.

Cleaner shrimp start life as males...

and grow up to become monogamous hermaphrodites.

Cute couple.

And the sorority of soft squishy sea slugs,

otherwise known as "nudibranchs"

is also a fraternity.

Nudis are simultaneous hermaphrodites.

They maintain a full set

of male and female reproductive organs

all their lives.

There are over 3,000 species of nudibranch,

so you know they're onto a good thing.

They're a Mardi Gras of dazzling colours...

and dazzling abilities.

This one has a detachable penis

coiled up inside its body.

Every time it mates, it sheds the end of its penis

like a lizard sheds its tail.

For all their abilities,

nudis still need to meet another of their kind.

They can't fertilize themselves.

Being hermaphrodites guarantees that when they do meet someone,

it'll be someone with the opposite sex.

How do they decide which one is what one?

They don't.

When two nudibranchs fancy each other,

they line up their organs,

male to female and female to male

and each fertilizes the other.

This little weirdo is no nudibranch.

The big giveaway? No gills.

That's these feathery bits on the nudi.

This alien dancer is a marine flatworm,

but it, too, is a simultaneous hermaphrodite

with a difference.

Flatworms are not sharing and caring

like their sea slug relatives.

When two flatworms arrange an assignation,

it's a duel.

Both combatants know that the cost of rearing children

is much higher than the cost of a bit of sperm.

They fight for the right to be the dad.

It's called penis fencing.

And if that's not weird enough, get this--

the father-to-be is the one that manages to stab the other

with his penis and inject his sperm.

Scientists call it traumatic insemination.

And finally in our roundup

of alternative reproductive strategies,

a shout-out to the seahorses.

These most bizarre-looking fish

have perhaps the most novel division of labor

among the sexes.

Mom made the eggs,

but it's dad that incubates them in his brood pouch.

This alien dad boldly goes

where no other fathers have gone before...

into labor.

It works for them because it frees the female up

to start making a new batch of eggs.

But even more traditional creatures

can have some seriously strange ways

to spawn the next generation.

Sometimes making new life is dicing with death.

Penguins may be familiar, but they're aliens twice over.

Birds so fully adapted to the life aquatic

that, on land, they're like fish out of water.

And yet, that terrestrial environment

is where they go to raise their young.

King penguins are slightly smaller relatives

of the more famous emperor.

They breed on rocky subantarctic islands

like South Georgia.

They share the emperor's fancy clothes...

so you might think you know how this tale goes.

You don't.

This one is much darker and disturbing.

It starts out normally enough.

One fine spring day,

some prospective penguin parents waddle up the beach.

Before they start courting, they moult.

Got to look your best.

Fresh feathers are ready at the start of summer

when their food is most plentiful.

It's a great time for highly energetic activities

like courting...

mating...

and taking it in turns to incubate the egg.

It gets really busy when the thing hatches.

The little darlings are insatiable.

Cue weeks and weeks of fishing and feeding...

fishing, and feeding.

The brown, fluffy chicks

segregate themselves in crèches.

They're so big and un-chick-looking

that early explorers thought they were a separate species,

which they called "the wooly penguin."

And then comes the alien twist.

Winter is here, and the chicks are not ready.

Having diligently fed them for weeks,

their parents abandon them.

The chicks must fast through the winter.

One breeding season simply isn't long enough

to raise them to adulthood.

Come the following spring,

mom and dad return to find the survivors

and fatten them up again.

Still alive, Junior? Wake up!

Junior fledges just as summer arrives,

and food in the sea is plentiful again.

That's good.

By now, it's too late in the season for mom and dad

to start a new family with any hope of success.

But they do it anyway.

That's not so good.

These late-born chicks usually die.

But at least that frees mom and dad up

to start early again in their third year.

Strange birds.

If birds can swim, then why shouldn't fish...

Fly?

These magnificent mutants have fins so aerodynamic,

they can leave the sea behind.

In the right conditions,

they can fly for hundreds of meters.

The wide-open seas of the Caribbean

are bound with freaky flying fish.

The sea and the airspace above...

flying is a great way to escape marine predators.

There's no telling where they'll touch down.

This flock is looking for a place to spawn...

but they're open-water fish, always on the move.

No solid reefs or seagrass beds for them.

So, when nature provides a suitable landing pad,

they waste no time.

The early birds launch themselves

onto the palm frond

and wiggle into the safest crevices

to spawn.

Below the waves, more flying fish respond,

working themselves up into a lather of eggs and sperm.

Within minutes, hundreds of fish

cover the floating island.

The drive to find a safe place for their eggs is so strong,

some become entombed in their own spawn.

The survivors leave the next generation

to drift with the currents and hatch who knows where.

It's time to fly.

Straddling two worlds is never easy.

You'll always be part alien in both.

Sea turtles are land animals that returned to the sea

millions of years ago.

They must surface to breathe.

That's turned their mating ritual

into a dance with death.

This receptive female has a male hanging off her back.

Scrap that.

She has a whole bunch of males trying to get on her back.

The first guy won't let go,

hoping to prevent any other males mating with her.

Pretty soon, an all-out brawl erupts...

On her back.

She's treading water with multiple hitchhikers

weighing her down.

She's a champion breath-holder,

but this is an underwater workout.

If she can't surface, she'll drown.

Such testosterone tournaments

are not uncommon in the animal world,

but there are other ways to win a partner over.

How about making a bit of a song and dance?

The song of the humpback whale...

Ethereal...

otherworldly...

alien even...

and utterly mysterious.

Here's what we do know--

only the males sing

and only in the breeding season.

So it has something to do with sex.

During the winter, the waters around Hawaii resound

with this submarine, soul music.

The half-hour songs have structure and phrasing.

Catchy new tunes spread from male to male.

It's some sort of communication...

Perhaps the closest thing

to an alien language we have on Earth.

Mothers with young calves

are the object of the singers' attention,

because right after she gives birth,

she ovulates.

Does this male's soulful music

help to trigger that process?

Is it a tender serenade

or a warning to other males?

All have been suggested,

but the truth is we have no idea.

What's soon apparent is that singing alone

isn't enough to win her over...

Not with an entire fleet of bulls

all with the same idea.

When the song is over,

testosterone gets the better of the males.

Mom takes off, baby in tow,

and her suitors in hot pursuit.

They blow bubble curtains to disorientate their rivals...

and showcase their strength...

by lashing out

and making an altogether less musical cacophony.

This heat run takes a lot of energy.

The biggest males with the biggest energy reserves

have the advantage...

And presumably the best chance to mate

if she accepts him.

We can't be sure of that

because no one has ever seen humpbacks make the beast

with two humps.

If you don't have the chops for a song,

try a visual serenade.

No one knows how to turn on the colour

like the flamboyant cuttlefish...

an intelligent life form that likes to flaunt it

when it flirts.

This tiny walking cuttlefish lives and loves

on the sandy seafloor around Indonesia.

It's one of only three known toxic cephalopods.

So people have assumed that its famous flamboyance

is some sort of warning signal.

But recently scientists have discovered

that the flamboyant cuttlefish's natural state

is actually rather drab.

They're usually so well camouflaged,

scientists don't notice them...

perfect for a daytime hunter.

They only turn on their spectacular display

for two reasons.

One is to tell a camera operator to back off.

The other is when they want some.

The much smaller male has a visual vocabulary

of seduction.

The female usually stays drab and utterly ignores him.

He makes tender kissing gestures with his arms

and strobes his admiration for her.

And then...

Is this the moment she turns into an alien monster

and devours him?

No.

This terrifying gesture is her way of telling him

he's been accepted.

He gallantly responds by depositing a packet of sperm

near her mouth for her to use at will.

Mom lays her eggs somewhere vaguely safe,

and that's her job done.

Her hatchlings are perfect miniatures.

They erupt flamboyantly...

But soon settle down into cryptic colours.

If you can't sing or serenade in semaphore,

then you'd better be handy.

You're going to have to build a love nest.

But what sort of alien fish makes a nest?

The sea, with its shifting waves and currents,

is a difficult place

to construct a monument to love.

Very few fish can truly be called builders.

It's an altogether alien thing to do down here.

The fact that the garibaldi tries it at all

in California's swirling kelp forests

makes him a very strange fish indeed.

His nest is the dark patch on this rock.

Don't laugh.

He's carefully constructed it

by trimming a patch of red algae

to the right length

and eating away everything else.

To be fair, the females don't seem that impressed either.

What they're really looking for

is a nest that already has eggs in it.

After all, that must mean other females

thought he was worthy.

So how does a guy attract that all-important first female

to his empty nest?

He's gonna have to dance.

Once he convinces one female, the rest will follow.

A week later, his hard work and suave moves

have paid off.

His nest is laden with masses of yellow eggs.

He's now busier than ever seeing off egg thieves,

real or imagined.

In a bizarre twist,

dad can be the worst egg thief of all.

The females like to lay their eggs next to fresh ones,

so papa garibaldi eats some of the older ones,

gambling that they'll be replaced

by even more fresh eggs.

For decades, the garibaldi nest was the state of the art

as far as fish nests were concerned.

We only really showed it to you to emphasize how impressive

the next international man of mystery

really is.

Around the turn of the century,

it seems aliens landed in Japan.

We can infer this

because they made their signature crop circles.

Curiously, they only invaded this one shallow bay

off Amami Island.

Question was,

who or what was making the circles?

Was it an octopus's garden...

The lair of an evil super villain...

The work of a school of merry pranksters...

Or a bizarre natural phenomenon?

After ten years of searching, the culprit turned out to be--

drum roll, please...

E, none of the above.

It was a nondescript, 12-centimeter-long fish

no one had ever heard of before.

Not an actual extraterrestrial

but new and very alien to science.

Take a bow, white-spotted pufferfish

from Amami Island off southern Japan.

This small sand-colored fish

living in a featureless sandy bay

does something so odd

that it's the only fish that does it.

Art.

Like so many male endeavours,

his art serves one purpose...

to impress a female.

There, that should do it.

But let's back this up a bit...

because this love nest

is a marvel of science and engineering,

as well as art

He starts on a featureless plane

of mostly coarse sand.

But he knows that female puffers

like to lay their eggs in soft, fine sand.

And he's too well camouflaged to attract attention.

He sets to work, solving both problems.

First, he clears a rough circle.

Then he starts plowing furrows from the outside to the centre.

With only his fins for tools, he works for ten days or more

to make an intricate design two meters across.

His geometric precision can only be described

as out of this world.

No matter from which direction the current flows,

it funnels the finest sand to the middle of his nest.

There, his pièce de résistance.

Now for those finishing touches...

And just try résistance-ing that, ladies.

His masterwork quickly gets noticed.

He stirs up the fine sand to show it off.

A peck on the cheek.

And watch closely.

Ten days of tireless work have led up to this moment.

Talk about an anticlimax.

The male stays

to see if he can attract a few more females

and to protect his developing eggs

from the resident, evil genius.

But the male no longer maintains his nest.

It slowly deteriorates.

When his eggs hatch in a few weeks' time,

he'll start a completely new work of art.

A parent dedicated enough to protect his eggs

is hard to find in the sea.

Most marine creatures simply sow their wild oats

and let nature take its course.

Extremists gather in huge numbers

to broadcast their genetic material

to the world in unison.

In the Alien Abyss,

broadcast spawning is the rule rather than the exception.

Even the coral itself does it.

What is broadcast spawning?

All the males and females release eggs and sperm

into the water at exactly the same time.

This magical wonder of the natural world

is the reef mating with itself.

Timing is everything.

Guided by the moon,

the corals spawn in supernatural synchronicity.

In the space of half an hour or so,

millions of coral polyps release eggs and sperm

into the water.

Each is only viable for a few hours,

so they need to get together quickly to create new life.

To maximize their chances,

the fatty egg and sperm cells float up to the surface,

where there'll be in closer contact.

The newly created embryos will drift off on the currents

to start new colonies elsewhere.

The famous plankton soup that feeds everything

from jellyfish to whale sharks

is made up almost entirely of the eggs

and developing young of broadcast spawners.

A tidal channel in one coral atoll

attracts one of the world's largest spawning aggregations.

No, not the sharks.

They're here to watch the show--

watch and snack.

700 or more gray reef sharks,

collectively known as the wall of sharks.

More apex predators than could possibly survive

in such a small area,

if it wasn't for one thing.

A progression of different fish species

come here to broadcast spawn over the winter months.

The most spectacular show

is the one put on by the camouflage grouper.

Camouflage groupers from all over French Polynesia

descend on Fakarava Atoll to spawn.

The groupers are sequential hermaphrodites.

They start life as females, which are slightly darker.

The older male fish

are normally solitary and territorial.

Confronted with so many rivals, they get into fights.

Some mute their camouflage colours

in an attempt to avoid confrontations.

But often, it's just too crowded.

Because groupers come from far and wide,

they not only maximize their chances of success.

They also minimize inbreeding.

Their numbers build for two weeks,

leading up to the full moon.

By day, an eerie truce holds

between the sharks and their snacks.

The sharks are nocturnal predators.

At night, they turn into highly active,

agitated hunters that ferret out food.

Thanks to the massive aggregations of spawning fish,

hundreds of sharks rarely need to leave the area.

Morning reveals brutal injuries among the survivors.

These must be some of the bravest

prospective parents in the ocean.

Finally, at dusk on the night of the full moon,

the groupers are ready to spawn.

The females take in water to hydrate the eggs

they have been carrying all this time,

causing their bellies to swell.

Groups of groupers rise into the tide

to release millions of eggs and sperm...

While still dodging the sharks.

Within an hour and a half, it's all over.

The extra-high full moon tide sweeps the fertilized embryos

out to sea to join the plankton soup.

Groupers spawn conventionally for fish,

just on an alien scale.

But what about the secondary players

in this tale...

the sharks?

As it turns out, they're the real weirdos

when it comes to mating.

Sharks don't broadcast their eggs and sperm

to the world.

They're strictly person to person...

and it's awfully awkward...

because doing it in the open water

is about as easy as it would be in the weightlessness of space.

And the only thing these freaky fish have to hold on with...

Is their teeth...

Which makes it almost impossible for him

to pump air over his gills.

If she's not interested, the female can arch her tail

to prevent access,

knowing he'll run out of breath.

Only if she consents

can he insert one of his claspers

into her cloaca.

He fills a sack that runs along his belly with seawater

to pump his sperm inside her...

before he suffocates.

Whether it's alien crop circles,

otherworldly orgies...

or synchronized spawning...

the most bizarre rituals in the ocean

are usually about finding a mate

and passing on your genes.

But you have to wonder,

who are the real aliens down here--

the creatures going about their business

or the ones in space suits

recording what goes on

down in the Alien Abyss?