Original subtitles

[soft expectant music]

- The Jura Mountains on the French-Swiss border

are in the grip of winter.

The ground has been frozen solid for months.

This is a tough place in which to live.

I'm told that clearings like these

could be the home of a real giant.

At this time of the year, it'll be in hiding.

But evidence of its existence,

these strange mounds, is everywhere.

Inside here, deep down and protected from the cold,

the giant is asleep.

Beneath the thatch of spruce needles

lies a maze of tunnels and chambers,

the home of hibernating wood ants.

Individually they're tiny,

but they're members of a giant super-colony.

When temperatures rise, over half a billion of them

will emerge and dominate this landscape.

Scientists are only just working out

how ants manage to survive up here, but in fact,

there's a much greater and more profound mystery

that has brought me up this mountain.

Among ants, cooperation between colonies is very rare,

warfare is common, yet these nests over a great area

live at peace with one another.

This may sound like an epic tale of war and peace,

but does it also contain an echo of human nature?

These ants in some extraordinary way

have exchanged war for peace.

It's now recognized as one of the largest

of all insect super societies, and its very existence

conflicts with some of the laws of evolution

as we presently understand them.

[dramatic expectant music]

[bird cawing]

It's been a long cold winter

here in the Swiss Jura mountains.

It's hard to believe that any insect

could survive in this frozen landscape,

but now change is in the air.

Soon ant nests all over this mountain will come to life.

Some of these mounds are independent colonies,

but others are part of one huge super-colony.

Over the coming months,

I will be looking at the differences

between these two wood ant societies,

one that wages war with all its neighbors,

and the other which welcomes them and lives at peace.

[soft thoughtful music]

As the grip of winter eases,

sentries emerge from the mounds to check on conditions.

They detect the sign that they've been waiting for.

The temperatures are rising, spring is on the way.

[soft thoughtful music]

The ants survived the winter

thanks to their own central heating system,

warmth given off by the slow decomposition

of the dead vegetation in the nest's fabric,

and that prevented them all from freezing.

Now by swarming all over the surface of the nest,

they're recharging their batteries,

absorbing heat directly from the sun's rays.

[dramatic expectant music]

This behavior only happens over one or two days

in the early spring.

The worker ants have emerged into the sunshine,

and are now clumping together,

and they're not just sunbathing.

It could well be that the ultraviolet rays of the sun

cure them of any infections from viruses or fungi

that may have happened during their long sleep underground.

You can almost feel the enthusiasm

with which these little creatures

are enjoying their sunbathe.

[soft expectant music]

This is unusual enough,

but now here is something truly extraordinary.

There is a queen.

She's almost twice the size of her subjects.

She's also the most important member of her family,

and what's more, there's another.

To see a queen exposed and vulnerable outside the nest

is very rare indeed.

There's one, and there's another,

shining wonderfully in sunshine.

A normal wood ant nest usually has just a single queen

who lays all the eggs, but clearly this is not so here.

There's another, there's another.

Several of them, amazing. [soft expectant music]

After a few moments in the sunshine,

the only time they see daylight in the whole year,

the queens disappear and make their way

back to the brood chambers, deep in the nest.

[soft uneasy music]

Those unwilling to go are dragged back.

We may call them queens, but there's no sovereign rule here.

The workers govern by consensus, and they decide

when and where the queens will go.

[soft thoughtful music]

There may be hundreds of queens in this single nest,

and there are over a thousand

such mounds as this, all interconnected.

So across the super-colony,

there may be as many as a million queens.

[soft thoughtful music]

It's now early April.

The queens' return below to prepare for the egg-laying

started a race against the clock.

They must complete their most important work below

in the next two months. [soft thoughtful music]

Using infrared light, which is invisible to the ants,

we can watch them inside their nest without disturbing them.

[soft thoughtful music continues]

Most of the first eggs to be laid

will produce the next generation of breeding individuals,

the queens and the males, both of whom will have wings.

Inside the thousand nests of the super-colony,

over a half a billion mostly unrelated worker ants

cooperate to ensure that the queens and the males

will be ready for their mating flights in mid-June.

With all these developments on the way,

it's imperative that the workers collect

more food as soon as possible,

but many of the mounds are still surrounded by snow,

so the workers can't reach their feeding grounds.

But there is something they can collect, heat.

The nest needs more heat

than that which comes from the rotting vegetation,

if the eggs are to hatch in time for their June appointment.

Now however, the ants have another source of warmth.

[soft expectant music]

Using their bodies as solar panels,

the ants harvest the sunlight.

We have a heat-sensitive camera

that detects differences in temperature.

The nest appears black, because it's hotter

than the surrounding environment.

It shows a similar difference in the ants.

Those going down into the nest are black

because they've been heated by the sun,

whereas those coming out are white because they're cold,

having transferred their body heat to their charges

in the brood chambers below.

It's this kind of selfless collaboration

that is the key to success of any ant colony.

In normal ant colonies, all the workers

are related to one another and to the queen,

and the theory is that that is why they all cooperate.

But that is not the case here.

There are hundreds of queens here.

Over a thousand have been counted in a single nest,

so all the workers can't have the same parents

and genetics have confirmed that this is so.

It's this cooperation between unrelated ants

in a single colony that appears to be

rewriting the rules of insect evolution,

but we still don't really know how this has come about.

[soft thoughtful music]

Spring is now well on the way.

The snow has disappeared, and color comes to the meadows.

[gentle thoughtful music]

By late April, there there are piles of eggs in the nest

and the first larvae are hatching.

The workers labor unceasingly to ensure

that the growing brood will be ready to emerge

in six weeks' time, at the peak of the short Jura summer.

[gentle thoughtful music]

But not every ant nest on this mountain can be so focused.

Some will soon have to deal

with threats to their very survival.

Just a short distance away, on the borders

of the super-colony's woodland territory,

there are other wood ants.

The mounds here on this side of the mountain

look exactly the same as those of the super-colony,

and so do the ants themselves.

The inhabitants of each nest here

are all the offspring of its single queen,

and the colonists compete aggressively with one another.

After the winter hibernation,

the territories between that nest over there

and this one here have become blurred,

and the frontier has to be reestablished.

And in order to do that, workers from both nests

are now scouring the ground,

and that brings neighboring ants into contact

for the first time this season.

[dramatic expectant music]

When foragers from the different nests meet,

they immediately recognize that they're from rival families.

They then dash back to their nests,

and within minutes both colonies know

the territory on their frontier is being disputed.

Armies assemble. [dramatic expectant music]

This is war, and the weapons being used are chemical.

Formic acid [sniffing], I can smell it in the air.

They're squirting it from the end of their abdomen,

and if they can bite their opponents

so that the formic acid gets beneath

the outer shell of an ant,

it will dissolve its internal organs.

[dramatic expectant music]

As they grapple, each tries to restrain its opponent

by clamping its jaws around a leg or an antenna.

[dramatic expectant music continues]

Soldiers from both sides tug at their opponents' limbs.

[dramatic expectant music continues]

It could take seven ants to subdue a single enemy.

One holds each leg, and the seventh uses its mandibles

to cut open sections of their opponent's exoskeleton,

exposing the insides.

An attacker brings forward its abdomen under its body,

and squirts acid onto its victim.

Battles are going on everywhere.

[dramatic expectant music]

Each colony carries its own chemical badge,

invisible to our eyes,

but clear to the ants' sensitive antennae.

Fighters touch each other, to confirm whose side they're on.

Here and there, individuals clamber up the vegetation.

Are they having a rest, or are they surveying progress

to see where help is needed?

[dramatic expectant music]

The smell of formic acid reaches the colony,

and more ants from both sides run to join the battle.

[soft dramatic music] [birds chattering]

These wars can continue for over a week.

At their peak many thousands are fighting,

and thousands are killed. [soft dramatic music]

The victors will certainly have enlarged their territory,

but some say they have also gained other rewards.

They're taking off the bodies of their victims,

and carrying them back to the nest over there

to feast upon them.

Both sides have suffered heavy losses.

For the ants in the meadow,

it has been a costly start to the year.

Higher up the mountain in the territory of the super-colony,

the inhabitants of different nests are also meeting,

but here things are very different.

These ants come from a mound about half a mile away.

If that mound was a separate independent colony,

then these, when they land there, will be savagely attacked.

But let's see what happens.

[soft expectant music] [birds chattering]

At first, the resident ant makes an aggressive gesture,

but then the other strokes the first's antennae.

That gesture is a request for food,

and the other obligingly feeds her.

This behavior, known as trophallaxis,

is in itself not unusual.

Most ants do it at times.

What is unique is that these ants

are almost certainly unrelated, yet they treat each other

as if they were from the same nest.

They do this because they share the super-colony's scent,

a chemical signature that is transferred,

together with the food.

In one experiment, scientists fed a distinctive chemical

to a nest on one side of the super-colony,

and eight weeks later, that same chemical appeared

far away on the other side.

It's this sharing of food

between over half a billion individuals

that makes this super society so truly remarkable.

[soft thoughtful music]

Because of this, super-colony ants

can move freely between mounds,

and they have as a result

created over a hundred kilometers of trails

that link over a thousand nests.

These trails not only allow the ants

to make new nests deep in the forest,

they also give all the members of the super-colony

access to resources of great value to them.

[soft thoughtful music]

It comes from the spruce trees.

[soft thoughtful music continues]

The ants don't feed directly on the spruce trees.

They become farmers, and these are their flocks, aphids.

The presence of the ants keeps insect predators at bay,

so the aphids can feed unmolested.

They drink the tree sap,

and excrete what they don't need

as a sugary liquid called honeydew, and the ants love it.

[gentle thoughtful music]

Just as human farmers milk their cows,

so the ants stroke the aphids with their antennae,

to persuade them to release their honeydew.

[gentle thoughtful music continues]

Once the aphids are milked, and the ants have drunk

as much honeydew as they can carry,

they head down the tree, abdomens bulging,

and return to the nest.

[bright thoughtful music]

The honeydew is not only food

with which to sustain themselves, some use it

to raise the heat of their bodies well above normal,

and so warm the atmosphere within the nest,

a valuable ability in the fickle climate of the Jura.

The spruce trees themselves also produce a substance

that the ants can use directly.

These ants have collected little flakes of resin.

That's a sort of gum that oozes

from the broken twig of a coniferous tree.

The tree uses it to seal off an injury,

but what are the ants using it for?

Inside the nest, the extra warmth produced by honeydew

helps the queens to keep laying,

and the larvae to keep growing.

However, constant warmth can create problems.

Despite regular cleaning, diseases can thrive.

The ants have a remarkable solution to that problem.

They cover the surface of the mounds

with tiny nuggets of resin,

and also take it into the chambers below.

One nest contained over four kilos of it.

It is in fact ant medicine.

The ants combine acid from their bodies with the resin,

and so produce a very effective antibiotic.

This is one of the most sophisticated

animal pharmacologies known to science.

It's been shown that wood ants living in nests

that contain resin are better able

to survive diseases than those that don't,

and the eggs are far less likely to be infected by fungi.

[wind whooshing] [birds chattering]

This immense, peaceful super-colony has few enemies,

but now at the end of May, a new threat has arrived.

[cowbells clanking] [cows mooing]

The Jura is famous for producing

some of Europe's finest cheese.

For generations, farmers have made

small clearings in the woods,

to create meadows where cattle can graze.

Only now is it warm enough for cows

to be brought up to these high pastures.

[cows mooing] [cowbells clanking]

Somehow the ants need to make sure that they're left alone,

and that nothing damages their nests,

and that's a considerable challenge even for a super-colony.

[cows mooing] [dramatic expectant music]

But these ants are very determined.

When one squirts it's acid, others follow suit.

[dramatic expectant music continues]

The result is a coordinated barrage.

[acid splattering] [soft dramatic music]

The cows are not harmed,

but they do get a dose of acid in the nose,

which they don't like,

and they tend thereafter to avoid these mounds.

[cows mooing] [cowbells clanking]

[insects chewing]

By now, in June, the larvae have become big and greedy.

They must be given special care,

because they will produce the next generation of royalty,

so the workers labor hard to meet their demands.

In summer, hundreds of thousands of eggs

are hatching every day, and honeydew is not enough.

The ants go in search of something else,

a supplement, fresh meat. [bee buzzing]

The lush green hills and mountains of the Jura

are now teeming with all sorts of life,

and nearly all of it is potential food.

[soft expectant music]

The ants spread out from the nest,

scouring every square inch of the ground in search of prey.

[soft expectant music] [bee buzzing]

As the hunters approach, those that can take flight.

[bee buzzing] [wings fluttering]

And the ants' vision is not very acute.

They can only see a target if it moves.

A wolf spider however, can see the ants clearly,

but as long as she doesn't move,

they won't know that she's here.

[soft expectant music]

She's carrying a little sac full of eggs.

[soft expectant music continues]

She decides to run for it,

and her sudden movement alerts the hunters.

[soft dramatic music]

That first fleeting touch by an ant left a faint scent mark,

and now fellow hunters can home in on their target.

The spider has a venomous bite, but that is no use now.

Eight powerful legs are her only hope,

but her speed is the very thing

that enables the ants to follow her.

[soft expectant music]

Slow motion reveals the basic ant hunting technique,

lunge with jaws open and hope for the best.

[dramatic expectant music]

At last, an ant manages to grab her.

Like a pride of lions taking down a buffalo,

the ants surround her.

Two restrain their catch, while another delivers

the flesh-dissolving acid. [dramatic tense music]

The wolf spider is just one of many victims.

Alone, an ant can take only the smallest prey,

but by working as a team,

they can capture creatures many times their size.

[tense expectant music]

A super-colony can make hundreds of millions

of kills every year.

Beetles, caterpillars, worms, flies,

they will tackle almost any living thing.

[tense expectant music continues]

Whatever the prey, it's first cut up

and eaten by the workers, who then regurgitate it

to feed to the larvae.

[insects chewing]

Once they have grown to full size,

the larvae spins silk cocoons for themselves.

Inside each a featureless larva is changing into an adult,

their time in the sun is approaching.

[soft thoughtful music]

Wood ants live in one of the most highly-organized

and complex of insect societies.

They fight wars over territory,

they hunt in packs, and farm other species.

They build complex homes with central heating.

They produce their own medicine.

And one group of them we now know, has made another advance.

The super-colony has extended this collaboration

beyond the frontiers of the family,

to form a super society of such dimensions

that we can perhaps begin to compare it with that other

great social creature on this planet, ourselves.

People studying the origins of human culture

suggest that shared myths were one of the factors

that bound early human societies together.

But what about ants?

Well, in many species, it is certainly the case

that all the individuals are very closely related

to one another, but that is not so in the super-colony.

And in some days in June,

such colonies continue to break the rules.

[bright expectant music]

As midsummer approaches, the Jura briefly

becomes a paradise of wild flowers.

And something new appears inside each of the nests, wings.

The royal generation, male and female,

has finally hatched, and booth will be able to fly.

Winged individuals are the only ones

that are capable of breeding.

The males are little more

than animated insemination devices,

and they will soon achieve their purpose and die.

But the females, which are emerging just now,

this is the beginning of a long life of servitude.

[gentle thoughtful music]

When the weather is just right, sunny and not too windy,

the nests suddenly become covered with winged ants.

There's an excitement in the air.

[gentle expectant music]

The males, which have matte black bodies,

are incapable of feeding themselves.

So once they leave the nest,

they only have a short time to live.

There's no time to waste.

The virgin queens who are also black but splendidly shiny,

have a rather clumsy beginning to their lives.

They're heavy with fat reserves and swollen ovaries,

so that getting airborne is not easy for them.

This is the most important flight of their lives,

but it's also their first.

Many test their wings before takeoff.

They may need several attempts

before they achieve complete flight control.

[thoughtful expectant music]

Over a few days, half a million winged ants

of both sexes take the air and head off for new territory.

[bright dramatic music]

They then all assemble here,

in the heart of the super-colony.

It's not clear how they find this meadow,

but year after year, virgin males and females

from across the super-colony

are drawn here for their nuptial flight.

[bright dramatic music]

The queens congregate in small patches of taller plants

and begin to release sex pheromones,

airborne chemicals that attract males.

[bright dramatic music continues]

Detecting this scent on the wind,

the males home in on the females.

[bright dramatic music continues]

The virgin queens may only get the chance to mate once,

and they need to obtain enough sperm to fertilize the eggs

they will be producing for years to come.

But with plenty of males in the meadow,

they can afford to be choosy.

The males are so driven, they even try to mate

with females who are already doing so.

[bright dramatic music]

Those males fortunate enough to couple quickly

make the most of their few remaining hours of life.

Once they've mated, their service to the colony is over,

and they die of exhaustion.

[soft thoughtful music]

The queens now have no further use for their wings

and they try to get rid of them,

but they are necessarily rather firmly fixed.

[soft expectant music]

Trying to remove a backpack with your feet,

even if you have six of them,

is clearly a frustrating process.

[soft expectant music continues]

Eventually, the meadow is marked

with little drifts of discarded wings.

Such breeding swarms are fairly typical of ants generally,

but now the queens of the super-colony

do something much less common.

To understand why they behave so differently,

we must first return to the spring battlefields

of the ordinary wood ants

outside the empire of the super colony.

[soft thoughtful music]

The warring colonies on this side of the mountain

have now accepted their frontiers,

and summer brings a brief pause in their battles.

The mating system they use may seem at first sight

to be the same as that of the super-colony,

but in fact, it's fundamentally different.

Every decision taken by a mated female

is fraught with danger.

The colony this queen comes from

is at war with all its neighbors.

So if she meets any of them, they will try to kill her.

She needs a home, but she can't build it without help.

Her solution to the problem is extraordinary and radical.

[soft expectant music]

Under this rock, a different species,

field ants, have built a nest.

These small ants, less than a third of her size,

are common, and live in meadows on the edge of the forest.

The only way this wood ant queen can get her own nest,

is by taking over one of theirs.

She will become a parasitic queen.

She lurks near the nest,

trying to pick up the scent of the field ants.

She avoids groups of them, because they could overpower her.

Instead, she tackles individuals.

There's a brief duel, and then she retreats.

But each time she's left with a trace of their scent,

so that she slowly begins to build up a chemical disguise.

These contests go on for several days.

Gradually her disguise becomes more and more convincing.

[soft expectant music]

The entrance to the field ants' nest is unguarded.

Cautiously, she enters.

Inside, she is vastly outnumbered.

Wood ant behavior inside a field ant nest

has never been observed in detail before, let alone filmed.

So what happens next must be interpreted with caution.

[dramatic expectant music]

There are fights, and most wood ant queens

are in fact killed at this stage.

But after she has endured repeated attacks,

some of the field ants become less aggressive towards her.

Eventually, a confused field ant worker

feeds the wood ant queen, and when it does that,

the fate of the nest is sealed.

The wood ant queen has now acquired the colony scent.

She oozes queenly pheromones,

and the field ants seem entranced

by their new foreign queen.

The gamble has paid off,

and she has a fully-functioning nest

ready to receive her first batch of eggs.

Taking over a nest of field ants is the way

typical wood ants start a new family.

But how about the queens from a super-colony

with their multifamily, communal nests?

Have they found a more peaceful strategy?

Each mated female has to set out on her own journey.

If she's to become a true queen, she has to find a nest

that will accept her, and that is where the tolerance

of the members of the super-colony is tested once again.

Being already in the heart of a super-colony,

these newly-mated queens don't have to walk far

before encountering their own kind.

But even for a super colony-queen,

walking straight up to a busy trail is risky.

If the workers she meets are not in a welcoming mood,

they will tear her to pieces.

[soft expectant music] [birds chattering]

Slowly, one by one, workers come to investigate her.

Some seem uncertain whether to attack or not,

but others lick and clean her. [soft expectant music]

After a few tense moments,

a worker starts to drag her towards the nest.

This is a sign that she will be adopted.

And now scientists have made a further discovery.

Many nests in the super-colony shortcut the whole process.

The winged males and the queen ants

don't even bother to leave the nest.

Many different families live here,

so there's no need to fly away to avoid inbreeding.

The winged queens can simply mate

with one of the males that hatched here.

Perhaps this unusual behavior is the next stage

in the evolution of the super-colony.

[bright expectant music]

With these innovative mating systems,

the super-colony queens don't take the same risks

as normal wood ant queens.

They don't need to infiltrate the nest of field ants

to start a family.

The workers just build new nests when needed,

enabling the super-colony to extend deep into the forest,

where there are no field ants.

It's changes in behavior like this

that most likely gave rise

to the super colony in the first place,

and colonized this new habitat with all its riches.

It's possible that this kind of cooperation

between different nests is becoming more common among ants.

New super-colonies are still being discovered

in different species across the world.

Are we perhaps witnessing the next stage

of the social conquest of the earth?

The super-colony consists of literally thousands

of different families all working in cooperation.

It's a development that mankind achieved

a very long time ago, and could be seen

as one of the reasons why we have come to dominate

so many parts of the planet.

Could it be that peace is the winning strategy

on this ant mountain too?

[bright dramatic music]