A Perfect Planet - First Season

A Perfect' Planet'.

There is a nuclear reactor 93 million miles away.

We call it the sun.

Its rays, travelling through space,

reach the Earth in just eight minutes...

...and give power to life

throughout the planet.

Its daily and yearly rhythms

shape the existence of every creature on Earth...

...and has clone so for over three billion years.

In the beginning...

...there was light.

Surprisingly, perhaps, almost every part of the Earth's surface

receives the same quantity of sunlight each year...

...4,380 hours of it.

But it's delivered in varying amounts at different times of the year,

depending on where you are.

It's only here in the tropics, close to the equator,

that there are 12 hours of guaranteed daily sunlight the year round.

And here, that has created a great richness of life -

the tropical forest.

Each leaf is a natural solar panel which collects the sun's energy

and fuels a multitude of plants.

And in Southeast Asia, gibbons live here.

A five-year-old female...

...and her lifelong partner are on a mission.

Every morning, they head out across their territory to look for ripe fruit.

There is one kind of tree here that they need more than any other.

The fig tree.

These are the only plants in the entire forest that produce fruit

all year round.

Their flowers grow in dense clusters

inside undeveloped figs,

but these have not yet been pollinated

and are not yet edible.

The gibbons will have to wait.

To produce ripe fruit, the fig still needs two things...

...a large dose of sunlight

and some of the smallest creatures in the forest.

Tiny fig wasps.

They're only two millimetres long.

The figs have a unique partnership with these insects.

A female wasp has the space of just a single day

when the fig will allow her to burrow into the undeveloped fruit.

It's such a tight squeeze that her wings are ripped off.

But she's not going to use them again.

Once inside, she makes her way to the tiny, tightly packed internal flowers.

And here within, she lays hundreds of eggs.

She then carefully unpacks fig pollen from her abdomen...

...and with it fertilises the tiny flowers.

When she's finished laying,

she dies...

...inside the unripe fig

alongside her eggs.

The sunlight now slowly ripens the figs

and helps the young wasps inside to develop.

After just five weeks, the eggs start to hatch.

The first to emerge are the golden, wingless males.

Things now become stranger than fiction.

These males start to mate with their unhatched sisters.

To reach them, they use a telescopic penis

that's twice their body length.

While their now-pregnant sisters are beginning to hatch,

the males themselves burrow their way to the outside world.

The brothers' final act is a chivalrous one.

They sacrifice themselves to marauding ants.

They're serving as decoys

so their sisters can take to the skies.

The young females, loaded with pollen, live for just 48 hours,

in which time they must find another fig tree at just the right stage

into which they themselves can burrow, as their mothers did.

With the sun's helping hand, the figs are now ready to eat.

The gibbons know all the fig trees in their territory.

And each day they travel up to two miles

to find one with fruit that's ready to eat.

Ripe figs at last...

...a major part of their diet and available the year round.

Thousands of animals rely on fig trees.

This abundance is only possible in a world without seasons

and constant daily sunlight.

But this 12-hour cycle of light and darkness

only happens close to the equator.

Elsewhere, the amount of sunlight fluctuates across the year.

That is because the Earth does not spin in an upright way.

Its axis is on a tilt.

23.5 degrees.

So as the Earth makes its annual orbit around the sun,

keep your eye on the North Pole.

For the first half of the year, it's angled away from the sun,

bringing darkness and winter to the northern hemisphere.

For the second part of the year,

the North Pole swings towards the sun, bringing summer.

The Earth's tilt gives us the seasons.

And life has adapted to deal with even the most extreme changes in light.

The High Arctic.

After six months of being angled towards the sun,

it begins six months of freezing darkness.

This is Ellesmere Island,

the closest land to the North Pole.

It's winter,

and for the last four long months, the only light here has come from the moon.

Few creatures can survive this sustained darkness.

They have become specialists in living for months without sunlight.

Muskox.

Remnants of the last ice age.

Having grazed all summer, they've built up fat reserves

that will enable them to survive the brutal cold of winter.

And this makes them a prime target for other sub-zero specialists.

Arctic wolves.

The moon provides just enough light for them to see.

This alpha female leads the hunt.

Target in sight.

If her pack is to survive, they need to make a large kill

at least once every three weeks.

The alpha female signals the start of the attack.

They run at the muskox and the herd panics.

The muskox close ranks.

The wolves look for weakness.

Charging risks isolation from the crowd.

And that is just what the wolf pack wants.

The wolves can sense victory.

But the herd comes to the rescue.

And once again, they close ranks.

Most winter hunts end in failure for the wolves.

- (ROARS) - (WHINES)

As the long polar nights drag on,

the hungry wolves turn to their only other source of food...

...arctic hares.

They've gathered together in their hundreds for safety.

Trying to catch one hare among hundreds is harder than you might think.

Even if they do catch one, it's not much of a meal.

Sometimes you just have to admit defeat.

But life is about to get better for the wolves.

For the first time in six months, the sun rises above the horizon.

Its appearance marks the beginning of half a year of continuous light.

The sun's warmth will allow the muskox to give birth,

and that will provide easier hunting for the wolves.

It's early spring,

and much of North America is still locked in ice.

As our tilted planet orbits the sun,

the northern hemisphere receives increasing sunlight...

...and wakens an animal with an almost supernatural ability.

It is frozen solid,

like a block of ice,

and has been all winter.

An ordinary-looking frog...

...but an extraordinary one.

A wood frog.

Its heart has stopped beating completely.

But as the sun's power increases,

almost miraculously, it begins to change.

Its frozen blood is melting

and begins to flow through its veins...

...as its heart begins to beat again.

The wood frog is cryogenic.

In just 12 hours,

it thaws and comes back to life, as if by magic.

This defrosting ability

means it's ready for the moment when, at last,

spring arrives.

All across the northern hemisphere,

the sun's warmth is bringing dramatic change.

As the sun rises higher and spring takes hold,

the warming air reaches the ground and the rocks beneath.

Here, thousands of animals begin to stir.

Garter snakes,

one of Canada's most northerly reptiles.

After six months of hibernation,

the males are the first to emerge.

They haven't eaten for months.

Even so, it's not food that is on their minds, it's something else...

...females.

But they stand no chance of doing anything about that

until they've charged their batteries.

Snakes are cold-blooded

and they need to absorb the sun's heat before they're able to move quickly.

After a few hours, the males are raring to go.

20,000 snakes,

the largest emergence of reptiles

anywhere on Earth.

Now a few females appear.

They're much bigger than the males...

...and warming will take them longer.

She releases a scent, a pheromone,

that attracts the males.

They outnumber her a hundred to one.

To speed her own return to activity, she will absorb heat from them.

Intoxicated by her scent, the males compete for her,

wrapping themselves around her.

She now has hundreds of males on top of her,

making mating near impossible.

But she has a way of weeding out the men from the boys.

She'll make a daring ascent of the nearby cliff.

She barges her way through the crowd to get to the rock face.

As she climbs, only the strongest, fittest males can keep up with her.

She's made it to the top.

Only a few of her suitors have managed to rise to the occasion,

and she may reward them all.

This entire mating jamboree only lasts for one short week

in the year.