24 Hours on Earth Page #2

50 degrees.

Out in the open, these kangaroos

are becoming dangerously hot.

The shade gives some relief,

but it's not enough.

The air surrounding them is baking.

To prevent heatstroke,

these roos have a trick or two

up their sleeves.

Along their forearms, vessels full

of hot blood run close to the skin.

They lick themselves.

As their saliva evaporates,

a little body heat is lost with it.

And by digging away

the hottest layers of earth...

..and resting on the cooler

layers below...

..these resourceful roos have found a

way to survive the midday onslaught.

Shade is hard to come by

in the Namibian sand dunes.

Our cold-blooded chameleon

is in danger of being cooked

in his own skin.

But life in this uncompromising place

has forced an incredible adaptation.

Doing what chameleons

all over the world do best,

it's changed colour.

Dark brown to brilliant white.

Reflecting the heat off its skin

and keeping its internal temperature

just cool enough to survive...

..and to hunt.

A solar-powered,

turbo-charged chameleon.

Well, relatively speaking.

Not everyone finds the midday sun

such a challenge.

In a lake, on a remote island

in the Pacific...

..a golden jellyfish is sunbathing.

This is no ordinary jelly.

Over 12,000 years ago,

its ancestors were marooned here.

Faced with starvation,

this seafarer became a farmer.

Absorbing lake algae into its body

and cultivating them.

The algae use light

to photosynthesise,

sharing the energy generated

with their hosts.

The jellies carefully tend the algae,

following the path of the sun

across the lake.

It's such a successful relationship

that now,

there are 13 million jellies...

..all clustered under the midday sun.

Gently spinning, to give their crop

just the right amount of light.

From midday onwards,

the angle of the sun begins to wane.

But it becomes no less dangerous.

The ground temperature

carries on rising.

While most animals

wait for the Earth to cool...

..amongst the craggy peaks of

the Ethiopian mountains...

..a quirky-looking crowd

is gathering.

Lammergeyers are vultures,

scavengers.

Collectors of bones.

Partial to the marrow

found inside them.

Heavy duty stomach acid

dissolves small bones,

but they're not exactly nutritious.

A lamb femur full of marrow

is much more like it.

But there's a problem -

the bone's far too big to swallow.

In the warmth of the afternoon,

this lammergeyer

senses an opportunity.

Heat, radiating from

the plains below,

has built into huge columns

rising into the atmosphere.

Warm-air thermals -

perfect for flight.

The lamb bone matches

her own bodyweight,

but the early-afternoon thermals

create an invisible elevator,

making flight possible.

At any other time,

this manoeuvre would prove dangerous

and costly in energy.

But by seizing her chance,

she's been rewarded.

Delicious.

While the lammergeyer

rides early-afternoon thermals

close to the Equator...

..a polar bear,

right at the top of the Earth,

is facing a very different challenge.

Because of the tilt

of the Earth on its axis,

the Arctic summer is filled

with almost endless light.

Hunting seals under the sea ice,

he's in no rush.

At three o'clock in the afternoon,

the sun is still high in the sky...

..but the radiant heat

from days of endless summer

is melting his Arctic world.

The sun will stay high over

the Arctic for another two months.

Soon, there'll be

no ice left to hunt on.

He will have to fast

until the seasons change again.

It's this seasonal journey of

the sun in the sky

that causes the greatest movement

of animals across the planet.

Driven by changes in weather,

by opportunity,

and danger,

migrants criss-cross the planet.

Across continents and through oceans.

WHALE SINGS:

Even the lives of the greatest

travellers are ruled by the sun.

This family of humpback whales

spent the winter breeding

in tropical waters...

..which made the perfect nursery

for the new calf...

..but are low on stocks

of krill and small fish,

the things 30-tonne adults

like to eat.

The calf is now strong enough

to swim the 3,000 miles north

towards the family's next big meal.

Navigating across thousands of miles

of featureless ocean

is an incredible challenge.

And with the adults running on empty,

they can't afford to get lost.

But the sun throws them a lifeline.

Humpbacks are expert navigators.

They use the sun

to keep their bearings.

Its changing position in the sky,

combined with information sensed

from the Earth's magnetic field,

creates a reliable compass.

So effective is their reckoning

that between sunrise

and this point in the afternoon,

the family will have deviated

less than one degree

from last year's course.

Late afternoon.

The sun's time in the sky

is running out.

Its power is fading.

Animals face

an urgent new challenge -

to make the most of the remaining

light and warmth

before it disappears.

Back in Namibia,

the sand is beginning to cool...

..and the chameleon has undergone

his most bizarre transformation yet.

He's split himself

right down the middle.

Black side faced towards the sun

to absorb every last bit

of remaining warmth.

White in the shade,

to stop his body heat being lost.

Being two chameleons at once

will help him survive

the cold night ahead.

And he's not the only animal

torn between the heat of the day

and a chilly desert night.

In the mountains of Oman,

a rock hyrax family

are soaking up all the

late-afternoon heat they can get.

They could also be accused of having

a bit of an identity problem.

Hyrax look like rodents,

but their closest relative

is actually an elephant.

And although they're mammals,

they need to bask to keep warm,

just like lizards.

Sunbathing in the late afternoon

is a serious business.

Every extra minute spent

absorbing warmth from the rocks

gives them a better chance

of surviving

the cold night ahead.

But stretching out in the open

like this is dangerous.

They've no choice

but to make themselves targets.

And stonebaked hyrax

is a black eagle favourite.

The family are on high alert.

The eagle's only chance

is a stealth attack...

..and the afternoon sun

provides the perfect disguise.

Diving at the same angle,

the glare is an invisibility cloak.

But hyrax have a unique adaptation.

In their eye,

the coloured iris slightly shields

the top of the pupil.

An in-built sun visor,

perfect for eagle spotting.

There won't be hyrax

on the menu tonight.

There's less than two hours left

before sunset.

The sun has lost its strength,

but it has not lost

its grip on our planet.

It has one last hand to play.

The phenomenal energy

absorbed by the ground

during the hottest parts of the day

is released back into the atmosphere.

Fast-rising, unstable, hot air

colliding with higher, colder air

creates weather.

THUNDER ROARS:

If you live near the Equator,

rain in the afternoon is just

something you've got to put up with.

Rate this script:0.0 / 0 votes