David Attenborough's Conquest of the Skies 3D Page #4

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for several million years.

They were the mammals.

The first of them to take

to the air were doubtless gliders.

And one mysterious creature

still alive today,

can give us an idea

of what they were like.

It lives in the rainforests of Borneo,

and its called the Cobego.

It has an enormous blanket

of furry skin, that stretches

from the side of its head,

right down to the very tip of its tail.

But to see how it travels through the air,

we must wait until nightfall.

As soon as it lands, it regains

the height it's inevitably lost,

by clambering up the trunk.

It's by far the most skilful

of the forest gliders,

and can travel over

a hundred metres in one leap.

It's undoubtedly a very ancient animal,

and some believe that it may well

have survived virtually unchanged

from that time long ago,

when mammals first took

to the skies as gliders.

But soon, the mammals

did better than that.

This is a fossil that dates

from about 52 million years ago.

Here's its head, with very

well-developed teeth, backbone and ribs,

and long tail, hind legs,

and most important of all,

from our point of view,

hands with enormously elongated fingers.

And there was skin between those fingers.

These were wings, and they could flap.

This is the earliest fossil

yet discovered, of a bat.

We have new evidence to show

exactly how a bat's fingers

first began to lengthen,

to support their wings.

But we can understand

how those early bats flew,

by looking at their modern descendants.

These are some of the largest.

They're so big,

that they're often called Flying Foxes.

And they have a wingspan of over a metre.

When you slow a bat's flight

down like this, you can see

that its four fingers

are spread wide on the down-stroke,

keeping the membrane wide and taut,

and then clump together on the up-stroke,

with just a thumb at the top free.

This folding of the wings

reduces the bat's air resistance,

between each beat.

To maximise the size of its wing,

the back edge of the wing membrane

is attached to the ankles.

Bats roost by hanging upside down.

And this is how they tend

to spend their days.

It's thought that the first mammals

were nocturnal,

that doubtless was the best thing to be,

out of the way of the dinosaurs

that were rampaging

around during the day.

So the bats continued

the nocturnal habit of their ancestors,

and they had also inherited

the acute sensors, needed

to move around at night.

Eyes specially adapted

to operating well in low light,

and an acute sense of smell that

enables them to find food in the dark.

In any case, birds already

dominated the daytime skies.

With their wings of skin

and nocturnal senses, the bats

became a huge global success.

Today, there are

over 1,100 species of them,

that's over a fifth of all mammals.

So, by 50 million years ago,

three groups of large backboned animals,

had joined the insects in the air.

The pioneers were reptiles, Pterosaurs,

with membranes of skin,

stretched from elongated fingers.

Then, came a group of dinosaurs,

that acquired feathers and became birds.

But when the Pterosaurs

and Dinosaurs were swept away

in a global extinction event,

the stage was set for the birds,

and the newly emerge bats

between them,

to take command of the skies.

Each of these two groups

had evolved its own techniques

for getting into the air,

and each was destined

to bring their skills

to astonishing extremes.

Next time, we see how birds

adapted and diversified

to become the remarkable creatures

we see in our skies today.

Lethal hunters.

Formation flyers.

And aerial acrobats.

We explore how the bats

developed a new super sense,

that enabled them to hunt

in the pitch-blackness of the night.

And we visit one spectacular place,

where the battle for the skies,

between insects, bats and birds,

still continues.

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