Episode 1 David Attenborough's Natural Curiosities

The natural world is full of extraordinarily shaped creatures...

..but how have the stretched bodies of some given them an edge?

I have had the fortune to meet

some of the planet's most enchanting creatures -

but some stand out more than others

because of their intriguing biology.

Our knowledge of some of these creatures extends back centuries.

Others, we've discovered more recently.

In this series, I share their stories

and reveal why they are considered natural curiosities.

In this programme, I investigate two creatures

that have taken the ordinary and make it extraordinary.

The chameleon, that has an extra long tongue to catch prey...

..and the giraffe, with a neck so long it can reach the top of trees.

How and why have these animals stretched nature to the limit?

The chameleon is a truly bizarre creature,

both in its behaviour and its appearance

unlike anything else on Earth.

So, not surprisingly, it has given rise

to all kinds of legends and myths.

This is the History of the Four-Footed Beasts

by Edward Topsell,

written in the 17th century, and he calls the chameleon

"a fraudulent, ravening and gluttonous beast,

"impure and unclean by the law of God."

Some believed it was constructed by the devil

from parts of other animals -

the tail of a monkey, the skin of a crocodile, the tongue of a toad,

the horns of a rhinoceros, and the eyes of - who knows what?

It was a creature sent to the world to spy for a demon master.

When I first came face to face with a chameleon, more than 50 years ago,

I was struck not only by its beauty, but intrigued by its strange body.

Particularly by its tongue.

The outlandish appearance of the chameleon made it much sought after

by curiosity hunters -

but scientists and naturalists, too,

were greatly puzzled by its extraordinary behaviour and anatomy.

It looked and behaved like no other reptile.

Even today, we are still discovering new things about its unique eyes,

its astonishing tongue,

and its ability to change its appearance.

Chameleons are notoriously hard to find.

Partly because they move so slowly,

but also because they match their surroundings,

in terms of colour, so very well.

This one in front of me is a dwarf chameleon

from Natal in South Africa.

If it is threatened by a snake,

it doesn't bother to change its colour very much

because a snake's colour vision is not very good,

but if it is threatened by a bird,

it does camouflage itself very well indeed.

Some species of chameleon -

and there are 85 different species in the family -

can even fine-tune their camouflage.

If they detect a snake approaching from below,

they become lighter in colour and so less noticeable against the sky.

On the other hand, if the threat comes from above,

they become darker to match the background beneath them.

A chameleon's colour is affected not only by its surroundings,

but by the temperature and the light and its emotional state.

Behind this screen, there is a rival male.

Let's see what happens if I remove the screen

and let them see one another.

This highly coloured male is dominant,

and he immediately adds bright, aggressive colours to his display.

The other male remains dark

and too frightened to change colour and fight back.

It's clear who's the boss.

Chameleons are emotional creatures.

Darker colouration signals anger.

This female on the right is not in the mood to accept the approaches

of this brightly coloured and hopeful male.

Exactly how chameleons achieve such dramatic colour changes

greatly puzzled early naturalists.

An Englishman named Barrow,

who travelled in Africa in the 19th century,

thought that changing colour was caused by something to do with air.

He wrote, "Previous to the chameleon assuming a change in colour,

"it makes a long inspiration,

"the body swelling up to twice its usual size,

"and as this inflation subsides,

"the change of colour gradually takes place."

Well, that's an accurate observation of what happens

when a chameleon gets angry, and then its anger subsides -

but actually the change of colour has nothing to do with air.

A French biologist, Milne-Edwards, soon after that got it about right.

He wrote,

"There exist two layers of membranous pigment

"placed one above the other,

"but disposed in such a way to appear simultaneously

"under the cuticle

"and sometimes in such a manner that one may hide the other."

Which is indeed so.

Today, we know that the chameleon's skin has three layers

of expandable pigmented cells called chromatophores.

They contain red, yellow, blue and white pigments,

with a deeper layer of darker melanin,

which controls the reflection of light.

The chameleons use colour change not only to camouflage themselves,

but also to communicate with one another.

Anyone who looks closely at a chameleon

is bound to be fascinated by its eyes.

They protrude on either side of its heads,

as though they were mounted on turrets.

And in fact, their eyelids are fused together,

except for one tiny spot right in the middle.

But the most extraordinary thing about them

is that they move independently.

So that means the chameleon at one and the same time

can be viewing above it and below it,

so any insect that lands nearby

is going to be spotted almost immediately.

It seems that its brain

receives separate messages

from each eye

and views them and receives them

alternately, very fast,

but independent to one another.

They are not integrated.

But the advantage of that

is that it does give this all-round three-dimensional view

which is unrivalled.

This extraordinary vision is an essential element

in the way the chameleon uses its most astonishing feature,

its hugely elongated tongue.

How this tongue worked and its construction

greatly intrigued early naturalists -

and understandably.

This remarkable preserved specimen shows us in detail

the impressive elongated tongue of a chameleon.

The physical structure

of the chameleon's tongue was easy enough to explain,

although it proved to be a somewhat complicated organ -

a hollow tube

with a tapered cartilaginous rod at its base.

The pad at the end

was thought to be rough and sticky

so that it could snag its prey.

But the mystery of how a contraption like this

could be lengthened and projected out of the mouth

took a little longer to fully explain.

Perhaps the way a frigate bird inflates the balloon under its beak,

or how a calling frog blows up its throat sac could give clues.

Both do it with air.

Or maybe the tentacles that carry a snail's eyes -

it projects them by using its blood as a hydraulic fluid.

But none of them fitted the bill.

It is a much more complex process.

The tongue is a muscular tube that, when relaxed,

sits on a rod of cartilage.

When the chameleon is ready to strike,

muscles at the back of the tongue push it into launch position.

When the prey is lined up and the distance detected,

superfast muscles contract

and propel the tongue forward at lightning speed.

As the tongue shoots off the end of the cartilage,

an extra wave of energy drives it forward to its target.

Then, like a stretched elastic band,

its elasticity pulls it back into the chameleon's mouth.

Recently, high speed images revealed a new detail.

The tip of the tongue, once thought to be sticky,

is covered in microscopic protrusions

that generate suction and secure its prey.

Chameleons really are the most extraordinary creatures,

and they hold surprises for us even today.

Only this year,

a scientist working in Madagascar discovered a tiny little chameleon,

only 29 millimetres long.

It's the smallest known vertebrate in the world.

It's astounding to realise

that all the organs of a vertebrate body

could be fitted into such a tiny little creature -

including that extraordinary tongue.

Next is the story of another amazing elongated structure.

Not a tongue, but a neck.

The giraffe is an animal that can't fail to impress.

Up to six metres or 19 feet in height, it's hugely imposing,

intriguing in appearance and mysterious in its biology.

Our attraction to this unusual creature goes back centuries,

and one feature in particular has piqued our curiosity -

its elongated neck.

Such a structure seemed an impossibility of nature,

but now we better understand the complex biology

behind the giraffe's bizarre body.

Our growing knowledge of this creature

can be traced back to three very special giraffes

and the story of a royal fascination for the exotic.

In the 19th century, a giraffe named Zarafa, Arabic for charming one,

made a big impact on Europe, socially and scientifically.

She was one of three captured in 1826

at the order of the Viceroy of Egypt,

who wanted to use them as gifts

to curry favour with France, Austria, and England.

Zarafa, the strongest of the three, was given to the French,

seen here in a painting by Jacques Raymond Brascassat.

She travelled from Egypt to Marseille by ship.

On reaching France,

her keepers thought it was too risky to continue by boat,

so the decision was made to walk Zarafa from Marseille in the south

all the way to Paris -

an overland journey

of more than 550 miles.

To some, this looked like a journey

doomed to failure.

But careful planning and the unique biology of the giraffe

were in its favour.

Very wisely, the forward-thinking and eminent French scientist

called Geoffroy Saint-Hilaire was put in charge of the giraffe.

But there was something very significant about Zarafa

that would be key to the success of her long journey.

It was her age.

She was a youngster, just eight months old.

Baby giraffes are very robust,

and can stand up and run within an hour of being born.

They have particularly long legs in relation to their bodies,

only half a metre shorter than those of an adult.

Such long legs help them keep up with their mothers,

so young Zarafa was well-equipped for walking.

Crucial, too, was the fuel for Zarafa's journey.

Young giraffes suckle for up to a year,

and Zarafa was bottle-fed.

Throughout the journey,

she drank up to 25 litres of milk a day

supplied by three milking cows.

She marched on at a steady pace with her trusty entourage.

After nearly 200 miles, Zarafa reached Lyon

and Saint-Hilaire broke the walk.

He hoped to put is Zarafa onto a boat,

to go downriver for the rest of the journey.

As they waited, 30,000 people flocked to see Zarafa.

To the public, she was a strange and exotic creature,

and they were intrigued why such a long neck should exist,

and curious about how an animal could support its weight.

In those early days, giraffes were seen as freaks -

strange, horned camels whose humps had been flattened

by the stretching of their necks.

But this was exactly what attracted Saint-Hilaire to Zarafa.

He was fascinated by genetic exaggerations

and how they came to be.

Clearly, the giraffe's long neck enables them to feed on leaves

beyond the reach of other browsers.

But how could they physically hold up such a long neck vertically?

HE CHUCKLES

Studies of giraffe anatomy

have revealed just how the neck is supported.

A long, thick ligament like a cable runs the whole length of the neck.

This counterbalances the weight of the head and the neck,

and, in its relaxed position, it's tight,

so keeping the neck straight and the head up

involves very little muscular effort.

Bending the neck to reach down is more difficult,

because the tough ligament has to be stretched.

But was the ability to feed from tall trees

the only reason for having a long neck?

As the habits of giraffe in the wild became better known,

people discovered that rival males fought one another

by jousting with their necks.

Was that the reason that they had developed long necks?

But then someone pointed out that the females had long necks too,

so that suggestion was discarded.

In truth, there isn't a neat, single answer.

But access to high food,

better vigilance and temperature regulation

may all have shaped the giraffe's long neck.

As she walked on, Zarafa continued to attract inquisitive onlookers.

Few had set eyes on such a creature.

She appeared a natural impossibility.

How could a giraffe pump the blood up such a long neck to its brain?

And why didn't the blood rush back down into its feet?

The giraffe's neck may be very tall,

but in fact, it contains exactly the same number of bones as our own -

that is to say, seven.

But its blood pressure is twice as high as ours.

In fact, it's higher than any other known animal.

The pump that produces this pressure - the heart -

surprisingly, is not particularly big, but it is unusually powerful.

This is the left ventricle, that has been cut through,

and you can see how thick the muscle is,

getting on for about eight centimetres.

This great pump produces blood,

squirts it up the artery to the head,

and then, when it comes down through the jugular vein,

there are pocket-shaped valves

which prevent the blood from flowing backwards into the head

if the animal lowers its head in order to have a drink.

Giraffes find it very awkward to drink from the ground,

and, in fact, they rarely do so.

They get most of their water from leaves and shoots.

The only way to get their mouths down to the water

is to splay their four legs or bend them at the wrist joint.

The giraffe, in fact, has a relatively short neck

compared to its legs.

Antelope and zebra can reach down to the ground

without bending their legs.

Only the giraffe and its rainforest relative the okapi

have necks that are so short relative to their legs

that they must splay or bend them.

So perhaps the most remarkable feature of the giraffe

is the length of its legs.

They certainly were key to Zarafa's success.

At Lyon, there was a plan to rest her legs from walking

and to finish the journey to Paris by boat -

but all didn't go according to plan.

The boat didn't appear in Lyon,

so she walked on and finally got to Paris.

It took her a total of 41 days

to complete the journey of 550 miles to Paris.

Saint-Hilaire, her trusty companion, was exhausted -

but the giraffe was very fit.

He wrote, "She gained weight and much more strength

"from the exercise.

"Her muscles are more defined,

"her coat smoother and glossier upon her arrival

"than they were in Marseille."

Zarafa was presented to King Charles X

and temporarily installed in a greenhouse

in the grounds of the Jardin des Plantes.

She was a true animal ambassador

and 60,000 people saw her in the first three weeks in Paris.

In the early 19th century, giraffes were a novelty,

and their biology and lives in the wild were still a mystery.

Zarafa's success was due to a unique interplay

of the giraffe's unusual characteristics and good timing.

Her youth, long legs,

and a diet with milk powered her journey right across France.

Her body, that was first considered bizarre,

was revealed to be perfectly evolved.

Our story began with three giraffes that were given to Europe.

Zarafa was the most robust of them, and she lived a further 18 years.

The Austrian one lasted just a year,

and the one sent to King George the fourth of England died after two.

Saint-Hilaire learned much from Zarafa,

and he became a key figure

in the blossoming zoological research in France.

The giraffe brought to England

triggered a surge of interest in animal research

that shifted the centre of zoological gravity

from France to England.

So, we can thank Zarafa for her early role

in unravelling the biological mysteries

of the giraffe's extraordinary body and stretched neck.

Creatures like the outlandish giraffe and chameleon

continue to reveal their biological secrets.

They really are true natural curiosities.