Dragons of the Dry Life in Cold Blood

About 340 million years ago,

a brand-new family of animals was evolving in the primeval swamps.

They were to go one step further than the amphibians,

who had emerged onto dry land before them.

For they would eventually completely cut their ties with water.

They were the ancestors of today's lizards.

They evolved scaly, impermeable skins and moved up into the forests.

They diversified into a multitude of different shapes and sizes.

They developed signalling systems to communicate with one another.

And they squabbled as animals do over mates and territory.

For food, they hunted insects

that were already well-established on the land in great numbers.

And here, without returning to water, they produced their families.

They powered their bodies not only with food

but with the heat that they drew directly from the sun.

As they diversified,

so they spread into the harshest of the land's habitats,

the baking, waterless deserts,

which eventually, they would come to dominate.

The bigger ones are truly powerful and fierce.

Rearing up, they're well able to defend themselves

with their front legs if they're threatened.

This is a very intelligent animal.

It is observing me just as I am observing it.

It's a monitor lizard

and it's king of this country, the Australian outback.

It is frightened of pretty well nothing, obviously including me,

and it will chase and hunt and eat pretty well anything.

There are several thousand lizards round the world

and they are truly the dragons of the dry.

Their eggs on land had to be encased in shells

to prevent them from drying out.

And what better place to lay them could a mother lizard find

than a termite's nest?

Worker termites labour unceasingly to keep the temperature and humidity

virtually constant for their own benefit.

But that also makes their mound a near-perfect incubator for eggs of others.

After ten months, they're beginning to hatch.

These are baby lace monitors.

But they face a major problem.

A termite nest's walls can be a foot thick and extremely hard,

too hard for the young monitors to break through.

They are imprisoned with no food.

For a week after hatching, they are sustained by the last of the yolk

that remains in their stomachs.

But when that comes to an end, they could starve.

An adult lace monitor is nearby.

It may or may not be the baby's mother.

If not, then it could be a threat, for monitors are hunters

and will eat most small animals, including baby lizards.

She's nearing the termite nest within which the young are trapped.

She could be looking for a place to lay her eggs.

Alternatively, she might be searching for food, such as little lizards.

The babies are released unharmed.

Perhaps she is indeed the babies' mother,

and not only remembered exactly where she laid her eggs a year ago,

but knew that her babies would need her help to escape from their incubator.

The young, however, are free.

But the outside world is a dangerous place.

They head for safety, up into the trees.

In the branches, there are other kinds of lizards.

Jacky dragons.

Each has its own territory and warns others to keep out.

A wave of the front leg and a bob of the head

is a Jacky dragon's way of claiming territory.

Here, the action is slowed down.

In reality, the leg flick is so swift

it's hard for us to see, but it's very plain to another Jacky dragon.

But sometimes, signals are not enough.

Physical violence is needed.

He's won. The vanquished acknowledges his defeat

with a different signal - a slow leg wave with no head bob.

The winner returns to his territory in the branches and announces his victory...

..which his neighbour acknowledges.

So now both can live alongside one another in peace.

Once Jacky dragons stop signalling,

it's quite hard to spot them up in the branches.

American anoles are so well camouflaged that they are virtually invisible.

There is one on this tree right in front of me.

But he too needs to draw attention to himself to warn off rivals

and then to disappear from predators.

This mirror may persuade him to reveal his solution to the problem.

Now then, what do you think of that?

Who's that?

Yes, it's a rival.

A tail wag.

Yes!

HE LAUGHS

You're not going to get rid of me that way.

Show us your signals.

Well, press-up certainly is a keep-away challenge.

And there, that's it!

The full works.

Ah, lovely!

Once more.

Thank you, and again.

He obviously thinks that his position is being contested

and he is displaying to show that he is as good as anyone else.

So I guess I'll leave him in peace.

An anole's throat flap appears for only a second or so,

and then vanishes.

And its owner, after sending his message,

returns to camouflaged obscurity.

Another family of lizards living in the tree-tops

has an even more varied repertoire of signals.

They use not only gestures, but body colours.

They're chameleons.

Their stronghold is the island of Madagascar.

Here, there are over 60 different species of them,

almost more than in the rest of the world put together.

This is a panther chameleon

and it's marvellously adapted

for life among the branches.

Its toes are divided into two bundles, three and two,

and that means that it can use them just like forceps.

Their grasping feet, supplemented by their gripping tail,

enable them to become remarkable slow motion acrobats.

I suppose chameleons are best known for their ability to change colour,

and that does help in camouflage,

but actually, they also use colour change

as a way of communication and expressing their emotions.

When a male panther chameleon spots a rival,

he expresses his fury in glorious technicolour.

Malawi, in central Africa, may not have as many species

of chameleon as Madagascar, but it has one of the largest.

Meller's chameleon,

that can be 60 centimetres, nearly two feet, from nose to tail.

Rival males, when they do battle,

deploy a range of threats that is truly formidable.

If signals don't deter, then they start to joust.

It's not only males that fight.

There are also battles between the sexes.

This is the South African dwarf chameleon, a male in full courtship costume.

This, somewhat less colourful, is a female.

She is not welcoming his advances.

As her mood darkens, so does her skin.

She's driven him away, but why?

There is a reason.

She's pregnant.

Her home, the South African Cape, can get quite cold,

so instead of laying her eggs on the ground as most chameleons do,

she retains them within her body

and warms them by seeking out the sunniest places and sunbathing.

Now they're ready to emerge, alive.

Producing babies in the branches might seem to be a risky business,

but the membrane enclosing each one will stick to a twig.

If it hits one.

And when at last the babies disentangle themselves,

they immediately deploy their formidable chameleon grip.

By the time they are properly dried out,

the babies are as much at home in the branches as their mother.

But for the most extraordinary chameleons of all,

you have to look, not up in the trees,

but down here on the leaf litter.

A whole range of species live on the ground,

many of which have only recently been discovered.

This is surely the most extraordinary of all chameleons.

It's the pygmy leaf chameleon.

This is a male and he is fully grown, believe it or not.

And yet, within this tiny little body,

there are all the anatomical details of a normal-sized chameleon.

What an extraordinary creature.

Like all chameleons, it catches its food with its tongue.

It eats tiny flies.

Grasshoppers are popular with normal-sized chameleons.

The tongue contains a tapered rod encircled by muscle.

As the muscle contracts, the tongue shoots forward off the rod.

The tip physically grasps the prey

and then longitudinal muscles contract to pull the tongue

back onto its rod, bringing the prey with it,

which may weigh half as much as the chameleon itself.

The whole action in reality is completed in a second or so.

The canopy of a tropical forest is full of food,

and lizards clamber around looking for it in many ways.

Chameleons use their toes to grip the twigs,

and geckos use theirs to stick to leaves,

for their toes have adhesive pads on the ends.

Most geckos feed on insects, but some take nectar from flowers,

and a few collect liquid from insects in much the same way as we take milk from cows.

The insect, a treehopper, is sitting head down drinking sap from the tree.

It would be invisible were it not vibrating its abdomen.

And that is what the gecko wants from it, a drop of honeydew.

Honeydew is what remains of tree sap after the hopper has extracted the protein from it.

It's very sweet and the gecko plainly loves it.

Other less colourful species of gecko also drink honeydew,

and some order it from the hopper by vibrating their heads.

The hopper tells the gecko that a drink is on the way

by waggling its abdomen.

How the hopper benefits from this arrangement is not clear.

Perhaps the gecko keeps predatory insects away

and the honeydew is protection money.

Most geckos are much less conspicuous,

and are very difficult to see.

It's the Madagascan leaf-tailed gecko.

And its tail has wide flanges on either side

so that it has become leaf shaped.

But these aren't the only flanges.

It has also got them all round its toes, its legs, and down its flank.

And the consequence is that if it presses itself close to the bark

and spreads those frills, it sheds no shadow at all.

The irises of its eye are also part of this amazing camouflage.

They have a kind of mottled, pale surface which makes them look

exactly like one of these little blotches of lichen on the bark.

All in all, it's a most extraordinary disguise.

It, and indeed the majority of geckos,

only really become active at night.

Here in Bangkok, as in cities throughout the tropics,

geckos have discovered that mankind's lights attract a great banquet of insects.

As a result, almost every building has its own resident gecko population.

Lizards, for the most part, are not known for being caring parents.

But there are exceptions.

It's spring in the woodlands of North America.

An American robin is nesting,

warming her eggs with the heat generated by her own body.

And below on the forest floor, a five-lined skink

is warming her cold-blooded body by basking in the sunshine,

so that she can do the same thing.

She has a nest below the log.

It can get quite chilly in these woodlands, and she warms her eggs

by transferring to them the heat that she's collected from the sun.

She takes just as much care of her eggs as the robin does.

A month later, and her eggs are hatching.

The robin's eggs have hatched, too.

Her nestlings are helpless, and need constant feeding.

The young skinks, however, are already capable of finding food for themselves.

Within a day or so, they've left their mother

and are independently exploring the woodland floor for themselves.

But there are other skinks whose family life lasts rather longer.

These fields in South Australia are home to a little lizard

that is so rare that it had been thought to be extinct for over 30 years

until it was rediscovered in 1992.

And the equipment you need to find it is,

believe it or not, a fishing rod.

Now let's see if I can tempt him out with this.

Oh! Gosh.

Now come up a little farther so we can see what you look like.

That is a very rare little creature.

It's a pygmy blue-tongued skink,

and it lives in the holes that are made by trap-door spiders.

And this one's clearly very hungry.

Come on, won't you come out a little more? Come on.

Just for us. Oh, ha-ha!

It won.

Let's have a closer look.

I can do that with this optical probe

with this viewing screen on the end.

He's quite a long way down.

There he is,

all safe and snug.

And he really is safe down here.

Even a bushfire sweeping by wouldn't harm him, and of course

this explains why no-one had seen these little lizards for so long.

They're very difficult to find.

But what's really special about this little lizard is its family life.

Just look at these shots we got with that optical probe.

That is a close-up of an adult's head,

and there, just beside her head, is a tiny little head of a baby.

That's one, and if we push past her,

there's a baleful look of Mum, who doesn't appreciate this,

and beyond, two.

Two more babies. So that's three.

Quite a crowded little home.

So there they are, a nice little lizard family.

And the babies will stay in that crowded hole for three weeks or so

before they're ready to be able to go out into the outside world

and look for a spider's burrow for themselves.

There's another skink here whose family relations last for decades.

This is a shingleback,

or as it's called here in its home in Australia,

a sleepy lizard.

It's really quite a baffling creature because

its head and the tail look very similar,

maybe that confuses the predator.

But if you get closer, it quickly shows which end is which,

by threatening with this gape display.

Ha-ha.

Oh, you're very perky.

And I have to be reasonably careful

because it can bite,

but at this time of the year, in the spring,

it also has another, rather more gentle side to its character.

There, I'll let you get on with it.

A female catches the eye of a male.

He starts to follow her wherever she goes.

Couples stay side by side for up to two months.

He courts her by gently nudging and licking her.

Six months pass,

and then eventually the results of this prolonged courtship begin to arrive.

It's a long and strenuous business for a mother shingleback.

She produces not a small egg, like the five-lined skink,

but a live baby.

It's a whopper.

And there's another one to come.

Together, the two weigh as much as a third of her bodyweight,

the equivalent in human beings of carrying a three-year-old child.

Like the Cape chameleon in South Africa,

the female has been acting as a mobile incubator,

seeking out the warmest spots she can find in order to bask.

Producing such well-developed young is the shingleback's response

to the fact that it can get quite cold in South Australia.

Her young are so advanced that they soon leave her.

But when spring returns, the same male and female

will once again seek one another out and mate again.

In fact, a pair will remain faithful to one another for as long as 20 years or more.

The bond between them may even endure after death.

They're slow-moving creatures and only too often,

when crossing a road,

they're unable to get out of the way of a passing car.

If one of the pair is run over

the other will often remain at its side for days, tenderly nudging it.

You might even say that it was grieving.

On the other side of the world,

there are lizards with a very different lifestyle.

They gather together in groups with densities higher than you can find anywhere else.

And the reason they are able to do so,

you can see alongside the waters of this,

the Orange River in South Africa.

The river is the breeding ground for vast swarms of black flies,

excellent food for a lizard if it can catch them.

In the early morning, the Augrabies flat lizards

emerge from the cracks in the rocks where they've spent the night

and bask in the sun to warm up.

The males are the brightly coloured ones,

as you can see from his marvellous blue head.

But it's not his head that impresses his rivals so much,

it's the underside,

which, if he's a high status male,

will be bright orange and yellow.

And if another one turns up

he will try and impress his rival by exposing that.

These awkward looking postures

reveal why these creatures are called flat lizards.

By regularly displaying their vivid badges,

the males repeatedly confirm

their place in the pecking order, and so keep fighting to a minimum.

As a female moves from one territory to another,

so each male courts her in turn.

And now they're really warmed up and active,

and whole groups of them begin to travel down across the rocks

towards the river where they'll find their food.

But down here, where the flies swarm, it's a free for all.

And that causes a lot of trouble.

Catching flies is necessarily an acrobatic business.

But you can't leap for flies and still keep properly spaced out.

So there are inevitably quarrels between rival males.

Females, on the other hand, are only interested in getting a good meal.

Fired-up males, however, have other ideas.

For them, there is more to life than just dinner.

And some won't take no for an answer.

The females want food.

They need a square meal

to nourish the eggs that are developing within them.

But they won't get any peace until they leave the restaurant

and get back home, where life is better regulated.

The high-octane social life of the flat lizards,

with its constant squabbling, seems to be very stressful.

But for other lizards,

fighting is less frequent but altogether more impressive.

A Mexican beaded lizard.

One of the few lizards in the world with a poisonous bite.

And a very virulent one it is, too.

In the spring, rival males fight,

according to a very specific set of rules.

They use neither their sharp, powerful claws,

nor their poisonous bite in their battles.

At first they grapple rather warily, to assess each other's strength.

Then they begin to wrestle in earnest,

each trying to pin down the other on the ground.

These two are evenly matched.

Neither can get the crucial throw.

It's rather like an arm-wrestling contest,

and the bout can continue for several hours.

The eventual winner is the one who ends up on top most frequently.

It's a controlled test of strength in which,

despite their lethal weaponry, no-one gets seriously hurt.

Other lizards defend themselves,

not with physical strength, but by deceit.

The South African desert.

A bushveld lizard.

This is another.

It looks very different, but that is because it's a baby.

It not only has different colouration,

it also walks in a very different and quite extraordinary way.

It appears to be imitating

one of the local beetles,

that one.

And to discover why,

I'm going to take defensive measures with these goggles.

This beetle is known as an oogpister - an eye-spitter.

And that is because it's squirting formic acid at me.

Yeah, and if any of that got into my eye it would be extremely painful.

It's a defensive system,

and the lizards are benefiting

by imitating a beetle with that kind of armoury.

A young lizard closely matches the beetle,

both in its appearance and its walk.

So birds that prey on lizards

assume it has a nasty spray, and leave it alone.

Lizards can cope with dry, hot conditions so well

they dominate the fauna in tropical deserts around the world,

including those in central Australia.

Their tough, scaly skins prevent their bodies from losing moisture,

so that they can flourish in these

arid, baking hot lands that other animals find so testing.

Some wear the most elaborate suits of armour.

This is surely the most enchanting of lizards.

It's called the thorny devil or Moloch,

after Moloch, the god in the Bible who ate little children.

Both names surely are a slander

on such an engaging little animal.

It feeds entirely on ants,

and, as you can see,

there's not much of a meal in any one of them.

But the good thing about ants as far as Moloch is concerned,

is that there's always some around.

And this little creature

will sit by an ant trail patiently,

for hours on end,

simply picking off one ant at a time.

The Australian desert is also home

to one of the most powerful of the family.

Monitors are the kings of lizards,

and this is the perentie,

the biggest species of monitor in Australia.

It can grow up to two metres long, six feet.

And it's a highly intelligent animal.

It's got very acute senses of sight and hearing and taste and smell,

and, like all monitors, it can do something no other lizard can do.

It can run continuously for a very long time.

And that enables it to become an endurance hunter,

chasing down its prey.

Most lizards inflate their lungs using the same muscles they use for walking,

so they can't run and breathe effectively at the same time.

But monitors have big muscular throats

which they use like bellows to pump air

into their lungs.

And they can do that even when they're running.

This special way of breathing

enables them to reach speeds of over 20 miles an hour.

Over distance, they are one of the fastest of all reptiles.

The cold-blooded perentie can even out-run a warm-blooded rabbit.

So, the lizards have colonised the world.

From swamps to rainforests, from woodland to desert.

And in doing so, they reveal such a variety of form and behaviour

that they truly can be called the dragons of the dry.

Much of our filming for this programme was done in Australia.

There, there are lizards everywhere.

Just walk around in the bush and you'll see them.

But usually you won't get much more than a brief glimpse.

To film their intimate behaviour, we needed help from experts.

We travelled to Australia to meet an expert called Mike Bull.

He knows Australian lizards as well as anyone.

He and his team study many species in one small area north of Adelaide,

using all manner of gadgets and gizmos,

to investigate every part of their lives.

We are particularly interested in the lizards

that Mike understands best of all, the shingleback or sleepy lizard.

He knows 10,000 of them individually.

On the face of it, the sleepy lizard doesn't seem to do a lot,

but Mike knows so much about them

that we were able to make them one of the stars of our film.

He's discovered that they're the only lizards in the world

that remain faithful to one partner for all their lives.

But that wasn't the reason that he began to study them.

Tell me first how you first saw sleepy lizards

and what attracted you to them.

I started because I was interested in parasites that live on the lizard.

To find the parasites I had to look at the lizards

and discovered they were more interesting than the parasites.

I think they're one of the most handsome animals you'll ever find.

The other thing is it's probably the only animal that

you know if you're driving in a car and see one 100 metres down the road, you know you've caught it,

and it's also one that I think I'm going to be sufficiently agile

to keep on catching until I'm well past 80!

And even I, I think could scrag a sleepy lizard.

I'll see whether I can manage it.

Sleepy lizards like to bask on warm roads, so they're easy to find,

and they move so slowly they're easy to pick up.

So the team were able to weigh and measure a whole population,

and thus discovered that pairs remained together in a way

that was previously known only in birds and mammals.

But that was just the start.

Next, they turned to technology,

some of it advanced, some a little bizarre.

They used remotely-controlled rubber sleepy lizards

to test how lizards reacted to one another.

In this case, not very much.

Mike's team suspected that another lizard in the area,

the gidgee skink, had an even more complex social life,

but this was difficult to prove because when approached

the skinks wedged themselves in cracks in the rocks, making it impossible to identify who's who.

The solution was to microchip each lizard

so it could then be scanned just like your supermarket shopping,

with a barcode reader on the end of a pole.

This clever use of technology

revealed what looked like a jumble of lizards on a pile of rocks,

to be actually a little lizard family, with young

that stay with their parents for life.

I'm sure that there are going to be many other complex social organisations

that will be uncovered in those species if we just simply take the time to look at them.

But it's just the time and the patience to watch them,

and watching a lizard is very unrewarding

because they will come out and bask, sit by a bush,

and if they see you're there, they'll decide they're not going to do very much for the rest of the day.

To find out just what sleepy lizards get up to when no-one's around,

Mike's team use a rather bizarre device they call a "waddleometer".

It may look a little odd, but it records a lizard's GPS co-ordinates,

counts its steps and even notes whether it's in sun or shade,

all without troubling the lizard and without anyone having to be there.

So you think there's probably the secret world of the lizard

which no human being has ever seen,

because if a human being is there the lizard won't behave that way?

I'm sure that's part of it. It's the uncertainty principle,

the closer you get to watch something the less normally it's behaving.

And so it's only by getting these remote and new technologies

that allow us to really get into the secret world of the lizards,

that we can find these amazing things that they're doing.

How extraordinary.

One of their latest techniques uses miniature cameras which they use to study

a very special lizard that we were also particularly keen to film.

It's so rare that it was thought to be extinct for over 30 years,

until it was thrust back into the public eye

when it was discovered in some very unusual circumstances.

A group of biologists were doing a standard biological survey.

They were just coming back to town to pick up supplies and just on the road they saw a dead brown snake.

Most people wouldn't even look at it as they're so common around here,

but these were dedicated biologists.

They had a look, noticed there was a bulge,

so they thought, "Let's see what it's been eating."

Opened it up and there was this lizard that no-one had seen for 30 years, the pygmy blue-tongued lizard.

How lovely, though I dare say it wasn't all that lovely when they actually saw it.

Miniature cameras have produced images

that are slowly helping to build up a comprehensive picture of the life of these rare little creatures.

Their burrows are more than just homes.

They're also hiding places where they can wait in ambush for spiders and crickets.

But they don't seem too keen on ants.

They also serve as bolt holes when danger approaches.

Despite all this work,

Mike's team had never recorded their life underground.

So we were able to help with a little of our own technology

and record the first ever pictures of a pygmy blue-tongue family.

Three babies alongside their mother in their little hole.

But all this technology, ingenious though it is,

is no substitute for years of dedicated observation.

Mike's approach of simply driving for miles across the Australian outback

is very fruitful, and you see lots of other things as well as lizards.

Up here is just a wonderful place for lizards and kangaroos.

Ha, boy! Eastern grey, beautiful.

Now, you won't catch a lizard doing that.

Oh, look, there's a pair just down there.

It turned out that Mike had spotted two old friends.

This is the male and the female.

This is 1172 and 3345,

-I think they've been together for about ten years.

-Really?

We've got some other pairs that have been together for over 20 years.

They stay together during the springtime

and mate towards the end of the spring and then they separate,

but the next year the same two lizards,

we'll find them back together again, usually in the same place along this road.

Aren't they terrific?

They use their tongues to pick up chemical signals

and you can see they're actually sensing each other at the moment.

I think that's really very touching.

I'd say that's a risky business.

With obsessive dedication and ever-advancing technology,

who knows what Mike and his team will uncover

about the secret lives of sleepy lizards?