0:00:36 > 0:00:39About 340 million years ago,
0:00:39 > 0:00:43a brand-new family of animals was evolving in the primeval swamps.
0:00:48 > 0:00:52They were to go one step further than the amphibians,
0:00:52 > 0:00:55who had emerged onto dry land before them.
0:00:57 > 0:01:02For they would eventually completely cut their ties with water.
0:01:04 > 0:01:08They were the ancestors of today's lizards.
0:01:12 > 0:01:18They evolved scaly, impermeable skins and moved up into the forests.
0:01:33 > 0:01:37They diversified into a multitude of different shapes and sizes.
0:01:43 > 0:01:48They developed signalling systems to communicate with one another.
0:01:55 > 0:02:00And they squabbled as animals do over mates and territory.
0:02:00 > 0:02:05For food, they hunted insects
0:02:05 > 0:02:10that were already well-established on the land in great numbers.
0:02:15 > 0:02:20And here, without returning to water, they produced their families.
0:02:27 > 0:02:31They powered their bodies not only with food
0:02:31 > 0:02:34but with the heat that they drew directly from the sun.
0:02:38 > 0:02:40As they diversified,
0:02:40 > 0:02:44so they spread into the harshest of the land's habitats,
0:02:44 > 0:02:46the baking, waterless deserts,
0:02:46 > 0:02:49which eventually, they would come to dominate.
0:02:54 > 0:02:58The bigger ones are truly powerful and fierce.
0:02:58 > 0:03:02Rearing up, they're well able to defend themselves
0:03:02 > 0:03:04with their front legs if they're threatened.
0:03:07 > 0:03:13This is a very intelligent animal.
0:03:13 > 0:03:19It is observing me just as I am observing it.
0:03:19 > 0:03:21It's a monitor lizard
0:03:21 > 0:03:26and it's king of this country, the Australian outback.
0:03:26 > 0:03:32It is frightened of pretty well nothing, obviously including me,
0:03:32 > 0:03:37and it will chase and hunt and eat pretty well anything.
0:03:37 > 0:03:41There are several thousand lizards round the world
0:03:41 > 0:03:46and they are truly the dragons of the dry.
0:04:01 > 0:04:05Their eggs on land had to be encased in shells
0:04:05 > 0:04:08to prevent them from drying out.
0:04:08 > 0:04:12And what better place to lay them could a mother lizard find
0:04:12 > 0:04:15than a termite's nest?
0:04:15 > 0:04:20Worker termites labour unceasingly to keep the temperature and humidity
0:04:20 > 0:04:22virtually constant for their own benefit.
0:04:22 > 0:04:29But that also makes their mound a near-perfect incubator for eggs of others.
0:04:33 > 0:04:36After ten months, they're beginning to hatch.
0:04:55 > 0:04:59These are baby lace monitors.
0:05:10 > 0:05:12But they face a major problem.
0:05:12 > 0:05:17A termite nest's walls can be a foot thick and extremely hard,
0:05:17 > 0:05:20too hard for the young monitors to break through.
0:05:20 > 0:05:23They are imprisoned with no food.
0:05:30 > 0:05:34For a week after hatching, they are sustained by the last of the yolk
0:05:34 > 0:05:36that remains in their stomachs.
0:05:36 > 0:05:39But when that comes to an end, they could starve.
0:05:47 > 0:05:51An adult lace monitor is nearby.
0:05:58 > 0:06:02It may or may not be the baby's mother.
0:06:02 > 0:06:06If not, then it could be a threat, for monitors are hunters
0:06:06 > 0:06:10and will eat most small animals, including baby lizards.
0:06:16 > 0:06:20She's nearing the termite nest within which the young are trapped.
0:06:29 > 0:06:32She could be looking for a place to lay her eggs.
0:06:32 > 0:06:38Alternatively, she might be searching for food, such as little lizards.
0:07:12 > 0:07:15The babies are released unharmed.
0:07:15 > 0:07:18Perhaps she is indeed the babies' mother,
0:07:18 > 0:07:21and not only remembered exactly where she laid her eggs a year ago,
0:07:21 > 0:07:26but knew that her babies would need her help to escape from their incubator.
0:07:32 > 0:07:33The young, however, are free.
0:07:33 > 0:07:37But the outside world is a dangerous place.
0:07:43 > 0:07:46They head for safety, up into the trees.
0:07:51 > 0:07:54In the branches, there are other kinds of lizards.
0:07:56 > 0:07:58Jacky dragons.
0:07:58 > 0:08:03Each has its own territory and warns others to keep out.
0:08:03 > 0:08:06A wave of the front leg and a bob of the head
0:08:06 > 0:08:08is a Jacky dragon's way of claiming territory.
0:08:08 > 0:08:12Here, the action is slowed down.
0:08:12 > 0:08:14In reality, the leg flick is so swift
0:08:14 > 0:08:20it's hard for us to see, but it's very plain to another Jacky dragon.
0:08:23 > 0:08:27But sometimes, signals are not enough.
0:08:27 > 0:08:29Physical violence is needed.
0:08:47 > 0:08:50He's won. The vanquished acknowledges his defeat
0:08:50 > 0:08:56with a different signal - a slow leg wave with no head bob.
0:08:58 > 0:09:03The winner returns to his territory in the branches and announces his victory...
0:09:05 > 0:09:07..which his neighbour acknowledges.
0:09:14 > 0:09:19So now both can live alongside one another in peace.
0:09:23 > 0:09:26Once Jacky dragons stop signalling,
0:09:26 > 0:09:29it's quite hard to spot them up in the branches.
0:09:30 > 0:09:36American anoles are so well camouflaged that they are virtually invisible.
0:09:36 > 0:09:41There is one on this tree right in front of me.
0:09:41 > 0:09:46But he too needs to draw attention to himself to warn off rivals
0:09:46 > 0:09:50and then to disappear from predators.
0:09:50 > 0:09:55This mirror may persuade him to reveal his solution to the problem.
0:09:55 > 0:09:58Now then, what do you think of that?
0:09:58 > 0:10:01Who's that?
0:10:01 > 0:10:03Yes, it's a rival.
0:10:06 > 0:10:09A tail wag.
0:10:09 > 0:10:11Yes!
0:10:13 > 0:10:16HE LAUGHS
0:10:16 > 0:10:18You're not going to get rid of me that way.
0:10:18 > 0:10:21Show us your signals.
0:10:21 > 0:10:25Well, press-up certainly is a keep-away challenge.
0:10:28 > 0:10:30And there, that's it!
0:10:32 > 0:10:34The full works.
0:10:38 > 0:10:39Ah, lovely!
0:10:41 > 0:10:44Once more.
0:10:44 > 0:10:46Thank you, and again.
0:10:48 > 0:10:54He obviously thinks that his position is being contested
0:10:54 > 0:10:59and he is displaying to show that he is as good as anyone else.
0:10:59 > 0:11:01So I guess I'll leave him in peace.
0:11:05 > 0:11:08An anole's throat flap appears for only a second or so,
0:11:08 > 0:11:11and then vanishes.
0:11:11 > 0:11:13And its owner, after sending his message,
0:11:13 > 0:11:16returns to camouflaged obscurity.
0:11:19 > 0:11:22Another family of lizards living in the tree-tops
0:11:22 > 0:11:25has an even more varied repertoire of signals.
0:11:25 > 0:11:30They use not only gestures, but body colours.
0:11:43 > 0:11:45They're chameleons.
0:11:49 > 0:11:55Their stronghold is the island of Madagascar.
0:11:55 > 0:11:58Here, there are over 60 different species of them,
0:11:58 > 0:12:00almost more than in the rest of the world put together.
0:12:02 > 0:12:07This is a panther chameleon
0:12:07 > 0:12:10and it's marvellously adapted
0:12:10 > 0:12:12for life among the branches.
0:12:14 > 0:12:19Its toes are divided into two bundles, three and two,
0:12:19 > 0:12:25and that means that it can use them just like forceps.
0:12:25 > 0:12:29Their grasping feet, supplemented by their gripping tail,
0:12:29 > 0:12:34enable them to become remarkable slow motion acrobats.
0:12:44 > 0:12:49I suppose chameleons are best known for their ability to change colour,
0:12:49 > 0:12:51and that does help in camouflage,
0:12:51 > 0:12:55but actually, they also use colour change
0:12:55 > 0:13:00as a way of communication and expressing their emotions.
0:13:06 > 0:13:10When a male panther chameleon spots a rival,
0:13:10 > 0:13:14he expresses his fury in glorious technicolour.
0:13:21 > 0:13:25Malawi, in central Africa, may not have as many species
0:13:25 > 0:13:30of chameleon as Madagascar, but it has one of the largest.
0:13:30 > 0:13:32Meller's chameleon,
0:13:32 > 0:13:36that can be 60 centimetres, nearly two feet, from nose to tail.
0:13:45 > 0:13:48Rival males, when they do battle,
0:13:48 > 0:13:52deploy a range of threats that is truly formidable.
0:14:47 > 0:14:51If signals don't deter, then they start to joust.
0:15:20 > 0:15:22It's not only males that fight.
0:15:22 > 0:15:26There are also battles between the sexes.
0:15:26 > 0:15:30This is the South African dwarf chameleon, a male in full courtship costume.
0:15:35 > 0:15:39This, somewhat less colourful, is a female.
0:15:45 > 0:15:48She is not welcoming his advances.
0:15:55 > 0:15:59As her mood darkens, so does her skin.
0:16:20 > 0:16:22She's driven him away, but why?
0:16:30 > 0:16:33There is a reason.
0:16:33 > 0:16:35She's pregnant.
0:16:35 > 0:16:40Her home, the South African Cape, can get quite cold,
0:16:40 > 0:16:44so instead of laying her eggs on the ground as most chameleons do,
0:16:44 > 0:16:47she retains them within her body
0:16:47 > 0:16:52and warms them by seeking out the sunniest places and sunbathing.
0:16:52 > 0:16:56Now they're ready to emerge, alive.
0:17:05 > 0:17:09Producing babies in the branches might seem to be a risky business,
0:17:09 > 0:17:12but the membrane enclosing each one will stick to a twig.
0:17:12 > 0:17:15If it hits one.
0:17:17 > 0:17:21And when at last the babies disentangle themselves,
0:17:21 > 0:17:25they immediately deploy their formidable chameleon grip.
0:18:19 > 0:18:22By the time they are properly dried out,
0:18:22 > 0:18:27the babies are as much at home in the branches as their mother.
0:18:51 > 0:18:55But for the most extraordinary chameleons of all,
0:18:55 > 0:18:57you have to look, not up in the trees,
0:18:57 > 0:18:59but down here on the leaf litter.
0:19:06 > 0:19:09A whole range of species live on the ground,
0:19:09 > 0:19:12many of which have only recently been discovered.
0:19:17 > 0:19:22This is surely the most extraordinary of all chameleons.
0:19:22 > 0:19:28It's the pygmy leaf chameleon.
0:19:28 > 0:19:33This is a male and he is fully grown, believe it or not.
0:19:33 > 0:19:36And yet, within this tiny little body,
0:19:36 > 0:19:41there are all the anatomical details of a normal-sized chameleon.
0:19:41 > 0:19:43What an extraordinary creature.
0:19:49 > 0:19:54Like all chameleons, it catches its food with its tongue.
0:19:56 > 0:19:58It eats tiny flies.
0:20:02 > 0:20:08Grasshoppers are popular with normal-sized chameleons.
0:20:29 > 0:20:34The tongue contains a tapered rod encircled by muscle.
0:20:34 > 0:20:40As the muscle contracts, the tongue shoots forward off the rod.
0:20:40 > 0:20:44The tip physically grasps the prey
0:20:44 > 0:20:48and then longitudinal muscles contract to pull the tongue
0:20:48 > 0:20:51back onto its rod, bringing the prey with it,
0:20:51 > 0:20:54which may weigh half as much as the chameleon itself.
0:21:05 > 0:21:09The whole action in reality is completed in a second or so.
0:21:21 > 0:21:24The canopy of a tropical forest is full of food,
0:21:24 > 0:21:29and lizards clamber around looking for it in many ways.
0:21:29 > 0:21:31Chameleons use their toes to grip the twigs,
0:21:31 > 0:21:35and geckos use theirs to stick to leaves,
0:21:35 > 0:21:38for their toes have adhesive pads on the ends.
0:21:40 > 0:21:45Most geckos feed on insects, but some take nectar from flowers,
0:21:45 > 0:21:51and a few collect liquid from insects in much the same way as we take milk from cows.
0:21:55 > 0:22:00The insect, a treehopper, is sitting head down drinking sap from the tree.
0:22:00 > 0:22:03It would be invisible were it not vibrating its abdomen.
0:22:05 > 0:22:10And that is what the gecko wants from it, a drop of honeydew.
0:22:10 > 0:22:15Honeydew is what remains of tree sap after the hopper has extracted the protein from it.
0:22:15 > 0:22:19It's very sweet and the gecko plainly loves it.
0:22:19 > 0:22:23Other less colourful species of gecko also drink honeydew,
0:22:23 > 0:22:28and some order it from the hopper by vibrating their heads.
0:22:40 > 0:22:43The hopper tells the gecko that a drink is on the way
0:22:43 > 0:22:45by waggling its abdomen.
0:22:57 > 0:23:00How the hopper benefits from this arrangement is not clear.
0:23:00 > 0:23:05Perhaps the gecko keeps predatory insects away
0:23:05 > 0:23:07and the honeydew is protection money.
0:23:09 > 0:23:11Most geckos are much less conspicuous,
0:23:11 > 0:23:14and are very difficult to see.
0:23:22 > 0:23:26It's the Madagascan leaf-tailed gecko.
0:23:26 > 0:23:30And its tail has wide flanges on either side
0:23:30 > 0:23:33so that it has become leaf shaped.
0:23:33 > 0:23:36But these aren't the only flanges.
0:23:36 > 0:23:42It has also got them all round its toes, its legs, and down its flank.
0:23:42 > 0:23:46And the consequence is that if it presses itself close to the bark
0:23:46 > 0:23:53and spreads those frills, it sheds no shadow at all.
0:23:53 > 0:23:59The irises of its eye are also part of this amazing camouflage.
0:23:59 > 0:24:03They have a kind of mottled, pale surface which makes them look
0:24:03 > 0:24:09exactly like one of these little blotches of lichen on the bark.
0:24:09 > 0:24:13All in all, it's a most extraordinary disguise.
0:24:15 > 0:24:18It, and indeed the majority of geckos,
0:24:18 > 0:24:21only really become active at night.
0:24:29 > 0:24:33Here in Bangkok, as in cities throughout the tropics,
0:24:33 > 0:24:39geckos have discovered that mankind's lights attract a great banquet of insects.
0:24:44 > 0:24:50As a result, almost every building has its own resident gecko population.
0:25:05 > 0:25:10Lizards, for the most part, are not known for being caring parents.
0:25:10 > 0:25:12But there are exceptions.
0:25:12 > 0:25:15It's spring in the woodlands of North America.
0:25:15 > 0:25:18An American robin is nesting,
0:25:18 > 0:25:23warming her eggs with the heat generated by her own body.
0:25:23 > 0:25:27And below on the forest floor, a five-lined skink
0:25:27 > 0:25:31is warming her cold-blooded body by basking in the sunshine,
0:25:31 > 0:25:34so that she can do the same thing.
0:25:41 > 0:25:45She has a nest below the log.
0:25:50 > 0:25:55It can get quite chilly in these woodlands, and she warms her eggs
0:25:55 > 0:25:59by transferring to them the heat that she's collected from the sun.
0:26:12 > 0:26:17She takes just as much care of her eggs as the robin does.
0:26:26 > 0:26:29A month later, and her eggs are hatching.
0:26:42 > 0:26:45The robin's eggs have hatched, too.
0:26:45 > 0:26:50Her nestlings are helpless, and need constant feeding.
0:26:50 > 0:26:55The young skinks, however, are already capable of finding food for themselves.
0:27:04 > 0:27:07Within a day or so, they've left their mother
0:27:07 > 0:27:10and are independently exploring the woodland floor for themselves.
0:27:18 > 0:27:24But there are other skinks whose family life lasts rather longer.
0:27:24 > 0:27:28These fields in South Australia are home to a little lizard
0:27:28 > 0:27:34that is so rare that it had been thought to be extinct for over 30 years
0:27:34 > 0:27:37until it was rediscovered in 1992.
0:27:37 > 0:27:40And the equipment you need to find it is,
0:27:40 > 0:27:44believe it or not, a fishing rod.
0:27:44 > 0:27:47Now let's see if I can tempt him out with this.
0:27:48 > 0:27:52Oh! Gosh.
0:27:52 > 0:27:57Now come up a little farther so we can see what you look like.
0:27:57 > 0:28:02That is a very rare little creature.
0:28:02 > 0:28:05It's a pygmy blue-tongued skink,
0:28:05 > 0:28:11and it lives in the holes that are made by trap-door spiders.
0:28:11 > 0:28:15And this one's clearly very hungry.
0:28:15 > 0:28:19Come on, won't you come out a little more? Come on.
0:28:19 > 0:28:22Just for us. Oh, ha-ha!
0:28:22 > 0:28:24It won.
0:28:27 > 0:28:28Let's have a closer look.
0:28:28 > 0:28:32I can do that with this optical probe
0:28:32 > 0:28:36with this viewing screen on the end.
0:28:36 > 0:28:38He's quite a long way down.
0:28:38 > 0:28:40There he is,
0:28:40 > 0:28:42all safe and snug.
0:28:42 > 0:28:45And he really is safe down here.
0:28:45 > 0:28:51Even a bushfire sweeping by wouldn't harm him, and of course
0:28:51 > 0:28:55this explains why no-one had seen these little lizards for so long.
0:28:55 > 0:28:57They're very difficult to find.
0:29:00 > 0:29:06But what's really special about this little lizard is its family life.
0:29:06 > 0:29:10Just look at these shots we got with that optical probe.
0:29:10 > 0:29:13That is a close-up of an adult's head,
0:29:13 > 0:29:20and there, just beside her head, is a tiny little head of a baby.
0:29:20 > 0:29:24That's one, and if we push past her,
0:29:24 > 0:29:27there's a baleful look of Mum, who doesn't appreciate this,
0:29:27 > 0:29:32and beyond, two.
0:29:32 > 0:29:34Two more babies. So that's three.
0:29:35 > 0:29:39Quite a crowded little home.
0:29:39 > 0:29:43So there they are, a nice little lizard family.
0:29:43 > 0:29:49And the babies will stay in that crowded hole for three weeks or so
0:29:49 > 0:29:53before they're ready to be able to go out into the outside world
0:29:53 > 0:29:57and look for a spider's burrow for themselves.
0:30:01 > 0:30:06There's another skink here whose family relations last for decades.
0:30:08 > 0:30:12This is a shingleback,
0:30:12 > 0:30:15or as it's called here in its home in Australia,
0:30:15 > 0:30:17a sleepy lizard.
0:30:17 > 0:30:20It's really quite a baffling creature because
0:30:20 > 0:30:24its head and the tail look very similar,
0:30:24 > 0:30:25maybe that confuses the predator.
0:30:25 > 0:30:31But if you get closer, it quickly shows which end is which,
0:30:31 > 0:30:34by threatening with this gape display.
0:30:34 > 0:30:36Ha-ha.
0:30:36 > 0:30:39Oh, you're very perky.
0:30:39 > 0:30:42And I have to be reasonably careful
0:30:42 > 0:30:47because it can bite,
0:30:47 > 0:30:50but at this time of the year, in the spring,
0:30:50 > 0:30:56it also has another, rather more gentle side to its character.
0:30:56 > 0:30:59There, I'll let you get on with it.
0:31:02 > 0:31:05A female catches the eye of a male.
0:31:17 > 0:31:20He starts to follow her wherever she goes.
0:31:28 > 0:31:32Couples stay side by side for up to two months.
0:31:46 > 0:31:50He courts her by gently nudging and licking her.
0:32:11 > 0:32:13Six months pass,
0:32:13 > 0:32:19and then eventually the results of this prolonged courtship begin to arrive.
0:32:24 > 0:32:28It's a long and strenuous business for a mother shingleback.
0:32:44 > 0:32:50She produces not a small egg, like the five-lined skink,
0:32:50 > 0:32:52but a live baby.
0:33:06 > 0:33:07It's a whopper.
0:33:31 > 0:33:35And there's another one to come.
0:33:35 > 0:33:38Together, the two weigh as much as a third of her bodyweight,
0:33:38 > 0:33:42the equivalent in human beings of carrying a three-year-old child.
0:33:49 > 0:33:52Like the Cape chameleon in South Africa,
0:33:52 > 0:33:56the female has been acting as a mobile incubator,
0:33:56 > 0:34:00seeking out the warmest spots she can find in order to bask.
0:34:01 > 0:34:06Producing such well-developed young is the shingleback's response
0:34:06 > 0:34:09to the fact that it can get quite cold in South Australia.
0:34:16 > 0:34:20Her young are so advanced that they soon leave her.
0:34:26 > 0:34:30But when spring returns, the same male and female
0:34:30 > 0:34:34will once again seek one another out and mate again.
0:34:34 > 0:34:41In fact, a pair will remain faithful to one another for as long as 20 years or more.
0:34:47 > 0:34:53The bond between them may even endure after death.
0:34:54 > 0:34:57They're slow-moving creatures and only too often,
0:34:57 > 0:34:59when crossing a road,
0:34:59 > 0:35:03they're unable to get out of the way of a passing car.
0:35:06 > 0:35:08If one of the pair is run over
0:35:08 > 0:35:12the other will often remain at its side for days, tenderly nudging it.
0:35:12 > 0:35:16You might even say that it was grieving.
0:35:22 > 0:35:23On the other side of the world,
0:35:23 > 0:35:27there are lizards with a very different lifestyle.
0:35:27 > 0:35:33They gather together in groups with densities higher than you can find anywhere else.
0:35:33 > 0:35:35And the reason they are able to do so,
0:35:35 > 0:35:37you can see alongside the waters of this,
0:35:37 > 0:35:41the Orange River in South Africa.
0:36:04 > 0:36:09The river is the breeding ground for vast swarms of black flies,
0:36:09 > 0:36:13excellent food for a lizard if it can catch them.
0:36:30 > 0:36:33In the early morning, the Augrabies flat lizards
0:36:33 > 0:36:38emerge from the cracks in the rocks where they've spent the night
0:36:38 > 0:36:40and bask in the sun to warm up.
0:36:44 > 0:36:47The males are the brightly coloured ones,
0:36:47 > 0:36:52as you can see from his marvellous blue head.
0:36:52 > 0:36:56But it's not his head that impresses his rivals so much,
0:36:56 > 0:36:58it's the underside,
0:36:58 > 0:37:01which, if he's a high status male,
0:37:01 > 0:37:04will be bright orange and yellow.
0:37:04 > 0:37:06And if another one turns up
0:37:06 > 0:37:10he will try and impress his rival by exposing that.
0:37:13 > 0:37:15These awkward looking postures
0:37:15 > 0:37:18reveal why these creatures are called flat lizards.
0:37:20 > 0:37:23By regularly displaying their vivid badges,
0:37:23 > 0:37:25the males repeatedly confirm
0:37:25 > 0:37:30their place in the pecking order, and so keep fighting to a minimum.
0:37:34 > 0:37:37As a female moves from one territory to another,
0:37:37 > 0:37:40so each male courts her in turn.
0:37:51 > 0:37:55And now they're really warmed up and active,
0:37:55 > 0:37:59and whole groups of them begin to travel down across the rocks
0:37:59 > 0:38:02towards the river where they'll find their food.
0:38:08 > 0:38:12But down here, where the flies swarm, it's a free for all.
0:38:12 > 0:38:14And that causes a lot of trouble.
0:38:16 > 0:38:21Catching flies is necessarily an acrobatic business.
0:38:30 > 0:38:34But you can't leap for flies and still keep properly spaced out.
0:38:34 > 0:38:39So there are inevitably quarrels between rival males.
0:38:47 > 0:38:51Females, on the other hand, are only interested in getting a good meal.
0:38:53 > 0:38:56Fired-up males, however, have other ideas.
0:38:57 > 0:39:00For them, there is more to life than just dinner.
0:39:12 > 0:39:15And some won't take no for an answer.
0:39:28 > 0:39:30The females want food.
0:39:36 > 0:39:38They need a square meal
0:39:38 > 0:39:41to nourish the eggs that are developing within them.
0:39:48 > 0:39:51But they won't get any peace until they leave the restaurant
0:39:51 > 0:39:54and get back home, where life is better regulated.
0:39:57 > 0:40:00The high-octane social life of the flat lizards,
0:40:00 > 0:40:04with its constant squabbling, seems to be very stressful.
0:40:04 > 0:40:05But for other lizards,
0:40:05 > 0:40:10fighting is less frequent but altogether more impressive.
0:40:31 > 0:40:34A Mexican beaded lizard.
0:40:34 > 0:40:38One of the few lizards in the world with a poisonous bite.
0:40:38 > 0:40:41And a very virulent one it is, too.
0:40:42 > 0:40:46In the spring, rival males fight,
0:40:46 > 0:40:48according to a very specific set of rules.
0:40:56 > 0:40:58They use neither their sharp, powerful claws,
0:40:58 > 0:41:02nor their poisonous bite in their battles.
0:41:20 > 0:41:25At first they grapple rather warily, to assess each other's strength.
0:41:34 > 0:41:37Then they begin to wrestle in earnest,
0:41:37 > 0:41:39each trying to pin down the other on the ground.
0:41:54 > 0:41:56These two are evenly matched.
0:41:56 > 0:41:58Neither can get the crucial throw.
0:41:58 > 0:42:01It's rather like an arm-wrestling contest,
0:42:01 > 0:42:04and the bout can continue for several hours.
0:42:41 > 0:42:46The eventual winner is the one who ends up on top most frequently.
0:42:46 > 0:42:49It's a controlled test of strength in which,
0:42:49 > 0:42:53despite their lethal weaponry, no-one gets seriously hurt.
0:42:57 > 0:42:59Other lizards defend themselves,
0:42:59 > 0:43:03not with physical strength, but by deceit.
0:43:04 > 0:43:06The South African desert.
0:43:08 > 0:43:09A bushveld lizard.
0:43:13 > 0:43:15This is another.
0:43:15 > 0:43:19It looks very different, but that is because it's a baby.
0:43:21 > 0:43:23It not only has different colouration,
0:43:23 > 0:43:28it also walks in a very different and quite extraordinary way.
0:43:38 > 0:43:39It appears to be imitating
0:43:39 > 0:43:41one of the local beetles,
0:43:41 > 0:43:42that one.
0:43:42 > 0:43:44And to discover why,
0:43:44 > 0:43:48I'm going to take defensive measures with these goggles.
0:43:50 > 0:43:55This beetle is known as an oogpister - an eye-spitter.
0:43:55 > 0:43:58And that is because it's squirting formic acid at me.
0:43:58 > 0:44:04Yeah, and if any of that got into my eye it would be extremely painful.
0:44:04 > 0:44:05It's a defensive system,
0:44:05 > 0:44:08and the lizards are benefiting
0:44:08 > 0:44:12by imitating a beetle with that kind of armoury.
0:44:14 > 0:44:17A young lizard closely matches the beetle,
0:44:17 > 0:44:20both in its appearance and its walk.
0:44:20 > 0:44:22So birds that prey on lizards
0:44:22 > 0:44:26assume it has a nasty spray, and leave it alone.
0:44:35 > 0:44:38Lizards can cope with dry, hot conditions so well
0:44:38 > 0:44:42they dominate the fauna in tropical deserts around the world,
0:44:42 > 0:44:45including those in central Australia.
0:44:49 > 0:44:54Their tough, scaly skins prevent their bodies from losing moisture,
0:44:54 > 0:44:56so that they can flourish in these
0:44:56 > 0:44:59arid, baking hot lands that other animals find so testing.
0:45:09 > 0:45:13Some wear the most elaborate suits of armour.
0:45:21 > 0:45:27This is surely the most enchanting of lizards.
0:45:27 > 0:45:32It's called the thorny devil or Moloch,
0:45:32 > 0:45:37after Moloch, the god in the Bible who ate little children.
0:45:37 > 0:45:39Both names surely are a slander
0:45:39 > 0:45:41on such an engaging little animal.
0:45:41 > 0:45:45It feeds entirely on ants,
0:45:45 > 0:45:47and, as you can see,
0:45:47 > 0:45:50there's not much of a meal in any one of them.
0:45:50 > 0:45:55But the good thing about ants as far as Moloch is concerned,
0:45:55 > 0:45:58is that there's always some around.
0:45:58 > 0:46:00And this little creature
0:46:00 > 0:46:03will sit by an ant trail patiently,
0:46:05 > 0:46:07for hours on end,
0:46:07 > 0:46:11simply picking off one ant at a time.
0:46:13 > 0:46:16The Australian desert is also home
0:46:16 > 0:46:20to one of the most powerful of the family.
0:46:20 > 0:46:24Monitors are the kings of lizards,
0:46:24 > 0:46:27and this is the perentie,
0:46:27 > 0:46:32the biggest species of monitor in Australia.
0:46:32 > 0:46:37It can grow up to two metres long, six feet.
0:46:37 > 0:46:41And it's a highly intelligent animal.
0:46:41 > 0:46:46It's got very acute senses of sight and hearing and taste and smell,
0:46:46 > 0:46:52and, like all monitors, it can do something no other lizard can do.
0:46:52 > 0:46:56It can run continuously for a very long time.
0:46:56 > 0:47:01And that enables it to become an endurance hunter,
0:47:01 > 0:47:02chasing down its prey.
0:47:08 > 0:47:13Most lizards inflate their lungs using the same muscles they use for walking,
0:47:13 > 0:47:18so they can't run and breathe effectively at the same time.
0:47:24 > 0:47:27But monitors have big muscular throats
0:47:27 > 0:47:30which they use like bellows to pump air
0:47:30 > 0:47:31into their lungs.
0:47:31 > 0:47:35And they can do that even when they're running.
0:47:41 > 0:47:43This special way of breathing
0:47:43 > 0:47:47enables them to reach speeds of over 20 miles an hour.
0:47:47 > 0:47:50Over distance, they are one of the fastest of all reptiles.
0:47:52 > 0:47:57The cold-blooded perentie can even out-run a warm-blooded rabbit.
0:48:02 > 0:48:04So, the lizards have colonised the world.
0:48:04 > 0:48:08From swamps to rainforests, from woodland to desert.
0:48:08 > 0:48:13And in doing so, they reveal such a variety of form and behaviour
0:48:13 > 0:48:18that they truly can be called the dragons of the dry.
0:48:28 > 0:48:33Much of our filming for this programme was done in Australia.
0:48:33 > 0:48:36There, there are lizards everywhere.
0:48:36 > 0:48:39Just walk around in the bush and you'll see them.
0:48:39 > 0:48:43But usually you won't get much more than a brief glimpse.
0:48:47 > 0:48:51To film their intimate behaviour, we needed help from experts.
0:48:55 > 0:48:59We travelled to Australia to meet an expert called Mike Bull.
0:48:59 > 0:49:03He knows Australian lizards as well as anyone.
0:49:03 > 0:49:08He and his team study many species in one small area north of Adelaide,
0:49:08 > 0:49:11using all manner of gadgets and gizmos,
0:49:11 > 0:49:14to investigate every part of their lives.
0:49:22 > 0:49:24We are particularly interested in the lizards
0:49:24 > 0:49:29that Mike understands best of all, the shingleback or sleepy lizard.
0:49:29 > 0:49:32He knows 10,000 of them individually.
0:49:36 > 0:49:40On the face of it, the sleepy lizard doesn't seem to do a lot,
0:49:40 > 0:49:42but Mike knows so much about them
0:49:42 > 0:49:46that we were able to make them one of the stars of our film.
0:49:46 > 0:49:49He's discovered that they're the only lizards in the world
0:49:49 > 0:49:53that remain faithful to one partner for all their lives.
0:49:53 > 0:49:56But that wasn't the reason that he began to study them.
0:49:56 > 0:50:00Tell me first how you first saw sleepy lizards
0:50:00 > 0:50:01and what attracted you to them.
0:50:01 > 0:50:05I started because I was interested in parasites that live on the lizard.
0:50:05 > 0:50:08To find the parasites I had to look at the lizards
0:50:08 > 0:50:11and discovered they were more interesting than the parasites.
0:50:11 > 0:50:14I think they're one of the most handsome animals you'll ever find.
0:50:14 > 0:50:17The other thing is it's probably the only animal that
0:50:17 > 0:50:22you know if you're driving in a car and see one 100 metres down the road, you know you've caught it,
0:50:22 > 0:50:27and it's also one that I think I'm going to be sufficiently agile
0:50:27 > 0:50:30to keep on catching until I'm well past 80!
0:50:30 > 0:50:34And even I, I think could scrag a sleepy lizard.
0:50:34 > 0:50:37I'll see whether I can manage it.
0:50:37 > 0:50:42Sleepy lizards like to bask on warm roads, so they're easy to find,
0:50:42 > 0:50:45and they move so slowly they're easy to pick up.
0:50:45 > 0:50:49So the team were able to weigh and measure a whole population,
0:50:49 > 0:50:52and thus discovered that pairs remained together in a way
0:50:52 > 0:50:56that was previously known only in birds and mammals.
0:50:56 > 0:50:58But that was just the start.
0:50:58 > 0:51:00Next, they turned to technology,
0:51:00 > 0:51:05some of it advanced, some a little bizarre.
0:51:05 > 0:51:10They used remotely-controlled rubber sleepy lizards
0:51:10 > 0:51:12to test how lizards reacted to one another.
0:51:14 > 0:51:16In this case, not very much.
0:51:20 > 0:51:23Mike's team suspected that another lizard in the area,
0:51:23 > 0:51:27the gidgee skink, had an even more complex social life,
0:51:27 > 0:51:30but this was difficult to prove because when approached
0:51:30 > 0:51:36the skinks wedged themselves in cracks in the rocks, making it impossible to identify who's who.
0:51:37 > 0:51:41The solution was to microchip each lizard
0:51:41 > 0:51:45so it could then be scanned just like your supermarket shopping,
0:51:45 > 0:51:48with a barcode reader on the end of a pole.
0:51:51 > 0:51:53This clever use of technology
0:51:53 > 0:51:57revealed what looked like a jumble of lizards on a pile of rocks,
0:51:57 > 0:52:00to be actually a little lizard family, with young
0:52:00 > 0:52:02that stay with their parents for life.
0:52:04 > 0:52:10I'm sure that there are going to be many other complex social organisations
0:52:10 > 0:52:14that will be uncovered in those species if we just simply take the time to look at them.
0:52:14 > 0:52:18But it's just the time and the patience to watch them,
0:52:18 > 0:52:21and watching a lizard is very unrewarding
0:52:21 > 0:52:26because they will come out and bask, sit by a bush,
0:52:26 > 0:52:32and if they see you're there, they'll decide they're not going to do very much for the rest of the day.
0:52:33 > 0:52:37To find out just what sleepy lizards get up to when no-one's around,
0:52:37 > 0:52:42Mike's team use a rather bizarre device they call a "waddleometer".
0:52:42 > 0:52:46It may look a little odd, but it records a lizard's GPS co-ordinates,
0:52:46 > 0:52:50counts its steps and even notes whether it's in sun or shade,
0:52:50 > 0:52:54all without troubling the lizard and without anyone having to be there.
0:52:54 > 0:52:58So you think there's probably the secret world of the lizard
0:52:58 > 0:53:00which no human being has ever seen,
0:53:00 > 0:53:04because if a human being is there the lizard won't behave that way?
0:53:04 > 0:53:08I'm sure that's part of it. It's the uncertainty principle,
0:53:08 > 0:53:12the closer you get to watch something the less normally it's behaving.
0:53:12 > 0:53:16And so it's only by getting these remote and new technologies
0:53:16 > 0:53:19that allow us to really get into the secret world of the lizards,
0:53:19 > 0:53:22that we can find these amazing things that they're doing.
0:53:22 > 0:53:23How extraordinary.
0:53:25 > 0:53:29One of their latest techniques uses miniature cameras which they use to study
0:53:29 > 0:53:34a very special lizard that we were also particularly keen to film.
0:53:39 > 0:53:42It's so rare that it was thought to be extinct for over 30 years,
0:53:42 > 0:53:45until it was thrust back into the public eye
0:53:45 > 0:53:49when it was discovered in some very unusual circumstances.
0:53:51 > 0:53:54A group of biologists were doing a standard biological survey.
0:53:54 > 0:54:00They were just coming back to town to pick up supplies and just on the road they saw a dead brown snake.
0:54:00 > 0:54:04Most people wouldn't even look at it as they're so common around here,
0:54:04 > 0:54:06but these were dedicated biologists.
0:54:06 > 0:54:08They had a look, noticed there was a bulge,
0:54:08 > 0:54:11so they thought, "Let's see what it's been eating."
0:54:11 > 0:54:18Opened it up and there was this lizard that no-one had seen for 30 years, the pygmy blue-tongued lizard.
0:54:18 > 0:54:23How lovely, though I dare say it wasn't all that lovely when they actually saw it.
0:54:24 > 0:54:26Miniature cameras have produced images
0:54:26 > 0:54:33that are slowly helping to build up a comprehensive picture of the life of these rare little creatures.
0:54:35 > 0:54:37Their burrows are more than just homes.
0:54:37 > 0:54:43They're also hiding places where they can wait in ambush for spiders and crickets.
0:54:43 > 0:54:45But they don't seem too keen on ants.
0:54:47 > 0:54:50They also serve as bolt holes when danger approaches.
0:54:56 > 0:54:58Despite all this work,
0:54:58 > 0:55:01Mike's team had never recorded their life underground.
0:55:01 > 0:55:05So we were able to help with a little of our own technology
0:55:05 > 0:55:09and record the first ever pictures of a pygmy blue-tongue family.
0:55:09 > 0:55:13Three babies alongside their mother in their little hole.
0:55:19 > 0:55:22But all this technology, ingenious though it is,
0:55:22 > 0:55:25is no substitute for years of dedicated observation.
0:55:25 > 0:55:29Mike's approach of simply driving for miles across the Australian outback
0:55:29 > 0:55:35is very fruitful, and you see lots of other things as well as lizards.
0:55:35 > 0:55:40Up here is just a wonderful place for lizards and kangaroos.
0:55:40 > 0:55:43Ha, boy! Eastern grey, beautiful.
0:55:43 > 0:55:46Now, you won't catch a lizard doing that.
0:55:53 > 0:55:56Oh, look, there's a pair just down there.
0:56:03 > 0:56:08It turned out that Mike had spotted two old friends.
0:56:13 > 0:56:15This is the male and the female.
0:56:15 > 0:56:19This is 1172 and 3345,
0:56:19 > 0:56:22- I think they've been together for about ten years.- Really?
0:56:22 > 0:56:25We've got some other pairs that have been together for over 20 years.
0:56:25 > 0:56:27They stay together during the springtime
0:56:27 > 0:56:31and mate towards the end of the spring and then they separate,
0:56:31 > 0:56:33but the next year the same two lizards,
0:56:33 > 0:56:37we'll find them back together again, usually in the same place along this road.
0:56:37 > 0:56:40Aren't they terrific?
0:56:40 > 0:56:43They use their tongues to pick up chemical signals
0:56:43 > 0:56:46and you can see they're actually sensing each other at the moment.
0:56:46 > 0:56:49I think that's really very touching.
0:56:51 > 0:56:53I'd say that's a risky business.
0:56:54 > 0:56:59With obsessive dedication and ever-advancing technology,
0:56:59 > 0:57:02who knows what Mike and his team will uncover
0:57:02 > 0:57:05about the secret lives of sleepy lizards?