Life In Cold Blood
Dragons Of The Dry – programme three
From iguanas emerging out of a tropical swamp to a face-to-face encounter with a monitor lizard in the Australian desert, David Attenborough traces the lizards' colonisation of the Earth as they ultimately became the Dragons Of The Dry.
The first step in their success was the evolution of hard shelled eggs. In Australia, lace monitors lay eggs in termite mounds leaving the babies with a problem when it comes to hatching – an adult has to dig them out. Once freed, like many small lizards, they take to the trees for safety.
Male jacky dragons use their tree perches to display by head bobbing and arm waving. Sometimes, they fight to back up their signalling and the loser admits submission with a slow arm wave. In Florida, David encourages an anole to display by using a mirror to simulate a rival. It head bobs and then flashes a vibrant red dewlap flap on its throat at the "imposter".
But the real masters of colourful display are the chameleons. In Madagascar, David meets the smallest in the world – the minute pygmy leaf chameleon. In Malawi, there is a joust between two dinosaur-like Mellor's chameleons and, in South Africa, a Cape dwarf chameleon gives birth to a litter of young in a tree. As the babies drop, their fall is broken by a sticky substance that catches on the branches.
The secrets of the chameleon's hunting technique are revealed as the action is slowed down by up to 80 times using an ultra-high-speed camera. The tip of the tongue actually grasps and enfolds the prey.
New discoveries are also made about the elusive pygmy blue-tongued skinks. David tempts one out of its burrow with a fishing rod, and a special probe camera reveals the secrets of its underground family life. The babies remain with their mothers for weeks just like birds in a nest.
Less touching, but more dramatic, is the free-for-all mating frenzy of the brilliantly coloured South African flat lizards. Females are constantly harassed by ardent males and have to thrash them with their tails and flailing arms to keep them under control. Equally impressive are the bizarre wrestling bouts of the Mexican beaded lizards, which can last over an hour. Males circle and grasp each other, eventually locking together to form an arch while still trying to push each other over. The one that gains the most submissions is the winner.
Other lizards owe their success to deceit rather than strength. In South African deserts, baby bushveld lizards mimic the black and white warning colouration and stiff legged, hunched gait of a beetle. It serves as protection because this particular beetle has a very unpleasant form of defence. David experiences at first hand how it squirts acid at predators. Finally, he returns to the baking deserts of central Australia, home to the bizarre ant-eating thorny devil and the largest of Australian lizards, the 5ft-long perentie – a true Dragon Of The Dry.
Under The Skin – Family Affairs
David Attenborough meets Mike Bull and his team who study the social lizards of South Australia. They know thousands of the reptiles individually and have discovered that sleepy lizards are monogamous. Using a range of weird and wonderful gadgets they investigate their secret lives.
The aptly named "waddleometer" measures the lizard's rate of movement and its position automatically. Then there is "robo-lizard" mounted on a toy truck to test how the lizards react to intruders.
Mike's team also suspected that another local lizard – the gidgee skink – had an even more enduring family life than the sleepy lizard. They micro-chipped each animal so that it could then be scanned, with a bar-code reader on the end of a pole. This revealed that the groups of lizards seen on rock piles are actually close-knit families whose young stay with them till adulthood.
Now Mike is studying a lizard that was believed extinct for over 30 years – the Pygmy Blue-tongued skink. Further investigation revealed exactly why it has stayed hidden for so long – it lives in tiny trap-door spider burrows. To unlock its secret lifestyle, Mike and the Life In Cold Blood team join forces to record, for the first time ever, its family life – three baby skinks nestled in the burrow with their mother.
- The slow hand wave used as a white flag by a submissive male jacky dragon is the same as the come hither signal used by females.
- The duelling Mellor's chameleon at 60cm (about 2ft) long is one of the largest chameleons in the world. They are even known to eat birds.
- The Cape dwarf chameleon produces up to a dozen young who have to gain their climbing skills immediately after birth or face plummeting to the ground below.
- The longest known relationship between a pair of sleepy lizards is 22 years.
- The pygmy blue tongued skink was believed extinct till 1992 when one was accidentally found in the belly of a brown snake. It's one of the most endangered of Australian lizards with only 5,000 still in existence in the wild.
- A wrestling match between Mexican beaded lizards can last for hours – each trying to pin the other to the ground to get a submission. Despite being venomous, they don't use their venom, instead fighting by the rules – which are rather like those of an arm wrestling contest.