Life In Cold Blood
The Cold Blooded Truth – programme one
Reptiles and amphibians are as dramatic in combat, colourful in their communication and tender in their parental care as other animals. They also live their lives on a totally different time scale and harness their energy from the sun. The Cold Blooded Truth reveals the secret of their success.
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Sir David Attenborough begins the story on the Galapagos Islands, among massed ranks of marine iguanas. Stunning thermal imagery reveal how these lizards bask in the sun until they are as warm as he is, and then pour like hot golden lava into the cold sea as the heat they have accumulated powers their dives.
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In California, side-blotched lizards fight for the best sun-baked rock-piles to use as radiators. Here, the females choose the males with the hottest rocks as mates.
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Mediterranean wall lizards have also discovered a novel heat source. They bask on the bizarre Dead Horse Arum flowers that produce living heat as a by-product of making a disgusting odour to attract flies. Sat on theses hotplates, the lizards get heat and regular meals of flies.
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Surprisingly, on a chilly, windswept island off the coast of South Africa, David finds a riot of reptiles – the highest concentration of angulate tortoises on Earth. They, too, sunbathe to power their hot-blooded jousting, using "lances" on the front of their shells. A "tortoise cam" reveals just how they flip each other over in these vicious fights.
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But reptiles don't waste their energy, and they use solar power very efficiently. Snakes will remain still for days before striking with lightning speed. They can switch instantly from "pilot light" to "full power", and their bodies respond with a biochemical explosion of activity. Amazingly, their livers double in size in two days and their hearts can grow by 40%.
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Reptiles can be sensuous, too – the tenderest courtship is surprisingly performed by the ultimate cold-blooded killer on Earth today – the saltwater crocodile. The five-metre-long gigantic male gently caresses the much smaller female while blowing bubbles to reassure her.
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Having revealed the truth about life in cold blood, David looks at some possible exceptions to the rule. After examining the oldest reptiles of all, the dinosaurs, he finds that they collected heat just like their modern relatives using solar panels. But that the sheer size of the Tyrannosaurus rex would have helped it retain heat so well that it was effectively warm blooded.
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Finally, David meets a modern giant reptile that is also an exception to the cold-blooded rule. The ancient leatherback turtle is the largest of living reptiles. As the female lays her eggs, thermal cameras reveal that her internal body temperature is above that of her surroundings.
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Producer/Miles Barton
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Under The Skin – Charismatic Chameleons
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David travels to Madagascar in search of the world's smallest reptile – an animal he has been waiting nearly half a century to see. After failing to find the pygmy leaf chameleon for Zooquest during his first visit to the country in 1960, he tries his luck 47 years later.
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This time, top chameleon biologist Bertrand Razafimahatratra was on hand to help find the elusive animal which is only as big as a thumbnail. They are active in daytime, but, because their pale skin stands out at night, Bertrand hunted in the dark using only torchlight.
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With Bertrand's help, they found many other chameleons during their night time safari, huge Oustalet's chameleons, enigmatic stump-tailed chameleons and colourful panther chameleons. But would they fulfil David's lifelong ambition of finding the tiniest one of them all?
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Fascinating facts
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- Female side blotched lizard choose the males with the hottest rocks.
- The "flower powered" Balearic wall lizards are the only diurnal lizards known to hunt using their hearing. They are also the first lizards to demonstrate a cultural tradition – that of feeding on the Arum fruits – which has been transmitted throughout the population in a matter of decades.
- Leopard gecko eggs incubated at 26 degrees produce 98% females, while those incubated at 31 degrees overwhelmingly produce males.
- Angulate tortoises joust and scarlet poison arrow frogs wrestle for over half an hour at a time.
- Armadillo lizards roll up in a ball by biting their tails to defend themselves against predators.
- Baby painted turtles can survive freezing at temperatures of –10 degrees centigrade.
- Male leopard geckos wag their tails with excitement when they meet a female.
- A python's heart can grow by 40% in two days, and they can go for a year without feeding.
- Male painted turtles win their partners' affections by sensuously strumming their faces with their long claws
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