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Page last updated at 08:59 GMT, Tuesday, 13 October 2009 09:59 UK
Lizards filmed 'walking on water'
By Matt Walker
Editor, Earth News

A brown basilisk or 'Jesus Christ' lizard (Basiliscus vittatus)

A "Jesus Christ" lizard, filmed from above and below the water

Remarkable slow-motion footage has been taken of two lizards that seem to do the impossible - walk on water.

A high-definition film, shot at 2,000 frames per second, shows a brown basilisk lizard running across the surface of a pond in Belize.

More footage shows how a species of gecko is so tiny that it can walk across a puddle without breaking the water's surface tension.

These amazing feats are captured for the BBC natural history series Life.

The group of animals known as basilisk lizards commonly lives along the edge of rivers running through rainforests, eating small insects among the foliage.

Because they run so fast they create a bubble as their feet hit the water and then they push off from this bubble before it bursts
Life assistant producer Simon Blakeney

The lizards need to bask in the sun to warm up each day, which leaves them vulnerable to being caught by predators, such as large birds of prey hunting from the air, or carnivores such as cats living on the jungle floor.

So the lizards have evolved an extraordinary escape mechanism.

They drop into the water and then run across it, earning the lizards their nickname, the "Jesus" or "Jesus Christ" lizard.

Exactly how they do so is revealed by the slow-motion, high-definition footage taken at 2,000 frames per second.

"Because they run so fast they create a bubble as their feet hit the water and then they push off from this bubble before it bursts," says Simon Blakeney, a producer on the Life series who helped direct and film the footage of both reptiles.

"They can only run at that speed. If they were going any slower, for example, they wouldn't stay upright, they would slip into the water and would have to swim."

Mr Blakeney and his colleagues filmed brown basilisk lizards (Basiliscus vittatus) running across ponds and rivers in the rainforest in Belize, around 60km from Belize City.

Capturing the footage of the animals in action proved tricky.

Brazilian pygmy gecko (Coleodactylus amazonicus)

To a Brazilian pygmy gecko, a raindrop could be deadly

"Around 80% of the time when they are escaping from things, they don't run, they swim. So filming them running was quite a difficult thing in itself."

The lizard has long thin toes that are covered by scales underfoot. These help create the air bubbles that enable the lizard to push off and walk across the water.

Scientists had also previously established that basilisk lizards produce massive sideways forces in their running stride, which, perversely, help them stay upright.

Slowing the action of the film to 1/80th of its real-life speed reveals the true spectacle, says Mr Blakeney.

"As the water lifts up it makes this incredible trail of splashes behind it, like a pebble dropping into the water.

"Then the lizard has already gone out of frame because they are so fast."

Float like a gecko

Another lizard, a tiny species known as a pygmy gecko, faces a different problem altogether.

At just 2 to 4cm long from head to tail, the Brazilian pygmy gecko (Coleodactylus amazonicus) could be battered by a raindrop and risk drowning in even the smallest pool of water.

So it has evolved to be essentially waterproof, which in turn allows it to walk across the surface of any puddle it encounters.

I've never seen anything like that to be honest
Life assistant producer Simon Blakeney

Mr Blakeney's team encountered the remarkable gecko near a place called Aripauna, on the edge of the Amazon in Brazil.

With the help of expert Dr Gabriel Skuk of the Federal University of Alagoas based in Maceio, Brazil, the team filmed the geckos surviving in the leaf litter on the forest floor.

"They don't really use water as an escape response, because even if they are trying to escape from something a puddle looks like a lake to them," says Mr Blakeney.

"Because they are so tiny, they are able to float on the surface of the water like a pondskater, so they don't break the surface tension.

"I've never seen anything like that to be honest."

The geckos have hydrophobic skin which repels water just like a waterproof jacket.

One hypothesis put forward by scientists, says Mr Blakeney, is that as the geckos became smaller, they needed to evolve a way to float, to avoid drowning when it rains.

The water-walking lizards can be seen on the BBC series Life, which is broadcast at 2100BST on BBC One on Monday 19 October.

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