The "snakebot", still only a lab prototype, is designed to be dropped out of helicopters and creep around a battlefield, using optical, audio and other sensors to build up a picture of enemy activity.

Because it hugs the ground and slithers along, the snake would be less visible and more versatile than conventional reconnaissance robots, which are bigger and move around clumsily on wheels or tracks and have little ability to adapt to breakdown or damage.

The spy snake comprises vertebrae made of modules that snap together like a child's toy and are moved by muscles made by a so-called shape-memory metal -- an alloy of nickel and titanium that shrinks when an electrical current is passed through it but recovers its shape when the current is off.

By switching the current on and off, the wires spring back and forward, making the snake wriggle.

But the smartest part of the device, the British weekly reports in next Saturday's issue, is the software, which takes a "survival of the fittest" approach to produce a system that continually evolves to improve itself.

The algorithmic programme starts off with a population of 20 "digital chromosomes," each corresponding to a binary digit that either activates or deactivates a muscle wire.

These chromosomes form the raw mathematical basis for the snake's movement.

Some chromosomes may result in the robot moving, and others will not. The programme tries them all out and awards them a fitness rating, depending on how far it makes the snake move.

The two best chromosomes are then saved, the remained are mixed up or randomly mutated like genes in nature, and the process is repeated.

After a number of generations, the amount of improvement gradually tapers off, signifying that the chromosomes have reached a plateau of the best possible arrangement.

The designers -- computer scientists Peter Bentley and Siavash Haroun Mahdavi at University College London -- tested the programme by disabling some of the robot's segments to see if it could adapt to injury.

Initially, the snake was immobilised but eventually its "brain" worked out how to move again, "albeit more awkwardly and with an ungainly, dragging gait -- but it was still good enough to get the robot to its destination."

The research has been funded by the British aerospace company BAE Systems, New Scientist says.

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