Media playback is unsupported on your device Media caption The remarkable footage was achieved using a technique called X-ray reconstruction

Scientists in the US have used X-rays to produce remarkable videos of bats in flight that reveal the movement of their skeletons.

Analysing this footage has revealed how the bats store and recycle energy in their tendons.

The tiny fruit bats the team studied have very stretchy tendons that connect their upper arm muscles to their bones.

This, say the scientists, make them very efficient fliers.

The research was presented at the Society for Experimental Biology's annual meeting in Valencia, Spain.

Since bats are also unique among mammals in their ability to fly, the scientists say the animals could inspire the design of the search-and-rescue robots.

Filming skeletons

The idea behind the study, according to lead researcher Dr Nicolai Konow from Brown University, was to show exactly "how the skeleton moves with in an organism".

"Bats don't like being on the ground, so we just put them on the ground and filmed them as they took off.

Dr Konow also measured the change in the length of the bats' muscles and tendons, which revealed the stretchy, energy-storing property.

"Most small mammals have stiff, thick tendons so they cannot stretch or store energy in them like we do in our Achilles tendon when we run or walk," he explained.

But this 20g fruit bat stores energy as it stretches its bicep and tricep tendons during take‐off and climbing flight.

Releasing this "elastic energy" - just like a stretched rubber band snapping back - gives the animal an extra power boost.

'Tiny but incredible'

The researchers say that this energy-recycling could be used to aid the design of more efficient flying robots.

"The way forward for bio-inspired design is to have energy is stored in the system, so it's available to power robotic movements," Dr Konow explained.

He added: "The fact that bats are able to pack such an incredible functional repertoire into such a tiny body utterly amazes me."

"And bats don't just fly - they walk, run jump and even swim, so we're pretty nicely set up to create the ultimate amphibian here.

"And that could have thrilling applications in terms of search and rescue in catastrophe zones."