X-Ray Video Reveals Recycled Energy of Powered Bat Flight

Bats are the only known living mammals that possess the ability of powered flight, swooping through the air as they swerve and dive in search of food. Now, scientists have examined this ability a little more closely. They've discovered that these airborne creatures can stretch and store energy in their bicep and tricep tendons during take-off and climbing flight, giving them the extra power boost that they need.

In order to examine a bat's ability to fly, the researchers took a closer look at Seba's short tailed fruitbats. These animals are native to Central and South America, living in forests and rainforests in the area. Acting as pollinators and seed dispersers, these creatures don't only just feed on fruit; they'll also eat pollen and insects, foraging close to the ground.

The researchers used a cutting edge 3D imaging technology called XROMM (X-ray Reconstruction of Moving Morphology) in order to visualize rapid internal skeletal movement of these bats. This system combines 3D models of bone morphology with movement data from biplanar x-ray video in order to create highly accurate re-animations of the 3D bones moving in 3D space. In other words, it can recreate bat flight in mathematical terms, allowing researchers to get a closer look at how it works.

"Energy is stored in the triceps tendon, which is used to power elbow extension--in essence, elbow extension happens using 'recycled' energy," said Nicolai Konow of Brown University in a news release. "State of knowledge, and our results, indicates that bats are unique among small mammals in stretching their tendons, as small mammal limb tendons are thought to be too thick and stiff to be stretched."

The researchers didn't only use this 3D recreation, though. They also employed a novel method called fluoromicrometry. This involves small radio opaque marks being implanted directly into muscle. It allowed the researchers to measure length change with high precision and accuracy during contractions.

"By combining information about skeletal movement with information about muscle mechanics, we found that the biceps and triceps tendons of small fruitbats are stretched and store energy as the bat launches from the ground and flies vertically," said Konow.

The findings reveal that the action of muscles powering animal movements through fluids may be influenced by series elasticity. In other words, some limb tendons in small mammals can be stretched by muscular and aerodynamic forces. The new research could have implications for the development of micro aircraft and amphibious search and rescue vehicles.

Want to see the bat fly for yourself? Check out the video below, courtesy of YouTube.