To better understand how bats power through a takeoff, scientists wanted to look at the animals up close – really up close.
To capture the flights of Seba’s short-tailed fruit bats, a common South American species, Brown University biologist Nicolai Konow and his team used a technology developed at the university called X-ray Reconstruction of Moving Morphology, or XROMM. This technique combines 3D models of bones, created with either CT scans, MRI or laser scans, with X-ray videos to create 3D visualizations of moving skeletons. Konow and his colleagues also implanted special beads directly in the bats’ muscles that show up opaque on an X-ray scan. Those radio-opaque beads allowed the team to see how the bats’ muscles contracted and lengthened as they beat their wings.
“Energy is stored in the triceps tendon, which is used to power elbow extension – in essence, elbow extension happens using ‘recycled’ energy,” Konow said in a statement. Both previous research and the current work indicate “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."
As the bat launches itself into the air, the tendons in its biceps and triceps stretch and store energy that it uses on the downbeat to keep flying vertically. Knowing how bats manage to take off from the ground could prove fruitful in designing small robotic air vehicles someday. The researchers presented their work last Thursday at a meeting of the Society for Experimental Biology in Valencia, Spain. The team also recorded a fruit bat takeoff in slow-motion, minus the X-ray vision:
Other researchers have used the same XROMM technology to tackle different projects. For instance, Brown researcher Megan Dawson and her colleagues captured X-ray video of a mallard duck feeding to better study how the bones of the bird’s bill and face move as it eats:
And another team used XROMM to observe the biomechanics at play in the knees of male and female athletes with either intact or reconstructed anterior cruciate ligaments. An ACL tear is one of the most common knee injuries, and surgery to reconstruct the ligament is almost certainly required if an athlete wants to return to sports.