Bats roost upside down, but they can’t fly upside down. So how do they land topsy-turvy on overhead perches without falling to the ground? 

A new study in PLOS Biology by biologists and engineers at Brown University finds that bats are masters of inertia. Much like a figure skater tucks her arms closer to her body to increase the speed of her spin, bats spin upside down by adjusting their relatively heavy wings. They retract one wing, and extend the other. Like so:

The researchers discovered this via high-speed video of five individual bats from two species, each attempting to land on the ceiling of a lab. The bats were trained to land in a specific corner of the room in front of the cameras with the help of smooth plastic that prevented them from landing elsewhere on the walls or ceiling. The researchers estimated changes in inertia by measuring the mass of a dissected bat wing, weighing it in 32 different pieces to figure out how movement would affect a bat’s inertia. 

When seen at 1000 frames per second, it became clear that the bats were rapidly reorienting their bodies by extending their flapping right wing and retracting their left, causing them to roll. Thus, they were putting the mass of their wings to good use, instead of relying on aerodynamics. This finding might be applied to flying robots one day. 

[h/t: PBS News Hour]