This is how bats can land upside down

How do bats land upside down? (Daniel Gerd Poelsler/imageBROKER/Corbis/Wisconsin Department of Natural Resources via AP, File)

When you think of a bat, chances are you're imagining it hanging upside down. It might hang from a tree branch or a cave ceiling. Now, scientists have figured out how bats effortlessly pull off this stunt. That is according to a study. It was published in PLOS Biology.

"Bats land in a unique way," Brown University biologist Sharon Swartz, said in a statement. "They have to go from flying with their heads forward to executing an acrobatic maneuver that puts them head down and feet up. No other flying animal lands the same way as bats do."

Relative to their body weight, bats have some of the heaviest wings in the animal kingdom. That seems like it would increase the difficulty of these gymnastic feats.

Bats also have to deal with having solid bones. This is unlike birds. The bones and joints of birds are hollow. But instead of being kept down by their weight, bats use their relatively heavy bodies to their advantage. They fling their bodies around. It is similar to how skateboarders and figure skaters pull off kick flips and pirouettes. This is according to Nsikan Akpan for the PBS Newshour.

To figure out how bats pull this trick off, Swartz teamed up with Brown University engineer Kenny Breuer. They studied the bats' landings. To do it, they used a high-speed video camera. They slowed down the bat's flight. They realized that the furry fliers directed their body's inertia by tucking in one wing and keeping the other extended. It shifted their center of gravity. That allowed them to flip around despite their weight.

"I would imagine that they use inertial forces for every aspect of their maneuvering," Breuer tells James Owen for National Geographic. "We don't have any direct evidence of this yet."

Birds can fly upside down and have lighter wings. But bats are more nimble fliers. That is thanks to having many more joints and muscles in their wings. This allows them to pull off deft movements using their own inertia very quickly. In Swartz and Breuer's experiment, it took the bats less than a second to flip upside down for their landings. It suggested that what they lack in aerodynamics, they make up for in mastering their own inertia, Akpan reports.

"It never would have occurred to me that aerodynamics would play such a small role in landing. I always think of flight as a primarily aerodynamic phenomenon. Wings are aerodynamic organs, and landing seems so obviously to be a flight behavior," Swartz tells Akpan. "Inertia can play an important role in flight dynamics, but the relative unimportance of aerodynamics is still quite astonishing."

Knowing how bats turn their body weight to their advantage doesn't just give scientists new insight into how they fly. It might also help engineers design new drones and small flying vehicles that can take advantage of shifting their mass in exchange for better control. But for now, Swartz and Breuer want to find out whether all bats use their inertia to help them control their landings.

"In Central America, there are some bats that roost head up thanks to suction disks on their wrists and ankles. They roost inside furled up leaves in tropical forests," Swartz tells Akpan. "They don't end up upside down. So how do they land? There's almost 1,400 species of bats, and we've just scratched the surface."

How is the way a bat lands different than the way a bird lands?