When you think of a bat, chances are you’re imagining it hanging upside down from a tree branch or a cave ceiling. Now, scientists have figured out how bats effortlessly pull off this stunt, according to a new study 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, which seems like it would increase the difficulty of these gymnastic feats.
Bats also have to deal with having solid bones unlike birds, whose bones and joints are hollow. But instead of being kept down by their weight, bats use their relatively heavy bodies to their advantage, flinging their bodies around similar to how skateboarders and figure skaters pull off kick flips and pirouettes, Nsikan Akpan writes for the PBS Newshour.
To figure out how bats pull this trick off, Swartz teamed up with Brown University engineer Kenny Breuer to analyze the bats’ landings using a high-speed video camera. When they slowed down the bat’s flight, they realized that the furry fliers manipulated their body’s inertia by tucking in one wing and keeping the other extended, shifting their center of gravity and allowing 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, adding that “we don’t have any direct evidence of this yet.”
While birds can fly upside down and have lighter wings, bats are more dextrous fliers thanks to having many more joints and muscles in their wings. This allows them to pull off deft maneuvers 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, suggesting 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.”