Bats have extremely heavy wings compared to birds and insects, and researchers have wondered what the purpose is behind this "detriment to maneuverability."
New research suggests bats' cumbersome wings actually help them land in an upside-down position, Brown University reported.
"Bats land in a unique way," said Sharon Swartz, a biologist at Brown University. "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."
Until now, the mechanisms that allow bats to perform incredible maneuvers, such as landing upside-down.
"When they come in to land they're not moving very fast, which makes it hard to generate the aerodynamic forces needed to reorient themselves," said Kenny Breuer from Brown's School of Engineering. "So the question is, how do bats get themselves in position to land?"
To answer these questions, a team of researchers observed bats in a special enclosure using high-speed cameras, and analyzed their data with sophisticated computer-modeling techniques. They found bats move their wings in a similar way to divers performing a flip or twist. They use the initial force generated by their heavy wings to reorient themselves, instead of relying on aerodynamic forces created by pushing against the air.
In the study, the team trained two types of bats to fly into an enclosure and land on a piece of mesh attached to the ceiling. The high-speed cameras picked up these bats' subtle wing maneuvers made only seconds before their upside-down landing. They observed that when the bats approached the ceiling, they subtly retracted one wing towards their bodies while flapping the other at full extension. This allowed the bats to rotate their bodies a half-turn so their feet could meet the mesh. The computer simulations revealed the effect of the maneuver was a result of inertia, as opposed to aerodynamics.
"What this tell us is that in bats, with their heavy wings, it's the inertial forces that are more important relative to aerodynamics," Breuer said. "That's a bit of a counterintuitive conclusion. Normally you'd think that an animal would not want to have such massive wings. But here, it turns out that the mass can be used to some benefit."
The findings could be applied to man-made flying machines and drones.
"From an engineering perspective, there's a lot of interest in drones and flying microvehicles," Breuer said. "Maneuvering or directing those robotic vehicles is a challenge. The idea here is that using redistribution of mass is not a bad approach to take."
The research was published in a recent edition of the journal PLOS Biology.
