How bats land upside down
Bats display astonishing aerial agility when re-positioning themselves upside down to roost. The mechanics of how this action is accomplished has always been a mystery as bats are unable to hover upside down. However Attila J. Bergou and colleagues have provided an answer to this mystery in their recent paper 'Falling with Style: Bats Perform Complex Aerial Rotations by Adjusting Wing Inertia'.
Using video from multiple high-speed cameras and a model-based tracking algorithm the authors were able to demonstrate that bats are able to execute their heels-to-head manoeuvres using primarily inertial forces, by controlled movements of their heavy wings. They found that to flip their bodies while landing, bats retract one wing and extend the other. This works as bats' wings are heavy with bone and muscle, allowing a bat to roll over swiftly by moving the mass of its wing relative to its body. This effect is called inertial reorientation. To find out more about this fascinating behaviour read the paper here.