Bat drinking on the wing

Bats are well known to perform complex flight maneuvers utilizing the many degrees of freedom in their skeletal wing structures and flexible wing membranes. Drinking during flight is one such critical maneuver commonly carried out by many bat species. Here, we present a comparative study between the well-explored straight flight mode and the drinking flight mode in bats using a combined experimental and theoretical approach. High speed video recordings are performed on two bat species (Hipposideros pratti and Rhinolophus ferrumequinum) to capture straight and drinking flight modes in a controlled environment (flight room). A kinematic analysis of the two flight modes after 3D reconstruction of landmark points on the bat shows that during drinking flight bats reduce their flapping amplitude and simultaneously increase the flapping frequency compared to the straight flight mode. We further carry out aerodynamic analyses based on quasi-steady lift and drag force models on both forward flight and maneuvering flight during drinking. This work emphasizes the importance of studying different flight maneuvers in bats to understand how modifications in wing kinematics and morphology are used to actively control the body posture for a specific task.