Meeting Abstract

88.5  Thursday, Jan. 7  Why does Madagascar’s sucker-footed bat roost head-up? RISKIN, D. K.*; RACEY, P. A.; Brown University; University of Aberdeen dkr8@brown.edu

Most bats hang head-down by their toes, but Madagascar’s endemic sucker-footed bat (Myzopoda aurita) clings head-up inside the furled leaves of trees by means of adhesive pads on its wrists and ankles. Based on previous anatomical studies, the pads were thought to function by means of suction, but no studies of attachment or detachment by live animals have been performed. We investigated the adhesive performance of 28 individuals to determine the mechanism of attachment, and found that adhesion to brass was not affected by the presence or absence of a seal around the pad-surface interface. Also, on smooth Lexan the wrist pads were more than nine-fold weaker when pulled perpendicular to the surface than when pulled parallel to it. Suction requires a seal, but wet adhesion does not, and that directional force dependence on a smooth surface is characteristic of wet adhesion, but not of suction. Thus, we conclude that despite its name, the sucker-footed bat grips smooth surfaces by means of wet adhesion. Furthermore, we found that while the wrist pads gripped strongly when the bat was pulled posteriorly along a surface, they unpeeled easily when the bat was pushed anteriorly. This occurred because the rolling of the pads caused their surfaces to be lifted perpendicular to the surface plane, the direction in which wet adhesion is weak. This unpeeling mechanism of detachment probably permits rapid crawling locomotion, but would also cause passive detachment if bats roosted head-down. This is the most likely explanation for the head-up roosting posture of Myzopoda aurita. Our results give insight into the morphological specialization that corresponds to novel roosting habits, linking biomechanics, behaviour, and roosting ecology for an enigmatic Malagasy endemic.