Bats typically roost head-under-heels but they cannot hover in this position, thus, landing on a ceiling presents a biomechanical challenge. To land, a bat must perform an acrobatic flip that brings the claws of the toes in contact with the ceiling and do so gently enough as to avoid injury to its slender hindlimbs. In the present study, we sought to determine how bats land, to seek a link between landing kinematics and ceiling impact forces, and to determine whether landing strategies vary among bat species. To do this, we measured the kinematics and kinetics of landing behaviour in three species of bats as they landed on a force-measuring platform (Cynopterus brachyotis, N=3; Carollia perspicillata, N=5; Glossophaga soricina, N=5). Kinematics were similar for all bats within a species but differed among species. C. brachyotis performed four-point landings, during which body pitch increased until the ventral surface of the body faced the ceiling and the thumbs and hindlimbs simultaneously grasped the surface. Bats of the other two species performed two-point landings, whereby only the hindlimbs made contact with the ceiling. During these two-point landings, the hindlimbs were drawn up the side of the body to come in contact with the ceiling, causing simultaneous changes in body pitch, roll and yaw over the course of the landing sequence. Right-handed and left-handed forms of the two-point landing were observed, with individuals often switching back and forth between them among landing events. The four-point landing of C. brachyotis resulted in larger peak forces (3.7±2.4 body weights; median ± interquartile range) than the two-point landings of C. perspicillata (0.8±0.6 body weights) or G. soricina (0.8±0.2 body weights). Our results demonstrate that the kinematics and kinetics of landing vary among bat species and that there is a correlation between the way a bat moves its body when it lands and the magnitude of peak impact force it experiences during that landing. We postulate that these interspecific differences in impact force could result because of stronger selective pressure for gentle landing in cave-roosting (C. perspicillata, G. soricina) versus foliage-roosting (C. brachyotis) species.
We thank the staff of Le Biôdome de Montréal, especially M. Delorme, for access to animals and laboratory space during pilot work for this study. A. A. Biewener, faculty, staff and graduate students at the Concord Field Station made our work possible there, and G. Spanjer Wright and C. F. Moss gave us access to animals and lab space at the University of Maryland. D. Green constructed an enclosure for pilot data collection. A. Sullivan and F. Male assisted with digitization of movie files. We thank J. Iriarte-Díaz, T. L. Hedrick, L. Richie, M. Srinivasan and the morphology group at Brown University for helpful discussion. S. Taylor, K. Middleton, J. Iriarte-Díaz and V. Cofer-Shabica assisted with the training of animals and with data collection. G. S. Sawicki and two anonymous reviewers provided helpful comments on an earlier draft of the manuscript, and N. I. Hristov assisted in the preparation of Fig. 3. This study was funded by a Natural Sciences and Engineering Research Council of Canada (NSERC) postgraduate scholarship and Sigma Xi grant to D.K.R., by NSERC and Danish Natural Sciences Research Council postdoctoral fellowships to J.M.R. and by United States Air Force Office of Scientific Research and National Science Foundation grants to S.M.S. and Kenneth S. Breuer.