Meeting Abstract
70.6 Tuesday, Jan. 6 Oh what a feeling: the kinematics and kinetics of landing on a ceiling. RISKIN, D K*; BAHLMAN, J Wm; HUBEL, T Y; RATCLIFFE, J M; KUNZ, T H; SWARTZ, S M; Brown University; Brown University; Brown University; University of Southern Denmark; Boston University; Brown University dkr8@brown.edu
Flying animals exhibit obvious adaptations for flight, but they must also be able to land and maneuver in association with solid surfaces. Bats are especially interesting in this regard, since to land on a ceiling they must throw themselves toward an overhead substrate and perform a flip. Bat hindlimbs are gracile compared to those of other mammals, so bats must land in a way that keeps impact forces low, so that hindlimb stresses stay small. We examined the kinematics and kinetics of landing behaviour in three species of bat: an Old World fruit bat (Pteropodidae: Cynopterus brachyotis), and two New World fruit bats (Phyllostomidae: Carollia perspicillata and Glossophaga soricina). Cynopterus increased body pitch throughout the landing sequence, until the ventral surface of the body faced the ceiling. Roll and yaw did not change significantly during the landing. We refer to these as four-point landings, because bats struck the ceiling with the thumbs and hindlimbs simultaneously. Carollia and Glossophaga performed landing maneuvers in which their legs were brought up along the side of the body, causing simultaneous changes in pitch, roll, and yaw during the landing sequence. Bats of those species only touched the ceiling with their hindlimbs, and we thus refer to those as two-point landings. Four-point landings resulted in significantly larger total impact forces (mean = 3.6 body weights) than two point landings did (mean = 0.74 body weights; P<0.0001). We postulate that hindlimb stresses are kept relatively small in these three species by minimizing the impact force using the specialized two-point landing, or by applying most of the force with the robust forelimbs during a four-point landing.
