Meeting Abstract

58.3  Tuesday, Jan. 5  Vertical climbing performance and reserve power in loaded and unloaded Lesser Dog-faced Fruit Bats (Cynopterus brachyotis) MACAYEAL, Leigh C.; RISKIN, Daniel K.; SWARTZ, Sharon M.; BREUER, Kenneth S.*; Brown University (Currently: Cornell University); Brown University; Brown University; Brown University kbreuer@brown.edu

All flying animals must sometimes fly while carrying loads. Load-carrying is especially relevant for bats, which experience nightly and seasonal fluctuations in body mass of 40% or more. In this study, we examined how the climbing flight performance of fruit bats (Cynopterus brachyotis) was affected by added loads. The body weights of animals were experimentally increased by as much as 21% by means of intra-peritoneal injections of saline solution, then flights were recorded as animals flew upwards in a small enclosure. Conventional analytical treatments of hovering flight were extended to include slowly climbing vertical and near-vertical flight. Using these analytic methods, we have estimated the power expended under unloaded and loaded conditions, and the relative power used for both weight support and climbing. We found that even our most heavily-loaded bats were capable of upward flight, but that as the magnitude of the load increased and the power requirement for weight support increased, flight performance (climbing velocity and angle, in particular) diminished. The total power expenditure increased with added load, and this was achieved primarily by increases in wingbeat frequency and stroke plane angle. Some intriguing aspects of the new theory regarding the scaling of hovering flight will also be discussed in the presentation.