28.5 Friday, Jan. 4 What is the relationship between pectoralis muscle recruitment intensity and air speed velocity in an un-laden bat? KONOW, N*; VON BUSSE, R; CHENEY, JA; BREUER, KS; SWARTZ, SM; Brown University email@example.com
Aerodynamics theory predicts a U-shaped relationship between flight power and speed: The cost of transport should be lower at intermediate than at low and high speeds, due to constraints imposed by lift and drag. A similar relationship between muscle recruitment intensity and in some cases actual power production, with respect to flight speed has been found in some birds and insects, but not in others. This relationship remains unknown for bats, the only other extant group that has evolved powered flight. We measured recruitment intensity in two regions of the pectoralis muscle in five Seba’s short-tailed bats (Carollia perspicillata) flying at 1-7 m/s air speeds in a wind tunnel. The relationship between muscle recruitment intensity (integrated area under the rectified electromyogram) and flight speed was U-shaped in one individual, ∩-shaped in two individuals and invariant in two individuals. Several factors may combine to produce this inconsistent relationship: Compared with birds and insects, bats can modulate their wingbeat kinematics more extensively, in part due to their numerous wing joints. These joints are crossed by muscles that may contribute to the down-stroke, so the bat pectoralis is not necessarily the only source of flight power. Bats also have muscles in their wing membrane that may modulate camber and thus alter aerodynamic power production differentially with speed. Like other flapping flyers, bats have diversified across a vast range of foraging strategies, and use flight modes that range from hovering to fast hawking. Kinematics differences between these diverse flight modes may constrain power production across speeds as well as individuals and species. Funded by AFOSR.