Numerical study of lancet furrows dynamics behaviour in greater horseshoe bats

The greater horseshoe bat (Rhinolophus ferrumequinum) emits biosonar pulses nasally. The nostril of bats has complicated noseleaf structures, which consist of lancet, anterior leaf, sella. For the three noseleaf parts, lancet is the only one that stays away from the nostril. In addition, lancet has several furrows on the surface. It is known that the furrows in static lancet possess frequency selection characteristics, however, the effects of furrows during the lancet deformation have yet to be investigated. In this study, the 3D noseleaf models were obtained by the 3D scanning of the greater horseshoe bats noseleaf sample. Then, finite element method (FEM) was used to simulate the biosonar beampattern under different degrees of lancet flexion with both natural furrow and voxel-filled furrow. From the numerical results, it was found that the lancet furrow can enhance the mainlobe energy gain, and regulate the sidelobes position in the acoustic beam. The results indicate that the lancet furrows in greater horseshoe bats can be critical in targeting the objectives as well as gathering environmental information around the target.