Foraging habitat and echolocation behaviour of Schneider's leaf nosed bat,Hipposideros speoris, in a vegetation mosaic in Sri Lanka

The Hipposideridae and Rhinolophidae are closely related families of bats t hat have similar echolocation (long-duration pure-tone signal, high duty cy cle) and auditory systems (Doppler-shift compensation, auditory fovea). Rhi nolophid bats are known to forage in highly cluttered areas where they capt ure fluttering insects, whereas the foraging habitat of hipposiderid bats i s not well understood. Compared to rhinolophids, hipposiderid calls are sho rter in duration, have lower duty cycles, and they exhibit only partial Dop pler-shift compensation. These differences suggest that the foraging habita t of the two families may also differ. We tested this hypothesis by studyin g foraging and echolocation of Hipposideros speoris at a site with a range of vegetation types. Bats foraged only while in flight and used all availab le closed and edge habitats, including areas adjacent to open space. Levels of clutter were high in forest and moderate in other foraging areas. Prey capture (n=42) occurred in edge vegetation where it bordered open space. Ec holocation signals of H. speoris lacked an initial upward frequency-modulat ed sweep and were of moderate duration (5.1-8.7 ms). Sequences had high dut y cycles (23-41%) and very high pulse repetition rates (22.8-60.6 Hz). Vari ation in signal parameters during search phase flight across foraging habit ats was low. H. speoris showed a greater flexibility in its use of foraging habitat than is known for any rhinolophid species. Our study confirmed tha t there are differences in habitat use between hipposiderid and rhinolophid bats and we suggest that this divergence is a consequence of differences i n their echolocation and auditory systems.