Waveform (a) and spectrogram (b) of one of the 30 pre-recorded bat echolocation call sequences (edited with SASLAB PRO (Avisoft Bioacoustics, Berlin, Germany; FFT size 1024)). Playback sequences were edited from calls where the search-phase component of the sequence recording (not shown) was identified as Nyctalus spp. based on existing echolocation parameters including: frequency of maximum energy (kHz), start frequency (kHz), end frequency (kHz), call duration (ms) and interpulse interval (ms) [18,19]. British Nyctalus spp. typically broadcast their loudest calls between 19 and 27 kHz [19], as is the case with our recordings.