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Fig 1. Spectrograms of six call types of the social call repertoire of swarming Myotis nattereri.
a Commonly recorded call types. (A) Short cheep-like call characterized by a steep frequency modulation with a shallowly modulated middle part. (B) Two element call with an upward hooked element followed by a steep frequency modulated (FM) element. The second element was omitted occasionally. (C) Fast modulated call characterized by a rapid downward-upward-downward frequency modulation. (D) Long broadband trill. b Rarely recorded call types. (E) Squawk with noisy signal. (F) Churring-like call consisting of short FM pulses.