FM/CF Calls

During manual review of 18,412 USV spectrograms, we identified four recurring call structures that did not match existing categories. These calls featured a combination of frequency-modulated (FM) and constant-frequency (CF) components: the FM segment describes a monotonic increase (FM-U) or decrease (FM-D) in frequency content, while ‘CF’ refers to the call’s flat component. We observed four distinct variants of this FM/CF structure across colony and individual recordings: FM-U_CF, CF_FM-U, FM-D_CF, and CF_FM-D, named for their structural resemblance to FM/CF bat calls.
In this dataset, we provide raw examples (.wav) files of these four USV types.