Minke Vocalisations in Irish Waters

Drop down drifting hydrophones were used to record minke vocalisations opportunistically in spring off the Beara Peninsula in West Cork, when minke whales were abundant and during observation of the whales. Three pulse trains were recorded from two specific individual animals photographed very close (<100m) to the drifting RIB (Rigid Inflatable Boat) during vocalisations; the first two pulse trains from what is believed to be the same individual, also produced clicks precisely concurrent with pulses, with a matching IPI (Inter Pulse Interval) and ICI (Inter Click Interval) of 0.6 seconds and associated with peak amplitude pulses, occurring simultaneously with the commencement of the pulse, with a clear well defined waveform, with few zero crossings and peak frequency of 10 kHz and 2.4 kHz. The peak frequency of the clicks is well below that recorded for common dolphins, which is above 23 kHz and characteristics of clicks is atypical of common dolphins.A number of other vocalisations were also recorded and these include upsweeps similar in duration to downsweeps already described elsewhere and typically of a consistent duration of 0.4 or 0.5 seconds though often in doublets. Longer combinations of these were also recorded up to 1.4 seconds but these may be atypical as these have not previously been described and the low amplitude of such calls means that a possible source of distant humpbacks while unlikely cannot be completely excluded. The purpose of these vocalisations to the whales is not known but it is generally assumed that pulse trains are associated with mating activity.