Common minke whale
(Balaenoptera acutorostrata)

Common minke whales are also infrequently recorded in Madeira. Their scarcity in the archipelago may be related to their stronger association with colder and more coastal waters than those typically found around Madeira (Freitas et al., 2012; Alves et al., 2018).

In the North Atlantic, common minke whales are acoustically characterized mainly by low frequency pulse trains/sequences, typically in the 50–400 Hz range (Mellinger et al., 2000; Risch et al., 2019). Three main pulse train types have been described: slow-down, constant, and speed-up (Risch et al., 2013). In slow-down trains, the intervals between successive pulses increase over time. In constant trains, inter-pulse intervals remain relatively stable, and in speed-up trains, the intervals between pulses decrease over time (Risch et al., 2013). A well described slow-down train typically lasts about 61 s and decreases from about 4.5 to 2.9 pulses per second over the course of the train (Mellinger et al., 2000; Risch et al., 2013). In the North Atlantic, acoustic presence is strongly seasonal, but the timing of peak detections varies among regions (Risch et al., 2013, 2019).