Fig. 1.

Dive and acoustic behaviour of two Sowerby's beaked whales (Mesoplodon bidens). Individuals (A) mb17 (mb17_224a) and (B) mb18 (mb18_219a) were tagged off Terceira Island, Azores, with DTAG sound and movement tags (mb17: 14:00–18:33 h local time, 12 August 2017; mb18: 12:46–18:55 h, 7 August 2018). Thick traces indicate where regular echolocation clicks were produced and delimit the search phase of foraging dives. Buzzes (presumed prey capture attempts) are shown by red circles. Blue dots near the surface indicate recordings of bouts of clicks from other toothed whales of uncertain species. (C) Cumulative histogram showing the proportion of time spent at depths shallower than those on the vertical axis by the two Sowerby's beaked whales and six Blainville's beaked whales (Mesoplodon densirostris; 107 h, from El Hierro, Canary Islands; data courtesy of N. Aguilar).