Data from: First direct measurements of behavioural responses by Cuvier’s beaked whales to mid-frequency active sonar

Most marine mammal strandings coincident with naval sonar exercises have
involved Cuvier’s beaked whales (Ziphius cavirostris). We recorded
acoustic and animal movement data on two tagged Ziphius and obtained the
first direct measurements of behavioural responses of this species to
mid-frequency active (MFA) sonar signals. Each recording included a
30-minute playback (one 1.6-s simulated MFA sonar signal repeated every 25
s); one whale was also incidentally exposed to MFA sonar from distant
naval exercises. Whales responded strongly to playbacks at low received
levels (89-127 dB re1µPa): after ceasing normal fluking and echolocation,
they swam rapidly, silently away, extending both dive duration and
subsequent non-foraging interval. Distant sonar exercises (78-106 dB re 1
µPa) did not elicit such responses, suggesting that context may moderate
reactions. The observed responses to playback occurred at received levels
well below current regulatory thresholds; equivalent responses to
operational sonars could elevate stranding risk and reduce foraging
efficiency.