Blue Whales Respond to Anthropogenic Noise
Long-term spectral average of 5 hours. Each orange “D” represents presence of D calls in 5-minute bins in the lower frequency band (25–100 Hz). Note the continuous presence of D calls for over 2 hours until the onset of MFA sonar (not a particularly close event, with signals every 10–30 seconds), at which time at which the whales cease production of D calls. After sonar cessation, blue whales start producing D calls again.