Acoustic Compensation to Shipping and Air Gun Noise by Mediterranean Fin Whales (Balaenoptera physalus)

Abstract

AbstractSeafloor recorders were deployed in the western Mediterranean Sea and adjacent Atlantic waters during 2006–2009 to monitor noise levels and fin whale presence. Acoustic parameters of 20-Hz pulses (pulse duration, pulse bandwidth, interpulse interval, and center and peak frequencies) were compared for areas with different shipping noise levels and different shipping intensities in the Strait of Gibraltar and during seismic air gun events. Significant differences were detected between noise contexts. In general, acoustic parameter values decreased with increased noise levels. In high-noise conditions, 20-Hz pulse duration shortened, bandwidth decreased, and center and peak frequencies decreased. Similar results were obtained in the presence of air gun events, and bearings to singing whales indicated that whales moved away from the air gun source and out of our detection area for a time period that extended well beyond the duration of the air gun activity. This study provides evidence that fin whales modify their acoustic behavior to compensate for increased ambient noise and shows that under some conditions they will leave an area for an extended period. Sensitization and habituation processes may play a role in these behaviors and are discussed in the context of these results. The biological consequences of these behavioral changes are not known, but the potential negative effect in their reproductive success and survival is discussed.KeywordsPeak FrequencyAmbient NoiseAcoustic ParameterPotential Negative EffectInterpulse IntervalThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.