Behavioral reactions of cetaceans to man-made noises are highly variable, ranging from attraction (e.g. bow riding by dolphins) or no response through short-term changes in behaviour to short- or long-term displacement. Noise can also mask important natural sounds or (if strong enough) cause hearing impairment or perhaps stress. This review summarizes the observed behavioral reactions of cetaceans to noise and other stimuli from Aircrafts, boats, tourism, marine industrial activities, seismic exploration, sonars, explosions, and ocean acoustics studies. Specific response thresholds have been determined for only a few combinations of species and noise type, and they tend to be quite variable even within species. In general, response thresholds are often low for variable or increasing sounds, e.g. approaching boat; intermediate for steady sounds, e.g. offshore drilling noise; and high for pulsed sounds, e.g. seismic survey pulses. With repeated exposure, many cetaceans habituate at least partially. However, cases of increased sensitivity following harassment are known. Long-term effects on individuals and populations are little known.

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