Blue whale vocal behavior is affected by man-made noise, even when that noise does not overlap the frequencies the whales use for communication, according to new research published Feb. 29 in the open access journal PLoS ONE. The whales were less likely to emit calls when mid-frequency sonar was present, but were more likely to do so when ship sounds were nearby, the researchers report.
The study was conducted in the Pacific Ocean off the coast of Southern California by Mariana Melcon and her colleagues from University of California San Diego. Blue whale vocalizations are important for a number of behaviors, including foraging and mating, but the effect of frequencies outside the blue whale production range had not been previously investigated. The researchers conclude that noise resulting from human activity has a strong probability of affecting the vocal behavior of blue whales, even when the noise is far from the frequencies blue whales produce, and the long-term implications of this effect remain unknown.