Anthropogenic Noise in the form of sonar and the response of Blue whale to it

Blue Whales Respond to Anthropogenic Noise

Mariana L. Melcón,Amanda J. Cummins, Sara M. Kerosky,Lauren K. Roche, Sean M. Wiggins and  John A. Hildebrand

PLoS ONE 7(2): e32681. doi:10.1371/journal.pone.0032681

This research went in to the vocalization response of endangered blue whales to anthropogenic noise sources in the mid-frequency range using passive acoustic monitoring in the Southern California Bight. The researchers found that Blue whales were less likely to produce calls when mid-frequency active sonar was present. When the sonar source was closer to the animal, at higher sound levels the impact was readily discernible.

The animals were equally likely to stop calling at any time of day in their sensitivity to sonar. There was no diel pattern in their sensitivity. On the other hand the likelihood of whales emitting calls increased when ship sounds were nearby. They did not show a differential response to ship noise as a function of the time of the day either.

 The scientists say their results demonstrate that anthropogenic noise, even at frequencies well above the blue whales' sound production range, has a strong probability of eliciting changes in vocal behaviour. The long-term implications of disruption in call production to blue whale foraging and other behaviours are currently not well understood.