Two studies have given more credence to the link between naval sonar and mass whale strandings, proving certain sound frequencies have huge effects on whale behaviour.
Both blue whales and Cuvier's beaked whales were studied to see how they responded to mid-frequency active sonar signals, and both species showed marked behavioural changes.
The Cuvier's beaked whales, which have been most prone to mass strandings, responded strongly by swimming rapidly and silently away from the sound, and extending both dive duration and intervals between feeding.
Similar reactions were observed among blue whales, despite the sound being significantly lower than some operational military systems.
Behavioural changes varied widely, from cessation of deep feeding to increased swimming speed and directed travel away from the sound source, the study found.
Both studies, published in biological science journals Proceedings of the Royal Society B and Biology Letters, concluded that sonar sounds could potentially have damaging effects, with the California study into blue whales concluding repeated exposure could be devastating.
“Repeated exposures could negatively impact individual feeding performance, body condition and ultimately fitness and potentially population health,” the study concluded.
“Anthropogenic sounds can significantly change blue whale behaviour, and in some cases, these types of mid-frequency sounds can disrupt foraging and substantially decrease feeding efficiency.”