An article in BBC news today (www.bbc.co.uk/news/science-environment-23115939) discusses new research by DeRuiter et al. (2013), and Goldbogen et al. (2013) on how sonar affects blue and beaked whales; a topic relevant to the research conducted by OSC on anthropogenic noise and marine mammals.
By attaching multi sensor Digital tags (D-TAG), which measure animal activity and the acoustic environment simultaneously, to blue and beaked whales, researchers were able to study how whales responded to simulated Mid Frequency Active (MFA) military sonar. The Controlled Exposure Experiments (CEE), conducted in Southern California, looked at the responses of 17 blue whales and 2 Cuvier’s beaked whales.
Responses of blue whales varied with individual and behaviour; deep feeding whales, and those not feeding were affected more than those feeding at the surface. Observed responses included horizontal displacement, for example a greater amount of time spend conducting mid-water dives, termination of deep foraging dives and avoidance of the sound source, shown by movement away. The authors hypothesised that termination of feeding dives could cost blue whales substantially, considering the amount of krill consumed during each dive. Cuvier’s beaked whale responses included swimming away from the sound source, extended dive duration, slow ascents, prolonged intervals between dives and cessation of echolocation, which is used when foraging. Responses continued up to 1.8 hours post exposure.