No one really knows why pods of whales spontaneously drive themselves aground. Military sonar may be one culprit, and the need to train and test submarine tracking technology in open water could put the US Navy in conflict with the gentle cetaceans that feed and pass through military ranges. Although solitary endangered blue whales are rarely victims of sonar stranding, this does not mean that they are unaffected by high intensity sonar. ‘We wanted to understand better what the common behavioural responses are in blue whales when they are exposed to [sonar]’, says Brandon Southall from the University of California, Santa Cruz, USA. So, he and a team of 14 colleagues embarked on a marathon tracking program to investigate the reactions of blue whales to sonar. The team publish their discovery that blue whales stop feeding on deep patches of krill when they encounter sonar in Journal of Experimental Biology.