Sonar from navy ships can affect the behaviour of beaked whales from a longer distance than first thought, research has suggested.
Professors from St Andrews and Iceland universities found the whales would swim away or go into a deep dive upon hearing the military sounds.
Using animal-attached sensors and deep-ocean acoustic listening devices, the whales were also shown to have stopped feeding.
Tests were conducted on 12 northern bottlenose whales near Jan Mayen, an island north of Iceland, in an area of the Arctic which still has relatively little noise pollution.
Professor Patrick Miller of the University of St Andrews said: “All tagged whales stopped feeding, and individuals started swimming away from the exposure site for several hours when a certain sound level was reached, regardless of their proximity to the source – up to 28 kilometres away.
“One of the whales immediately responded by diving to a depth of 1.6 kilometres that lasted 130 minutes, which, to the best of our knowledge, is the longest dive recorded for this species of whale.
“The data from the listening device indicated a large-scale response by animals in the exposed area.
“We used a sound source that is smaller than a typical operational naval sonar, so the concern is that the distances at which animals respond in the wild to real navy sonars may be significantly greater.”
The large research team discovered the creatures consistently reacted at low amplitudes of sonar compared to other cetaceans, regardless of their distance to the sound source.
Beaked whales inhabit areas frequently used by navies for sonar training and testing and are the second largest family of cetaceans in terms of the number of species.
Dr Paul Wensveen from the University of Iceland said: “Within the context of what is known about beaked whales, our results suggest that the relative pristineness of the environment might be an important factor in how these sensitive animals respond to sonar sounds.
“A lack of frequent or predictable exposures might mean fewer opportunities for the animals to learn that sonar signals pose lower risk when they come from far away.”
A Royal Navy spokesman said: “We will take this research into account when we review our marine life safety checks for underwater tasks.
“We continue to support other complementary research by Professor Miller into this issue.”
The new study is published on Wednesday in biological research journal Proceedings of the Royal Society B.