Military sonar affects whales even at long distance, study finds

Jack O'Donovan By: Jack O'Donovan
Date posted: 22 March 2019

Sonar technology used in British military activities is shown to have a sudden impact on beaked whales over 25 miles away from its source.

cuviers beaked whale
© Graeme Cresswell

The effects of underwater noise on marine mammals, particularly beaked whales, is becoming clearer. A new study has found that some beaked whales, and particularly those in remote populations that aren’t normally exposed to explosive sounds such as sonar, make sudden and dramatic behaviour changes in response to the noise.

The study, published in the journal Proceedings of the Royal Society B, reports that the animals are affected by intense forms of sonic waves that travel long distances through seawater, affecting animals both close by and tens of kilometres away.

In the study, by researchers from St. Andrews and Iceland Universities, sonar in use by military vessels was shown to be have an impact on diving and feeding behaviour. They found that whales stop feeding, swim away or enter a deep dive once exposed to military sonar.

Military activities, and research soundings (air gunning) for oil and gas industries can run repeatedly for weeks and even months at a time, and could affect these animals over a long period.

Tests were carried out 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. The team attached special sensors and listening devices to the whales to monitor their behaviour.

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.”

The study recorded one whale diving to a depth of 1.6 kilometres (5250 feet) in response to hearing the sonar. That is the deepest known depth ever dived by the species. The study also found that the whales did appear to recognise when sounds came from further away, and perceive this as less of a threat.

Marine noise pollution poses a serious threat to our marine wildlife, from whales to fish and even ocean invertebrates. Five Cuvier’s beaked whales washed up dead on the west coast of Ireland in a single week in August 2018, when it was suggested that British naval sonar could have been the cause for the unusual simultaneous deaths of these deep diving species.

A Royal Navy spokesman said: “We will take this research into account when we review our marine life safety checks for underwater tasks.”

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