A spate of whale deaths has been linked to the UK Ministry of Defence’s use of sonar in Scottish waters. Scientists were tracking the MoD’s North Atlantic Treaty Organization (NATO) war games last year, known as Joint Warrior, which lasted from October 4-15. These operations serve as a practice for conflict scenarios (such as terrorism, pirates or military aggression from other nations) and were conducted with the British Military as well as army troops from 13 other countries. The incident has brought into question the use of naval sonar in Scotland as it interferes with whales and how they communicate with one another. 

These exercises all took place along the northern Scottish coastline. Joint Warrior is a major bi-annual event for the Royal Navy with warship and submarine presence in Scottish seas. Some efforts were made by conservationists and marine divers to clear bottlenose whales from the more swallow waters of the River Clyde before these war games were due to take place. However, observed whale strandings were consistent with symptoms of rapid decompression (commonly called the bends) in two Sowerby’s beaked whales and possibly in three bottlenose whales that washed ashore soon thereafter.

Between October 13 and 17, one bottlenose whale was beached on the north-west island of Stornoway while two others were found in Clyde sea lochs, over 190 miles further south-west. The Sowerby’s beaked whales were discovered between October 13 and 14 along the Lothian coastline. The Scottish Marine Animal Stranding Scheme (SMASS) was able to determine the beaked whales displayed signs of significant internal trauma: “Notably, both animals showed an unusually high number and distribution of gas bubbles throughout the tissues- especially lung, liver and intestinal mesentery.” The scheme added that “a large number of bubbles, especially in deep diving species such as beaked whales, is suggestive of nitrogen emboli and decompression sickness (DCS). Given how sensitive beaked whales are to underwater noise, specifically naval sonar, we have to consider noise-mediated DCS as a possible cause for these two strandings.” However, due to the bodies of the bottlenoses being too decomposed, they were unable to determine a cause of death, but causes such as entanglement, plastic consumption, boat strike or disease were ruled out. 

Naval sonar causes significant distress to whales and other marine life due to the powerful intensity of the sound waves that are emitted and that travel through the water. Prior to the navy beginning to use sonar technology in the 1960’s, beaching of beaked whales were extremely rare. A 2019 study, published by the Royal Society, discussed the effects of sonar on beaked whales that lead to death, saying that “several mechanisms have been proposed to explain how sonar might lead to stranding and/or death of BWs including: (a) swimming away from the sound source into shallower waters and beaching, (b) a behavioural response disrupting their diving profile and resulting in nitrogen accumulation, bubble formation, and tissue damage, (c) physiological changes that secondarily result in nitrogen accumulation, bubble formation and tissue damage, or (d) direct damage of tissue by sound exposure.” 

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Use of sonar has become widespread in oceans. The US Navy has the authority to use low-frequency sonar across 70% percent of the oceans around the world to detect foreign submarine activity, but this can reach a whopping 235 decibels. To put that into perspective, the pain threshold for humans is 120-130 decibels. Experiments have shown distress from blue whales with exposure to 140 decibels, causing reactions such as fleeing from the sound source, loss of appetite and displacement. A study of a young beluga whale also displayed an elevated heart beat when exposed to 140-160 decibels

Scientists from Hebridean Whale & Dolphin Trust monitored and acoustically tracked sonar from this year’s Joint Warrior games, expressing concern that high frequency sound waves were found on 14% of all tracked lines in the Minch Ocean:  “We heard sonar consistently throughout the next four days, some of which we could hear through the headphones without even putting them on – from the next room! We could even hear sonar when we were storm bound.” The Royal Navy’s Environment and Sustainability Impact Statement assessment from this year said that their anti-submarine warfare (ASW) sonar would be “limited to a maximum” of 211 decibels and one class of ship would be using 210 decibels within The Minch sea, but it is unknown what the exact decibel level was. 

Overall, scientists and researchers were able to record 85 hours worth of recordings over 550 nautical miles. As a result of the five recent beachings, SMASS is requesting further data from the Ministry of Defence, saying “we are in the process of trying to find data on sources of noise in this region, including putting a request for activity logs to the MOD following the recent Joint Warrior naval exercises.”

In 2018, SMASS responded to the highest amount of dolphin and whale stranding cases recorded thus far – 930 in total. During Joint Warrior’s April 23 to May 3 2018 event, the Hebridean Whale & Dolphin Trust reported, “Thirty-five recordings of military sonar were made, 13 of which were categorised to our highest rating, meaning the sound was loud enough to mask all other oceanic noise. One of our citizen scientists described it as “the worst sound I have ever heard”.” From August to October 2018, a total of 80 whales (Bottlenoses, Cuvier’s beaked whales and Sowerby’s beaked whales) were beached along Scottish and neighbouring Irish coastlines. Many of these whales were thoroughly decomposed and had been deceased for weeks prior to their bodies being stranded on the coast. Because these whales washed ashore in quick succession, experts believe these cases point to a single mass die-off. Professor Peter Tyack, Professor of Marine Mammal Biology at University of St Andrews says, “In groups of beaked whales stranded across tens of kilometres of coastline within a few hours, that’s been associated with naval anti-submarine warfare exercises. It appears that the sonar that they use to hunt for submarines triggers a panic reaction. They may disrupt their diving, so they get decompression sickness. They then die at sea and may wash ashore.” The panicked reaction to the high frequency sound waves causes cetaceans to rapidly swim to the surface of the ocean, causing rapid decompression. It should also be mentioned that UK defence secretary, Gavin Williamson has stated that Russian submarine activity has increased significantly within the North Atlantic, and cannot be altogether ruled out. 

The UK’s Ministry of Defence has been called into question for its use of naval sonar in the past. In 2011, the Royal Navy detonated four underwater bombs in the north coast of Scotland, causing the deaths and mass strandings of 19 pilot whales. The first three stronger explosions, according to a report, would have had a “significant detrimental effect on the hearing and therefore navigational competence of any cetaceans in proximity.” Scottish member of parliament, Rob Gibson exclaimed the MoD was not forthcoming about this incident: “This report confirms what we already suspected: that the Ministry of Defence tried to cover up the detonating of bombs that led to whales being deafened, forced off course and dying on the beach at Kyle of Durness.” In 2008, the MoD admitted that it was “extremely likely” that the use of sonar off the south-west Cornish coast of England resulted in the mass death of 26 beached dolphins, after initially denying that operations were being conducted in the area. In 2006, the Royal Navy’s sonar was also linked to the death of four Cuvier’s whales on the Spanish Almeria coast from a NATO exercise. Post mortems by the University of Las Palmas de Gran Canaria concluded: “Based on current scientific knowledge, and the pathological findings in this study, the most likely cause is anti-submarine active mid-frequency sonar used during the military naval exercises.

In response to concerns about Joint Warrior’s use of sonar, a spokesperson for the Ministry of Defence has said the following: “The MoD takes its environmental responsibilities very seriously; environmental impacts are always considered in the planning of military exercises. During the planning of the exercise Environmental Impact Assessments have been produced and findings implemented where required, such as for the use of active sonar and live weapons.” 

Overall, more effort and focus needs to be made to ensure that marine life does not suffer silently from sonar within our oceans. High-decibel level sonar has proven to cause distress with serious repercussions to the health and well-being of sea life. With this in mind, the Royal Navy would benefit from reassessing the cataclysmic power that underwater frequencies have on these animals.