Scientists have known for decades that naval sonar had a negative influence on marine life. The sound is so loud that marine mammals will swim hundreds of miles, dive to incredible depths, or even beach themselves to escape the deafening din. Beaked whales, in particular, are prone to stranding as a result of sonar. The reason for this is explained in a new review paper published in the Proceedings of the Royal Society B.
Before the 1960s, beaked whale strandings were uncommon, but the Navy began to utilize a type of sonar called mid-frequency active sonar (MFAS) to identify submarines. If you’re a marine species, MFAS makes a tremendously loud noise that can be very frightening.
So it’s maybe not unexpected that more and more beaked whales washed up on beaches between 1960 and 2004, with a total of 121 mass stranding episodes observed. It began in France, then spread to Italy, the United States, and the Bahamas. Various species of beaked whales were discovered stranded, but Cuvier’s beaked whales were the most common. Many of the incidents occurred in locations where the US Navy and NATO were conducting training exercises, and were described as “atypical.”
Two or more animals beach themselves while alive at roughly the same time and place in a typical mass stranding. It’s unclear why these episodes occur; it could be due to disease, disorientation, or a predator chasing you into shallow water. We are still undecided. Atypical mass stranding episodes, on the other hand, entail two or more whales washing up within 74 kilometers (46 miles) of each other over the course of six days. Sound is generally connected with these types of strandings.
So, how can sonar sound induce the whales to come to a halt? The sonar distresses beaked whales to the point where they develop nitrogen bubbles in their blood, according to the new article, which summarizes what was discussed during a 2017 gathering of beaked whale researchers in the Canary Islands. Hemorrhaging and injury to their key organs are possible consequences. If you’re a diver, you’ll be familiar with decompression sickness, often known as the bends, which is an uncommon but life-threatening side effect of rapidly ascending to the surface.
But how did an animal that is well adapted to life underwater and can dive to depths of 2,000 meters (6,500 feet) develop the same problem as a nervous scuba diver?
“They become stressed when they hear sonar and swim vigorously away from it, modifying their diving style,” lead scientist Yara Bernaldo de Quiros told AFP.
“In other words, the stress response overrides the diving response, causing the animals to collect nitrogen. It’s like getting a jolt of adrenaline.”
The response varies from whale to whale, but it explains why anomalous strandings are common in areas where naval sonar has been placed. The findings are based on autopsy of dead whales, albeit a few animals died as a result of other human-caused risks such as ship collisions or entrapment in fishing nets, as well as sickness.
To reduce the impact of sonar on beaked whales, the scientists suggest banning its usage in places where they can be found. In 2004, the Canary Islands imposed an embargo on the use of MFAS, demonstrating how well it works: no anomalous strandings have occurred since. Other countries that use sonar, such as the United States, Greece, Italy, and Japan, should follow likewise, according to the researchers.