London, August 4 : A report has confirmed that sonar leads to behavioral changes in whales, with the animals subjected to sonar, neither diving nor feeding.
According to Nature News, this report was issued by the UK military, though it remained unpublished.
The impact of sonar on whales has become an increasingly fraught issue in recent years, with submarine exercises being linked to several high-profile mass strandings.
The US Navy has admitted concerns over sonar's effects on marine mammals, although actual evidence for harm has been in short supply.
But military-sponsored tests now suggest that low levels of sonar, which do not cause direct damage to whales, could still cause harm by triggering behavioural changes.
The UK military report details observations of whale activity during Operation Anglo-Saxon 06, a submarine war-games exercise in 2006. Produced for the UK's Defence Science and Technology Laboratory, it states the results are "potentially very significant".
The study used an array of hydrophones to listen for whale sounds during the war games. Across the course of the exercise, the number of whale recordings dropped from over 200 to less than 50.
"Beaked whale species appear to cease vocalizing and foraging for food in the area around active sonar transmissions," said the report.
"Since these animals feed at depth, this could have the effect of preventing a beaked whale from feeding over the course of the trial and could lead to second or third order effects on the animal and population as a whole," it added.
The report also references a second military document from 2005, which explains that these second- and third-order effects could include starvation and then death, depending on the severity of the sonar's initial effect on the whales.
According to a spokesperson for the UK's Ministry of Defence (MoD), "Active sonar releases energy into the ocean, and there is evidence to suggest that this may have an effect on marine mammals."
"Environmental Impact Assessments are mandatory prior to the use of military sonar, and the ability to predict and detect marine life continues to be developed in order to minimise any perceived threats to marine life," the spokesperson added.