July 17, 2012
Whales Coping With Undersea Noise
Brett Smith for redOrbit.com - Your Universe Online
Because extremely loud noises can travel underwater for thousands of miles, they cause over a quarter-million sea creatures to suffer some kind of hearing loss every year, a number experts warn is on the rise.
The good news is that whales are able to consciously decrease their hearing sensitivity and prevent hearing loss if given ample warning of an impending loud noise, according to a pair of marine biologists who published their research in the Journal of the Acoustical Society of America.
“It´s equivalent to plugging your ears when a jet flies over,” lead researcher Paul Nachtigall, a marine biologist at the University of Hawaii told the New York Times. “It´s like a volume control.”
It has been common knowledge that underwater noises – from engines, sonar, weapons testing, and oil rig drilling – are deafening whales and other sea mammals. Previous studies have shown that these activities, which can be heard from thousands of miles away, cause hearing-tissue damage and disorientation in sea creatures that use hearing to navigate, locate food and care for their young.
In their study, Nachtigall and his team found that the animals could adjust their hearing in response to the sharp clicks that they use for echolocation. The team then attempted to teach a false killer whale named Kina how to moderate her hearing based on the mammal´s Pavlovian response.
They started by playing a gentle tone repeatedly. Later, this dulcet tone was followed by a loud noise. After some conditioning, the soft warning signal alone caused Kina to cut the sensitivity of her hearing.
Nachtigall said the developments of the experiment were promising and could be used to prevent hearing loss for millions of sea creatures. He added that further study will hopefully determine if Kina can increase the amount to which she can protect her hearing. The team said they also plan to study the same auditory mechanism in bottlenose dolphins, beluga whales, and other captive species before attempting to apply their findings on wild populations.
Unfortunately, the topic of undersea noise levels, like other environmentally-based research, has become a political wedge issue, with conservatives standing in the way of any policy that might impede business or military development.
In 2008, the Supreme Court heard a lawsuit by the National Resources Defense Council against the Navy over ocean noise levels. The court ruled in a split, 5-4 decision that naval vessels could test sonar systems for hunting submarines.
In the majority opinion, Chief Justice John Roberts wrote that the Navy had been using sonar off of the California coast for 40 years with "without a single documented sonar-related injury to any marine mammal.”
"The president -- the commander-in-chief -- has determined that the training with active sonar is essential to national security,” the Republican-appointed justice wrote.
“We give great deference to the professional judgment of military authorities."
However, environmentalists saw an indirect victory in having the nation´s highest court split so evenly over the health of sea mammals in a debate over national security.