Written By Susan Kahoud – Navy Sonar and bombs used in anti-submarine war games, and Oil company sonar used to locate undersea oil deposits, can disturb, hurt, and kill seals, whales, and dolphins.
At issue now is how to regulate these activities. Ocean researchers are monitoring intense human-generated sounds from military exercises and chronic, widespread noise generated from commercial shipping, studying the negative effects on marine species, and developing plans to decrease, manage, and when possible, eliminate harmful man-made underwater noise.
One question is, if the ships start with softer noises and gradually get louder, does this give the animals time to actually adjust their hearing? Can some of them do that? It looks like maybe some can.
A study at the University of Hawaii that was published in the Journal of the Acoustical Society of America and presented at the Acoustics 2012 meeting in Hong Kong reveals that some whales may have the ability to reduce their hearing sensitivity and protect their hearing from loud noises. Research headed by Dr. Paul Nachtigall, demonstrates that a female false killer whale named Kina could learn a protective response by adjusting the sensitivity of her hearing when she was warned of an impending loud sound.
Photo of Kina by Aude Pacini. Kina, a false killer whale, learned to adjust her hearing sensitivity and protect her ears from loud noises.
False killer whales are toothed whales and members of the dolphin family that use echolocation for navigation and hunting for food. They emit a series of high frequency clicks and then listen for quiet echoes of those calls. Dr. Nachtigall and his colleague, Prof. Alexander Supin, first observed that these whales had the ability to turn down their hearing in response to their own sharp clicks– sounds they use for echolocation. To understand more about this behavior, scientists placed soft suction cup sensors on Kina’s body to monitor her brain waves associated with hearing. The study then proceeded by playing a soft pulse repeatedly followed by a loud pulse of 170 decibels. In a short time this conditioning taught Kina to protect her ears from intense sounds when she received a warning signal. Soon after, she naturally reduced her hearing sensitivity following the soft warning tone alone.
Photo by P. Nachtigall. Kina with suction cup sensors that monitor her brain activity.
The scientists plan to continue their work with other species of whales before expanding their studies in the wild. Dr. Nachtigall and his team are just beginning this research and this is the first study to be completed and published. They have tested this warning signal with only one toothed whale, but it shows promise.
Whales, dolphins, and other marine mammals are already coping with an amalgam of stressors including entanglements in gillnet gear, ship strikes, climate change, global toxic pollutants, and habitat loss. Turning the tide on noise pollution may give marine species the edge to sustain populations and allow them to flourish once again.
Information about biologically sensitive marine habitats and critical migration routes is known. New technologies ushering in a wealth of scientific data to help understand cetaceans’ patterns of behavior are available.
Common sense management measures–such as refraining from potentially harmful activities in sensitive locations and ramping up sounds prior to full-scale war-games, could help minimize adverse impacts on marine mammal species worldwide.
Ultimately it would be better for humans to practice peace instead of war. But for now it is up to us to discern the sympathetic threads that connect all of life, embrace our evolutionary kinship, and revere the essential worth of the magnificent creatures of the sea. Our task then is to strengthen our resolve to move wholeheartedly in their defense. If we fail, we face an accelerating decline of marine life in the oceans, and risk their uncertain future as well as our own. And actually, that’s exactly where we are at present.
This issue of harm to whales from sonar and bombs needs advocates who are concerned enough to get involved. The Natural Resources Defense Council (NRDC.org) can keep you up to date, if you get on their mailing list for this issue. Go to: http://www.nrdc.org/wildlife/marine/sonar.asp
Susan Kahoud is a longtime environmentalist with special interest in protecting endangered wildlife and habitat.