Mat 14, 2014 — The ocean is an increasingly industrialized space. Shipping, fishing, and recreational vessels, oil and gas exploration and other human activities all increase noise levels in the ocean and make it more difficult for marine mammals to hear and potentially diminish their range of hearing.
“Hearing is the main way marine mammals find their way around the ocean,” said Aran Mooney, a biologist at Woods Hole Oceanographic Institution (WHOI). It’s important to know whether and to what extent human activity is negatively impacting them.
But how can we get marine mammals living in the wild to tell us what they’re able to hear?
“Same way we do it with human infants,” said Mooney. “You play a sound, then you measure the brain's response to the sound.”
Though Mooney makes it sound easy enough, he and his colleagues are the first to publish a study of hearing in wild marine mammals, with multiple marine mammals. The paper, “Baseline Hearing Abilities and Variability in Wild Beluga Whales (Delphinapterus leucas)” was published today in The Journal of Experimental Biology, on May 14.
In addition to Mooney, the research team included the paper’s lead author Manuel Castellote, from the Alaska Fisheries Science Center, which is part of the National Marine Fisheries Service, and the North Gulf Oceanic Society, and their colleagues from Alaska Department of Fish and Game, Alaska SeaLife Center, and the Georgia Aquarium.
The researchers worked over a two week period in southwest Alaska during the summer of 2012, capturing and testing seven Bristol Bay beluga whales, one of six subpopulations of beluga whales in the U.S. Enabling this study are recent advances in portable field testing equipment, rugged enough for field work. To conduct their hearing tests, the team temporarily maintained the individual animals as part of physical health exams. They used suction cups to attach a small speaker to its jaw—which in whales and dolphins conducts sound to both ears—and placed sensors on the animal’s head and back.
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