In "Calls of the Wild," Alan meets scientists studying animal behavior by listening in on elephants, birds, bats, bees and bugs. The science of using sound to study animals is called bioacoustics. As technology improves the quality of sound recording and processing devices, scientists are increasingly using bioacoustics to study - even save - species as common as the harbor porpoise and as elusive and mysterious as the giant squid.
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Saving Sealife

Each year, more than 80,000 dolphins and porpoises wind up as "by-catch," entangled and drowning in fishing gear meant to catch tuna and other fish. In an effort to stop the unintended slaughter, Dr. Scott Kraus of the New England Aquarium began investigating how sound might be used to keep dolphins and porpoises out of fishing nets.

View Scientific American Frontiers segment about bioacoustics, "Whale Warning"

In 1994, Kraus worked with fishermen in the Gulf of Maine to see how harbor porpoises would respond to underwater alarms attached to fishing nets. Kraus outfitted the netting on 15 fishing vessels with "pingers," alarms that emitted an audible beep every four seconds. After two months, fishing boats equipped with the pingers had caught only two porpoises, while boats without the pingers had caught 25.

"Fishermen recognized early on that they needed to do something about by-catch," says Kraus. "If things continued as before, some species would have ended up endangered-at least threatened-and fishermen would have been subject to severe restrictions."

Pingers are now required in the Gulf of Maine and off the coast of California. But an unexpected wrinkle—what Kraus calls the "dinner bell effect"—meant the pingers had to go through a number of redesigns. It turned out that the frequency emitted by the early pingers was audible to seals as well as their intended cetacean audience. But rather than avoiding the nets, the seals learned to associate the sound with a net full of fish. A New Hampshire-based company redesigned the pingers to emit a higher frequency, audible to the dolphins and porpoises, but not seals.

		Pingers could help protect the south American Pontoporia dolphin species. Learn more about the Pontoporia dolphin species.

Currently, Kraus has been collaborating with Argentine biologists to decrease the by-catch of the Pontoporia dolphin species indigenous to the waters off South America. Local fishermen, who bring their nets in by hand, are eager to avoid the hassle and damage to their gear that results from snagging dolphins and porpoises. So far, the results are promising. Kraus has seen a 90% reduction in the numbers of animals killed in nets.

Scientists at the U.S. Fish and Wildlife Services and National Marine Fisheries Service are looking into using similar technology to prevent the accidental netting and drowning of sea birds.

For more information about this research, click here.

Click here for more on recent "Dolphin Safe" classification.

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Images: NOAA; Mar del Plata Aquarium Foundation