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Elephant calls that humans can't hear.

Elephant calls that humans can't hear

Don't look now, but the largest land animals may be talking behind our backs. Cornell university researchers have discovered that elephants produce low-frequency sounds inaudible to humans but well suited to communicating within herds.

The sounds, probably produced by the elephant's vocal cords, set up a sympathetic vibration in its forehead. Seeing that flutter and feeling a throbbing sensation in the air led Katharine Payne, William Langbauer Jr. and Elizabeth M. Thomas to discover the infrasonic sounds.

The vibrations were measured at 14 to 24 hertz. (The human hearing threshold is about 30 hertz, unless sounds are very intense.) Asian elephants are known to be capable of detecting tones with frequencies of 17 hertz, and Asian and African elephants alike probably can hear sounds of much lower frequencies than that, Langbauer says.

"We were only getting part of the picture in the past," says Thomas Lovejoy of the World Wildlife Fund in Washington, D.C., which is one of the project's sponsors. "The interesting question, of course, is whether there were certain kinds of things they were communicating so that we couldn't hear."

The researchers don't know for certain whether the elephants use these sounds to communicate. If they do, the infrasonic calls might indeed serve a different purpose than harder-to-miss bellows, since low-frequency sounds travel farther than those bellows in forests and open plains.

Long-distance, low-frequency communication could explain puzzling aspects of elephant behavior, including the ability of males to find females during the brief conjunction of male "must" (heightened sexual activity) and female fertility; and the highly coordinated movements within herds that seem to occur without signaling. In July, the researchers will travel to Namibia, in southwest Africa, to investigate the distance over which elephants can hear the infrasonic calls, and to look for correlations between the calls and elephants behavior.
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Publication:Science News
Date:Feb 22, 1986
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