Subsonic mating bellows generate Faraday waves
Alligators flirt with physics. When males attract attention by quivering their spiky backs underwater, they create Faraday waves, researchers reported May 23 in Seattle at a meeting of the Acoustical Society of America. These sophisticated patterns are usually seen only in man-made devices.
"Faraday waves haven't really been seen in nature before," says John Allen, an acoustician at the University of Hawaii at Manoa who was not involved with the research.
When a male alligator craves company, he issues a sound from his lungs that is too low to be heard. This infrasound causes him to vibrate violently and whips the water on his back into a froth of waves and leaping fountains.
Acoustician R. Glynn Holt of Boston University saw a video of this "water dance" and was reminded of physicist Michael Faraday. In 1831 Faraday discovered that liquid above a vibrating object sometimes forms surface waves that move up and down at half the speed of the vibrations.