Alligators use Faraday waves to get some tail

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Not only do male alligators use Faraday waves to get a mate, but they may also produce the only examples (biological or physical) of these kind of waves in nature.

When a male alligator decides its time to start a family, he puts the word out by bellowing. Some of those calls are audible to human ears above water. Some of them radiate below the water. They're inaudible to people, but they are visible. The products of this rumbling growl are spikes of water that seem to jump up from the sides of the alligator's back. They don't ripple outwards, as most disturbances of water do. They just keep erupting in the same place.

These aren't just jets of water, though. They're Faraday waves. Most waves travel visibly. The crest starts in one place, and observers can see it move outwards. Faraday waves are standing waves. They do move, but they bounce off each other and off their surroundings in such a way that they seem to be simply rising up from the water. One of the characteristics of Faraday waves is that they have exactly half the frequency of the vibrational source.

These waves are tough to create. In the lab, they are usually only achieved in a closed container with carefully measured and stable vibrations. Yet when physicists took measurements of the frequency of the waves and the rumbling that the alligators produced, they found that the alligators were creating Faraday waves with nothing more than their backs, some uncontained pond water, and the force of their love. It's possible that female gators are big fans of Faraday, or that the minimal disturbance of the water somehow helps the alligator's message get through. Either way, these creatures may be the only natural creators of Faraday waves in the world.


Via Physics Central (Podcast) and Wired.