The ferret sound discrimination idea is very interesting. Unlike R D, however, I doubt very much that ferrets are communicating using subsonic frequencies. This is just a guess but it is based on sound (no pun intended... by that I mean real) physics. The problem with low frequencies is that it usually takes large physical structures to create them. Some whales, for example, generate subsonics that can travel as much as 100 miles (in water). And that is why the woofers in your speaker system tend to be larger than the tweeters. I'm not saying it's impossible that ferrets voice subsonics; only that it is unlikely. On the other hand, if ferrets create high-frequency sounds, it is unlikely that they are outrageously high frequencies, for the same reason that whales use those very low frequencies: higher frequencies do not travel as far. The higher the frequency, the faster it fades with distance. This is why bats use frequencies that are generally just a little above human hearing. It is easy for their little bodies to generate, but it is still low enough that it will carry a short distance. It should be pretty easy to find out if ferrets actually do this. If anyone has access to recording equipment that is sensitive to high frequencies, just record some ferrets for a while. Getting hold of the recording equipment would probably be the hard part. Then upload the recording(s) to a computer, and slow them down. That part is not hard to do: Audacity is one of many programs that will do it, and it's free software that you can download for Windows, OS X, or Linux. Lonny Eachus [Posted in FML 7669]