About 3 weeks ago, Urban F. asked if there were any studies done concerning ultrasonic communication among ferrets. I could't find any references about it then, but I just ran across this one which might, perhaps, give us a clue. I haven't gotten around to getting the article (I may never get around to it), but, I guess if Urban is interested enough to check it out, here's a lead: AUTHORS: Farley, Sean D.; Lehner, Philip N.; Clark, Tim. ARTICLE TITLE: Vocalizations of the Siberian ferret (Mustela eversmanni) and comparisons with other mustelids. SOURCE/DATE: 68:413-16 May 1987 Journal of Mammalogy Bill [Posted in FML issue 0329]