Perhaps one of the easiest ways to approach the Board is with a text in hand...and the one I would recommend is "Walker's Mammals of the World"...any edition (I believe the newest is the 5th, although any edition will work...but obviously the newer the better). This 2 Vol set is the mammologists "bible" and recognized worldwide as such. Rat's, mice etal will be found in Vol one under "Rodentia" as will ferrets under "Carnivora". That should end any further discussion on the matter...but just in case...one of the easiest ways to separate ferrets (or any carnivores) from rodents is by looking at the dentition. This alone is so definitive as to be irrefutable. Of course then you need a skull or two to present the board (just kidding...there are many mammal field guides available in a library that have skull and dentition photos). If they need reference from a wildlife biologist, you may have them contact me...I'd be happy to help out... putorius [Posted in FML issue 3965]