I'd been "half" of The Ferret & Dove Sanctuary during its entire, now-defunct , existence and at one point we had 7 cats with an average of 30 to 70 ferrets. Some ferrets are intolerant of any other critters other than "their" human. Many ferrets can't seem to resist teasing at or going-so-far-as to chomp onto the bellies of any cats they can reach unless the cat stays high out of easy chomping reach (which six of ours soon learned to do the hard way :) and just one little white mothering cat, Sphynx Mysteria, decided in her own mind that the ferrets were all her own adopted-strange kittens and treated them each and every one just that way...she was never "chomped" but would gently bat any potential gnosher away with a paw that had its rat-killer claws carefully sheathed. Once when a new grown cat was introduced to the household, she made the grave mistake of thinking to sniff noses with a pair of the ferrets who were out playing at the time and while sniffing with one, got her belly CHOMPED-on by the other who wasn't about to let go (pit-bull-ferrety-style), so the poor cat was yowling and trying to run around in circles, which brought Sphynx Mysteria out to what-was-all-the-ruckus and she hauled off and WHAMMED the luckless new cat for "disturbing her kittens" ...shut her up in blank-eyed surprise! Then Sphynx gave that gentler little "bat" to the chomper who released his "death-hold" , allowing the new cat to escape to the highest book-case-top she could possibly leap to. So I tell you what...it's mostly a personality-thing. NO two cats OR ferrets being alike, but what it is, is no matter what, supervise EVERYBODY very closely when and if they're all out, together...whether one species or several. (pics of former critters of the Sanctuary are here, including some of the cats near the bottom...only Elrond Buttontail Cat is still alive and with me. First two pics will be of my late husband and president of the Sanctuary, whom after he died I had to sell our only car to pay the property taxes and close down. ) http://www.angelfire.com/theforce/ferret_rescuer/index.html [Posted in FML 7887]