Allowing ferrets to mix with other animals requires rational thought as to the likely hood of injury either pet. Large animals can injure a ferret and a ferret will kill a rabbit.
   I know of a case where several ferrets escaped from their cage inside a pet shop over night, killing the rabbits and guinea pigs also wrecking the the shop displays.  This is an extreme example. Ferrets are placid and good natured pets, but to see one grab a rabbit when ferreting is another story.

Ferrets need to be watched indoors as they investigate all opportunities that arise. Two examples.

Ferrets need to be watched!