Ferret Spike and puppy Yuki eating a mouse. Ferrets are obligate carnivores. The natural diet of their wild ancestors consisted of whole small prey, i.e., meat, organs, bones, skin, feathers, and fur. Ferrets have short digestive systems and quick metabolism, so they need to eat frequently. Prepared dry foods consisting almost entirely of meat (including highgrade cat food, although specialized ferret food is increasingly available and preferable) provide the most nutritional value and are the most convenient, though some ferret owners feed prekilled or live prey (such as mice and rabbits) to their ferrets to more closely mimic their natural diet.
Source: http://en.wikipedia.org/wiki/Ferret