I tend to believe it was the ferret, since even a puupy-edition pit bull probably couldn't manage to bite off anything as small as a 1 month old baby's toes without taking off a whole lot more. But these parents must have been sleeping off a MAJOR meth run. A one month old baby would let out a massive howl at the first nibble on her toe (that is, assuming she'd been been fed within the past 24 hours and wasn't half-dead from malnourishment and dehydration), and she was right next to them! These parents are obviously the sort of people who shouldn't be allowed to own a ferret, much less a pit bull. Naturally our useless "justice" system won't have them sterilized, and they'll pop out their next little victim in short order.
I suspect you are right. My roommate had ferrets and they would come out from under the couch and bite my toes. Hated the F'ers.
I definitely agree with child endangerment by having animals loose around the baby without proper supervision but without knowing more about a ferret's behavior and chewing abilities, as well as the child's specific injuries, I can't go further than that. I'm not assuming that it took several minutes for the ferret to injure this child.
As for the pit bull comments, one rarely sees newspaper stories about poodles or daschunds biting children. It's not exactly sensational. Although, there was that pomeranian that killed a newborn baby a few years ago. Let's ban poms!