A: Some would say their teeth. Others, their cunning.
These people are wrong.
Ferrets survive for one reason only: Their shoulder mounted lasers.
That's how all my ferrets survive. I've been mounting lasers on the shoulders of my ferrets and sending them out into the wild for over a decade and I haven't lost one yet.
As far as I know. Designing, building and mounting lasers takes up most of my day, leaving me very little time to track my ferrets. But the lasers are pretty powerful. I assume they keep the ferrets safe. I haven't heard any complaints yet.