I have had two ferrets this year shed half the hair on their tail.  It
worried me at first, but after a month or so it began to grow back.  You
can speed the process by washing their tail in antibacterial soap once or
twice a day, but it will still take a couple of months for the hair to
come back in full force.
 
 From:
 Lori and Rat's Brats
[Posted in FML issue 4307]