This post may be late for some but, People should not let their ferrets eat
wild mice because of the poisoning risk from mouse / rat baits.  Even if
you don't lay it there may be some at a neighbours ,old bait from previous
occupiers etc.
 
Dying mice are easy for ferrets to catch and will come into a ferrets cage
for water or food .  While the dosage may not be high enough to kill a
ferret outright it may be very painful / harmful to it .
 
People who have outside cages should make them mouse proof as I have seen
the little buggers enter the cage while the ferrets are sleeping and steal
the ferrets food and water .
 
Good luck all
Richard Ardern
 
[?]
Most vets don't think to check for rat / mouse bait poisoning and it is
very scary to see it .  the cage is 4 inches off the ground and has 19mm
mesh which is not quite mouse proof size (12mm) as We / I never thought
mice would enter it .  I'm going to make the next cage very mouse proof
by using 10mm mesh as I don't want any more risks for the little ones.
 
Inside should have some ferret proof mouse traps laid permanently so as
to stop mice sharing the ferrets environment.
[Posted in FML issue 3109]