A bit of history and clarification...
 
Ferrets are a European/African animal.  North American mice don't have a
natural fear of ferrets.  The Rats over here are mostly European imports
and DO have a fear of rats.  European mice would probably fear ferrets as
well.  Same goes for American versus European rabbits (not quite a rodent
though).
 
Ferrets were domesticated and kept in houses in Europe and Africa well
before cats to keep out rodent vermin.  Until 30 or 40 years ago ferrets
were still used to hunt down and exterminate rats.  Ratters would take
their ferrets and terriers to an infested building.  Let the ferrets go
in the walls to chase out the rats were men with clubs and the terriers
would kill them.  Ratters like this were very important in the first half
of this century to the point where New London Ohio became known as
Ferretville because that is where the biggest breeders were.  They ship
the ferrets on trains to rest of the country.
 
You can still use what we scoop out of the litter pans to keep rats away.
If you have a shed out back that rats are hanging out in try dumping the
litter pans around the building.  Rats are not happy with even that much
ferret.
 
As amusing sidenote, there is a mail-list devoted to Volkswagen Vans and
we just had a humorous thread running on the pros and cons of ferrets in
chasing rodents out of the duct work.  There are at least two of us on
both the VW Van list and the Ferret list.
 
bill and diane killian
zen and the art of ferrets
[Posted in FML issue 1334]