A non-toxic and largely effective repellant for rodents has been
used in granaries for many years now and there are many reports on the
effectiveness against rats.  There is little (if any) evidence for mice
although I have found it quite effective.

Rodents do not like bright flashing lights.  I have used LED
strobe lights that can be found on the Internet for very little money.
The commercial units use xenon strobes which are brighter but have to
be replaced regularly.

You can also find little LED bulbs with built-in flashers that are used
as running lights on trucks.  These are those annoying all the time
flashing things that you sometimes see on trucks.  I installed these in
my engine compartment to keep rats away and they work pretty well but
not perfectly.

I have never tried black pepper but red pepper powder that contains
capsicum is quite effective, but I think it also might be corrosive.

Spencer Chase

 [ See also http://www.mmdigest.com/Archives/KWIC/R/rodent.html 
 [ -- Robbie