Garth Williams asked about cage heaters....
 
You might want to investigate heating pads designed for reptile enclosures.
The general opinion around here is that Ultratherm are the best pad type
heaters while Flexwatt heat tape is the best "strip type".  I would use the
Flexwatt because you buy it by the foot in either 3 or 11 inch widths.  The
three inch width would be easier to use to setup a proper heat gradient in
the cage so your fuzzy can pick the best temperature.  One strip of 3 inch
tape along the short side of the cage would probably do the trick.
 
Their general range is from 70-90 degrees, much safer than a human heating
pad which get WAY too hot.  Use a rheostat from your local hardware store
(in a proper ferret-proof enclosure) to regulate the heat.  These heaters
will not burn through the bottom of a typical ferret cage.  Be sure to
conceal the wires to avoid chewing!
 
Please note that for safety, you should never, ever use any kind of reptile
heating device by itself.  ALWAYS, ALWAYS, ALWAYS, use these heating
products (undertank pads, heat tape, or ESPECIALLY Sizzlestone hot rocks
(not that you *would* with a ferret)) with a rheostat or thermostat to
control the heat output.
 
Hope that helps.
[Posted in FML issue 1451]