Been there, done that. I once had two females who were IDENTICAL, same
weight, same markings, etc. I microchip my ferrets here and also have
an AVID reader so I could use that to tell them apart when it really
mattered, such as vet visits or meds. Their Marshall's tats were a
tad bit different but that's a lot of trouble to examine each time.

Otherwise, there are simpler ways to tell them apart. I raise orphaned
wildlife and often have to mark them tell tell them apart for their
weights, meds, etc. I use a surgical marker (the kind surgeons use to
mark where the incision will be) but I have only used those directly
on the skin. I'm not sure if they will work on fur. They are used only
once in the OR, so if you know someone who works in a hospital, see if
they can grab you some after surgeries, or order from a medical supply.
You can clip the fur off the end of one's tail, straight across - this
is probably the easiest. You can try a couple of drops of food coloring
on one. If you use the marker or food coloring, you will need to
re-apply every few days. I'm sure there are more ways but any of these
will work.

Katharine
Florida

[Posted in FML 6472]