Okay, my math sucks in the previous post but I think the idea has merit.
Using up to four positions for dots per ferret ear and both the right and
left ear you could code for the year (up to 15 years without repeating) on
the right ear and the twelve months on the left ear.  What with ferret
longevity this should be more than enough before there is a need to recycle
the code.  With dots in positions 1-4 (single dots), positions 1&2, 1&3,
1&4, 2&3, 2&4, 3&4 (double dots), Positions 1&2&3, 1&2&4, 1&3&4, 2&3&4
(triple dots), and all four positions you get 15 years or using the first 12
combos you get 12 months.  Thus if your ferret had marks on postions 1&2&3
on the right ear (year ear) and positions 1&2 on the left ear (the month
ear) your ferrets birthday is in the 11th (or 26th if we're into cycle 2)
year of the study in May.
 
With toe dots you have 20 positions and up to 20 dots per ferret but I think
that it would be better to use paws as place holders ie left front paw =
thousands, right front paw = 100s, left back paw = 10s, right back paw =1s.
With two dots per paw you can easily represent numbers up to at least 9999.
 
right front paw toes 1-5 = 1000-5000, toes 1&2 = 6000, toes 1&3 = 7000 ect.
lf paw toes 1-5 = 100-500 ect
rr paw toes 1-5 = 10-50 ect
rl paw toes 1-5 =1-5 ect
 
So say you have a ferret with the toes marked as follows lf paw toe 1 (from
left to right on the ferret), rf paw 3rd toe, lr paw 1st & 2nd toes, rr paw
5th toe, your ferret would be #1,365th born in the year and month indicated
by his ear code.
 
Max
 
I'm sure that many such codes are possible so this just illustrates that it
could be done fairly cheaply, at least at the marking step.  The record
keeping would still be very labor intensive and I'm not sure that MF would
really want know what happens to their ferrets but it could be done.
 
Max
[Posted in FML issue 1987]