There was a FML question as well as several e-mails on if teeth really were
a good indication of age.  Answer?  Sometimes; depends on the technique.
 
The first technnique is to estimate age using tooth eruption sequences.
There are two periods of time when the detention is fairly accurate at
predicting age: 1) during the eruption of the deciduous (baby) teeth, and 2)
during the eruption of the permanent teeth.  The eruption times are fairly
consistent, for example, the eruption of the permanent upper canines (fangs)
at about 8 weeks.  However, it is important to realize that all values can
be off by as much as a week or more.  But of all the techniques, it is the
most reliable and accurate, but is limited to the first few months of the
ferret' life.
 
Another technique is to estimate age using tooth wear as a criterion.  The
idea is the average tooth wear is fairly consistent over time and space.
(Right, and I'm a hunk...) This technique does not result in knowing the age
of the ferret; only that one ferret is older than the other because its
teeth are more worn.  A slightly modified version of the technique takes
into account the number of missing teeth.  Generally (and I mean *very*
generally) the sequence of tooth loss is a) incisors b) premolars c) molars
d) canines.  While this method cannot take into account genetic differences
between animals, individual diet, malnutritional changes in the dentine,
etc., it is quite effective at guessing which animals within a limited
population are older than the others.
 
Because most ferrets in the USA eat a dry pelleted chow, the wear rates can
be fairly constant accross the board (on the *average*, mind you.  Still
lots of room for error) and the method can be and is used by lots of people,
including in my experience, vets.  With practice, the careful observer may
be able to guess an age within a year.  but there is no scientific way that
age can be prove.  It is an estimate only.  But it is quite prone to error,
only shows one ferret is older than another, and requires lots of experience
to recognize the differences in wear.
 
A third method is to use the transparency of the canines as a guide.  This
is based on the idea that as teeth get older, the root canals fill with
dentine, which changes the light absorbancy characteristics of the tooth,
making them appear transluscent, and canines are long and thin enough for
these changes to show.  Since the root canals fill-in from the crown of the
tooth towards the root, the relative amount of transluscence can be used to
estimate age.  This technique suffers from all the problems of the 2nd
method (wear) plus one more problem.  The deposition of cement and dentine
in the root is highly influenced by load bearing (the amount of work the
teeth do).  Like poeple, ferrets can be highly individualistic in terms of
chewing, so this technique is subject to great gobs of error.  The least
accurate of the three.
 
A fourth technique is the patterning method.  Knowing the only technique
that gives a real age is tooth eruption, and after that, all you know is one
ferret has more wear or tooth changes than another, this technique compares
the general state of the teeth to other physical changes in the ferret's
body to arrive at an estimation of age.  The method is quite subject to
individual error; still, the experienced observer can generally estimate a
ferret's age to within a year or two, using some combination of all three
techniques (and body condition, alertness, etc).
 
Other techniques that can be done to estimate age from teeth, but they are
destructive to the tooth, or require the tooth to be placed in scanning
electron microscopes, or even radioactive chambers.  Hard to do when the
ferret is alive, unless you don't mind pulling a tooth.  (I do).  With dead
animals, lab techniques can give good ages for the first three or four
years, then the error rate increases to a year or more.  Like with humans,
it is easy to say "this ferret is *at least* X-years-old" but very hard to
say "this ferret *is* X-years-old." (A cool trick is to know the average age
at death is between 7-10 years old.  When you come across a middle-aged
ferret, inspect it carefully, then say "This ferret is between 4- and
7-years-old, plus or minus 3 or 4 years." The statement covers almost every
ferret over a year old.  You are rarely wrong, and those times you get a
really old ferret, just comment how *young* it looks--a certain reflection
of owner care--and they won't care if you are wrong.)
 
Thats the tooth, 'n I'm sticking by it.  You can crown me if you like; even
snap at me (I'll re-fang from nasty replies), but that's the tooth of it (or
at least a quick re-dentition).  If you have an apatite for more, ask and we
can chew the subject privately.  I won't bite your head off; I'd rather
cement our relationship than to damage it at the root.  In either case, my
cap is off to anyone enameled enough with the subject to learn more.
 
BTW, BIll, you'll never get a copy of the tape.  Elizabeth hopes to date
during her immediate lifetime.  (Ba ha ha ha!) Besides, she wants to run in
the Nationals (he he he).
 
Bob and the 14 Masticating Monsters.
 
[Moderator's note: FERRET BITE ALERT!!!  We have to test Bob for rabies
before it's too late!  Now let's see, how do we test... hmmm... Bobbit,
one O?  (Of course if we had the tape we may be able to figure out what
*really* happened without resorting to testing....) BIG]
[Posted in FML issue 1615]