Q: What is the most accurate way to age living ferrets?
 
A: Card 'em, and don't let any under 21 in the nudie bars.
 
There isn't any *accurate* way.  Even the best methods can be full of error,
which is why you see "4 years +/- 6 months."
 
TEETH: There are four ways to age ferrets based on teeth; 1) dental wear and
attrition, 2) transparency of teeth, 3) dental eruption, and 4) dental
cement annuli.
 
Dental wear and attrition (loss of teeth) is based on the assumption teeth
wear the same and the ferrets have the same diet, both wrong.  Poole wrote
he could tell the difference between polecats and ferrets based on tooth
wear, with the ferrets having much more worn teeth because of their diet.  I
have also noticed this; I give my ferrets lots of real meat and bone, and
their teeth are *clean* (ie, NO NO NO dental calculus!) and sharp.  But, in
a small population, it can be useful in ranking the ferrets into "That one
is older than this one" types of categories.  No real ages.
 
Tooth transparancy is based on the phenomenon that the root canals of teeth
fill with cement over time, making the tooth tip look more transparent.  A
better method than the one above, it still only results in a ranking type of
category because so many factors can change the deposition rates.  No real
ages, but better than wear and attrition.
 
Dental eruption is fairly accurate, but only useful in the first few months
of the ferret's life.  It is based on the premise that most ferrets will
lose their baby teeth in a particular order at a particular time.  For
example, the baby canines are lost at about 8 weeks.  Results in approximate
ages for the first year only.
 
Dental calculi is based on the phenomenon that dental cement can be
seasonally laid on the root of a tooth; you can see it by pulling the tooth
and cutting it into thin sections and counting the rings.  Used to age bear
and other wild animals.  About as accurate as dental eruption, *if* you have
the data base to back you up.
 
BACULA: There are two ways to age ferrets based on bacula; 1) Relative size
of the bacula, and 2) bacula morphology.
 
The bacula grows for most (if not all) of the male ferret's life, and the
changes in the size and shape are fairly predictable.  In living ferrets,
you can feel the bacula through the skin (you know where...); the larger the
bump at the bottom, the older the ferret.  Results in a ranking category,
not real ages.
 
If you have the bacula, you can compare it with other bacula of known ages
and get an approximate age of the ferret based on morphology and size.  It
is about as accurate as dental eruption, if you have the data base.
 
SKULL: There are two basic ways to age a dead ferret by the skull; 1)
cranial suture fusion, and 2) size of the crests on the top and the back of
the skull.
 
The older the ferret, the more fused the cranial sutures, and some can
disappear and smooth with enough time.  Results in a ranking category at
worst, or very rough approximate age at best, if you have a data base.
 
Some people have tried to use the size of the occipital or saggital crests
to age skulls, but I have found them to be too inaccurate for anything but
the most basic of ranking categories, and do not recommend them.
 
SKELETON: There are three basic ways to age dead ferrets based on their
skeleton; 1) The degree of fusion of the skeleton, 2) The amount of bone
remodeling, and 3) the amount of arthritis present.
 
Many bones of the skeleton are composed of two basic parts separated by a
thin sheet of cartilage; the sheet of cartilage is where growth takes place
(some bones can have more than one area of growth, some just one, some don't
have the cartilage sheet).  As the bone reaches its final size, those
separate bones fuse together into a single bone.  The rate of fusion is
environment and diet correlated, so skeletal fusion rates are ranking
methods at worst, and rough approximations at best.
 
Bone remodeling occurs in all mammals (although many die before it is likely
to much take place) and is a fairly consistant process throughout life,
although it is also nutritionally mediated.  As the bone ages, old bone is
replaced by new bone, and you can see this by cutting the bone into thin
sections and counting the new osteons.  Results in approximate ages if you
have the data base to back you up.
 
The older the skeleton, the more arthritis is present, which in ferrets
tends to concentrate in the lower back and hips.  Results in ranking
categories only, no real ages.
 
BODY: There is no specific number of ways to tell; it is based on the
overall appearance or condition.  Can be used for both live and dead ferts.
Essentially, you judge how old the ferret might be based on coat and body
condition, cataracts, muscle tone, etc.  Because of the number of factors
which can influence the body condition, or harm it, this results in a
ranking category only.
 
BEHAVIOR: Same as above, but based on behavior rather than appearance.
Cannot be used on dead ferrets.  Essentially, babies act like babies,
juveniles like juvenile, etc.  Most mammals have age-related behaviors, and
after a while, if you are observant enough, you can tell an old ferret from
a young one just based on how they act.  Basic ranking only.
 
OVERALL: Because ferrets are sort of seasonal in their births, they can be
basically lumped into yearly cohort categories, such as first year, third
year, etc.  This doesn't work with breeders that use artifical lights to
maintain year-round breeding, but with most others it does.  Early neutering
changes bone growth rates, especially in males, which can confuse the issue.
Illness or diet confuses things, as does plain ol' genetics (natural
variability).  BTW, this is not an inclusive list; I know of many other
methods not included on this list.
 
Observant people who have seen mucho numbers of ferts can usually guess age
to within a year, which is about the same thing as guessing a human's age to
the decade (assuming a 10 YO ferret = a 100 YO human; admitedly rough).
Using a combination of methods is more accurate than a single one, and the
older the ferret, the more error exists.  Personally, I prefer tooth
transparency, dental wear, and behavior.  I add bacula development for
males, which is probably one of the most accurate ranking methods.  The key
to all is simple practice; the more you do, the better you get.  Guessing
ferret age could be a cool game at a ferret show.
 
Bob C and the 20 MO Whoop-De-Ferts
[Posted in FML issue 2098]