These facts DO answer the question.  It is not so much what the ferret
is eating as much as the mechanical characteristics of the food.  For a
polecat to survive, they have to catch prey, kill it, transport it, tear
it open, shear through tendon and bone, and cut off chunks that can be
swallowed.  The teeth are constantly being abraded against fur, skin,
muscle tissue, bone, tendons, and ligaments.  This constant abrasion
scours the teeth, rubbing off the dental plaque that calcifies into
calculus.  The scouring action also polishes teeth, gently smoothing out
imperfections where plaque can accumulate and mineralize.  It is not the
food; it is the mechanics of eating.
 
In contrast, pet ferrets that eat kibble have NO method for cleaning the
teeth of plaque.  Kibble is often marketed as an aid to dental calculus
reduction, but in truth, it fails miserably at the job.  The crunchy
nature of the material supposedly cleans the teeth of plaque, but it
only cleans the part of the tooth that comes into contact with it at
the time of consumption the wear facets of the crowns.  In a dog, having
wide molars and a thick carnassial, tartar reducing kibble helps some
(reduces but does not prevent), but ferrets have minimal molariform
tooth surfaces, and the cheek teeth are thin and blade like.  The only
significant parts of the teeth kibble comes into contact with in ferrets
are the wear facets.  That is why ferrets on a kibble diet have huge
accumulations of dental calculus on their teeth.  A kibble diet will not
help; at least any kibble currently on the market.
 
Note that 2.3% of feral New Zealand ferrets had dental calculus.  I'm not
convinced these were true feral New Zealand ferrets.  This number may
reflect lost or abandoned pet ferrets what were caught in traps designed
to catch feral animals.  If that is the case, it might be possible for
New Zealanders to check the cleanliness of teeth of captured or killed
ferrets to ascertain the origin of a ferret captured in the wild; if the
teeth have significant amounts of dental calculus, it was probably a pet.
The same may be true in the United States where wildlife officials have
a bad habit of claiming lost or abandoned ferrets are feral .  Remember
that 99.0% off all teeth having dental calculus came from pet ferrets.
 
Why are ferrets so susceptible to dental plaque and calculus?  There
are no published studies that can answer that question (many document
the phenomenon, but none explain it), but I have a hypothesis that
might provide an answer.  Ferrets are descendants of wild polecats, and
polecats have been prowling the Earth for millions of years.  During
that time, they evolved into primary, obligate carnivores.  That is to
say they primarily eat animals, they are obligated to do so to obtain
essential nutrients, and they have a digestive mechanics and physiology
adapted to such a diet.  All polecats share this trait, and polecats have
undergone little change in the last 2 to 5 million years.  To put that
period into perspective, realize humans evolved within that time frame.
I suspect that during that long period of primary carnivory, the polecat
lost some of those mechanisms that help to keep the mouth clean of dental
calculus found in other species.  Such traits are energy expensive and
since the polecat was consuming a diet that mechanically cleaned the
teeth anyway, there would be little need to conserve the traits.
Simplistically, it is possible polecats lost some of the mechanisms that
help prevent the formation of dental calculus simply because they were
consuming a diet that came packaged in toothbrush form.  Mind you, this
is an untested hypothesis, but it makes sense.
 
So, what can be done to prevent dental plaque and calculus?  The only
way diet can be used to prevent it is to place the ferret on the same
diet as a polecat; that is, whole animal bodies.  There is no way kibble
can help and just eating bone alone, even with the occasional mouse,
doesn't do the job although it does help somewhat.  The only real
solution is mechanical cleaning, mimicking the job done by the fur and
tissue in animal bodies.  That means you have to brush the ferret's teeth
and periodically you have to have the teeth professionally cleaned.  That
IS the bottom line; the only diet that can keep the ferret's teeth clean
is consistent meals of whole animal bodies, and by consistent, I mean
daily.  I cannot do that, the vast majority of ferret owners will not do
that, and current pet food marketing cannot meet the demand.  That means
the ONLY solution is tooth brushing and periodic professional cleaning.
 
There are some products that can help.  It has been reported that
allowing a ferret access to Cheweasels helps to keep the teeth clean.
I am currently testing that claim with some of my ferrets that decline
to consume frozen mice.  Totally Ferret has recently marketed a dental
cleansing swab that may help, but I haven't been able to get enough of
the product for a comprehensive test.  Allowing the ferret to chew off
the soft ends of bones help, as does giving them access to BOILED pig's
ears (if not boiled until soft, the dehydrated cartilage doesn't have
time to completely rehydrate in the ferret's stomach, and can potentially
cause intestinal blockages).  Aside from that, the only thing I can say
is a whole mouse per day helps keeps the dentist away.
 
As for toothbrushes, well, try to find one that easily fits into a
ferret's mouth.  I found the big boys can accommodate brushes designed
for cats, but they gag the poor little girls.  I have modified an
infant's toothbrush by trimming down the bristles, and it works well
enough for my girls.  For some of my ferrets, I use 6 in. swabs to rub
the teeth with dentifrice.  My ferrets seem to tolerate cat toothpaste,
but all seem to like the toothpaste for toddlers better, if you can
define the occasional gag as tolerates better (note: infant toothpaste
can be safely swallowed by ferrets).  None of my ferrets like their teeth
being brushed, so I just get a good scruff on them and start brushing.
Some will fight, some will do the spin trick, some refuse to open their
mouths, but most will give up trying to escape and just chew on the
toothbrush while you struggle to polish their pearly whites.  It isn't
easy, but it HAS to be done!
 
In the next installment, I will discuss periodontal disease in ferrets.
 
Bob C
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[Posted in FML issue 4517]