Message Number: YG3280 | New FHL Archives Search
From: RRC
Date: 2001-05-05 19:34:00 UTC
Subject: Bob C: Ferret Molars

From an off-list question:

>I've read on the FHL that you know a lot about ferret skeletons
>and teeth. Maybe you can settle a bet between me and my roommate...
>I say ferrets don't have molars and she says they do....It's for
>a bottle Wild Turkey...

Since I'm a beer man and dislike the hard stuff, there is no danger my
answer can be influenced by some sort of alcoholic payback. But you can
tell your roommate that she owes me an ice-cold beer. You lose.

Ferrets indeed have molars, although as a percentage of the overall
dental arcade, they are minimal. While there are differences between
males and females due to sexual dimorphism, the dental arcade is about
an inch long, from front to back. Of that entire distance, roughly about
7/8ths is composed of puncturing or cutting teeth, and about 1/8th is
crushing teeth. In terms of percentages, the only other mammalian
carnivore with a lower percentage of cutting teeth to molars are cats,
where some species have completely lost their molars. The reason
ferrets, or rather the polecat progenitor, has maintained crushing teeth
despite their obligate, primary carnivore status is because they consume
hard-bodied insects and crustaceans, and the molars were retained to
crush the exoskeletons. Also, polecats eat a lot of tiny rodents, and
the molars help to break the bones prior to swallowing. These are not
the type of molars typically used to grind vegetation to a pulp.

In the upper, or maxillary arcade, on each side there are two tiny
molars in the back, behind the cutting teeth. If you look in your
ferret's mouth when they are yawning, the first molar is the one which
looks like it was twisted sideways. That molar is about 1/8 by 1/4 of an
inch, and it has two tiny cones at either end, the function of which
I'll explain later. Behind that tooth is a very tiny little molar, about
1/16th by 1/8th of an inch. This is a weird tooth, but is typical of
mustelids (and one of the easiest ways to identify their remains). One
explanation for the tooth size and shape is that it was a molar
originally being lost, but during the evolutionary simplification of the
dental arcade, the remnant part started to serve a function, so just the
reduced portion was retained. You can see why when you look at the
mandibular arcade.

There is only a single molar on each side in the lower, or mandibular
arcade; a round cone-topped tooth that is only about 1/8th inch in
diameter if it is lucky. This tooth butts against the last premolar,
which sort of has a mountain-like profile with a tall peak, followed by
a short peak, then a sort of flat area in the back supporting a tiny
cone. This tooth is called the carnassial, or cutting tooth (in some
older texts it is called the sectorial tooth). This is the tooth which
the ferret uses to cut food apart; either dry extruded foods or fresh
bone and muscle. If you carefully place the upper and lower arcade
together, you will see the upper molar partially strikes the flat area
on the back of the lower carnassial, with the remaining half hitting the
front of the small round molar. The tiny 2nd upper molar hits the back
of the lower 1st molar. This creates a sort of interlocking action
similar to what you would see in the jaws of vise grips.

Biomechanically, this is absolute proof the molars are used to crush
bones and exoskeletons rather than to pulp plant material. How? Have you
ever cut glass or cracked hard nuts? If you use an anvil with two
points, and strike the unsupported area with a pointed hammer, the
material easily fractures in a controlled way. That's why the ferret
molars (and carnassial) have the cones on top of the flattened areas,
and why parts of teeth (with the gaps between them) are used rather than
a single upper and lower tooth. The construction of these teeth create a
powerful nutcracking action which can break off segments short enough to
be easily swallowed. Pure genus!

Pet ferrets use their "jawcrackers' to break dry kibble or extruded
foods, and that's the number one problem I've seen in the teeth of pets.
The kibble is very hard, but not arguably harder than bone or some parts
of insect or crustacean exoskeletons. Ferrets will place the dry food on
the carnassial, and use the cutting edge and flat area to cut or crush
the food into swallowable size. In a natural diet, this hard work only
occurs as a tiny percentage of chewing time, and much of the time the
teeth are cushioned from the hard parts with meat or other tissue. Under
these circumstances, the back teeth can last the lifespan of the animal.
But when eating dry foods, such as kibbled or extruded foods, the hard
stuff is not cushioned by tissue, and tooth damage (wear) is continuous.
This causes a tooth wear rate from 2 to 5 times faster than in ferrets
eating a natural diet.

In a practical sense, the wear rate in the back of the mouth is much
higher than the front, which makes sense considering where the work is
being done, so a quick inspection of the dental arcade doesn't
necessarily show tremendous wear. However, in the back where the heavy
work is done, the upper 1st molar (the one that looks like it was
twisted sideways) is often so worn down that it has fractured into two
pieces. The tiny upper and lower molars are often ground down to their
roots. On the lower carnassial, the rear flat area is so worn that it is
at or below the gumline, and the cutting edge is clearly blunted and
flattened. As I said, this is hard to see in living ferrets; you have to
open the mouth nearly as wide as it will go and peer into the back to
see what I am talking about. There is ALWAYS reactive bone tissue
present at the gumline, which indicates chronic inflammation, probably
due to low grade gum disease. This dental wear is exclusively a
byproduct of eating hard, dry food and is NOT found in wild polecats,
feral ferrets, or pet/working ferrets fed a natural diet.

I'll post some photos which will clearly illustrate these problems in a
week or so, as soon as I can finished the basement and get the paper off
for review (the paper is about introduced Post-Columbian epizootics and
wildlife populations). You will be as shocked as I was when you see the
differences in the wear rates of the teeth, as well as in the diseased
state of the bone supporting the teeth.

As for solutions, the best solution is for the pet food maker to modify
the food so it isn't as hard, but that is unlikely to happen. Simply
put, dry food has little odor, can be stored almost anywhere, and
doesn't spoil in the dish. It keeps the teeth somewhat clean because it
wears them down, although not as good as often suggested. People like
that, and they buy such foods in vast quantities. Softer food would
either require some sort of preservative, or would have to be treated to
special storage conditions, which people don't like. So even if pet food
manufacturers wanted to create a food better on the ferret's teeth, it
is unlikely they could get enough people buying it to make it
economically possible. All I can suggest is that you buy dry food in
small quantities and store it in a humidity controlled area, such as a
refrigerator. You can add some broth to the food prior to feeding to
soften the material, with maybe some dry stuff sprinkled on the top to
add in cleaning the teeth. Other than that, have yearly checkups of your
ferret's teeth (or more if your ferret has problems), have them
professionally cleaned, and perhaps consider brushing their teeth at
least a few times a week. If you do that, then you can add some softer
foods to the diet, such as the canned ferret foods I've seen in a few markets.

Bob C