[Moderator's note: Part 3, yes, but posted in 3 parts, combined here.  BIG]
 
3. Bones are dangerous for ferrets to eat.
 
FALSE.  What exactly are the objections about feeding bones to ferrets?
Bones could stick in the back of the mouth, the esophagus, or in the
intestines.  The sharp edges and points of bone fragments could cut or
puncture parts of the gastrointestinal tract.  They could choke on bone
fragments.  Bone slivers could cause an intestinal blockage.  Fragments
could stick in the gums.  They could break their teeth on the hard bone.
There might be more concerns, but these cover most of the objections I've
read and heard over the years.
 
Most arguments about sharp, poky bones making trouble in one way or
another are improbable.  They lie in the realm of "what ifs," or "my
friend says," rather than based on empirical evidence.  A common dilemma
is overt exaggeration of risk, such as "bones could cut the gums."
Perhaps, but would you stop eating chips because one poked you in the
gums?  Other overt exaggeration of risks include "bones can choke
ferrets" (ferrets routinely choke on dry food and water), and "bones can
hurt teeth" (hardly anything is as bad on the teeth and gums as dry,
extruded food).  Using humans as an example, people are routinely warned
about the dangers of choking on fish bones, but in a recent survey, the
number one reported cause of choking in restaurants was dry bread.  The
perception of risk is usually greater than the actual risk.
 
The majority of objections about ferrets eating bone are based on dogs
having problems, such as from wolfing down chicken or fish bones.  The
question is, does this sort of analog stand scrutiny?  A dog crunching up
and bolting down a chicken bone does NOT compare to a ferret gnawing on a
bone larger than their head.  Dogs are domesticated wolves and evolved a
food consumption style of tearing off and bolting chunks of flesh as fast
as possible.  Polecats have strong instincts to hide while eating; they
are a self-preservation behavior, as well as a method to preserve
proprietary rights to their prey.  It is hard for a larger predator to
steal a polecat's dinner -- or to eat the polecat--when it is eating it
while hiding in a burrow.  The instinct to hide when eating is still so
strong in ferrets that even after being domesticated for 2500 years, many
will still snatch a bite of kibble, and then run and hide in a secluded
area to eat it.
 
This makes food consumption comparisons of dogs to ferrets a very poor
analog; a more homologous one would be a cat, where common knowledge and
experience suggest they are capable of handling small bones in their diet
far better than dogs can.  Both cats and ferrets are delicate eaters,
picking through their food to select favored morsels, while dogs Hoover
down their food without apology.  It is no wonder dogs have so many
problems with small bones: predicaments that are mostly non-existent in
cats and ferrets.
 
The polecat progenitor evolved mechanisms to deal with bones of various
sizes, otherwise we wouldn't have ferrets.  Polecats eat most animals
smaller than themselves, and some much larger.  Those prey species
subsumed within the Vertebrata have, in fact, many small bones.  I know
of no way a carnivore can consume small prey animals without eating many
tiny or fragmented bones.  In fact, one of the primary ways scientists
determine the diet of a carnivore is by identifying the teeth and bones
found in the feces.  Ferrets were primarily domesticated as mousers and
ratters.  Later, as cats supplanted that particular function and rabbits
were introduced into greater Europe, ferrets were used for rabbiting.
Because of this, as well as the frequent crossing of ferrets back to
polecats to insure stronger hunting drives lost through domestication,
while behaviors and physiology has been changed greatly, the shape and
size of the body has remained about the same.
 
This quite simply means that if polecats possess the mechanical ability
to eat bone, so does ferrets.  This is supported by the presence of
feral ferrets in New Zealand, whose diet is composed mostly of rabbits,
rodents, lizards, birds, and carrion--all containing small bones.  As a
bit of additional evidence, consider the historic diet of ferrets, which
always included part or complete animal carcasses.  At one time these
included culled chickens, rats, mice, snakes, fish, and eels, making it
hard for the ferret NOT to encounter bone on occasion.  There are NO
historical documents, at least that I can find, that suggest ferrets have
ever had a problem eating bone.
 
A primary reason dogs are poor analogs for ferrets eating bone is because
they have undergone significant morphological changes to their mouth and
throat during the process of domestication.  Tooth row length in most
dogs is significantly shorter and wider (or longer and narrower) than in
wolves, and the base of the skull has changed in many breeds.  Not just
the width or length of the mouth is important in swallowing, but also
the angle at the back of the throat.  Minor changes to the basilar skull
can shift the angle of the hyoid apparatus.  The base of the hyoid is
embedded in the root of the tongue, and two short chains of tiny bones
attach it to the base of the skull at one end, and the larnyx at the
other.  Changes in the angle of the hyoid can potentially have a great
influence on how the tongue is suspended in the back of the throat.  In
some cases, these changes make it easier for the dog to swallow bones
that could lodge in the esophagus.  Ferrets have many changes due to
domestication, but skull changes have been relatively minor.  The
biomechanics of swallowing are virtually unchanged from the polecat,
and it is safe to assume domestication has not altered the biomechanics
of bone eating.
 
While anecdotes abound, there are only a handful of confirmed problems
caused by bone eating in carnivores, much less mustelids.  As a whole,
data confirming the dangerousness of ferrets eating bone is a statistical
phantom.  That is not to say some people aren't convinced eating bone has
harmed their ferrets, nor is it implying that problems don't occur.  My
only implication is that if it was as dangerous for ferrets to eat bone
as some people imply, not only would there be better evidence, but there
would be demonstrable evidence capable of withstanding statistical
analysis.  There isn't.
 
Still, millions of years of evolution, thousands of years of
domestication, and hundreds of years of modern science notwithstanding,
there is obviously some risk to eating bone.  What exactly are the risks
associated with a ferret eating bone?  That is difficult to say since
there are no known data quantifying the number of ferrets eating bone,
the number of ferrets that eat bone having problems, or even an accurate
number of ferrets in America for that matter.  ANY numeric estimate would
be a guess, making the determination of absolute risk impossible.  Still,
with the knowledge that feeding ferrets bone-containing foods has been
quite common for the last 25 centuries, and the number of confirmed
reports that ferrets have died from consuming bone are quite small, we
can safely assume the risk of such practices would also be exceedingly
small, and the issue is moot.  Still, there are two problems with real
concern.  Can bones cut or puncture a ferret's gastrointestinal tissues?
Can bones break a ferret's teeth?
 
Mammalian predators, over millions of years of evolution, have developed
extremely effective ways to deal with the problems of eating bone.  Most
carnivores, including ferrets, keep their stomach pH very low, at a
range of 1 to 3 pH.  While the ferret's stomach is structurally and
functionally similar to that of people, humans (like most omnivores) keep
their stomach at about 4 to 6 pH -- quite a difference.  Carnivores,
including the ferret, are so well adapted to consuming bits of skeletons
that the presence of bone calcium stimulates production of gastrin.
Gastrin, in turn, stimulates the production of stomach acid and digestive
enzymes.  The more calcium present, the more gastrin secreted (to a
point), and the more digestive enzymes and acid produced.  In short, the
presence of bone in the diet actually improves the ability of the
carnivore stomach to digest bone.
 
The implication of this tie between calcium and gastrin excretion in
carnivores is extremely important to understand; it means ferret stomachs
are specifically adapted to digest bone.  Some may suggest if eating bone
increases the secretion of acids and digestive enzymes, then the excess
acid may be a problem for ferrets prone to ulcers.  Actually, the exact
opposite is true.  When the acid contacts the bone, the bone dissolves,
neutralizing the acid.  Bone is a carnivore's version of Tums.
 
Bone reactivity to acids cannot be overemphasized.  Without such
reactivity to acid, bone would remain sharp and pointed, and could slice
into tissue, or poke through gastrointestinal walls.  Fortunately for the
small carnivore, stomach acid quickly rounds prickly points, dulls sharp
edges, and even significantly reduces the overall mass of the bone
fragment.  In the case of the ferret, a cortical bone fragment isn't
in the stomach long enough to completely dissolve, but a few minutes in
a churning stomach filled with acid and the bone becomes smooth and
polished, effectively rendering it safe for passage to the nearest pile
in the corner.  Smaller particles of bone dissolve faster in acid than
larger ones.  The reason being smaller particles have a proportionately
larger ratio of surface area to internal volume, allowing more acid to
contact the bone.  Bone will actually dissolve faster along edges and
points compared to flat bone surfaces.  Stomach acid literally rounds the
edges and points of a bone fragment, significantly decreasing the chances
of gastrointestinal injury.
 
So, what about the dangers of eating bone for teeth?  Broken teeth are
quite commonplace in predators.  In fact, they are so widespread in
mammals that various researchers have been able to construct tooth
fracture frequency tables for many predators, including some species of
mustelids.  Canine teeth are the most frequently broken, followed by
premolars, molars, and incisors.  For mammalian predators of all types,
the chance that they will break one or more teeth during their lifespan
is about 25%.  However, the tooth fracture frequency is NOT equal among
mammalian predators.  For a long time, it was accepted that larger
predators had higher tooth fracture frequencies because they killed
and ate larger, stronger animals, with thick, hardened bones.  This
conclusion seemed clear because tooth fracture frequencies were lowest
in the smallest predators and highest in the largest.  Other research,
however, suggests a correlation of tooth fracture frequencies to aging;
in mammals, larger predators tend to live longer lives.  Many suspect it
is some combination of the two; a life of chronic tooth injury is
exacerbated by the stresses of killing large prey.  Put simply, if a
polecat lived as long as a lion, the tooth fracture rates would be about
the same, regardless of what the other was eating.
 
In ferret-sized carnivores, there are numerous risk factors that could
cause tooth injury, eating bone is just one.  I know of NO instance where
a ferret broke a tooth on a bone where it couldn't be shown the ferret
had a history of biting or pulling on cages, had taken a fall to a hard
floor, or had other dental problems.  Nonetheless, it is clear that
breaking teeth on bone can -- and does -- occur, although the actual
risk is statistically small and remains undocumented.
 
Several excellent studies show wild carnivores regularly damage teeth.
In the best of those studies, the probability of a predator (averaged
from all types of carnivores) breaking at least one tooth during their
lifespan was 0.25.  This means one out of four predators will break at
least one tooth during their lifespan.  Hyenas, specializing in eating
the hardest bones, have the greatest probability of damaging one or more
teeth, greater than 0.40.  Wolves, also habitual bone eaters, have a 0.29
probabibility for having a damaged tooth.  The probability for small cats
and mongeese is 0.15.  No one has published the probability of tooth
damage in polecats (yet), but it should be less than or equal to that of
small cats and mongeese.  In my own research, I have found the
probability of tooth damage for New Zealand feral ferrets being 0.05.
That means about five ferrets out of a hundred (all age classes combined)
have one or more broken teeth.
 
Ready for the really interesting part?  I have found pet ferrets (all age
classes combined), most having never touched a bone, have a probability
of 0.68 they will have one or more damaged teeth.  Ferrets eating bone
SHOULD have a probability that they will damage one or more teeth
somewhere between 0.05 (feral ferrets) and 0.25 (averaged carnivore), but
NEVER exceeding 0.40 (hyenas).  Yet, the probability of tooth damage
within the pet ferret population greatly exceeds that number.  I'll bet
most of you could confirm this number.  Randomly pick out ten ferrets of
various ages, and about 6 or 7 of them will have either have a cavity,
missing a tooth, or have one that is cracked, broken, chipped, extremely
worn, pitted, dead, or otherwise injured.  Some people will have a few
more, some less, but that is to be expected.
 
This is an EXTREMELY significant finding.  What it means is the
probability that your ferret will damage one or more teeth during it's
lifetime, just doing the things pet ferrets do, is FAR GREATER than if it
was living wild and eating bone!  Many factors can be held responsible
for this tremendous increase in risk, including biting or tugging on
cages, nutrition, age of neutering, chewing on inappropriate objects,
falls, fighting, starchy diet, accidental trauma, and aging.
 
Benefits of bone eating can be divided into four basic categories:
psychological, physiological, nutritional, and hygienic.  Hygienic
benefits include plaque removal and tooth polishing.  Chewing bone
reduces the risk of gastrointestinal blockage caused by hairballs.  Bone
is high in fat and protein, rich in essential fatty acids, vitamins and
proteins, and minerals.  The haemopoietic tissue found in red bone marrow
is nearly a perfect food for mammalian carnivores.  The mineral part of
bone has a perfect calcium-phosphate ratio, and is easily absorbed.
Physiological benefits of bone eating include supplying the body with
chemical buffers that help maintain a constant body pH.  Bone marrow has
iron in a perfect ionic configuration for absorption.  Psychological
benefits of bone eating are controversial because they are so difficult
to prove.  Polecats are known to habitually chew bones, and fragments of
partially consumed bones have been found within their dens.  I think
ferrets have an inborn desire to gnaw bones, and chewing them supplies
stress-reducing satisfaction.
 
Personally, I suspect ferrets suffering from adrenal disease and ulcers
can potentially benefit from eating bone.  In the later case, the bone
chewing may reduce stress, and the bone itself may act as a buffering
agent in the stomach.  In the former case, eating bone could be extremely
helpful in preventing osteoporosis, a side effect I have discovered to be
quite common in ferrets suffering from adrenal disease.  Will eating bone
actually help ferrets overcome these problems?  Probably not, but it
can't hurt.
 
Bob C
[Posted in FML issue 3939]