Q: "Why are my ferret's teeth so long?  Are they longer [in proportion]
than in other species?" "It seems I am always cutting my ferret's nails.
Do they grow extra fast?" "Why do ferret's have such tiny eyes?"
 
A: All the better to bite, render, and serve you up for supper, my dear.
Nailed that one by the skin of my teeth, didn't eye?
 
All three are modified for the hunting activities of wild polecats--the
ancestors of the domesticated ferret.  The ferret just happened to inherit
them.  The teeth are long, but not proportionately longer than in many
other species of the same size.  Many civets, mongeese, and smaller wild
cats also have "long" canines, and there is basically two reasons for this.
First, small animals run a tremendous risk as predators; the prey species
have a very real defensive ability and can (and do) kill them.  The odds
given in many of the older ferreting/ratting books place the ferret's odds
at beating a Norway rat at about 50%.  The long fangs possessed by the
ferret are excellent for piercing the neck and skull bones, rendering an
instantaneous death and saving the predator the risk of serious or mortal
injury.  The second reason is biomechanics; the larger the tooth, the
"blunter" because the tooth needs to be thicker to withstand the biting and
shearing forces placed on it during a kill.  Skinny teeth snap off, as many
a sad Smilodon can testify.  But in smaller mammals, the teeth do not have
the same heavy biomechanical forces and the teeth are thinner.  This makes
them look longer and sharper compared to a dog's tooth.  Remember, wild
polecats eat animals that are their body size or less, while animals such
as wolves eat animals many times their body size.
 
Ferret nails are not much different from most other mammals, including
ourselves.  Technically, a nail is flat while a claw is curved, but some use
"nail" interchangably.  Ferrets have claws.  At first glance, a claw (or
unguicula) looks like it is a solid piece of kornified tissue, but it is
actually a piece folded in the middle with the lower parts (the underside
of the claw) near or touching each other, but not fused.  So a nail is a
flatened-out claw, see?  Some species (and at least one reference suggests
ferrets may belong to this group) have claws who's growth responds to use;
that is, digging may help to make the claw grow faster (and usually
stronger).  In most species, the claw grows at a "set" rate.  Claws in
digging animals tend to grow at a faster rate than in most other mammals
(save hoofed animals, perhaps), which is designed to offset their wearing
down during digging.  The shape, thickness and length of the claw reveals
its use.  A cat's claw is short, extremely curved and doesn't extend far
past the interior bone (ungual process of the terminal phalange), a ferret's
claw can extend quite some distance past the interior bone, while the badger
has a claw that is almost a nail, and extends a great distance past the
bony part.  The main reason for this structural difference is due to the
cat using it's claws for prey capture, compared to the ferret, which uses
their claws for digging.  Ferrets evolved as diggers, and the instinct can
be hard to break, as many carpets can testify.
 
Ferret eyes are indeed proportionately smaller than in other animals of the
same size.  There are two basic reasons for this, the first being ferret
have small eyes because they use their sense of smell as their primary
hunting weapon.  The brain cannot be larger than the skull which contains
it, and since head size is allometricly tied to body size, there is not a
lot of room for the brain to grow.  But increasing the dependence on the
sense of smell creates problems....where does all the increased wiring go?
One nifty way to solve the problem of increased dependence on a single sense
is for some other sense to decrease, allowing the more important sense to
have expansion room in the limited space of the brain-case.  Ferrets seem to
have "opted" for this solution, decreasing vision and associated "wiring" to
allow for the increase size of the olfactory expansion and wiring.  Dogs
"opted" for increasing both, which is why they have foreheads and the ferret
doesn't--the forehead allowed expansion room for both the sense of small and
vision.  The ferret, or rather, the polecat, cannot afford a forehead to get
in the way while running down tight burrows  (Can't you imagine the sound,
"trot, trot, trot, bump, ferret chattering fert-cuss words, trot, trot,
trot, bump?") Second, because ferrets have such a strong adaptation to
hunting in burrows, the smaller eyes help in keeping dirt out.  Besides,
burrows are dark, and eyes are not as important as with daytime killers.
 
Bob C and 22 MO Eye-Toothed Terrors
[Posted in FML issue 2420]