>...more on its eyesight than ever before.  Did this then lead to the
>degeneration of its paired infra-red sensors and the improvement of its
>vision?  Even today most ferreters realize that the ferret's vision is
>not its keenest sense, this perhaps an indication that the ferret is still
>evolving and nowhere near "domesticated," in the normal sense of that
>currently misused word.  Would emphasis placed on skull studies of the
>earliest recovered skulls of ancient ferrets reveal the presence of tiny
>orifices in the skull through which nerves would have passed to the brain
>from these infra-red sensors above the eyes?
 
Ed, the structure you describe above the eye of the ferret is indeed a
sensory receptor, but not one for IR radiation.  It is a tactile receptor,
and you can find them in numerous locations on the ferret's face.  By
the same token, you can find them all over the face of cats and dogs,
rats, rabbits, mice, and most other noctural rodents and carnivores.
The structures you have noticed house vibrissae, which are those long
whisker-like tactile hairs sprouting out of the face and chin of ferrets.
These structures are considered minor sense organs, and are used to
determine the location of objects.  Ever wonder why a blind ferret rarely
walks into something?  Or knows exactly the level of the water when getting
a drink?  The vibrissae allow the ferret to go down jet black burrows and
still find its way around without running into objects.
 
They don't do it using infrared; they do it by the sense of touch.  A
vibrissa has nerve receptors at its base and the hair itself acts like a
long lever--anchored at the skin--so any movement at all stimulates the
nerve endings letting the ferret know that its about to bump into
something.  The vibrissae are also useful in hunting (especially so in
cats).  When a carnivore bites, or strikes, at prey, they typically close
their eyes and open their mouth as their heads move forward in the bite.
The little tactile hairs are the trigger for our little mouse traps with
needle-sharp teeth; during the strike, tiny muscles pull at the base of the
vibrissae so they all point forward, and at the first moment of contact,
they send a signal to the brain saying "if you want to eat, you will shut
your mouth about now." The length of vibrissa, nerve transmission time,
speed of strike and mouth shutting time all time themselves perfectly so
that when the vibrissal trigger is set off, by the time the canines hit the
prey, the mouth has started clamping shut.  So, in essence, the vibrissae
have a dual function; as canes for the blind and as triggers for the dental
trap.
 
As for your idea about light sensors to the brain.  Well, you are right but
you are also wrong as well.  The brain does seem to have a light sensor;
it is the pineal gland (or pineal body) deep in the brain.  Among other
things, it is thought the pineal gland regulates the estrous cycle in
photoperiodic animals, such as the ferret.  Traditionally, it has been
thought light hitting the retina stimulates the pineal gland, but recent
experiments suggests that light striking the head can transmit *THROUGH*
the skull (much in the same way you can shine light through your hand with
a flashlight) and stimulates the pineal gland directly.
 
Now, in all fairness, there might be some truth to Ed's idea, but not as he
expressed it.  Some research (non-extensive and needs to be duplicated) has
indicated some predators are also sensitive to temperature changes.  In
other words, to increases in heat (much as your hand can detect the heat
coming off an burner on an electric stove).  Apparently, there seems to be
some evidence of extra nerve endings which detect heat, BUT that is not the
same thing as an IR detector by any means.  It would be similar to the
difference between your elbow detecting heat compared to your finger tips.
Unlike a vit viper which can detect heat several feet away, this added heat
sense would only be effective when in extreme close range, and is probably
used in conjunction with the vibrissae to detect proximal contact.  It is
important to realize this research has not yet been confirmed
independently.
 
As for the skull aspect of Ed's idea, I have made 22 measurements per skull
(56 if your count the tooth measurements) on more than 350 ferret, polecat
and black-footed ferret skulls, and I can say (since I am actually looking
at a ferret skull right now) that no structure, pit, foramen, or "spot"
exists on the skull which would support the idea that ferrets have a
degenerated IR receptor.  And, setting down the ferret skull and picking up
the polecat skull, nor does one exist in it's probable ancestor.  In fact,
having looked at quite literally more than a 1000 mink and weasel skulls, I
can say such a structure does not exist on them either.  Nor is there any
reference to such a structure in the literature, and as well as the mink
and black-footed ferret (and lately the polecat) has been studied, you
would think it would have been noticed and reported.
 
One thing about your statement bothers me Ed.  Its your attitude about the
ferret not being completely domesticated.  By your standards, dogs, cats,
cattle, rabbits, well, NOTHING would be domesticated.  The ferret has skull
and dental changes, physiological changes, breeding changes, behavioral
changes, increased variability, and fur changes as great or greater than
any other domesticated animal.  It fits every standard for domestication
that exists, without exception.  Perhaps what you should do is write down
exactly why you think the ferret is only partially domesticated, and I can
look at it and respond directly to your argument.  Otherwise, I'm inclined
to catalog your statements into the logorrhea file and forget them.  And
that would be too bad because you *DO* have good ideas, and many times your
remarks spur informative debate.
 
Now, for the rest of the FML, I am definately NOT flaming Ed, whom I have
met and have had delightful conversation with.  Ed is a nice guy, has some
good looking ferrets that get to dig some nice holes in front (or the
side?) of his house, and spends as much time or more promoting the positive
side of ferretdom.  I am simply debating his idea.
 
Bob C and 17 Mo' Chicken Snarfers (Missing Apollo)
[Posted in FML issue 2701]