Ok, a weak joke, but I'm burned out and my "season" is upon me, so things
will not get better for some time soon.  I still have lots (!) of mail to
catch up on, and I'm afraid some was dumped, so if you wrote and I don't
respond, assume it evaporated into the ether.
 
Ed G. asked about interspecies breeding in mustelids and the differences
between polecats and ferrets.  In the genus Mustela, a sub-group is
sometimes distinguished as the subgenus Vison, and includes weasels,
polecats, and mink (including the extinct sea mink).  Other groups include
the otters, the skunks, the badgers, etc.  As can be infered by the subgenus
status, these animals are quite closely related to each other, and many
species can successfully interbred, such as the black-footed ferret and the
steppe polecat, and several species of weasels.  This is important, because
one of the main criterion for designating the ferret as a "domesticated
European polecat" is that it can breed with them, and produce viable
offspring.  As far as I know, the only member of the subgenus Vison the
ferret can interbreed with is the European polecat, and vice-e-verse-e.  Of
course, no one really knows who can and can't interbreed; one of the
difficulties in this research is the lack of comparative studies on the
various species' genetic structures.  There is considerable variation in the
numbers of chromosomes between the different species.
 
Interspecies-breeding is not uncommon throughout the animal kingdom; just
about any Canis species can interspecies-breed, producing viable offspring
(Many scientists, with gobs of genetic research in hand, now believe the red
wolf, an endangered species found the the SE of the USA, is in fact the
result of wolves making merry with coyotes....an idea rejected by those
whose living depends on breeding and releasing them...) Many felids do the
same, as do different species of deer, skunks, God-knows-how-many rodents,
etc.  Without getting into species-concepts or genetics, lets just say that
interspecies-breeding illustrates a strong and close relationship, but does
not necessarily prove they are the same species.  (This is why I use
"Mustela furo" rather than "Mustela putorius furo" to designate the ferret;
also included in the reasoning is the complete lack of archaeological
evidence, and differences in skull shape and morphology, and other stuff
already mentioned in past posts).
 
There are many significant differences between the European polecat and the
domesticated ferret, mostly behavioral in nature, but including
physiological changes as well.  Polecats have better eyesight, hearing, and
prey-tracking abilities compared to ferrets.  Skull differences and muscle
tone may be due to domestication, but they could also be due to cage
confinement, nutrition, type of diet (a big one!  A lot of skull morphology
is due to muscle use during mastication, which is quite different
biomechanically when eating dry pellets compared to animal tissues), and
other factors too numerous to mention.  After I catch up some, I will post a
comparison list of these differences in more detail.
 
As for the hyrids of ferrets and polecats, it has been reported that they
tend to be more-or-less intermediate in behavior and physiology between the
two.  Duh.  So are the hybrids of white-tail and mule deer, or lions and
tigers, or you name it.  If the polecat and the ferret are indeed the same
species, as they probably are (my greatest objection in the matter is the
assumption they are the same; the relationship is yet to be proven), then
the vast majority of their genetic code would be the same.  Hybrids escaping
and introducing their genes to the polecat-pool would have no long-term
effect; the genes are already there--just in different frequencies.  There
could be some good towards the ferret-pool if it is suffering from
inbreeding or lack of vitality.  However, just like the wild polecats,
whatever genes were introduced would quickly become "diluted" in a few
generations.
 
This is confusing; I've been confused by it, as have other scientists. In
Caroline King's book "The Handbook of New Zealand Mammals," R. B. Lavers
and B. K. Clapperton contributed the section of ferrets, and stated the
feral population was probably not hybrids, but true domesticated ferrets.
Their reasoning is flawed, not because true-blooded polecats can be tamed
quite easily (although not as reliably), but because they haven't studied
the behaviors of captured individuals to see if they were polecat-like,
ferret-like, or some intermediate type.  It is just a blanket statement,
based on observing a few individuals, and not a representitive sample of the
population.  I'm surprised King didn't catch it.  (The original population
was primarily ferrets, but polecats were also released by the government and
private individuals).
 
The thing is, the genes of the polecat reside in the ferret, but at lower
frequencies and in different percents of expression.  It takes a lot of time
and effort to change those frequencies and percentages (the lure behind
inbreeding is the speed in which those frequencies can be altered).  So
distinguishing hybrids can be rather difficult.
 
I might add that, as with human color variation, the color of the coat is
the least reliable method of distinquishing a domesticated ferret from a
polecat.  There is just too much variation; ferrets look like European
polecats...European polecats look like steppe polecats...steppe polecats
look like black-footed ferrets...and on and on.  All polecats (and their
domesticated version) have the same basic coloration: light bellies, dark
back, darker legs and tail, dark mask on light face.  Mink also have this
coloration, although it is really dark on not-quite-so-dark, so it is kind
of hard to notice.  I assume a breeding program with really dark sables
might ultimately result in an apparently all-dark coloration, but it would
take time and scores of generations.  But not hard; as far as I know, coat
color in ferrets is simple Mandelian genetics.
 
Bob and the 13 Misfits of Science
[Posted in FML issue 1523]