John asked:
>I have been told & believed that the following is true as a 'very
>general' observation... that the more white in the faces of the kits
>or adults, that the better the chance that they could be deaf.  Is
>this a reliable sign?
 
Geneticist, Dr. Brett Middleton has said that the amount of whiteness
ear or on the ears is a good predictor usually.  See:
http://fhl.sonic-weasel.org/browse.php?msg=YG3069
including (I have standing permission to quote him.):
 
>There are a zillion problems (scientifically speaking B-) associated
>with various types of depigmentation.  Failure of the neural tube to
>close, cleft palate, enlarged colon, anemia, infertility, behavioral
>disorders, reduced intelligence, limb malformations, problems with
>balance, etc.  It all depends on which gene or genes are causing the
>depigmentation.
 
and
>There are some interesting aspects to hearing problems associated
>with white markings, especially where the KIT gene is involved. For
>example, I mentioned that this gene is involved with both spotting and
>deafness in Dalmatians.  However, the incidence of hearing loss in
>Dalmatians with black patches on the ears is much lower.  The KIT gene
>is also responsible for the white head, belly, feet and tail switch of
>Hereford cattle, yet I've never heard that deafness is a particular
>problem for this breed. Note that Herefords have pigmented ears.
 
and
>While I don't know what genes are responsible for the markings of panda
>bears, I do note that they, also, have pigmented ears.  This seems to
>indicate that genotypes exist that allow pigment cells to migrate to
>the ear during embryonic development -- resulting in normal hearing --
>while restricting migration to the skin and coat sufficiently to
>produce the white markings that many find desirable.
>Unfortunately, we don't yet know how this works, though it probably
>involves some modifier gene(s) that interact with the KIT gene.  We also
>don't know if ferrets are one of the species in which this could be
>accomplished.  (We also don't know how far we could go in eliminating
>deafness in Dalmatians.  Patches are considered a disqualification in the
>Dalmatian breed standard!  Talk about shooting yourself in the foot...)
 
and
>Behavioral problems associated with depigmentation are another
>interesting phenomenon, and are related to all types of depigmentation
 
and
>The responsibility of breeders to consider the well-being of the
>animal in their selection programs is an aspect of animal welfare that
>is too often neglected.  Too many people who would never consider
>beating or starving their animals suddenly seem to lose all sense of
>ethical limits when it comes to breeding them.
 
There is a lot more in there and be sure to read other posts from Dr.
Brett Middleton in both http://fhl.sonic-weasel.org  and
http://groups.yahoo.com/group/Ferret-Genetics/
[Posted in FML issue 4888]