Okay, I found it.  This came from a brochure called "Ferret Facts" and then
it says -compliments of Dr Susan Brown and Dr J A Neuman- This is a small
excerpt in a several page long brochure: "Hair loss on the tail has been
frequently observed in our area of the country (Midwest) and other areas,
particularly in the fall of the year.  The alopecia occurs only on the tail
and may be total or partial.  A reddish brown waxy deposit or black spots
may also be present.  We find that the condition resolves on its own in 1-3
months.  No medications are necessary.  This is probably a function of the
adrenal gland in response to changes in the photoperiod.  The true etiology
is unknown." I will paraphrase a bit more of the brochure: Dietary problems
do not generally lead to alopecia; skin parasites other than fleas are
uncommon; the most common reason (95%) for hair loss in neutered pet is
adrenal neoplasia but other causes have been granulosa cell, tumors,
luteomas and fibrosarcomas in both intact and neutered animals; mast cell
tumors of the integument have also been associated with alopecia, resolves
when tumors are removed; in warm weather ferrets experience thinning of the
coat, poor nutrition results in dry or sparse coats.  Charlene
[Posted in FML issue 1265]