Several of my ferrets get very thin tail hair by the end of the summer, sometimes accompanied by that rusty crust, sometimes not (no crust this year, but still thin tail hair). None of them have great looking tails by late summer. Every fall, after they shed and look really ratty for a few weeks, they grow nice thick tail hair that lasts at least through the spring. This is not related to adrenal disease, which two of my ferrets also have. Blessings Judith P.S. Still hoping to hear about flax seed oil dosage for the two adrenals. [Posted in FML issue 3201]