Haven't posted in a while. Football season is in full swing with younger son starting highschool ball and my self still coaching youts. Fact or fiction I thoought it was a matter of anatomy? For the same reason that some of the first fly lines were Stallion tail and not Mare. Urine breaks down the hair and makes it brittle and hard to consistantly dye. Deer hair is usually from the belly and is hollow and there fore warmer for the animal, and greater floatability for tying.