First let me say that I can only comment about non water fur bears. I will use coyotes as an example. As the daylight hours shorten,tempertures lower, and several other factors, the circlatory system in the animals skin starts to change the amount and routing of blood flow.When this transformation is complete the hair shedding is very little,and if the hide was tanned at this stage the hair will stay on.But the winter hair growth is not complete and not at its most attractive stage.Later when the hair growth is complete and before the animal starts to rub is when it is prime.