Week 44 Fur. I will regard fur to be synonymous with hair for this exercise, although originally I considered there to be a difference. When fur is layered, the short ground hair, known as undercoat or down, is mainly for insulation. The long guard hair, which is coarser, straighter and has more pigmentation is sometimes water repellent. There can be a third intermediate layer, it's called awn hair. Again I am at the zoo.