Furriness - Nature of Fur

Nature of Fur

Fur usually consists of two main layers:

• Ground hair (known also as undercoat or down hair) — the bottom layer consisting of wool hairs, usually wavy or curly without straight portions or sharp points; down hairs tend to be shorter, flat, curly, and more numerous than the top layer. Its principal function is thermoregulation; it maintains a layer of dry air next to the skin and repels liquid water, thus providing thermal insulation.
• Guard hair — the top layer consisting of longer, generally coarser, nearly straight shafts of hair that stick out through the underfur. The distal ends of the guard hairs provide the externally visible layer of the coat of most mammals with well-developed fur. This zone of the coat displays the most marked pigmentation and gloss, including coat patterns adapted to display or camouflage. It also is adapted to shedding water and blocking sunlight, protecting the undercoat and skin from outside factors, such as rain and ultraviolet. Many animals such as cats erect their guard hairs as part of their threat display when agitated.

As a rule, mammals with well-developed down hairs and guard hairs also have large number of awn hairs; awn hairs begin their growth much as guard hairs do, but change their mode of growth, usually when less than half the length of the hair has emerged. This portion of such a hair is the so-called awn. The rest of the growth is thin and wavy, much like down hair. In many species of mammals the awn hairs comprise the bulk of the visible coat. The proximal part of the awn hair shares the function of the down hairs, whereas the distal part aids the water-shedding function of the guard hairs, though their thin basal portion prevents their being erected like true guard hairs.