Differences between Fur and Hair

Fur vs. Hair

Fur and hair are chemically indistinguishable, as both are composed of keratin, a fibrous structural protein. The term "hair" is a general descriptor for the filamentous structures that grow from follicles in the skin of mammals, while "fur" typically describes a dense, short, and fine coat of hair. Common usage often associates "fur" with non-human mammals and "hair" with humans, although this is not a strict scientific distinction. The key differences between what is commonly called fur and hair lie in their density, structure, and growth cycles.

Comparison Table

Category	Fur	Hair
Density	Very high density of follicles, creating a thick coat for insulation. Sea otters can have up to 160,000 hairs per square centimeter.	Lower density on most of the body compared to animals with fur.
Structure	Often consists of a double coat: a soft, dense underfur for insulation and longer, coarser guard hairs for protection.	Typically a single layer of hair without the distinct underfur and guard hair structure.
Growth Cycle	Generally has a shorter anagen (growth) phase, leading to a predetermined length and more frequent, often seasonal, shedding.	Can have a much longer anagen phase, particularly on the human scalp, allowing for significant growth in length.
Primary Function	Primarily insulation, camouflage, and protection from moisture and UV radiation.	Functions include insulation, protection from UV rays, sensory input, and social signaling.

Venn diagram comparing Differences between Fur and Hair

Growth Cycles

All hair, whether classified as fur or hair, undergoes a cyclical growth pattern consisting of three main phases: anagen, catagen, and telogen.

• **Anagen (Growth Phase):** This is the active growth period where cells in the follicle divide rapidly to form the hair shaft. The length of the anagen phase determines the maximum length of the hair. For much of what is called fur, this phase is relatively short, resulting in hairs of a specific length that are shed regularly. In humans, the anagen phase of scalp hair can last for several years.
• **Catagen (Transitional Phase):** A brief period where hair growth stops and the outer root sheath shrinks and attaches to the root of the hair. This phase signals the end of active growth.
• **Telogen (Resting Phase):** The follicle is dormant, and the hair shaft is fully formed. At the end of this phase, the hair is shed, often pushed out by the growth of a new anagen hair. Animals with dense fur often synchronize the telogen phase for seasonal molting.