Most people don’t know the differences and more importantly, the similarities, of hair, fur and wool on mammals.

All mammals, with rare exception, have more or less hair on their bodies, including the head. This is one evolutionary characteristic that sets us apart from other members of the animal kingdom.

When taken collectively, hair is considered fur. There’s your first bit of knowledge.

Fur can occur as dense or sparse. We all know it can be soft or coarse. Fur naturally occurs in colorful or drab hues. On others, fur can be one color or even intricately patterned.

Three types of hair make up our fur. Vibrissae are sensitive tactile receptors. The best example are whiskers that in fact are used to sense the environment. Guard hairs are the most common and what most people recognize for serving a protective function. Underhairs are those with the primary purpose of insulation.

Taken together, the density, thickness and length of these three types of hair are what constitute the wide variety of differences seen in the mammalian world. Just consider the diversity between a lion’s mane and the fur on its body, and say, a zebra, or a seal’s whiskers.

Now what about wool as it appears on sheep? Yep, it is a form of hair, too. More on this in a minute.

All hair is made of keratin, a fibrous protein filament that is the primary component in fingernails, claws, horns (not antlers), hooves and feathers. Typically, without doting care regimes we humans conduct, most hair grows in varying lengths from tiny up to about 3 feet before it then begins to break and fall away.

For kids being home schooled or other interested adults, the FBI produced a definitive text in 2004 (see that helps differentiate animal hair from human hair. Our hair is not as differentiated as it is in other animals. As a result, it serves both functions as a guard hair and an underhair.

Wool growers don’t like people calling their fibrous product known as wool, “hair.” It is hair, however, except it is very specialized. Wool fibers are crimped and elastic, and they have scale (see the FBI manual noted above), which, taken in combination, give wool its unique and wonderful qualities. It is without a doubt the best insulating form of hair on the sheep where it is produced.

But only certain varieties of domestic sheep produce wool as most people think of it. If domestic wool-producing breeds are not sheered regularly, that thick fleece can become very matted and a place for parasites to invade and insects to colonize. That’s why one doesn’t see wooly sheep like our domestic breeds in the wild.

Other sheep, such as bighorn sheep, grow more recognizable hair as most know it. They also produce those magnificent horns, in both males and females. Still other domestic breeds produce long staple wool valued by spinners and weavers.

Sheep started being domesticated about 11,000 B.C. But it took from then to 4,000 to 3,000 B.C. before fleeces began being collected. And around 1,900 B.C., the British learned that the structure of the individual wool fibers made them ideal for spinning and weaving. The oldest known woolen garment was found in a Danish bog and dated back to about 1,500 B.C. Finally, the British established a woolen production center and trade area in Winchester, U.K., about 50 A.D.

There you have it, the basics of hair on ourselves and our mammal friends, plus a link to the fascinating FBI publication.

Powell is the public information officer for the Washington State University College of Veterinary Medicine, which provides this column as a community service. For questions or concerns about animals you’d like to read about, email

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