Master hair, cover hair, outer hair, and primary hair all refer to what most of us call “guard hair.”  Each guard hair is surrounded by between six and twelve downy hairs (put another way, each hair follicle has one guard hair and up to 15 secondary hairs emerging from the same follicle). Guard hairs are typically stiffer, harder, glossier, smoother, coarser, longer and/or thicker in diameter than the softer undercoat of a dog, The hair acts as an additional layer of insulation, a “topcoat,” if you will, to protect a dog from cold weather. It also helps prevent injuries to the dog’s skin, and, to a large extent, determines the dog’s appearance because of its unique coloring.

It probably doesn’t need to be said (but we’ll say it anyway) that guard hairs vary widely among our dog breeds.  The guard hair of wire-haired breeds is characterized by a crisp, hard texture, while breeds developed to work in water generally have a high oil content in their coat so that water runs off their guard hairs to protect undercoat and skin from being saturated. Guard hair of nordic breeds is usually stiffer and often longer to protect the undercoat and skin from wind and cold weather. Smooth-haired terriers and Toy Poodles, meanwhile, are said to have the highest density of follicles which gives these breeds a lot of guard hairs (German Shepherd Dogs, Airedales and Rottweilers have only half as many follicles, but twice as many under-hairs coming from each follicle).

So the next time you’re picking hair off your dark coat, vacuuming it off the couch, and sweeping up dust bunnies that are 75% dog hair, try to marvel at how a dog’s coat works, and remember that since guard hairs are the strongest part of dog hair and meant to be permanent, it’s less likely that these are the hairs that are adhering to your sticky roller hair remover. Undercoat is mostly what sheds naturally and ends up on your black merino coat.

For anyone who wants a little “light” reading on the subject of guard hairs, check out this abstract entitled, “Statistical comparison of dog and cat guard hairs using numerical morphology.” 

A perverse sense of humor has us posting an image of the Peruvian Inca Orchid Dog by Olde Time Mercantile with this post. Prints of this drawing is available for purchase here.