Horse markings
Markings on horses are usually distinctive white areas on an otherwise dark base coat color. Most horses have some markings, and they help to identify the horse as a unique individual. Markings are present at birth and do not change over the course of the horse's life. Most markings have pink skin underneath most of the white hairs, though a few faint markings may occasionally have white hair with no underlying pink skin. Markings may appear to change slightly when a horse grows or sheds its winter coat, however this difference is simply a factor of hair  coat length; the underlying pattern does not change. On a gray horse, markings visible at birth may become hidden as the horse turns white with age, but markings can still be determined by trimming the horse's hair closely, then wetting down the coat to see where there is pink skin and black skin under the hair. Recent studies have examined the genetics behind white markings and have located certain genetic loci that influence their expression. In addition to white markings on a base coat, there are other markings or patterns that are used to identify horses as with Appaloosa , Pinto or Brindle, as well as artificial markings such as branding. Types of white markings. Facial markings. Facial markings are usually described by shape and location. There may be more than one distinct facial marking and if so, will be named separately. Occasionally, when a white marking extends over an eye, that eye may be blue instead of brown, though this is not consistently seen in all cases. Common facial markings are: Additional terms used to describe facial markings include the following: Leg markings. Leg markings are usually described by the highest point of the horse's leg that is  covered by white. As a general rule, the horse's hoof beneath a white marking at the coronary line will also be light-colored ("white"). If a horse has a partial marking or ermine spots at the coronary band, the hoof may be both dark and light, corresponding with the hair coat immediately above. Where the leopard gene is present, the hoof may be striped even if markings are not visible at the coronary band. From tallest to shortest, common leg markings are: Additional terms used to describe white leg markings include: Inheritance of white markings. A horse's genes  influence whether it will have white markings, though the exact genes involved could differ between breeds. Chestnut horses generally have more extensive white markings than bay or black horses. Horses with the W20 allele typically have white face and leg markings. Other markings. Horses may have isolated body spots that are not large or numerous enough to qualify them as an Appaloosa, Pinto or Paint. Such markings are usually simply called "body spots," sometimes identified by location, i.e. "belly spot," "flank spot," etc. When this type of isolated spotting occurs, it may involve one of the dominant white or sabino  alleles. Horses may develop white markings over areas where there was an injury to the animal, either to cover scar tissue from a cut or abrasion, or to reflect harm to the underlying skin or nerves. One common type of scarring that produces patches of white hairs are "saddle marks," which are round or oval marks on either side of the withers, produced by a pinching saddle that had been worn over a long period of time. Natural markings. "Birdcatcher spots" are small white spots, about the size of a dime to the size of a quarter. They have not  been linked to any specific breed, but they do tend to run in families. These spots may occur late in a horse's life, or may occur and then disappear. The spots may look like scars, but they are not caused by skin damage. The name comes from a Thoroughbred horse named Birdcatcher, who had similar flecks of white on his flank and tail. "Ticking" or "rabicano" involves white flecks of hair at the flank, and white hairs at the base of the tail. The most minimal form can have only striped white frosting at the base of the tail , called a "coon tail" or "skunk tail". Flecks of white on the root of the tail or scattered over the flanks may also be called "Birdcatcher ticks". Scarring, skin disease and injury. Scarring on a horse usually results in white hairs growing in over the injured area, though occasionally there may be no hair growth over the scar at all. Other identifying features. Horses can be uniquely identified by more than just markings or brands. A few other physical characteristics sometimes used to distinguish a horse from another are: Coat colors with distinctive patterns. Some horse coat colors are distinguished  by unique patterns. However, even for horses with coat colors that are arranged in a manner unique to each individual horse, these patterns are not called "markings." Some coat colors partially distinguished by unique patterning include: