Q: I have a 12-year-old chestnut Arabian (almost straight Egyptian) mare, who darkens up in the fall and winter to nearly liver chestnut. I noticed about two weeks ago that she has developed white spots on her body, legs, face and back ranging from the size of a quarter and down to a dime. She has no Egyptian roaning, and I am just amazed. There are no signs of injury to explain this and I have never had another horse develop anything like this. Where did these spots come from?
[For your bookshelf: Equine Color Genetics]
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A: Your mare fits the description for a classic case of "birdcatcher spots." These small, random white spots, no larger than an inch across, pop up spontaneously on the body of horses of practically any solid color and usually appear later in life. Sometimes the markings seem to move around a bit, vanishing and reappearing elsewhere on the body. They may also disappear entirely over time. However, unlike other white hairs that can appear from ill-fitting tack or leg wraps that rub, these marks have no relation to injury or skin damage.
The spots are named for the Irish-born Thoroughbred stallion Birdcatcher (1833), who displayed similar odd white flecks of hair along his flank and above his tail. No formal studies have been done on this rare coat characteristic to link them genetically to a specific breed, but they do tend to run in families.
D. Phillip Sponenberg, DVM, PhD
College of Veterinary Medicine